ORCID Profile
0000-0003-1972-1222
Current Organisations
University of Western Australia
,
Lions Eye Institute
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Psychology | Sensory Processes, Perception and Performance | Vision Science | Sensory Processes, Perception And Performance | Opthalmology And Vision Science | Sensory Systems | Optometry and Ophthalmology | Sensory Systems | Neurosciences | Open Software | Optometry and Ophthalmology not elsewhere classified | Transport Engineering | Bioinformatics Software |
ANZSRC Socio-Economic Objective (SEO)
Hearing, Vision, Speech and Their Disorders | Hearing, vision, speech and their disorders | Health related to ageing | Computer Software and Services not elsewhere classified | Road Safety | Computer software and services not elsewhere classified | Health Related to Ageing
Related Links
Publications
Behavioral measures of cortical hyperexcitability assessed in people who experience visual snow
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 03-2017
DOI: 10.1212/WNL.0000000000003784
Abstract: To determine whether visual perceptual measures in people who experience visual snow are consistent with an imbalance between inhibition and excitation in visual cortex. Sixteen patients with visual snow and 18 controls participated. Four visual tasks were included: center-surround contrast matching, luminance increment detection in noise, and global form and global motion coherence thresholds. Neuronal architecture capable of encoding the luminance and contrast stimuli is present within primary visual cortex, whereas the extraction of global motion and form signals requires extrastriate processing. All these tasks have been used previously to investigate the balance between inhibition and excitation within the visual system in both healthy and diseased states. The visual snow group demonstrated reduced center-surround contrast suppression ( p = 0.03) and elevated luminance increment thresholds in noise ( p = 0.02). Groups did not differ on the global form or global motion task. Our study demonstrates that visual perceptual measures involving the suprathreshold processing of contrast and luminance are abnormal in a group of in iduals with visual snow. Our data are consistent with elevated excitability in primary visual cortex however, further research is required to provide more direct evidence for this proposed mechanism. The ability to measure perceptual differences in visual snow reveals promise for the future development of clinical tests to assist in visual snow diagnosis and possibly a method for quantitatively assaying any benefits of treatments.
Backward and forward visual masking in schizophrenia and its relation to global motion and global form perception
Publisher: Elsevier BV
Date: 12-2010
DOI: 10.1016/J.SCHRES.2010.07.008
Abstract: Whilst visual backward masking deficits in schizophrenia have been reliably reported and may reveal magnocellular dysfunction, forward masking, which may rely more heavily on the parvocellular system, has been under investigated. In a group of 64 schizophrenia patients and 65 matched controls we undertook a visual masking paradigm containing both conditions, together with tests of 'global motion' and 'global form' perception, two 'down-stream' visual tasks reflecting later processing linked to magnocellular and parvocellular function respectively. In the patient group, a significant but small deficit on the masking task, equivalent across forward and backward conditions was seen. Correlations between the masking and motion/form tasks supported the predominant theoretical framework describing the neural processes involved in masking. Performance on the motion and form tasks was differentiated by a trend-level motion processing deficit but near-normal form processing. The results suggest an 'early visual' processing deficit in both magno- and parvocellular systems but one which is only transferred to 'down-stream' processing areas with predominantly magnocellular input.
Simultaneous retinal and cortical visually evoked electrophysiological responses in between migraine attacks
Publisher: SAGE Publications
Date: 16-07-2012
Abstract: Purpose: People with migraine often report aversion to flickering lights and show abnormal results on behavioural tasks that require the processing of temporal visual information. Studies have reported that the cortically evoked electrophysiological response to a flickering visual stimulus is abnormal however, none have considered whether there is an underlying pre-cortical abnormality. In this cross-sectional study, we consider whether people with migraine have retinal and cortical electrophysiological abnormalities to flickering stimuli. Methods: Monocular transient (1 Hz) and steady-state (8.3 Hz) pattern reversal electroretinograms (PERGs) and pattern visual evoked responses (PVERs) were measured simultaneously in 45 people with migraine (26 without aura, 19 with aura) and 30 non-headache controls at a time between migraine attacks. Results: PERG litude and timing did not differ significantly between groups. Transient PVER litude was significantly reduced (28%) in the migraine with aura group compared to the controls F(2,72) = 3.6, p = 0.03). Both migraine groups showed significant reductions (32%, 39%) in steady-state PVER litude relative to controls (F(2,70) = 4.3, p = 0.02). Conclusions: This study finds normal retinal processing of flickering stimuli in the presence of abnormal cortical function between migraine attacks.
An Electrophysiological Comparison of Contrast Response Functions in Younger and Older Adults, and Those With Glaucoma
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 31-01-2019
Abstract: Aging and glaucoma both result in contrast processing deficits. However, it is unclear the extent to which these functional deficits arise from retinal or post-retinal neuronal changes. This study aims to disentangle the effects of healthy human aging and glaucoma on retinal and post-retinal contrast processing using visual electrophysiology. Steady-state pattern electroretinograms (PERG) and pattern visual evoked potentials (PVEP) were simultaneously recorded across a range of contrasts (0%, 4%, 9%, 18%, 39%, 73%, 97% 0.8° diameter checks, 31° diameter checkerboard) in 13 glaucoma patients (67 ± 6 years), 15 older (63 ± 8 years) and 14 younger adults (27 ± 3 years). PERG and PVEP contrast response functions were fit with a linear and saturating hyperbolic model, respectively. PERG and PVEP magnitude, timing (phase), and model fit parameters (slope, semi-saturation constant) were compared between groups. PERG responses were reduced and delayed in older adults relative to younger adults, and further reduced and delayed in glaucoma patients across all contrasts. PVEP signals were also reduced and delayed in glaucoma patients, relative to age-similar (older) controls. However, despite having reduced PERG magnitudes, older adults did not demonstrate reduced PVEP magnitudes. Older adults with healthy vision demonstrate reduced magnitude and delayed timing in the PERG that is not reflected in the PVEP. In contrast, glaucoma produces functional deficits in both PERG and PVEP contrast response functions. Our results suggest that glaucomatous effects on contrast processing are not a simple extension of those that arise as part of the aging process.
Test-Retest Variability of Fundus-Tracked Perimetry at the Peripapillary Region in Open Angle Glaucoma.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 08-07-2016
Abstract: To examine the association between the measured level and local gradient of visual sensitivity on the magnitude of test-retest variability of its measurements at the peripapillary region using fundus-tracked perimetry in eyes with glaucoma. A total of 30 participants with open angle glaucoma underwent three examinations in one eye on fundus-tracked perimetry using a stimulus pattern that s led the peripapillary region densely. Factors associated with the magnitude of test-retest variability at each location were examined. There was no significant change in average pointwise sensitivity (PWS) between tests 1 and 2 (P = 0.855), but a significant reduction between tests 2 and 3 (P < 0.001). Therefore, all subsequent analyses were performed only between tests 1 and 2. Multivariate analyses revealed that the magnitude of test-retest variability at a given location was significantly associated with its average sensitivity and gradient of sensitivity relative to the immediately adjacent locations (P ≤ 0.001), meaning that locations with low levels of sensitivity (4-18 dB) with low gradients of sensitivity ( 4 dB/location). On a pointwise basis, the test-retest variability of visual sensitivity in glaucoma is not just related to its measured level, but also its local gradient when using fundus-tracked perimetry. Locations with low sensitivity do not necessarily demonstrate very high test-retest variability, depending on the local uniformity of visual field damage.
Reduced audiovisual recalibration in the elderly.
Publisher: Frontiers Media SA
Date: 27-08-2014
Vernier Acuity Is Normal in Migraine, whereas Global Form and Global Motion Perception Are Not
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 07-2006
DOI: 10.1167/IOVS.05-1549
Abstract: A recent study has demonstrated that some people with migraine display impairments of intermediate stages of motion and form processing. Deficits were identified by using tasks that required that local stimulus attributes be integrated into global percepts. Neurons capable of global processing of form and motion are known to be present in extrastriate cortical areas V4 and V5, respectively. It is not clear from the literature whether deficits of global processing in migraineurs are likely to arise from reduced input to extrastriate cortex from primary visual cortex (V1). The purpose of the study was to compare presumed measures of V1 performance (vernier acuity) to measures of global form and motion perception in migraineurs. Thirty migraineurs (17 with aura, and 13 without) and 20 age-matched nonheadache control subjects participated. Intermediate level motion and form perceptions were measured using global dot motion stimuli and Glass patterns, respectively. Vernier stimuli were broad vertical bars composed of small dot elements. Both a static luminance stimulus and a motion defined form vernier stimulus were used. Mean migraine and control group performance were not significantly different for either vernier task (static: t(48)=0.39, P=0.70 motion: t(48)=0.29, P=0.77). Mean migraine group performance was significantly worse than in control subjects for both the global form (t(48)=2.06, P=0.04) and global motion (t(48)=2.87, P<0.01) tasks. On average, migraineurs demonstrate abnormalities of intermediate stages of both motion and form processing. These abnormalities do not appear to arise from dropout of performance at V1, as vernier acuity was normal in the same in iduals.
Suprathreshold Approaches to Mapping the Visual Field in Advanced Glaucoma
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 28-06-2023
DOI: 10.1167/TVST.12.6.19
Individualized structure-function mapping for glaucoma
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 28-03-2014
Abstract: We have developed customized maps that relate visual field and optic nerve head (ONH) regions according to in idual anatomy. In this study, we aimed to determine feasible map resolution for research use, and to make a principled recommendation of sector size for clinical applications. Measurement variability in fovea-ONH distance and angle was estimated from 10 repeat OCT scans of 10 healthy people. Errors in estimating axial length from refractive error were determined from published data. Structure-function maps were generated, and customized to varied clinically-plausible anatomical parameters. For each parameter set (n = 210), 200 maps were generated by s ling from measurement/estimation error distributions. Mapped 1° sectors at each visual field location from each parameter set were normalized to difference from their mean. Variation (90% ranges) in normalized mapped sectors represents the precision of in idualized maps. Standard deviations of repeated measures of fovea-ONH distance and angle were 61 μm and 0.97° (coefficients of variation 1.3% and 12.0%, respectively). Neither measure varied systematically with mean (Spearmans's ρ = 0.26, P = 0.47 for distance, ρ = -0.31, P = 0.39 for angle). Variation (90% ranges) in normalized mapped sectors varied across the visual field and ranged from 3° to 18° when axial length was measured accurately, and from 6° to 32° when axial length was estimated from refractive error. The 90% ranges represent the minimum feasible ONH sector size at each visual field location. For clinical use an easily interpretable scheme of 30° sectors is suggested.
Assessing the GOANNA Visual Field Algorithm Using Artificial Scotoma Generation on Human Observers
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 09-2016
DOI: 10.1167/TVST.5.5.1
Aging alters surround modulation of perceived contrast
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 05-2009
DOI: 10.1167/9.5.11
Is primary open‐angle glaucoma part of a generalized sensory neurodegeneration? A review of the evidence
Publisher: Wiley
Date: 02-07-2012
DOI: 10.1111/J.1442-9071.2012.02812.X
Abstract: Open-angle glaucoma is an optic neuropathy that has a multifarious aetiological profile. Emerging theories suggest that a group of factors induce optic nerve injury in innately susceptible aging optic nerves. These factors have the potential to impact on the function of other vulnerable neurons within the central nervous system of older patients. Although changes within the visual pathways due to retinal ganglion cell dysfunction and death are well established, research exploring the behaviour of other sensory systems in in iduals with glaucoma is limited. This review summarizes what is known about these other non-visual sensory changes, explores whether glaucoma is in fact part of a global neurodegenerative condition, and suggests areas for future research direction.
Flicker-defined form stimuli are minimally affected by centre-surround lateral contrast interactions
Publisher: Wiley
Date: 06-01-2016
DOI: 10.1111/OPO.12268
Impacts of older age on the temporal properties of collinear facilitation
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 12-12-2019
DOI: 10.1167/19.14.5
Abstract: Collinear facilitation is a visual phenomenon by which the contrast detection threshold of a central target is reduced (facilitation) when placed equidistant between two high-contrast flankers. The neural mechanisms underpinning this phenomenon originate from feed-forward lateral facilitation between cell layers in V1 (slower) and feedback facilitation from extrastriate visual areas to V1 (faster). The strength of these contributions has been explored in younger adults by presenting the central target and flankers at varying timing offsets. Here, we investigated the effects of older age on collinear facilitation with flankers presented in sync, before, and after target onset, to allow the inference of any characteristic effect of older age on feed-forward and feedback facilitatory mechanisms. Seventeen older and 19 younger observers participated. Our data confirms previous findings of an age-related reduction in facilitation when flankers and target occur at synchrony, but no age difference was found at other timings. Marked interin idual variability in facilitation for the different flanker onset timings was present, which was repeatable within in iduals. Further research is required to ascertain the mechanistic underpinnings for different facilitation profiles between in iduals. Longitudinal study across an in idual's life span is needed to determine whether an in idual's facilitation profile changes with age.
Feature issue: Visual function and the ageing visual system
Publisher: Wiley
Date: 07-2014
DOI: 10.1111/OPO.12144
Motion perception at mesopic light levels: effects of physiological ageing and eccentricity
Publisher: Wiley
Date: 24-01-2021
DOI: 10.1111/OPO.12783
Abstract: To explore the differential effects of age and eccentricity on the perception of motion at photopic and mesopic light levels. Thirty‐six visually normal participants (18 younger mean age 25 years, range: 20–31) and (18 older mean age 70 years, range: 60–79) underwent two testing sessions, one at photopic and one at mesopic light levels. In each session, motion perception was tested binocularly at two eccentricities (centrally, and peripherally at 15° rightwards and 5° superior to the horizontal) for four motion tasks: minimum contrast of a drifting Gabor to identify motion direction (motion contrast) translational global motion coherence biological motion embedded in noise and the minimum duration of a high‐contrast Gabor to determine the direction of motion, using two Gabor sizes to measure spatial surround suppression of motion. There was a significant main effect of light condition (higher thresholds in mesopic) for motion contrast ( p 0.001), translational global motion ( p = 0.001) and biological motion ( p 0.001) a significant main effect of age (higher thresholds in older adults) for motion contrast ( p 0.001) and biological motion ( p = 0.04) and a significant main effect of eccentricity (higher thresholds peripherally) for motion contrast ( p 0.001) and biological motion ( p 0.001). Additionally, we found a significant three‐way interaction between light levels, age and eccentricity for translational global motion (similar increase in mesopic thresholds centrally for both groups, but a much larger deterioration in older adult’s peripheral mesopic thresholds, p = 0.02). Finally, we found a two‐way interaction between light condition and eccentricity for translational global motion (higher values in central mesopic relative to peripheral photopic, p = 0.001) and for biological motion (higher values in peripheral mesopic relative to central photopic, p 0.001). For the majority of tasks assessed, motion perception was reduced in mesopic relative to photopic conditions, to a similar extent in both age groups. However, because some older adults exhibited elevated thresholds even under photopic conditions, particularly in the periphery, the ability to detect mesopic moving stimuli even at high contrast was markedly impaired in some in iduals. Our results imply age‐related differences in the detection of peripheral moving stimuli at night that might impact hazard avoidance and night driving ability.
Spatial frequency bands used by patients with glaucoma to recognize facial expressions
Publisher: Informa UK Limited
Date: 10-03-2022
Eye movement characteristics provide an objective measure of visual processing changes in patients with visual snow syndrome
Publisher: Springer Science and Business Media LLC
Date: 05-05-2021
DOI: 10.1038/S41598-021-88788-2
Abstract: Visual snow syndrome (VSS) is a poorly understood neurological disorder that features a range of disabling sensory changes. Visual processing changes revealed previously in VSS appear consistent with poor attentional control, specifically, with difficulty controlling environmentally driven shifts of attention. This study sought to confirm this proposal by determining whether these changes were similarly evident where attention is internally driven. Sixty seven VSS patients and 37 controls completed two saccade tasks: the endogenously cued saccade task and saccadic Simon task. The endogenously cued saccade task correctly (valid trial) or incorrectly (invalid trial) pre-cues a target location using a centrally presented arrow. VSS patients generated significantly shorter saccade latencies for valid trials ( p = 0.03), resulting in a greater magnitude cue effect ( p = 0.02), i.e. the difference in latency between valid and invalid trials. The saccadic Simon task presents a peripheral cue which may be spatially congruent or incongruent with the subsequent target location. Latencies on this task were comparable for VSS patients and controls, with a normal Simon effect , i.e. shorter latencies for saccades to targets spatially congruent with the preceding cue. On both tasks, VSS patients generated more erroneous saccades than controls towards non-target locations (Endogenously cued saccade task: p = 0.02, saccadic Simon task: p = 0.04). These results demonstrate that cued shifts of attention differentially affect saccade generation in VSS patients. We propose that these changes are not due to impairment of frontally-mediated inhibitory control, but to heightened saccade-related activity in visual regions. These results contribute to a VSS ocular motor signature that may provide clinical utility as well as an objective measure of dysfunction to facilitate future research.
The association between retinal vein pulsation pressure and optic disc haemorrhages in glaucoma
Publisher: Public Library of Science (PLoS)
Date: 28-07-2017
Sampling the visual field based on individual retinal nerve fiber layer thickness profile
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 22-02-2018
Abstract: Current perimeters use fixed grid patterns. We test whether a grid based on an in idual's retinal nerve fiber layer (RNFL) thickness profile would find more visual field (VF) defects. We describe the defect-based method for choosing test locations. First, the 26 VF locations with the highest positive predictive value to detect glaucoma from the 24-2 pattern are chosen. An additional 26 locations are chosen from a 2 × 2 degree grid based on RNFL thickness. An in idualized map was used to relate VF locations to peripapillary RNFL thickness. To test whether the 52 locations chosen by the defect-based method find more defects than other test grids, we collected a 386-location (2 × 2 degree grid) VF measurement on 23 glaucoma participants and classed each location in the dataset as either abnormal or normal using a suprathreshold test. Using this data, defect-based s ling was compared to: a method that s led VF locations uniformly around the optic nerve head (ONH) the 24-2 pattern a polar pattern and a reduced polar pattern. The outcome measure was the number of abnormal points that were selected as test locations. For 8 eyes, no method found more abnormal points than would be expected by chance (hypergeometric distribution, P < 0.05). Of the remaining 15 eyes, the defect-based method identified more abnormal locations on nine eyes, which was significantly better than the other three s ling schemes (24-2: 2 eyes, P < 0.001 polar: 2 eyes, P < 0.001 reduced polar: 2 eyes, P < 0.004 and uniform: 1 eye, P < 0.001). Using structural information to choose locations to test in a VF for in idual patients identifies more abnormal locations than using existing grid patterns and uniform s ling based on structure.
The relationship between central and mid‐peripheral motion perception and the hazard perception test in younger and older adults
Publisher: Wiley
Date: 12-06-2023
DOI: 10.1111/OPO.13180
Abstract: Vision standards for driving are typically based on visual acuity, despite evidence that it is a poor predictor of driving safety and performance. However, visual motion perception is potentially relevant for driving, as the vehicle and surroundings are in motion. This study explored whether tests of central and mid‐peripheral motion perception better predict performance on a hazard perception test (HPT), which is related to driving performance and crash risk, than visual acuity. Additionally, we explored whether age influences these associations, as healthy ageing impairs performance on some motion sensitivity tests. Sixty‐five visually healthy drivers (35 younger, mean age: 25.5 SD 4.3 years 30 older adults, mean age: 71.0 SD 5.4 years) underwent a computer‐based HPT, plus four different motion sensitivity tests both centrally and at 15° eccentricity. Motion tests included minimum displacement to identify motion direction ( D min ), contrast detection threshold for a drifting Gabor (motion contrast), coherence threshold for a translational global motion stimulus and direction discrimination for a biological motion stimulus in the presence of noise. Overall, HPT reaction times were not significantly different between age groups ( p = 0.40) nor were maximum HPT reaction times ( p = 0.34). HPT response time was associated with motion contrast and D min centrally ( r = 0.30, p = 0.02 and r = 0.28, p = 0.02, respectively) and with D min peripherally ( r = 0.34, p = 0.005) these associations were not affected by age group. There was no significant association between binocular visual acuity and HPT response times ( r = 0.02, p = 0.29). Some measures of motion sensitivity in central and mid‐peripheral vision were associated with HPT response times, whereas binocular visual acuity was not. Peripheral testing did not show an advantage over central testing for visually healthy older drivers. Our findings add to the growing body of evidence that the ability to detect small motion changes may have potential to identify unsafe road users.
A Comparison between the Compass Fundus Perimeter and the Humphrey Field Analyzer
Publisher: Elsevier BV
Date: 02-2019
DOI: 10.1016/J.OPHTHA.2018.08.010
Abstract: To evaluate relative diagnostic precision and test-retest variability of 2 devices, the Compass (CMP, CenterVue, Padova, Italy) fundus perimeter and the Humphrey Field Analyzer (HFA, Zeiss, Dublin, CA), in detecting glaucomatous optic neuropathy (GON). Multicenter, cross-sectional, case-control study. We sequentially enrolled 499 patients with glaucoma and 444 normal subjects to analyze relative precision. A separate group of 44 patients with glaucoma and 54 normal subjects was analyzed to assess test-retest variability. One eye of recruited subjects was tested with the index tests: HFA (Swedish interactive thresholding algorithm [SITA] standard strategy) and CMP (Zippy Estimation by Sequential Testing [ZEST] strategy), 24-2 grid. The reference test for GON was specialist evaluation of fundus photographs or OCT, independent of the visual field (VF). For both devices, linear regression was used to calculate the sensitivity decrease with age in the normal group to compute pointwise total deviation (TD) values and mean deviation (MD). We derived 5% and 1% pointwise normative limits. The MD and the total number of TD values below 5% (TD 5%) or 1% (TD 1%) limits per field were used as classifiers. We used partial receiver operating characteristic (pROC) curves and partial area under the curve (pAUC) to compare the diagnostic precision of the devices. Pointwise mean absolute deviation and Bland-Altman plots for the mean sensitivity (MS) were computed to assess test-retest variability. Retinal sensitivity was generally lower with CMP, with an average mean difference of 1.85±0.06 decibels (dB) (mean ± standard error, P < 0.001) in healthy subjects and 1.46±0.05 dB (mean ± standard error, P < 0.001) in patients with glaucoma. Both devices showed similar discriminative power. The MD metric had marginally better discrimination with CMP (pAUC difference ± standard error, 0.019±0.009, P = 0.035). The 95% limits of agreement for the MS were reduced by 13% in CMP compared with HFA in participants with glaucoma and by 49% in normal participants. Mean absolute deviation was similar, with no significant differences. Relative diagnostic precision of the 2 devices is equivalent. Test-retest variability of MS for CMP was better than for HFA.
Towards Patient-Tailored Perimetry
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 12-04-2013
DOI: 10.1167/TVST.2.4.3
Individual differences in Foveal shape: Feasibility of individual maps between structure and function within the macular region
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 13-09-2016
Visual contextual effects of orientation, contrast, flicker, and luminance: All are affected by normal aging
Publisher: Frontiers Media SA
Date: 18-04-2016
Visual object categorisation in people with glaucoma
Publisher: BMJ
Date: 08-08-2016
DOI: 10.1136/BJOPHTHALMOL-2015-308289
Abstract: There is evidence that people with glaucoma exhibit difficulties with some complex visual tasks such as face recognition, motion perception and scene exploration. The purpose of this study was to determine whether glaucoma affects the ability to categorise briefly presented visual objects in central vision. Visual categorisation performance of 14 people with glaucoma (primary open angle glaucoma and preperimetric) and 15 age-matched controls was measured, assessing both accuracy and response times. Grey level photographs of objects (size) were presented for 28 ms foveally. Perimetric thresholds were normal for all participants within the central 3°. Two levels of contrasts were included: one medium level at 50% and one with high contrast at 100%. On average, accuracy was significantly decreased by 7% (p=0.046) for the medium contrast stimuli in patients with glaucoma (87% of correct response, SD: 5%) compared with controls (94% of correct response, SD: 4.7%). Group average response times were significantly slower for the patients relative to the control group (712 ms, SD: 53 ms compared with 643 ms, SD: 34 ms for the control group p<0.01). Performance was equivalent in the two groups when the picture contrast was 100%. The impairment observed in the categorisation task supports previous work that demonstrates that people with glaucoma can have greater difficulties with complex visual tasks than is predicted by their visual field loss. The performance was equivalent to age-matched controls when contrast was maximised.
Orientation of the Temporal Nerve Fiber Raphe in Healthy and in Glaucomatous Eyes
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 24-08-2017
Abstract: To determine the normal variation in orientation of the temporal nerve fiber raphe, and the accuracy with which it may be predicted or approximated in lieu of direct measurement. We previously described an algorithm for automatic measurement of raphe orientation from optical coherence tomography, using the intensity of vertically oriented macular cubes. Here this method was applied in 49 healthy participants (age 19-81 years) and 51 participants with primary open angle glaucoma (age 51-80 years). Mean fovea-disc-raphe angle was 173.5° ± 3.2° (range = 166°-182°) and 174.2° ± 3.4° (range = 166°-184°) in healthy and glaucoma patients, respectively. Differences between groups were not significant. Fovea-disc-raphe angle was not correlated with age or axial length (P > 0.4), showed some symmetry between eyes in glaucoma (R2 = 0.31, P < 0.001), and little symmetry in the healthy group (P = 0.06). Fovea-disc angle was correlated with fovea-raphe angle (R2 = 0.27, P = 0.0001), but was not a good predictor for raphe orientation (average error = 6.8°). The horizontal axis was a better predictor (average error = 3.2° maximum error = 9.6°), but still gave approximately twice the error previously reported for direct measurement from macular cubes. There is substantial natural variation in temporal nerve fiber raphe orientation, which cannot be predicted from age, axial length, relative geometry of the disc and fovea, or the contralateral eye. For applications to which the orientation of the raphe is considered important, it should be measured directly.
Improving Spatial Resolution and Test Times of Visual Field Testing Using ARREST
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 31-10-2018
DOI: 10.1167/TVST.7.5.35
Home Monitoring of Retinal Sensitivity on a Tablet Device in Intermediate Age-Related Macular Degeneration
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 29-10-2018
DOI: 10.1167/TVST.7.5.32
Ionic channel changes in glaucomatous retinal ganglion cells: Multicompartment modeling
Publisher: IEEE
Date: 08-2014
The Proportion of Individuals Likely to Benefit from Customized Optic Nerve Head Structure–Function Mapping
Publisher: Elsevier BV
Date: 04-2017
DOI: 10.1016/J.OPHTHA.2016.12.016
Abstract: Interin idual variance in optic nerve head (ONH) position, axial length, and location of the temporal raphe suggest that customizing mapping between visual field locations and ONH sectors for in iduals may be clinically useful. Herein we quantify the proportion of the population predicted to have structure-function mappings that markedly deviate from "average," and thus would benefit from customized mapping. Database study and case report. Population database of 2836 eyes from the Beijing Eye Study and a single case report of an in idual with primary open-angle glaucoma. Using the morphometric fundus data of the Beijing Eye Study for 2836 eyes and applying a recently developed model based on axial length and ONH position relative to the fovea, we determined for each measurement location in the 24-2 Humphrey (Carl Zeiss Meditec, Dublin, CA) visual field the proportion of eyes for which, in the customized approach as compared with the generalized approach, the mapped ONH sector was shifted into a different sector. We determined the proportion of eyes for which the mapped ONH location was shifted by more than 15°, 30°, or 60°. Mapping correspondence between locations in visual field space to localized sectors on the ONH. The largest interin idual differences in mapping are in the nasal step region, where the same visual field location can map to either the superior or inferior ONH, depending on other anatomic features. For these visual field locations, approximately 12% of eyes showed a mapping opposite to conventional expectations. Anatomically customized mapping shifts the map markedly in approximately 12% of the general population in the nasal step region, where visual field locations can map to the opposite pole of the ONH than conventionally considered. Early glaucomatous damage commonly affects this region hence, in idually matching structure to function may prove clinically useful for the diagnosis and monitoring of progression within in iduals.
Motion Perception in Migraineurs: Abnormalities are Not Related to Attention
Publisher: SAGE Publications
Date: 09-2006
DOI: 10.1111/J.1468-2982.2006.01182.X
Abstract: Migraine groups have impaired ability to identify global motion direction in noisy random dot stimuli, an observation that has been used as evidence for cortical hyperexcitability. Several studies have also suggested abnormalities in cognitive processing, particularly in the domains of attention, visuo-spatial processing and memory. This study aimed to determine whether poor performance by migraineurs in motion coherence tasks could be explained by non-visual cognitive factors such as attention. Twenty-nine migraineurs and 27 non-headache controls participated. Global motion coherence thresholds were measured along with measures of neuropsychological function, using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). The migraine group had significantly higher motion coherence thresholds than controls. No significant difference in attention or any other RBANS index score was found between groups. Index scores did not correlate with motion perception thresholds. This study does not support inattention or other cognitive abnormality as an explanation for motion perception anomalies in migraine.
Rapid contrast adaptation in glaucoma and in aging
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 19-05-2014
Abstract: The visual system rapidly adapts to contrast changes, often with each fixation. One key anatomical site underpinning contrast adaptation is the retinal ganglion cell dendrites, where degenerative changes occur in glaucoma. This study investigated the effects of early glaucoma and aging on rapid contrast adaptation. Contrast detection and discrimination thresholds were measured in central vision for briefly presented (94 ms) Gabor patches with and without adaptation to 50% contrast Gabor patches (1000 ms). Fourteen people with glaucoma (aged 58-77 years), 17 age-similar controls (aged 50-72 years), and 19 younger adults (aged 20-31 years) participated. Detection thresholds were measured at various time points (47, 106, 200, 400, 600, and 1000 ms) post adaptation. Discrimination thresholds were measured post adaptation relative to a reference contrast below (30%), equivalent to (50%), or above (70%) the adaptor. The glaucoma group demonstrated elevated unadapted detection (P < 0.0001) and discrimination (P = 0.01) thresholds relative to age-similar controls. In normal observers, aging elevated unadapted thresholds (detection: P < 0.0001 discrimination: P < 0.0001). At 47 ms post adaptation, the glaucoma group demonstrated reduced effects of adaptation relative to controls (P = 0.009). Adaptation was also reduced when the reference contrast (50%) was equivalent to the adaptor (P = 0.02). Aging did not alter adaptation of normal observers. Glaucoma alters rapid contrast adaptation while aging does not. Contrast adaptation is key to visual processing in natural visual environments. Our results imply that glaucoma produces abnormalities in natural visual experiences in central vision.
Psypad: A platform for visual psychophysics on the iPad
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 11-03-2014
DOI: 10.1167/14.3.16
Abstract: This article introduces PsyPad, a customizable, open-source platform for configuring and conducting visual psychophysics experiments on iPads without the need for any code development for the iPad. Stimuli for experiments are created off-line as a library of images. The PsyPad app (obtainable from the Apple App Store) presents the images according to either built-in, customizable staircase or method of constant stimuli procedures, mapping stimuli levels to images based on the image file names. On-screen buttons for responses are configurable and matched to "correct" using the image file name of any given stimulus. All actions are logged into a text file and sent to a specified server at the end of the test if an Internet connection is available. If the iPad is not connected, the results are uploaded the next time the iPad is online. We provide a secure server for this purpose, but the server-side software is also open source if researchers choose to run their own server.
An Analysis of the Factors Associated with Visual Field Deficits Measured with Flickering Stimuli in-between Migraine
Publisher: SAGE Publications
Date: 05-2004
DOI: 10.1111/J.1468-2982.2004.00682.X
Abstract: We have previously demonstrated that perimetric performance measured with flickering stimuli is not normal in some in iduals who experience migraine with aura in the period between their attacks. In this study, flicker perimetric performance is measured in a broad group of migraineurs to determine whether the existence of such visual field deficits is dependent on the presence of visual aura, is correlated with the duration of migraine history, or frequency of attacks. Twenty-eight migraine with aura, 25 migraine without aura, and 24 non-headache control subjects participated. The performance of the migraine groups was not significantly different from each other. The migraine groups showed significantly lower general sensitivity across the visual field and higher incidence of localized visual field deficits relative to controls. Both length of migraine history and frequency of migraine occurrence over the past 12 months were significantly correlated with lower general sensitivity to flickering visual stimuli.
Eccentricity dependence of orientation anisotropy of surround suppression of contrast-detection threshold
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 09-07-2018
DOI: 10.1167/18.7.5
Abstract: Both neurophysiological and psychophysical data provide evidence for orientation biases in nonfoveal vision-specifically, a tendency for a Cartesian horizontal and vertical bias close to fixation, changing to a radial bias with increasing retinal eccentricity. We explore whether the strength of surround suppression of contrast detection also depends on retinotopic location and relative surround configuration (horizontal, vertical, radial, tangential) in parafoveal vision. Three visual-field locations were tested (0°, 225°, and 270°, angle increasing anticlockwise from 0° horizontal axis) at viewing eccentricities of 6° and 15°. Contrast-detection threshold was estimated with and without a surrounding annulus. At 6° eccentricity, horizontally oriented parallel center-surround (C-S) configurations resulted in greater surround suppression compared to vertically oriented parallel center-surround configurations (p = 0.001). At 15° eccentricity, radially oriented parallel center-surround stimuli conferred greater suppression than tangentially oriented stimuli (p = 0.027). Parallel surrounds resulted in greater suppression than orthogonal surrounds at both eccentricities (p < 0.05). At 6° the horizontal center was more susceptible to suppression than a vertical center (p < 0.001) for both parallel and orthogonal surrounds, while at 15° a radial center was more susceptible to suppression (relative to a tangential center), but only if the surround was parallel (p = 0.005). Our data show that orientation anisotropy of surround suppression alters with eccentricity, reflecting a link between suppression strength and visual-field retinotopy.
Detecting glaucoma from multi-modal data using probabilistic deep learning
Publisher: Frontiers Media SA
Date: 29-09-2022
Abstract: To assess the accuracy of probabilistic deep learning models to discriminate normal eyes and eyes with glaucoma from fundus photographs and visual fields. Algorithm development for discriminating normal and glaucoma eyes using data from multicenter, cross-sectional, case-control study. Fundus photograph and visual field data from 1,655 eyes of 929 normal and glaucoma subjects to develop and test deep learning models and an independent group of 196 eyes of 98 normal and glaucoma patients to validate deep learning models. Accuracy and area under the receiver-operating characteristic curve (AUC). Fundus photographs and OCT images were carefully examined by clinicians to identify glaucomatous optic neuropathy (GON). When GON was detected by the reader, the finding was further evaluated by another clinician. Three probabilistic deep convolutional neural network (CNN) models were developed using 1,655 fundus photographs, 1,655 visual fields, and 1,655 pairs of fundus photographs and visual fields collected from Compass instruments. Deep learning models were trained and tested using 80% of fundus photographs and visual fields for training set and 20% of the data for testing set. Models were further validated using an independent validation dataset. The performance of the probabilistic deep learning model was compared with that of the corresponding deterministic CNN model. The AUC of the deep learning model in detecting glaucoma from fundus photographs, visual fields, and combined modalities using development dataset were 0.90 (95% confidence interval: 0.89–0.92), 0.89 (0.88–0.91), and 0.94 (0.92–0.96), respectively. The AUC of the deep learning model in detecting glaucoma from fundus photographs, visual fields, and both modalities using the independent validation dataset were 0.94 (0.92–0.95), 0.98 (0.98–0.99), and 0.98 (0.98–0.99), respectively. The AUC of the deep learning model in detecting glaucoma from fundus photographs, visual fields, and both modalities using an early glaucoma subset were 0.90 (0.88,0.91), 0.74 (0.73,0.75), 0.91 (0.89,0.93), respectively. Eyes that were misclassified had significantly higher uncertainty in likelihood of diagnosis compared to eyes that were classified correctly. The uncertainty level of the correctly classified eyes is much lower in the combined model compared to the model based on visual fields only. The AUCs of the deterministic CNN model using fundus images, visual field, and combined modalities based on the development dataset were 0.87 (0.85,0.90), 0.88 (0.84,0.91), and 0.91 (0.89,0.94), and the AUCs based on the independent validation dataset were 0.91 (0.89,0.93), 0.97 (0.95,0.99), and 0.97 (0.96,0.99), respectively, while the AUCs based on an early glaucoma subset were 0.88 (0.86,0.91), 0.75 (0.73,0.77), and 0.92 (0.89,0.95), respectively. Probabilistic deep learning models can detect glaucoma from multi-modal data with high accuracy. Our findings suggest that models based on combined visual field and fundus photograph modalities detects glaucoma with higher accuracy. While probabilistic and deterministic CNN models provided similar performance, probabilistic models generate certainty level of the outcome thus providing another level of confidence in decision making.
Contrast and stimulus duration dependence of perceptual surround suppression in older adults
Publisher: Elsevier BV
Date: 05-2015
DOI: 10.1016/J.VISRES.2015.02.016
Abstract: Most natural visual tasks involve the extraction of visual features from suprathreshold contrast backgrounds, hence an understanding of how ageing impacts on contrast mechanisms is essential to understand elderly visual function. Previous studies have revealed increased perceptual surround suppression of contrast in older adults. We aimed to determine whether such age-related effects depend on the centre or surround stimulus contrast as the neurophysiological mechanisms underpinning contrast-contrast suppression depend on such contrast relationships. We also measured surround suppression of contrast for longer duration and shorter duration stimuli to explore for effects of surround adaptation Fifteen younger and 15 older adults performed a centre-surround contrast discrimination task for a variety of centre-surround contrast combinations (20%, 40% and 80% contrast). Stimulus duration was 500ms. The 40% centre, 80% surround condition was also presented for 100ms duration. Relative to younger adults, perceptual surround suppression was increased for the older group for low, but clearly suprathreshold, central contrasts (20% contrast), whilst both groups performed similarly for stimuli with high centre contrasts. Data was best fit by a model with both increased inhibitory and excitatory weightings in the older group. Reduced stimulus duration increased perceptual surround suppression for both groups consistent with reduced adaptation to the surround, and did not explain the difference in suppression magnitude between groups. Understanding the stimulus parameters that elicit increased surround suppression in older adults is key to directing future work exploring underlying neural substrates, in addition to potentially being useful for predicting performance on more complicated natural visual tasks such as object and scene perception.
Ocular motor measures of visual processing changes in visual snow syndrome
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 16-07-2020
DOI: 10.1212/WNL.0000000000010372
Abstract: To determine whether changes to cortical processing of visual information can be evaluated objectively using 3 simple ocular motor tasks to measure performance in patients with visual snow syndrome (VSS). Sixty-four patients with VSS (32 with migraine and 32 with no migraine) and 23 controls participated. Three ocular motor tasks were included: prosaccade (PS), antisaccade (AS), and interleaved AS-PS tasks. All these tasks have been used extensively in both neurologically healthy and diseased states. We demonstrated that, compared to controls, the VSS group generated significantly shortened PS latencies ( p = 0.029) and an increased rate of AS errors ( p = 0.001), irrespective of the demands placed on visual processing (i.e., task context). Switch costs, a feature of the AS-PS task, were comparable across groups, and a significant correlation was found between shortened PS latencies and increased AS error rates for patients with VSS ( r = 0.404). We identified objective and quantifiable measures of visual processing changes in patients with VSS. The absence of any additional switch cost on the AS-PS task in VSS suggests that the PS latency and AS error differences are attributable to a speeded PS response rather than to impaired executive processes more commonly implicated in poorer AS performance. We propose that this combination of latency and error deficits, in conjunction with intact switching performance, will provide a VS behavioral signature that contributes to our understanding of VSS and may assist in determining the efficacy of therapeutic interventions.
Choosing two points to add to the 24-2 pattern to better describe macular visual field damage due to glaucoma
Publisher: BMJ
Date: 23-03-2015
DOI: 10.1136/BJOPHTHALMOL-2014-306431
Abstract: A recent study has shown that the paracentral upper visual field in the macular region is often affected in glaucoma and suggested that two test locations within the central 10° should be added to the Humphrey 24-2 visual field test pattern to detect such damage. This study employed data collected using a different visual field test pattern to determine whether the same two-test locations are supported as the most informative regarding visual field loss. A data set of 62 patients with glaucoma and 48 controls had visual field assessments on the Medmont perimeter M700 (Central Threshold or Glaucoma test). Twelve 24-2 locations within central 10° of visual field were derived by interpolation of the nearest neighbours of the Medmont data. The remaining 24 Medmont locations in the central 10° of the glaucomatous set were labelled as abnormal if their thresholds fell outside the lower 5th centile of the age-corrected values for the same location from the control group. All possible pairs of the 24 locations were then assessed for diagnostic power by counting the number of patients that had 0, 1 or 2 abnormal locations in a pair. Overwhelmingly, pairs of locations in the superior macular region were more often abnormal than pairs in the inferior. About 50 pairs of locations had equivalent ability to detect damage, with the best pair having 74% of patients with at least one of the locations as abnormal, and 52% both. Adding a pair of locations to the superior macular region of the Humphrey Visual Field 24-2 pattern increases the number of abnormal locations identified in in iduals with glaucoma.
Shape perception is altered by normal aging
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 30-05-2012
DOI: 10.1167/IOVS.11-8807
Abstract: To compare the effects of aging on two shape-discrimination tasks: a closed shape task (radial frequency [RF] patterns) and a Glass pattern coherence task (discrimination of global shape signal from textured noise). We hypothesized that aging would impair the extraction of shape from texture more than the discrimination of closed shapes, consistent with evidence that aging impairs the ability to suppress irrelevant information when segmenting contours from noise. Fourteen younger (19-38 years) and 14 older (62-72 years) adults participated. Contrast-detection thresholds were measured for the RF and Glass stimuli, and then shape-discrimination tasks were performed using stimuli of 5-fold each in idual's contrast threshold. The threshold sinusoidal litude for the discrimination of an RF3 (triangular) versus an RF4 (square) was measured, in addition to the threshold signal coherence level for the discrimination of concentric from radial Glass patterns. Older adults had elevated shape-discrimination thresholds: RF: mean older = 27 second arc, younger = 18 second arc, t(26) = -3.14, P < 0.01 Glass patterns mean coherence: older = 29%, younger = 16%, t(26) = -5.67, P < 0.01. Relative to younger adult performance, the Z-scores for older adult performance on the Glass task were higher than the RF task (paired t-test P < 0.05). Shape perception is not robust to the effects of aging. Greater deficits were manifest for the discrimination of shape from texture than for the discrimination of closed contours.
Daily vision testing can expose the prodromal phase of migraine.
Publisher: SAGE Publications
Date: 07-11-2017
Abstract: Several visual tasks have been proposed as indirect assays of the balance between cortical inhibition and excitation in migraine. This study aimed to determine whether daily measurement of performance on such tasks can reveal perceptual changes in the build up to migraine events. Visual performance was measured daily at home in 16 non-headache controls and 18 in iduals with migraine using a testing protocol on a portable tablet device. Observers performed two tasks: luminance increment detection in spatial luminance noise and centre surround contrast suppression. Luminance thresholds were reduced in migraine compared to control groups ( p 0.05), but thresholds did not alter across the migraine cycle while headache-free, centre-surround contrast suppression was stronger for the migraine group relative to controls ( p 0.05). Surround suppression weakened at around 48 hours prior to a migraine attack and strengthened to approach their headache-free levels by 24 hours post-migraine (main effect of timing, p 0.05). Daily portable testing of vision enabled insight into perceptual performance in the lead up to migraine events, a time point that is typically difficult to capture experimentally. Perceptual surround suppression of contrast fluctuates during the migraine cycle, supporting the utility of this measure as an indirect, non-invasive assay of the balance between cortical inhibition and excitation.
The interpretation of results of 10-2 visual fields should consider individual variability in the position of the optic disc and temporal raphe
Publisher: BMJ
Date: 08-07-2018
DOI: 10.1136/BJOPHTHALMOL-2016-309669
Abstract: To clarify the anatomical relation between the optic disc and temporal raphe and to examine how these are related to test points in the 10-2 visual field test pattern. For 22 eyes of volunteers with normal vision (+0.75 D spherical equivalent 7.88 D), a volume scan was used to obtain en-face images from a plane fitted to the inner limiting membrane using optical coherence tomography (OCT). The clearest en-face retinal nerve fibre (RNF) image was chosen for each subject and superimposed on fundus photographs using blood vessels for alignment. In idual landmarks (disc, fovea and visual field blind spot) were then used to superimpose the Humphrey Field Analyzer 10-2 visual field on the OCT image to compare with the RNF image. The average disc–fovea–raphe angle was 169.4°±3.2°. Both the disc and temporal raphe were located above the horizontal midline (ie, were inferior in visual field space). For the 10-2 test pattern superimposed on the OCT image, in 54.5% of eyes, the temporal inferior test points adjacent to the horizontal midline mapped to the anatomical inferior hemifield. In 22.7% of eyes, nasal inferior test points adjacent to the horizontal midline mapped to the anatomical inferior hemifield. This mapping is opposite to typically assumed. The position of the disc and raphe affects the mapping between structure and function with respect to superior and inferior hemifields. In idual differences in the position of the temporal raphe should be considered when mapping between structure and function for the 10-2 test pattern.
Recurrent optic disc hemorrhage and its association with visual field deterioration in glaucoma
Publisher: Elsevier BV
Date: 11-2020
The axis of astigmatism in right and left eye pairs
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 08-1997
DOI: 10.1097/00006324-199708000-00029
Abstract: This study was designed to investigate the relationship between the astigmatic axes of right and left eye pairs, with particular attention given to determining the degree to which either direct or mirror symmetry (enantiomorphism) of the astigmatic axes exists. A s le of 192 "nonvisually" selected adults participated, with refractive error and corneal curvature data being measured using autokerato-refractive equipment. Total, corneal, and residual astigmatism were investigated, with residual astigmatism being taken as the vector difference between total and corneal astigmatism. There was no evidence for a predominance of either mirror or direct symmetry of the astigmatic axes within this s le. The patterns of astigmatic axis distribution of right and left eyes were remarkably similar but, within this context, there was no definite evidence for a definable association between the axis of the left and right pairs of in iduals. These findings remained unchanged when the effect of the modulus of astigmatism was incorporated, either through weighting the frequency distributions or through analyzing a subgroup of the overall population (those in iduals with greater than 0.50 D of astigmatism). We believe these findings contradict commonly held clinical impressions regarding the symmetry of astigmatic axes, and should be considered when performing statistical analysis of astigmatic data.
Relating the cortical visual contrast gain response to spectroscopy-measured excitatory and inhibitory metabolites in people who experience migraine
Publisher: Public Library of Science (PLoS)
Date: 07-04-2022
DOI: 10.1371/JOURNAL.PONE.0266130
Abstract: This study aimed to determine whether the visual response to flickering checkerboard patterns measured using electroencephalography (EEG) relate to excitatory or inhibitory metabolite levels measured using ultra-high (7Tesla/7T) magnetic resonance spectroscopy (MRS). Electrophysiological studies have shown altered visual cortical response litudes and contrast gain responses to high contrast flickering patterns in people with migraine. These contrast response anomalies have been argued to represent an imbalance between cortical inhibition and excitation, however the specific mechanism has not been elucidated. MRS-measured metabolite levels were obtained from the occipital cortex of 18 participants with migraine and 18 non-headache controls. EEG contrast gain response functions were collected on separate days from a subset of 10 participants with migraine and 12 non-headache controls. Case-control outcome measures were statistically compared between groups both before and after checkboard exposure. No significant difference in GABA and glutamate levels were found between groups nor checkerboard timepoint. Glucose levels were significantly reduced after checkerboard exposure in both participant groups. There was no metabolic signature in visual cortex in response to high-contrast flickering checkboards that distinguished those with migraine and without. There was also no correlation between MRS and EEG measurements in response to the flickering checkerboard. Our findings suggest that the mechanisms driving contrast-flickering stimulus aversion are not simplistically reflected by gross changes in metabolic activity in the primary visual cortex.
Recent developments in perimetry: test stimuli and procedures
Publisher: Informa UK Limited
Date: 03-2005
DOI: 10.1111/J.1444-0938.2005.TB06671.X
Abstract: Automated perimetry has evolved substantially in recent years, in part due to modern computer technology that enables more complex visual stimuli and test procedures to be realised than those incorporated in traditional white-on-white luminance increment perimetry. This paper reviews briefly a number of advances in automated perimetry. The review includes discussion of new test types: frequency doubling technology perimetry, short wavelength automated perimetry, flicker perimetry, high-pass resolution perimetry and rarebit perimetry. Test algorithms applied to perimetry such as zippy estimation of sequential thresholds (ZEST), Swedish interactive thresholding algorithm (SITA), tendency-oriented perimetry (TOP) and multi-s ling supra-threshold perimetry are also discussed.
Abnormal inhibition-excitation imbalance in migraine
Publisher: SAGE Publications
Date: 18-03-2016
Abstract: People with migraine show increased surround suppression of perceived contrast, a perceptual analogue of centre-surround antagonistic interactions in visual cortex. A proposed mechanism is that cortical ‘hyperexcitability’ or ‘hyperresponsivity’, a prominent theory in the migraine literature, drives abnormal excitatory-inhibitory balance to give increased local inhibition. The purpose of this cross-sectional study was to determine whether cortical hyperresponsivity and excitatory-inhibitory imbalance manifests in the visual cortical response of migraine sufferers. Interictal steady-state visual evoked potentials (VEPs) in response to 0 to 97% contrast were recorded in 30 migraine participants (15 without aura, 15 with aura) and 21 non-headache controls. Monotonicity indices were calculated to determine response saturation or supersaturation. Contrast gain was modelled with a modified saturating hyperbolic function to allow for variation in excitation and inhibition. A greater proportion of migraine participants (43%) than controls (14%) exhibited significant VEP supersaturation at high contrast, based on monotonicity index (chi-square, p = 0.028). Supersaturation was also evident by the trend for greater suppressive exponent values in migraine compared to control in iduals (Mann-Whitney rank sum, p = 0.075). Supersaturation in migraine is consistent with excess excitation (hyperresponsivity) driving increased network inhibition and provides support for excitatory-inhibitory imbalance as a pathophysiological disturbance in migraine.
Properties of Perimetric Threshold Estimates from Full Threshold, ZEST, and SITA-like Strategies, as Determined by Computer Simulation
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 11-2003
DOI: 10.1167/IOVS.03-0023
Abstract: To investigate the accuracy and precision of threshold estimates returned by two Bayesian perimetric strategies, staircase-QUEST or SQ (a Swedish interactive threshold algorithm [SITA]-like strategy) and ZEST (zippy estimation by sequential testing), and to compare these measures with those of the full-threshold (FT) algorithm. A computerized visual field simulation model was developed to compare the performance (accuracy, precision, and number of presentations) of the three algorithms. SQ implemented aspects of the SITA algorithm that are in the public domain. The simulation was tested by using standard automated perimetry (SAP) visual field data from 265 normal subjects and 163 observers with glaucomatous visual field loss and by exploring the effect of response variability and response errors on algorithm performance. SQ was faster than FT or ZEST, with a comparable mean error when simulating field tests on patients. Point-wise analysis revealed similar error and standard deviation of error as a function of threshold for FT and SQ. If the initial estimate of threshold for either procedure was incorrect, the means and standard deviations of the error increased markedly. ZEST produced more accurate thresholds than did the other two strategies when the initial estimate was removed from the true threshold. When simulated patients made errors, the accuracy and precision of sensitivity estimates were poor when the initial estimate of threshold either overestimated or underestimated the true threshold. This was particularly so for FT and SQ. ZEST demonstrated more consistent error properties than the other two measures.
Distribution of astigmatism in the adult population
Publisher: Optica Publishing Group
Date: 02-1996
Abstract: We have quantified statistically the astigmatic frequency distribution. Vectorial analysis was used, as it enables formal multivariate statistical techniques to be applied to astigmatic data, allowing the simultaneous inclusion of both modulus and axis in the analytical procedure. These methods were applied to population data for each of total, corneal, and residual astigmatism from a s le of 198 adults. Right and left eyes were analyzed separately. All the distributions were found to depart significantly from a normal distribution. All the distributions were significantly leptokurtic (p < 0.005), and the distributions of total right eye, corneal right eye, and residual left eye astigmatism were also found to be significantly skewed (p < 0.05). Significant mild correlations were found between total and corneal astigmatism (p < 0.05). These findings add to the database of knowledge of astigmatic refractive error and may be of interest to those investigating refractive-error development.
Quantifying adaptation and fatigue effects in frequency doubling perimetry
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 02-2007
DOI: 10.1167/IOVS.06-0685
Abstract: The second eye tested in frequency doubling perimetry has higher thresholds (reduced sensitivity) than the first. The authors investigated how this "second-eye effect" evolves over time and studied systematic changes in threshold in the first eye. Thresholds were measured in four subjects for 5 degrees -square, 0.5-cyc/deg sine wave gratings counterphase-flickered at 18 Hz, using a "method of a thousand staircases" to track changes in thresholds at 10-second intervals. Stimuli appeared in 1 of 5 interleaved horizontal locations. Subjects adapted binocularly (background, 45 cd/m(2)) for 5 minutes before performing a 5-minute test with one eye (the "first eye") followed immediately by the other (the "second eye"). These results were compared with baseline monocular thresholds measured over 3.5 minutes according to a conventional staircase procedure. In addition, two subjects repeated the main experiment with a translucent, rather than opaque, patch. On average, second-eye thresholds were raised by 6 dB (0.3 log) at the beginning of the test and were reduced to 4 dB toward the end. Little change was observed in the magnitude of the second-eye effect as a function of eccentricity. A significant "first-eye effect" was also observed in which thresholds increased by approximately 2 dB as the first-eye test progressed. Translucent patching largely abolished first- and second-eye effects, indicating neither was the result of fatigue. Steady adaptation in both eyes is important for obtaining stable perimetric thresholds. Unless appropriate tests are performed, the effects of adaptation could easily be mistaken for those of fatigue.
Visual processing, social cognition and functional outcome in schizophrenia
Publisher: Elsevier BV
Date: 07-2010
DOI: 10.1016/J.PSYCHRES.2009.09.013
Abstract: Visual processing deficits are well recognised in schizophrenia and have potentially important clinical implications. First, the pattern of deficits for different visual tasks may help understand the underlying pathophysiology of the visual dysfunction. Second, several studies report deficits correlating with functional outcomes, suggesting that outcome improvement is possible through visual remediation strategies. We investigated these issues in a group of 64 schizophrenia patients and matched controls with a battery of visual tasks targeting different points along the visual pathways and by examining direct and indirect relationships (via a potential mediator) of such deficits to functional outcome. The schizophrenia group was significantly worse on the visual tasks overall, with the deficit constant for low- and high-level processing. Zero-order correlations suggested minimal association between vision and outcome, however, correlations between three visual tasks and 'social perceptual' ability were found which in turn correlated with functional outcome path analysis confirmed a significant but small and indirect effect of 'biological motion' processing ability on functional outcome mediated by 'social perception'. In conclusion, the pathophysiology of visual dysfunction affects low- and high-level visual areas similarly and the relationship between deficits and outcome is small and indirect.
Enhancing Structure-Function Correlations in Glaucoma with Customized Spatial Mapping
Publisher: Elsevier BV
Date: 08-2015
DOI: 10.1016/J.OPHTHA.2015.04.021
Abstract: To determine whether the structure-function relationship in glaucoma can be strengthened by using more precise structural and functional measurements combined with in idualized structure-function maps and custom sector selection on the optic nerve head (ONH). Cross-sectional study. One eye of each of 23 participants with glaucoma. Participants were tested twice. Visual fields were collected on a high-resolution 3° × 3° grid (164 locations) using a Zippy Estimation by Sequential Testing test procedure with uniform prior probability to improve the accuracy and precision of scotoma characterization relative to standard methods. Retinal nerve fiber layer (RNFL) thickness was measured using spectral-domain optical coherence tomography (OCT 4 scans, 2 per visit) with manual removal of blood vessels. In idualized maps, based on biometric data, were used. To customize the areas of the ONH and visual field to correlate, we chose a 30° sector centered on the largest defect shown by OCT and chose visual field locations using the in idualized maps. Baseline structure-function correlations were calculated between 24-2 locations (n = 52) of the first tested visual field and RNFL thickness from 1 OCT scan, using the sectors of the Garway-Heath map. We added additional data (averaged visual field and OCT, additional 106 visual field locations and OCT without blood vessels, in idualized map, and customized sector) and recomputed the correlations. Spearman correlation between structure and function. The highest baseline correlation was 0.52 (95% confidence interval [CI], 0.13-0.78) in the superior temporal ONH sector. Improved measurements increased the correlation marginally to 0.58 (95% CI, 0.21-0.81). Applying the in idualized map to the large, predefined ONH sectors did not improve the correlation however, using the in idualized map with the single 30° ONH sector resulted in a large increase in correlation to 0.77 (95% CI, 0.47-0.92). Using more precise visual field and OCT measurements did not improve structure-function correlation in our cohort, but customizing the ONH sector and its associated visual field points substantially improved correlation. We suggest using customized ONH sectors mapped to in idually relevant visual field locations to unmask localized structural and functional loss.
Neuroplasticity in older adults revealed by temporary occlusion of one eye
Publisher: Elsevier BV
Date: 10-2021
Visual form perception from age 20 through 80 years
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 07-03-2013
Abstract: We measured performance on a battery of visual form perception tasks for adults s led evenly from each decade of adult life from 20 to 80 years. Measures were included that are considered to reflect processing at early through intermediate stages of the form processing pathways: collinear facilitation, center-surround contrast effects, global shape discrimination of contours of elements embedded in noise elements, and global shape discrimination in texture (Glass patterns). A total of 38 women and 20 men (mainly Caucasian, low refractive error) participated, aged between 20 and 82 years. With advancing age, contrast sensitivity decreased linearly (B = 0.009, t(56) = 8.14, P < 0.001), perceptual surround suppression of low contrast stimuli embedded in higher contrast surrounds increased (B = -0.006, t(56) = -3.32, P < 0.01), and coherence thresholds for detecting form in Glass patterns increased (B = 0.14, t(56) = 2.53, P = 0.02). Performance between tasks was not correlated. Several aspects of form perception alter gradually throughout the adult lifespan, namely context-dependent perception of contrast, and the extraction of global shape from texture. Our results suggested age-dependent differences under natural viewing conditions that are not predictable by standard clinical measures of visual function, and point to changes in neural function that are ongoing throughout adult life.
Effects of Criterion Bias on Perimetric Sensitivity and Response Variability in Glaucoma
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 08-01-2021
DOI: 10.1167/TVST.10.1.18
Migraine Increases Centre-Surround Suppression for Drifting Visual Stimuli
Publisher: Public Library of Science (PLoS)
Date: 11-04-2011
Improving personalized structure to function mapping from optic nerve head to visual field
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 08-01-2021
DOI: 10.1167/TVST.10.1.19
A depth-dependent integrated VF simulation for analysis and visualization of glaucomatous VF defects
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 12-02-2020
DOI: 10.1167/TVST.9.3.8
A Method for Reducing the Number of Presentations in Perimetric Test Procedures
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 15-04-2022
DOI: 10.1167/TVST.11.4.14
Spatial Summation Properties for Magnocellular and Parvocellular Pathways in Glaucoma
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 03-2009
DOI: 10.1167/IOVS.08-2517
Abstract: To examine the spatial summation properties for the magnocellular (M) and parvocellular (P) visual pathways in participants with glaucoma and approximately age-matched controls in central and midperipheral retinal eccentricities. Contrast discrimination thresholds were measured for six different stimulus array sizes, using steady- and pulsed-pedestal paradigms designed to measure function of the M and P pathways, respectively. This study involved 15 participants with glaucoma and 17 approximately age-matched controls. All participants completed trials foveally and at 12.5 degrees eccentricity. The peripheral stimulus location for each glaucoma participant was within a quadrant of early visual field loss, and locations were matched for the control group. The glaucoma group demonstrated significantly elevated thresholds compared with the control group (F((1,30)) = 16.29 P < 0.001). Thresholds were also significantly dependent on the stimulus sizes, testing location, and pedestal condition. Data obtained for the steady-pedestal paradigm were fit with an exponential decay function, whereas the pulsed-pedestal data were fit with a linear function, demonstrating different spatial summation properties for the M and P pathways, consistent with previous studies using this methodology. Analyses of the curve parameters obtained from the curve fits indicated no significant difference in the shape of the curves between glaucoma and control participants. Although spatial summation properties are different for presumed M- and P-mediated pathways, the underlying spatial summation properties associated with these pathways are similar in the control and glaucoma participants in this study, centrally and midperipherally.
Incorporating spatial models in visual field test procedures
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 11-03-2016
DOI: 10.1167/TVST.5.2.7
Contrast Increment and Decrement Processing in Individuals With and Without Diabetes
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 21-04-2023
DOI: 10.1167/IOVS.64.4.26
The open perimetry interface: An enabling tool for clinical visual psychophysics
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 2012
DOI: 10.1167/12.11.22
Abstract: Perimeters are commercially available instruments for measuring various attributes of the visual field in a clinical setting. They have several advantages over traditional lab-based systems for conducting vision experiments, including built-in gaze tracking and calibration, polished appearance, and attributes to increase participant comfort. Prior to this work, there was no standard to control such instruments, making it difficult and time consuming to use them for novel psychophysical experiments. This paper introduces the Open Perimetry Interface (OPI), a standard set of functions that can be used to control perimeters. Currently the standard is partially implemented in the open-source programming language R on two commercially available instruments: the Octopus 900 (a projection-based bowl perimeter produced by Haag-Streit, Switzerland) and the Heidelberg Edge Perimeter (a CRT-based system produced by Heidelberg Engineering, Germany), allowing these instruments to be used as a platform for psychophysical experimentation.
Identifying steep psychometric function slope quickly in clinical applications
Publisher: Elsevier BV
Date: 11-2010
DOI: 10.1016/J.VISRES.2010.08.032
Abstract: Knowledge of an observer's psychometric function slope is potentially useful in clinical visual psychophysics (for ex le, perimetry), however, the short test times necessary in a clinical setting typically prevent slope estimation. We explore, using computer simulation, the performance of several possible procedures for estimating psychometric function slope within limited presentations (aiming for approximately 30 or 140 trials). Procedures were based on either adaptive staircase or Bayesian techniques, and performance was compared to a Method of Constant Stimuli. An adaptation of the Ψ algorithm was best performing, being able to reliably identify steep from flat psychometric functions in less than 30 presentations, however reliable quantification of shallow psychometric functions was not possible.
Increased surround modulation of perceived contrast in the elderly
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2011
Relating excitatory and inhibitory neurochemicals to visual perception: A magnetic resonance study of occipital cortex between migraine events.
Publisher: Public Library of Science (PLoS)
Date: 10-07-2019
Increased internal noise cannot account for motion coherence processing deficits in migraine
Publisher: SAGE Publications
Date: 18-07-2011
Abstract: Aim: This study aimed to revisit previous findings of superior processing of motion direction in migraineurs with a more stringent direction discrimination task and to investigate whether increased internal noise can account for motion processing deficits in migraineurs. Methods: Groups of 13 migraineurs (4 with aura, 9 without aura) and 15 headache-free controls completed three psychophysical tasks: one detecting coherence in a motion stimulus, one discriminating the spiral angle in a glass pattern and another discriminating the spiral angle in a global-motion task. Internal noise estimates were obtained for all tasks using an N-pass method. Results: Consistent with previous research, migraineurs had higher motion coherence thresholds than controls. However, there were no significant performance differences on the spiral global-motion and global-form tasks. There was no significant group difference in internal noise estimates associated with any of the tasks. Conclusions: The results from this study suggest that variation in internal noise levels is not the mechanism driving motion coherence threshold differences in migraine. Rather, we argue that motion processing deficits may result from cortical changes leading to less efficient extraction of global-motion signals from noise.
Decreased Visual Field Sensitivity Measured 1 Day, Then 1 Week, after Migraine
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 04-2004
DOI: 10.1167/IOVS.03-0936
Abstract: To determine whether perimetric performance is worse the day after a migraine than prior interictal measurements, and if so, to determine whether differences have resolved by 1 week after migraine. Twenty-two nonheadache control subjects (aged 18-45 years) and 22 migraineurs (aged 18-45 years: 10 migraine with visual aura, 12 migraine without aura) participated. Standard automated perimetry (SAP) and temporal modulation perimetry (TMP) were measured by perimeter (model M-700 Medmont, Pty Ltd., Camberwell, Victoria, Australia). Control subjects attended two test visits: baseline and retest. Migraineurs attended three times: baseline (>or=4 days after migraine), the day after the offset of the next migraine, and 7 days later. Groups were compared using the global indices of the perimeter: Average Defect (AD) and Pattern Defect (PD), in addition to point-wise comparisons. Group migraineur TMP performance was significantly worse the day after a migraine, showing decreased general sensitivity and increased localized loss. Performance measured 7 days later was not significantly different from that measured the day after a migraine. Group migraineur SAP performance was not significantly worse after migraine however, a subgroup of six eyes from five patients had 10 or more visual field locations with decreases in sensitivity greater than control test-retest 95% confidence limits. Decreased visual field performance was present after migraine, as well as greater test-retest variability in the migraine group compared with control subjects. As migraineurs constitute 10% to 15% of the general population, the presence of this subgroup of patients with periodic prolonged decreased visual field sensitivity after migraine has implications for differential clinical diagnosis, and for clinical research using perimetry.
Do Additional Testing Locations Improve the Detection of Macular Perimetric Defects in Glaucoma?
Publisher: Elsevier BV
Date: 12-2021
DOI: 10.1016/J.OPHTHA.2021.06.012
Abstract: To evaluate the ability of additional central testing locations to improve detection of macular visual field (VF) defects in glaucoma. Prospective cross-sectional study. Four hundred forty healthy people and 499 patients with glaucomatous optic neuropathy (GON) were tested with a fundus tracked perimeter (CMP CenterVue) using a 24-2 grid with 12 additional macular locations (24-2+). Glaucomatous optic neuropathy was identified based on expert evaluation of optic nerve head photographs and OCT scans, independently of the VF. We defined macular defects as locations with measurements outside the 5% and 2% normative limits on total deviation (TD) and pattern deviation (PD) maps within the VF central 10°. Classification was based on the total number of affected macular locations (overall detection) or the largest number of affected macular locations connected in a contiguous cluster (cluster detection). Criteria based on the number of locations and cluster size were used to obtain equivalent specificity between the 24-2 grid and the 24-2+ grids, calculated using false detections in the healthy cohort. Partial areas under the receiver operating characteristic curve (pAUCs) were also compared at specificities of 95% or more. Matched specificity comparison of the ability to detect glaucomatous macular defects between the 24-2 and 24-2+ grids. At matched specificity, cluster detection identified more macular defects with the 24-2+ grid compared with the 24-2 grid. For ex le, the mean increase in percentage of detection was 8% (95% confidence interval [CI], 5%-11%) and 10% (95% CI, 7%-13%) for 5% TD and PD maps, respectively, and 5% (95% CI, 2%-7%) and 6% (95% CI, 4%-8%) for the 2% TD and PD maps, respectively. Good agreement was found between the 2 grids. The improvement measured by pAUCs was also significant but generally small. The percentage of eyes with macular defects ranged from about 30% to 50%. Test time for the 24-2+ grid was longer (21% increase) for both cohorts. Between 74% and 98% of defects missed by the 24-2 grid had at least 1 location with sensitivity of < 20 dB. Visual field examinations with additional macular locations can improve the detection of macular defects in GON modestly without loss of specificity when appropriate criteria are selected.
Processing of global form and motion in migraineurs
Publisher: Elsevier BV
Date: 2006
DOI: 10.1016/J.VISRES.2005.09.014
Abstract: Previous studies have identified anomalies of cortical visual processing in migraineurs that appear to extend beyond V1. Migraineurs respond differently than controls to transcranial magnetic stimulation of V5, and can demonstrate impairments of global motion processing. This study was designed to assess the integrity of intermediate stages of both motion and form processing in people with migraine. We measured the ability to integrate local orientation information into a global form percept, and to integrate local motion information into a global motion percept. Control subjects performed significantly better than migraineurs on both tasks, suggesting a diffuse visual cortical processing anomaly in migraine.
The effect of duration post-migraine on visual electrophysiology and visual field performance in people with migraine
Publisher: SAGE Publications
Date: 22-08-2014
Abstract: In between migraine attacks, some people show visual field defects that are worse when measured closer to the end of a migraine event. In this cohort study, we consider whether electrophysiological responses correlate with visual field performance at different times post-migraine, and explore evidence for cortical versus retinal origin. Twenty-six non-headache controls and 17 people with migraine performed three types of perimetry (static, flicker and blue-on-yellow) to assess different aspects of visual function at two visits conducted at different durations post-migraine. On the same days, the pattern electroretinogram (PERG) and visual evoked response (PVER) were recorded. Migraine participants showed persistent, interictal, localised visual field loss, with greater deficits at the visit nearer to migraine offset. Spatial patterns of visual field defect consistent with retinal and cortical dysfunction were identified. The PERG was normal, whereas the PVER abnormality found did not change with time post-migraine and did not correlate with abnormal visual field performance. Dysfunction on clinical tests of vision is common in between migraine attacks however, the nature of the defect varies between in iduals and can change with time. People with migraine show markers of both retinal and/or cortical dysfunction. Abnormal visual field sensitivity does not predict abnormality on electrophysiological testing.
Psychophysical Measurement of Neural Adaptation Abnormalities in Magnocellular and Parvocellular Pathways in Glaucoma
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 06-2004
DOI: 10.1167/IOVS.03-1225
Abstract: It is well established that contrast sensitivity is reduced in glaucoma. This study explored whether such contrast processing abnormalities consist of an absolute threshold level difference or a problem with contrast gain control. Seventeen patients with primary open-angle glaucoma and 17 approximately age-matched control subjects participated. Subjects were tested foveally and midperipherally (12.5 degrees ). Subjects with glaucoma were tested in a peripheral region of relatively normal visual field (neighboring locations required to be within the normal 95% confidence limit on the total deviation plot of their most recent SITA/full threshold Humphrey Field Analyzer assessment Carl Zeiss Meditec, Dublin, CA). Control subjects were tested in matching locations. Contrast discrimination was assessed using the steady-pedestal (magnocellular [M] pathway) and pulsed-pedestal (parvocellular [P] pathway) stimuli of Pokorny and Smith for seven pedestal luminances between 15 and 75 cd/m(2), presented on a background of 30 cd/m(2). Glaucoma group thresholds were significantly elevated compared with control subjects foveally and peripherally on both the pulsed-pedestal (P) and steady-pedestal (M) tasks (P < 0.01). Effect size statistics revealed slightly greater deficits on the P pathway task and greater deficits for pedestals that were decrements, rather than increments, from the surround luminance. Foveal deficits were of a magnitude to be explained by a reduction in contrast sensitivity however, the peripheral deficits were greater than predicted by this factor alone. Foveal and midperipheral dysfunction of both M and P pathways was identified in people with glaucoma, in areas of relatively normal visual field performance. These findings are supportive of nonselective neural adaptation abnormalities in early glaucoma.
Auditory and Visual Temporal Processing Disruption in Open Angle Glaucoma
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 21-09-2012
Abstract: Open angle glaucoma (OAG) is increasingly being viewed as an age-related neurodegenerative condition that may occur in in iduals who are innately susceptible to global (autonomic) neural injury. Recent data support the plausibility of auditory neural impairment in a proportion of in iduals with OAG, with results showing a key disruption to processing temporal properties of sound. This study tested the hypothesis that temporal processing deficits consistent with central (cortical) processing abnormalities are present in both the visual and auditory domains in in iduals with glaucoma. A series of tasks designed to test progressively more complex aspects of temporal processing were conducted in 25 OAG in iduals and 25 age- and sex-matched controls. For audition, baseline measurement of hearing sensitivity was followed by functional assessment of litude modulation detection, frequency discrimination at two reference levels, and speech perception. For vision, measures of foveal temporal contrast detection at two flicker rates, speed discrimination at two reference velocities, and coherent global motion detection were assessed. A significant proportion of the OAG cohort displayed an impairment in auditory low-frequency discrimination, speech perception, visual speed discrimination for slow velocities and/or visual global motion detection, compared to controls (36%, 25%, 39%, and 34% respectively, were outside the 90th percentile of control performance P < 0.05). A subgroup of in iduals with OAG displayed impaired auditory temporal processing concurrent with signs of visual temporal processing impairment. These temporal processing deficits were in the presence of normal sound detection and normal central luminance increment thresholds.
Foveal and parafoveal contrast suppression are different: Mechanisms revealed by the study of healthy aging
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 11-02-2016
DOI: 10.1167/16.3.10
Abstract: Visual contextual effects enable inference regarding neural mechanisms of cortical function, principally because of similarities between the stimulus properties influencing human perception and those modifying primate visual cortical neural responses. Most neurophysiology assesses nonfoveal cellular function and circuitry, while most human studies are foveal. Here we use parafoveal stimuli to measure center-surround perception of contrast in older and younger adults. We measure the influence of both near and far surround because neurophysiology demonstrates different circuitry for these areas. Contrast suppression from the near surround was reduced in older observers, while that from the far surround was intact. Our results are consistent with reduced intracortical inhibition with age and normal extrastriate feedback. Interestingly, in the same older observers, foveal surround suppression of contrast was strengthened relative to younger adults, demonstrating a clear distinction between foveal and parafoveal center-surround behavior. We assume that underlying alterations in cortical neurotransmitter levels with age should not differ substantially between the areas of visual cortex representing foveal and near foveal regions. Consequently, our results suggest regional differences in center-surround circuitry. That older adults have varied contextual effects of visual contrast as a function of retinal eccentricity suggests complex effects of aging on scene and object perception.
Spatiotemporal filters in the detection of background modulation targets
Publisher: Optica Publishing Group
Date: 05-2000
Abstract: The background modulation method has been proposed as a useful test of early visual mechanisms [Biol. Cybern. 37, 77 (1980) Biol. Cybern. 47, 173 (1983)]. The task involves measuring detection thresholds for a luminous spot (increment) drifting over a spatially or temporally modulated background. The study explores the nature of the detecting mechanism in terms of spatial and temporal filters for both spatial and temporal background modulations. In both cases we find that thresholds can be explained by spatial contrast cues generated by the moving spot and that their spatiotemporal characteristics suggest detection by magnocellular processes.
Visual Contrast Detection Cannot be Predicted from Surrogate Measures of Retinal Ganglion Cell Number and Sampling Density in Healthy Young Adults
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 18-11-2014
Abstract: Purpose: To establish whether a clinically-exploitable relationship exists between surrogate measures of retinal ganglion cell (RGC) number and functional s ling density and visual contrast sensitivity in healthy young eyes. Methods: Psychometric functions for contrast detection were measured at 9° eccentricity in superior and inferior visual field from 20 healthy adults (age 23-43, median 26 years). Functions were compared to corresponding localised regions of retinal nerve fibre layer (RNFL) thickness measured by optical coherence tomography, a surrogate of RGC number, and to grating resolution acuity, a psychophysical surrogate of RGC s ling density. Correlations between psychometric function parameters and RGC surrogates were measured by Spearman's rank correlation. Results: All measures exhibited a two- to four-fold variation in our s le. Despite this, correlations between measures were weak. Correlations between psychometric function parameters (threshold, spread) and RNFL thickness ranged in magnitude from 0.05 to 0.19 (p=0.43 to 0.85). Grating resolution was s ling-limited for 16 of 20 participants in superior visual field, and for 12 of 20 participants in inferior visual field. Correlations between psychometric function parameters and grating resolution acuities ranged in magnitude from 0.05 to 0.36 (p=0.12 to 0.85) when all data were considered, and from 0.06 to 0.36 (p=0.26 to 0.87) when only s ling-limited data were considered. Conclusions: Despite considerable variation in both psychometric functions for contrast detection and surrogate measures of RGC number and s ling density among healthy eyes, relationships between these measures are weak. These relationships are unlikely to be exploitable for improving clinical tests in healthy populations.
An anatomically customizable computational model relating the visual field to the optic nerve head in individual eyes
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 09-10-2012
DOI: 10.1167/IOVS.12-9657
Abstract: To present a computational model mapping visual field (VF) locations to optic nerve head (ONH) sectors accounting for in idual ocular anatomy, and to describe the effects of anatomical variability on maps produced. A previous model that related retinal locations to ONH sectors was adapted to model eyes with varying axial length, ONH position and ONH dimensions. Maps (n = 11,550) relating VF locations (24-2 pattern, n = 52 non-blind-spot locations) to 1° ONH sectors were generated for a range of clinically plausible anatomical parameters. Infrequently mapped ONH sectors (5%) were discarded for all locations. The influence of anatomical variables on the maps was explored by multiple linear regression. Across all anatomical variants, for in idual VF locations (24-2), total number of mapped 1° ONH sectors ranged from 12 to 90. Forty-one locations varied more than 30°. In five nasal-step locations, mapped ONH sectors were bimodally distributed, mapping to vertically opposite ONH sectors depending on vertical ONH position. Mapped ONH sectors were significantly influenced (P < 0.0002) by axial length, ONH position, and ONH dimensions for 39, 52, and 30 VF locations, respectively. On average across all VF locations, vertical ONH position explained the most variance in mapped ONH sector, followed by horizontal ONH position, axial length, and ONH dimensions. Relations between ONH sectors and many VF locations are strongly anatomy-dependent. Our model may be used to produce customized maps from VF locations to the ONH in in idual eyes where some simple biometric parameters are known.
A tablet-based retinal function test in neovascular age-related macular degeneration eyes and at-risk fellow eye
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 02-03-2018
DOI: 10.1167/TVST.7.2.2
The Effects of Glare on the Perception of Visual Motion as a Function of Age
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 20-09-2022
DOI: 10.1167/TVST.11.9.11
Clinical audit as an educative tool for optometrists: an intervention study in age-related macular degeneration
Publisher: Wiley
Date: 06-11-2021
DOI: 10.1111/OPO.12754
Abstract: Age‐related macular degeneration (AMD) is a major cause of vision loss. This study investigated whether performing clinical audit and receiving analytical performance feedback altered documentation of the AMD care provided by optometrists. Australian optometrists were recruited and completed a survey about their demographics and confidence in AMD care, and a three‐month audit of their practice records using an AMD audit tool (termed the pre‐audit evaluation). After receiving analytical feedback, participants identified areas for improvement and re‐audited their practices after three months to analyse changes in performance (termed the post‐audit evaluation). Paired t‐tests and Wilcoxon signed‐rank tests, as appropriate, were used to compare pre‐ and post‐audit data. Twenty optometrists, most practising in Victoria, Australia, completed the study. Participants primarily worked in corporate practice and/or rural settings and had a range of optometric experience (2–40 years). At baseline, participants felt confident in their: knowledge of AMD risk factors (65%), advice to patients about these factors (55%) and management of earlier stages of AMD (55%). Each clinician completed (median [IQR]): 15 [IQR: 10–19] and 12 [IQR: 8–16] audits of unique patient records, pre‐ and post‐audit, respectively. Post‐audit, average record documentation (per optometrist) improved for asking about: AMD family history (94% to 100%, p = 0.03), smoking status (21% to 58%, p 0.01), diet (11% to 29%, p 0.01) and nutritional supplementation (20% to 51%, p 0.01). For clinical examination, compliance with documenting pinhole visual acuity, performing an in‐office Amsler grid (upon indication) and using optical coherence tomography improved post‐audit ( p 0.05). Accuracy of severity documentation improved for earlier stages of AMD ( p 0.05). For earlier stages of AMD, documentation of counselling about modifiable risk factors significantly improved post‐audit ( p 0.05). Aspects well‐performed pre‐audit that did not change included documenting: medical histories (100% at both time points, p = 0.06) and retinal imaging (77% at both time points, p = 0.97). Self‐audit with analytical feedback improved clinical record documentation of: AMD risk factors, clinical examination, AMD severity classification and management advice. These findings support a role for audit to improve optometric clinical care of AMD, as evidenced by improved documentation of the AMD care delivered.
A Study Protocol for an Open-Label Feasibility Treatment Trial of Visual Snow Syndrome With Transcranial Magnetic Stimulation
Publisher: Frontiers Media SA
Date: 24-09-2021
DOI: 10.3389/FNEUR.2021.724081
Abstract: Background: Visual Snow (VS) syndrome is believed to be due to aberrant central visual processing. Positron Emission Tomography (PET) brain imaging and visual evoked potential studies provide evidence for excessive neuronal activity in the medial temporal lobe, specifically the lingual gyrus, and suggest the VS syndrome is a hyperexcitability syndrome. These data provide the basis for consideration of repetitive transcranial magnetic stimulation (rTMS) as a potential treatment for the VS syndrome. Objective: To publish the study protocol for a pilot study underway at the University of Colorado School of Medicine to investigate the use of rTMS intervention to improve symptoms and visual dysfunction associated with VS. The study aims to determine the adverse events and drop-out rate, evaluate performance of outcome measures, including a novel VS symptom scale, and describe changes in outcomes associated with treatment. Methods and Design: Up to 10 participants meeting criteria for VS syndrome, age 19–65 years, will undergo an open-label intervention consisting of 10 rTMS sessions, occurring 5 days a week over a 2-week period. Participants will complete pre-treatment and post-treatment assessments that include: the Colorado Visual Snow Scale (CVSS), the National Eye Institute Visual Functional Questionnaire—25 (VFQ-25), the General Anxiety Disorder—7 scale (GAD-7), and three psychophysical visual processing tasks. Discussion: Knowledge gained from this pilot study will inform future study planning and provide valuable lessons for future investigation of rTMS for the VS syndrome. An overview of study proceedings thus far demonstrates recruitment challenges associated with the COVID-19 pandemic, and additional challenges that are unique to the VS syndrome and to treatment schedules associated with TMS. Registration: This study has been approved by the Colorado Multiple Institutional Review Board. ClinicalTrials.gov Identifier: NCT04925232.
Primary eyecare provision for people living with dementia: what do we need to know?
Publisher: Informa UK Limited
Date: 14-11-2022
DOI: 10.1080/08164622.2022.2140032
Abstract: Dementia comprises a group of brain disorders characterised by loss of cognitive function. Sensory loss, predominantly vision (the focus of this review) and hearing, is a significant problem for people living with dementia. Eyecare practitioners such as optometrists therefore play an important role in identifying and addressing vision-related care needs. To support provision of high quality "dementia-friendly" eyecare, this scoping review summarises recent primary research findings and available clinical practice guidelines, to identify research gaps relating to vision and dementia, and make recommendations for future research and clinical practice. The review set
Increased Depth, Reduced Extent, and Sharpened Edges of Visual Field Defects Measured by Compass Fundus Perimeter Compared to Humphrey Field Analyzer
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 25-10-2021
Spatio-temporal patterns of event-related potentials related to audiovisual synchrony judgments in older adults
Publisher: Elsevier BV
Date: 07-2017
DOI: 10.1016/J.NEUROBIOLAGING.2017.03.011
Abstract: Older adults have altered perception of the relative timing between auditory and visual stimuli, even when stimuli are scaled to equate detectability. To help understand why, this study investigated the neural correlates of audiovisual synchrony judgments in older adults using electroencephalography (EEG). Fourteen younger (18-32 year old) and 16 older (61-74 year old) adults performed an audiovisual synchrony judgment task on flash-pip stimuli while EEG was recorded. All participants were assessed to have healthy vision and hearing for their age. Observers responded to whether audiovisual pairs were perceived as synchronous or asynchronous via a button press. The results showed that the onset of predictive sensory information for synchrony judgments was not different between groups. Channels over auditory areas contributed more to this predictive sensory information than visual areas. The spatial-temporal profile of the EEG activity also indicates that older adults used different resources to maintain a similar level of performance in audiovisual synchrony judgments compared with younger adults.
Delayed Onset of Inhibition of Return in Visual Snow Syndrome
Publisher: Frontiers Media SA
Date: 17-09-2021
DOI: 10.3389/FNEUR.2021.738599
Abstract: Visual snow syndrome (VSS) is a complex, sensory processing disorder. We have previously shown that visual processing changes manifest in significantly faster eye movements toward a suddenly appearing visual stimulus and difficulty inhibiting an eye movement toward a non-target visual stimulus. We propose that these changes reflect poor attentional control and occur whether attention is directed exogenously by a suddenly appearing event, or endogenously as a function of manipulating expectation surrounding an upcoming event. Irrespective of how attention is captured, competing facilitatory and inhibitory processes prioritise sensory information that is important to us, filtering out that which is irrelevant. A well-known feature of this conflict is the alteration to behaviour that accompanies variation in the temporal relationship between competing sensory events that manipulate facilitatory and inhibitory processes. A classic ex le of this is the “Inhibition of Return” (IOR) phenomenon that describes the relative slowing of a response to a validly cued location compared to invalidly cued location with longer cue/target intervals. This study explored temporal changes in the allocation of attention using an ocular motor version of Posner's IOR paradigm, manipulating attention exogenously by varying the temporal relationship between a non-predictive visual cue and target stimulus. Forty participants with VSS (20 with migraine) and 20 controls participated. Saccades were generated to both validly cued and invalidly cued targets with 67, 150, 300, and 500 ms cue/target intervals. VSS participants demonstrated delayed onset of IOR. Unlike controls, who exhibited IOR with 300 and 500 ms cue/target intervals, VSS participants only exhibited IOR with 500 ms cue/target intervals. These findings provide further evidence that attention is impacted in VSS, manifesting in a distinct saccadic behavioural profile, and delayed onset of IOR. Whether IOR is perceived as the build-up of an inhibitory bias against returning attention to an already inspected location or a consequence of a stronger attentional orienting response elicited by the cue, our results are consistent with the proposal that in VSS, a shift of attention elicits a stronger increase in saccade-related activity than healthy controls. This work provides a more refined saccadic behavioural profile of VSS that can be interrogated further using sophisticated neuroimaging techniques and may, in combination with other saccadic markers, be used to monitor the efficacy of any future treatments.
Evidence for increased internal noise in migraineurs for contrast and shape processing
Publisher: SAGE Publications
Date: 15-12-2012
Abstract: Aim: Increased contrast-level dependent internal noise has been reported in migraine. This study aimed to investigate whether a general increase in internal noise impacted on other tasks thought to assess functioning in cortical area V1 and was evident in global contour coding (V4). Methods: Eleven migraineurs (six with aura) and 12 headache-free controls completed three psychophysical tasks: (i) contrast detection, (ii) discrimination of the angle of a spiral path and (iii) detection of deformation from circularity. Internal noise estimates were obtained using an N-pass method that compared responses to repeated presentations of identical stimuli. Internal noise results in inconsistent responses across different runs. Results: Migraineurs had significantly higher contrast thresholds when there was high external luminance noise. There were no other significant group differences in thresholds. Increased multiplicative noise associated with contrast processing was replicated and increased additive noise, which is independent of the visual input, was found for the global form task. Conclusions: This study provides further evidence for increased multiplicative internal noise associated with contrast processing in migraineurs. However there is no generalised increase in internal noise in V1 as noise estimates for angular discrimination were normal. Increased additive internal noise was associated with the global shape task, co-occurring with increased efficiency.
Do Migraineurs have Difficulty Judging Direction of Simulated Heading?
Publisher: SAGE Publications
Date: 08-2006
DOI: 10.1111/J.1468-2982.2006.01154.X
Abstract: Some migraineurs have increased thresholds for the detection of global dot motion. We investigated whether migraineurs show consequential abnormalities in the determination of direction of self-motion (heading) from simulated optic flow. The ability to determine heading from optic flow is likely to be necessary for optimal determination of self-motion through the environment. Twenty-five migraineurs and 25 controls participated. Global dot motion coherence thresholds were assessed, in addition to performance on two simulated heading tasks: one with a symmetrical flow field, and the second with differing velocity of optic flow on the left and right sides of the participant. While some migraineurs demonstrated abnormal global motion coherence thresholds, there was no difference in performance on the heading tasks at either simulated walking (5 km/h) or driving (50 km/h) speeds. Increased global motion coherence thresholds in migraineurs do not result in abnormal judgements of heading from 100± coherent optic flow.
Contrast Sensitivity on 1/f Noise Is More Greatly Impacted by Older Age for the Fovea Than Parafovea
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 04-2021
DOI: 10.1097/OPX.0000000000001676
Abstract: Contrast sensitivity changes across the visual field with age and is often measured clinically with various forms of perimetry on plain backgrounds. In daily life, the visual scene is more complicated, and therefore, the standard clinical measures of contrast sensitivity may not predict a patient's visual experience in more natural environments. This study aims to determine whether contrast thresholds in older adults are different from younger adults when measured on a 1/f noise background (a nonuniform background whose spatial frequency content is similar to those present in the natural vision environments). Twenty younger (age range, 20 to 35 years) and 20 older adults (age range, 61 to 79 years) with normal ocular health were recruited. Contrast thresholds were measured for a Gabor patch of 6 cycles per degree (sine wave grating masked by a Gaussian envelope of standard deviation 0.17°) presented on 1/f noise background (root-mean-square contrast, 0.05 and 0.20) that subtended 15° diameter of the central visual field. The stimulus was presented at four eccentricities (0°, 2°, 4°, and 6°) along the 45° meridian in the noise background, and nine contrast levels were tested at each eccentricity. The proportion of correct responses for detecting the target at each eccentricity was obtained, and psychometric functions were fit to estimate the contrast threshold. Older adults demonstrate increased contrast thresholds compared with younger adults. There was an eccentricity-dependent interaction with age, with the difference between groups being highest in the fovea compared with other eccentricities. Performance was similar for the two noise backgrounds tested. Our results revealed a strong eccentricity dependence in performance between older and younger adults, highlighting age-related differences in the contrast detection mechanisms between fovea and parafovea for stimuli presented on nonuniform backgrounds.
Contrast-Processing Dysfunction in both Magnocellular and Parvocellular Pathways in Migraineurs with or without Aura
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 2003
DOI: 10.1167/IOVS.02-0630
Abstract: To assess contrast-discrimination thresholds in patients with migraine who have manifest visual field loss. This study was undertaken to determine whether contrast processing abnormalities in migraineurs are more readily identified by using stimuli that elicit a response from the subject that depends, at least in part, on adaptation mechanisms, and if so, whether deficits appear more pronounced in magnocellular (M) or parvocellular (P) visual pathways. Ten patients with migraine who had abnormal visual fields measured with flicker perimetry but had normal standard automated perimetry (SAP) thresholds participated, along with 15 age-matched control subjects. Contrast-discrimination performance was assessed with the steady-pedestal (magnocellular) and pulsed-pedestal (parvocellular) stimuli of Pokorny and Smith for seven pedestal luminances between 15 and 60 cd/m(2) on a background of 30 cd/m(2). Subjects were tested foveally and midperipherally at 12.5 degrees. Migraineurs were tested in the quadrant of worst visual field performance. Control subjects were assessed in locations matched to those of the migraine group. Foveal performance was not significantly different between the migraine and control groups for either task. At 12.5 degrees the migraine group had significantly raised thresholds for both conditions. Effect size statistics revealed similar deficit magnitudes for each test (steady pedestal, -1.06 pulsed pedestal, -1.04). Dysfunction in both the M and P pathways was identified in the midperipheral visual field of the migraine group. The P pathway dysfunction was not identified by SAP. These findings support the possibility of nonselective neural adaptation abnormalities in some subjects with migraine.
Occipital GABA levels in older adults and their relationship to visual perceptual suppression
Publisher: Springer Science and Business Media LLC
Date: 27-10-2017
DOI: 10.1038/S41598-017-14577-5
Abstract: Several studies have attributed certain visual perceptual alterations in older adults to a likely decrease in GABA (Gamma Aminobutyric Acid) concentration in visual cortex, an assumption based on findings in aged non-human primates. However, to our knowledge, there is no direct evidence for an age-related decrease in GABA concentration in human visual cortex. Here, we estimated visual cortical GABA levels and Glx (combined estimate of glutamate and glutamine) levels using magnetic resonance spectroscopy. We also measured performance for two visual tasks that are hypothesised to be mediated, at least in part, by GABAergic inhibition: spatial suppression of motion and binocular rivalry. Our results show increased visual cortical GABA levels, and reduced Glx levels, in older adults. Perceptual performance differed between younger and older groups for both tasks. When subjects of all ages were combined, visual cortical GABA levels but not Glx levels correlated with perceptual performance. No relationship was found between perception and GABA levels in dorsolateral prefrontal cortex. Perceptual measures and GABA were not correlated when either age group was considered separately. Our results challenge current assumptions regarding neurobiological changes that occur within the aging human visual cortex and their association with certain age-related changes in visual perception.
Retesting visual fields: Utilizing prior information to decrease test-retest variability in glaucoma
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 04-2007
DOI: 10.1167/IOVS.06-1074
Abstract: To determine whether sensitivity estimates from an in idual's previous visual field tests can be incorporated into perimetric procedures to improve accuracy and reduce test-retest variability at subsequent visits. Computer simulation was used to determine the error, distribution of errors and presentation count for a series of perimetric algorithms. Baseline procedures were Full Threshold and Zippy Estimation by Sequential Testing (ZEST). Retest strategies were (1) allowing ZEST to continue from the previous test without reinitializing the probability density function [pdf] (2) running ZEST with a Gaussian pdf centered about the previous result (3) retest minimizing uncertainty (REMU), a new procedure combining suprathreshold and ZEST procedures incorporating prior test information. Empiric visual field data of 265 control and 163 patients with glaucoma were input into the simulation. Four error conditions were modeled: patients who make no errors, 15% false-positive (FP) with 3% false-negative (FN) errors, 15% FN with 3% FP errors, and 20% FP with 20% FN errors. If sensitivity was stable from test to retest, all the retest algorithms were faster than the baseline algorithms by, on average, one presentation per location and are significantly more accurate (P < 0.05). When visual fields changed from test to retest, REMU was faster and more accurate than the other retest approaches and the baseline procedures. Relative to the baseline procedures, REMU showed decreased test-retest variability in impaired regions of visual field. The obvious approaches to retest, such as continuing the previous procedure or seeding with previous values, have limitations when sensitivity changes between tests. REMU, however, significantly improves both accuracy and precision of testing and displays minimal bias, even when fields change and patients make errors.
Customizing Structure–Function Displacements in the Macula for Individual Differences
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 22-09-2015
Abstract: In the macula, retinal ganglion cells (RGCs) are displaced from their receptive fields. We used optical coherence tomography (OCT) to customize displacements for in idual eyes by taking into account macular shape parameters, and determined the likely effect of in idual anatomical differences on structure-function mapping in the central visual field. Using the population average model of Drasdo et al. as a starting point, we altered the RGC count in that model based on the ratio of an in idual's RGC layer plus inner plexiform layer thickness to the population average on a pointwise basis as a function of eccentricity from the fovea. For 20 adults (age, 24-33 median age, 28) with normal vision, we computed displacements with the original model and our customized approach. We report the variance in displacements among in iduals and compare the effects of such displacements on structure-function mapping of the commonly used the 10-2 visual field pattern. As expected, customizing the displacement using in idual OCT data made only a small difference on average from the population-based values predicted by the Drasdo et al. model. However, the range between in iduals was over 1° at many locations, and closer to 2° at some locations in the superior visual field. In idualizing macular displacement measurements based on OCT data for an in idual can result in large spatial shifts in the retinal area corresponding to 10-2 locations, which may be important for clinical structure-function analysis when performed on a local, spatial scale.
Perceptual Center-Surround Contrast Suppression in Adolescence
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 18-05-2023
DOI: 10.1167/IOVS.64.5.14
Targeted spatial sampling using GOANNA improves detection of visual field progression
Publisher: Wiley
Date: 13-02-2015
DOI: 10.1111/OPO.12184
Abstract: A new automated visual field testing approach that s les scotoma edges at a finer spatial resolution, GOANNA (Gradient-Oriented Automated Natural Neighbour Approach) was previously shown to improve accuracy and precision around those regions compared to current procedures in computer simulation. The purpose of this study was to observe if this improvement translated to more accurate classification of glaucomatous progression. Computer simulations were undertaken on six procedures: three variants of GOANNA on 150 locations two variants of ZEST on 52 locations and the ideal case where true thresholds are perfectly measured. The median number of presentations of GOANNA was matched to ZEST. The procedures were run on 156 sequences of simulated progressing fields and 156 sequences of stable fields to determine sensitivity and specificity using point-wise linear regression. Reliable (0% FP, 0% FN) and typical false positive (15% FP, 3% FN) response error conditions were investigated. Area under ROC curves (AUC) were plotted against the number of visual fields acquired to evaluate the performance of these procedures. The GOANNA framework exhibited equal or greater AUC than ZEST at all visits when baseline fields were initially defective (under both response error conditions) and when baseline fields were initially healthy when no false responses were made. Retest implementations of GOANNA exhibited an improvement over the original GOANNA after the first seven visits when fields were initially healthy. The results suggest that the improvement in precision and accuracy around scotoma borders seen in the GOANNA framework translates to earlier and more accurate detection of progressing fields compared with ZEST, especially in the early stages of glaucomatous progression.
Do intense perimetric stimuli saturate the healthy visual system?
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 22-11-2016
Impact of peripheral field loss on the execution of natural actions: A study with glaucomatous patients and normally sighted people
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2016
Development of visual field screening procedures: A case study of the octopus perimeter
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 09-05-2016
DOI: 10.1167/TVST.5.3.3
Aging effects on collinear facilitation
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 15-06-2012
DOI: 10.1167/12.6.21
Abstract: Normal aging has been shown to alter performance on several suprathreshold spatial tasks such as contour integration and perceptual measures of center-surround interactions. The purpose of this study was to investigate the effects of aging on collinear facilitation. Despite all related lateral interactions that are presumed to involve neural architecture within primary visual cortex, collinear facilitation differs from contour integration and surround suppression tasks in that it is a purely foveal, threshold phenomenon. Collinear facilitation was measured for 20 younger (19-31 years) and 15 older (59-71 years) adults with measures repeated over two identical test sessions. Contrast thresholds were measured for a central Gabor patch in the presence of flankers of varying interelement distances and orientations. A reduced magnitude of facilitation was found for the older observers. Our results demonstrate abnormalities of spatial interactions in older adults.
Clinical impact of migraine for the management of glaucoma patients
Publisher: Elsevier BV
Date: 03-2016
DOI: 10.1016/J.PRETEYERES.2015.07.006
Abstract: Migraine is a common and debilitating primary headache disorder that affects 10-15% of the general population, particularly people of working age. Migraine is relevant to providers of clinical eye-care because migraine attacks are associated with a range of visual sensory symptoms, and because of growing evidence that the results of standard tests of visual function necessary for the diagnosis and monitoring of glaucoma (visual fields, electrophysiology, ocular imaging) can be abnormal due to migraine. These abnormalities are measureable in-between migraine events (the interictal period), despite patients being asymptomatic and otherwise healthy. This picture is further complicated by epidemiological data that suggests an increased prevalence of migraine in patients with glaucoma, particularly in patients with normal tension glaucoma. We discuss how migraine, as a co-morbidity, can confound the results and interpretation of clinical tests that form part of contemporary glaucoma evaluation, and provide practical evidence-based recommendations for the clinical testing and management of patients with migraine who attend eye-care settings.
Migraine Screening in Primary Eye Care Practice: Current Behaviors and the Impact of Clinician Education
Publisher: Wiley
Date: 07-08-2020
DOI: 10.1111/HEAD.13920
Entropy of the retina template
Publisher: Springer Berlin Heidelberg
Date: 2009
Pattern cues disambiguate perceived direction in simple moving stimuli
Publisher: Elsevier BV
Date: 10-2003
DOI: 10.1016/S0042-6989(03)00403-6
Abstract: Much of our knowledge about motion perception has been obtained by studying bars moving within apertures. When viewed within an ambiguously oriented aperture such as a circle, bars appear to move orthogonal to their orientation. We demonstrate that if the local orientation of the aperture edges is altered, a direction consistent with the edge orientation is seen. Indeed, the perceived direction can be strongly influenced by static lines separated from the edge of the moving stimulus. These results support recent suggestions that precise motion direction is likely to be determined by static orientation cues.
Age related changes to perceptual surround suppression of moving stimuli
Publisher: Brill
Date: 07-07-2012
Abstract: Perceptual analogues of centre–surround suppression have been applied as indirect measures of cortical inhibitory function in several clinical disorders. Two tasks have been used: a centre–surround contrast perception task and a motion direction discrimination task, where the stimulus size and contrast is varied to measure surround suppression effects. The tasks are markedly different, yet previous literature implies that both measures indirectly assess inhibitory function and that results will be complementary. This is not the case for age-related effects on surround suppression, however, as previous reports using the different measures are conflicting. Here we use a low-spatial frequency, drifting grating version of the centre–surround contrast perception task, and compare results to those obtained with the motion direction task in a single group of older observers. Older adults demonstrate significantly increased perceptual surround suppression of contrast for drifting, high contrast stimuli. Using the motion discrimination task, older observers showed similar amounts of surround suppression for the largest stimulus. This study confirms that visual surround suppression is altered by ageing. The complexity of neuronal systems involved in centre–surround interactions makes it unlikely that a single perceptual task will be sufficient to describe the effects of clinical disorders on surround suppression.
Relating optical coherence tomography to visual fields in glaucoma
Publisher: Informa UK Limited
Date: 05-2019
DOI: 10.1111/CXO.12844
Abstract: Combining information from optical coherence tomography (OCT) imaging and visual field testing is useful in the clinical assessment and monitoring of patients with glaucoma. Measurements of retinal nerve fibre layer thickness or neuroretinal rim width taken around the optic nerve head may be related to the visual field using a structure-function map. In this review, the structure-function mapping methods in clinical use are discussed. Typical clinical maps provide a population average, 'one size fits all' representation, but in recent years methods for customising structure-function maps to in idual eyes have been developed and these are reviewed here. In the macula, visual field stimuli stimulate photoreceptors for which associated retinal ganglion cells are peripherally displaced. Recently developed methods that relate OCT measurements to visual field test locations in the macula are therefore also reviewed. The use of structure-function maps to relate OCT measurements to localised visual field sensitivity in new applications is also explored. These new applications include the selection of visual field test locations and stimulus intensities based on OCT data, and the formal post-test combination of results across modalities. Such applications promise to exploit the structure-function relationship in glaucoma to improve disease diagnosis and monitoring of progression. Limitations in the validation and use of current structure-function mapping techniques are discussed.
Measurement of retinal sensitivity on tablet devices in age-related macular degeneration
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 30-06-2015
DOI: 10.1167/TVST.4.3.13
Short-Wavelength Sensitivity Deficits in Patients With Migraine
Publisher: American Medical Association (AMA)
Date: 02-2002
DOI: 10.1001/ARCHOPHT.120.2.154
Abstract: To examine short-wavelength sensitivity in patients with migraine using short-wavelength automated perimetry (SWAP) and Stiles 2-color increment threshold procedures. Twenty-five subjects with migraine with (n = 11) and without (n = 14) aura and 20 age-matched headache-free subjects underwent testing. All subjects underwent standard automated perimetry (SAP) and SWAP (using a Humphrey field analyzer 24-2 presentation pattern). In 2 migraine patients (one with and another without aura), the 2-color increment threshold procedure was used to determine whether sensitivity losses were specific to short-wavelength sensitivity pathways or a generalized loss to multiple pathways. No statistically significant differences between migraine patients and controls were found for mean deviation (MD) or pattern-standard deviation (PSD) for SAP. However, for SWAP, MD and PSD were worse for the migraine group (P =.04). Twelve migraine patients had more than 4 locations with sensitivity worse than the 5% probability level (reference value). Increment threshold determinations in the 2 selected migraine patients indicated a selectively greater loss for short-wavelength sensitivity mechanisms. Approximately 50% of subjects with migraine (with or without aura) demonstrate SWAP sensitivity losses, at times between migraine events. These findings, in conjunction with previous results for SAP and flicker perimetry, suggest that migraine patients should be excluded from normative databases of visual function, and warrant further investigations of the relationship between migraine and glaucoma.
Automatic identification of the temporal retinal nerve fiber raphe from macular cube data
Publisher: The Optical Society
Date: 15-09-2016
DOI: 10.1364/BOE.7.004043
Increasing the Spatial Resolution of Visual Field Tests Without Increasing Test Duration: An Evaluation of ARREST.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 16-12-2020
DOI: 10.1167/TVST.9.13.24
Center-Surround Visual Motion Processing in Migraine
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 11-2010
DOI: 10.1167/IOVS.10-5290
Abstract: It has been proposed that reduced cortical inhibition might be a key feature of migraine. Here the authors compared migraine and control group performance for two visual motion tasks in which performance was considered to reflect center-surround inhibitory processes. These tasks use the observations that healthy young observers require longer stimulus durations to detect the direction of motion of larger higher contrast stimuli, and these stimuli also elicit weaker motion aftereffect (MAE) strength. Both observations are considered to arise from center-surround inhibition. The authors measured stimulus duration thresholds for detecting the direction of motion of stimuli of different sizes and contrasts, and also examined motion aftereffect strength for similar stimuli presented for longer durations in 20 control participants and 30 people with migraine (15 with aura). The migraine group was assessed between migraines while they were asymptomatic. For the motion direction task, a significant interaction existed between experimental group and contrast for large stimuli (F((3.96, 190.01)) = 2.95 P < 0.05) however, the interaction was in the opposite direction from that expected from reduced inhibition. Similarly, the MAE data demonstrated a significant interaction between stimulus size and group, but it was in the opposite direction from that predicted (F((1, 48)) = 4.13 P < 0.05). Consistent with previous studies, the migraine group in this study demonstrated abnormal visual motion processing. However, the data from both the motion direction detection and the motion aftereffect tasks do not support a theory of reduced cortical inhibition.
Acute caffeine ingestion affects surround suppression of perceived contrast
Publisher: SAGE Publications
Date: 07-09-2018
Abstract: Caffeine is a widely used psychostimulant that is associated with increased acetylcholine levels in mammalian brain and acetycholinesterase antagonism. Acetylcholine, a neuromodulator, plays an important role in the processing of visual information. One key ex le in human vision, thought to at least partly involve cholinergic neuromodulation, is perceptual surround suppression of contrast, whereby the perceived contrast of a pattern is altered by the presence of a neighbouring pattern. Perceptual surround suppression is weaker with pharmacological administration of donepezil (a centrally-acting acetylcholine enzyme inhibitor) in healthy human observers. Here, we test whether temporarily manipulating caffeine levels (from complete washout to a controlled dose of caffeine) has a similar effect on perceptual surround suppression in 21 healthy young adults (aged 20-24 years, 11 females). Neither ingestion of a caffeine pill nor placebo altered contrast judgments when the target pattern was presented on a uniform grey background ( p=0.54). With caffeine ingestion, perceptual surround suppression strength was reduced relative to baseline (prior to pill ingestion, p=0.003) and placebo ( p=0.029), irrespective of whether the surround was oriented parallel or orthogonal to the central target. While daily habitual caffeine consumption of low-to-moderate doses (<400 mg/day, estimated from a written questionnaire) is not predictive of performance, our study indicates that acute consumption of caffeine on the day of testing influences perceptual surround suppression strength. Perceptual surround suppression is predominantly attributed to inhibitory processes involving the major cortical inhibitory neurotransmitter, gamma-aminobutyric acid. Our results point to the involvement of other neuromodulators, possibly cholinergic, in perceptual surround suppression.
Effect of fundus tracking on structure–function relationship in glaucoma
Publisher: BMJ
Date: 02-03-2020
DOI: 10.1136/BJOPHTHALMOL-2019-315070
Abstract: To investigate the effect of fundus tracking perimetry on structure–function relationship in glaucoma. Perimetric data were acquired with the Humphrey Field Analyzer (HFA) and the Compass fundus perimeter (CMP, equipped with fundus tracking). We included data from 696 eyes from 360 healthy people and 711 eyes from 434 patients with glaucoma from the original study, for which the circumpapillary retinal nerve fibre layer optical coherence tomography scan (Cp-RNFL) was available. We explored the structure–function relationship using both global indices (mean deviation and average Cp-RNFL thickness loss) and anatomically defined visual field clusters comparing the R 2 values from mixed-effect models. We then measured the diagnostic ability of a combined Structure Function Index (SFI) using perimetric data from either perimeter. The comparisons were based on partial receiver operating characteristic curves with a minimum specificity of 75% and their areas under the curve. The R 2 for the global structure–function relationship was 0.50 for the CMP and 0.48 for the HFA. When visual field clusters were included in the model, the R 2 was 0.29 for CMP and 0.30 for HFA. Overall, the discrimination ability of the SFI was not significantly higher than the Cp-RNFL for either the CMP (p=0.07) or the HFA (p=0.14). However, it was significantly better in eyes with perimetric damage (p .001), in which the CMP-SFI performed significantly better than the HFA-SFI (p=0.03). Structure–function relationship is similar between the two perimeters. Fundus tracking might improve discrimination ability with a combined SFI. ISRCTN13800424 .
Eye movement characteristics are not significantly influenced by psychiatric comorbidities in people with visual snow syndrome
Publisher: Elsevier BV
Date: 04-2023
Dichotomous miR expression and immune responses following primary blood- stage malaria
Publisher: American Society for Clinical Investigation
Date: 03-08-2017
Differential aging effects in motion perception tasks for central and peripheral vision
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 20-05-2020
DOI: 10.1167/JOV.20.5.8
Robot Assistants for Perimetry
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 28-06-2019
DOI: 10.1167/TVST.8.3.59
Ultra-high field magnetic resonance imaging of the retrobulbar optic nerve, subarachnoid space, and optic nerve sheath in emmetropic and myopic eyes
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 09-02-2021
DOI: 10.1167/TVST.10.2.8
Aliasing for rapidly counterphasing stimuli
Publisher: Optica Publishing Group
Date: 10-2000
Abstract: We investigated whether resolution is s ling limited for stimuli optimized for detection by magnocellular mechanisms. We measured peripheral (15 degrees and 30 degrees) spatial detection and resolution thresholds using 50% and 90% contrast flicker-defined gratings (25 Hz) and 90% contrast counterphasing sinusoidal gratings (25 Hz). Direction-discrimination performance for 90% contrast counterphasing sinusoidal gratings (25 Hz) was measured foveally. Our results indicate that resolution of rapidly counterphasing stimuli is s ling limited in peripheral vision but is consistent with limiting of performance by parvocellular mechanisms. Also, unders ling may not be necessary to account for motion reversals observed with gratings that both drift and flicker.
Eye health profile of affordable eye care service users
Publisher: Informa UK Limited
Date: 08-08-2022
DOI: 10.1080/08164622.2021.1949243
Abstract: Knowledge of the typical eye health profile of patients experiencing social or economic disadvantage is useful for health care modelling. The aim of this work is to profile the ocular health and sociodemographic characteristics of Australian College of Optometry service users of all ages and to explore the relationships between key sociodemographic characteristics and eye health. For 3093 eye examinations, best-corrected distance visual acuity and mean spherical equivalent refractive error were tested non-parametrically by clinic category, remoteness area, number of co-morbidities, gender and indigenous status, also correlated against age and socioeconomic advantage/disadvantage. Covariates of interest were entered into linear mixed models of visual acuity and mean spherical equivalent refractive error, controlling for age. Risk estimates are reported for visual impairment (defined as ≤6/12 best-corrected distance visual acuity in one or both eyes) and ocular diagnoses. Visual impairment is more prevalent amongst service users examined in domiciliary settings. Increasing co-morbidities were associated with poorer best-corrected distance visual acuity. Aboriginal and Torres Strait Islander service users had lower visual impairment prevalence overall but proportionally fewer aged ≥50 years attended for eye care, compared to non-indigenous. Domiciliary eye examinations detect remediable visual impairment. Federal public health interventions delivered by the Australian College of Optometry for Aboriginal and Torres Strait Islander eye care appear effective but may not reach all aged ≥ 50 years further research is required. Identification of multiple co-morbidities should prompt optometrists to tailor public health messages and signpost to low vision services earlier.
The effect of aging and attention on visual crowding and surround suppression of perceived contrast threshold
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 03-02-2017
Abstract: The purpose of this study was to study how, in midperipheral vision, aging affects visual processes that interfere with target detection (crowding and surround suppression) and to determine whether the performance on such tasks are related to visuospatial attention as measured by visual search. We investigated the effect of aging on crowding and suppression in detection of a target in peripheral vision, using different types of flanking stimuli. Both thresholds were also obtained while varying the position of the flanker (placed inside or outside of target, relative to fixation). Crowding thresholds were also estimated with spatial uncertainty (jitter). Additionally, we included a visual search task comprising Gabor stimuli to investigate whether performance is related to top-down attention. Twenty young adults (age, 18-32 years mean age, 26.1 years 10 males) and 19 older adults (age, 60-74 years mean age, 70.3 years 10 males) participated in the study. Older adults showed more surround suppression than the young (F[1,37] = 4.21 P < 0.05), but crowding was unaffected by age. In the younger group, the position of the flanker influenced the strength of crowding, but not the strength of suppression (F[1,39] = 4.11 P < 0.05). Crowding was not affected by spatial jitter of the stimuli. Neither crowding nor surround suppression was predicted by attentional efficiency measured in the visual search task. There was also no significant correlation between crowding and surround suppression. We show that aging does not affect visual crowding but does increase surround suppression of contrast, suggesting that crowding and surround suppression may be distinct visual phenomena. Furthermore, strengths of crowding and surround suppression did not correlate with each other nor could they be predicted by efficiency of visual search.
Mismatched summation mechanisms in older adults for the perception of small moving stimuli
Publisher: Elsevier BV
Date: 2018
DOI: 10.1016/J.VISRES.2017.10.001
Abstract: Previous studies have found evidence for reduced cortical inhibition in aging visual cortex. Reduced inhibition could plausibly increase the spatial area of excitation in receptive fields of older observers, as weaker inhibitory processes would allow the excitatory receptive field to dominate and be psychophysically measureable over larger areas. Here, we investigated aging effects on spatial summation of motion direction using the Battenberg summation method, which aims to control the influence of locally generated internal noise changes by holding overall display size constant. This method produces more accurate estimates of summation area than conventional methods that simply increase overall stimulus dimensions. Battenberg stimuli have a checkerboard arrangement, where check size (luminance-modulated drifting gratings alternating with mean luminance areas), but not display size, is varied and compared with performance for a full field stimulus to provide a measure of summation. Motion direction discrimination thresholds, where contrast was the dependent variable, were measured in 14 younger (24-34 years) and 14 older (62-76 years) adults. Older observers were less sensitive for all check sizes, but the relative sensitivity across sizes, also differed between groups. In the older adults, the full field stimulus offered smaller performance improvements compared to that for younger adults, specifically for the small checked Battenberg stimuli. This suggests aging impacts on short-range summation mechanisms, potentially underpinned by larger summation areas for the perception of small moving stimuli.
The effect of aging on the eccentricity dependency of orientation anisotropy of perceptual surround suppression
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 27-01-2021
DOI: 10.1167/JOV.21.1.13
What reduction in standard automated perimetry variability would improve the detection of visual field progression?
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 17-05-2011
DOI: 10.1167/IOVS.10-6255
Abstract: PURPOSE. The test-retest variability of standard automated perimetry (SAP) severely limits its ability to detect sensitivity decline. Numerous improvements in procedures have been proposed, but assessment of their benefits requires quantification of how much variability reduction results in meaningful benefit. This article determines how much reduction in SAP procedure variability is necessary to permit earlier detection of visual field deterioration. METHOD. Computer simulation and statistical analysis were used. Gaussian distributions were fit to the probability of observing any sensitivity measurement obtained with SAP and the Full Threshold algorithm to model current variability. The standard deviation of these Gaussians was systematically reduced to model a reduction of SAP variability. Progression detection ability was assessed by using pointwise linear regression on decreases of -1 and -2 dB/year from 20 and 30 dB, with a custom criteria that fixed detection specificity at 95%. Test visits occurring twice and thrice per annum are modeled, and analysis was performed on single locations and whole fields. RESULTS. A 30% to 60% reduction in SAP variability was required to detect pointwise deterioration 1 year earlier than current methods, depending on progression rate and visit frequency. A reduction of 20% in variability generally allowed progression to be detected one visit earlier. CONCLUSIONS. On average, the variability of SAP procedures must be reduced by approximately 20% for a clinically appreciable improvement in detection of visual field change. Analysis similar to that demonstrated can measure the improvement required of new procedures, assisting in cost-benefit assessment for the adoption of new techniques, before lengthy and expensive clinical trials.
Point‐of‐care tools to support optometric care provision to people with age‐related macular degeneration: A randomised, placebo‐controlled trial
Publisher: Wiley
Date: 14-03-2022
DOI: 10.1111/OPO.12970
Abstract: Age‐related macular degeneration (AMD) is a leading cause of vision impairment. This randomised placebo‐controlled trial investigated whether point‐of‐care tools can improve optometrists' AMD knowledge and/or care provision. Australian optometrists ( n = 31) completed a demographics survey and theoretical AMD case study multiple‐choice questions (MCQs) to assess their confidence in AMD care provision and AMD knowledge. Participants were then randomly assigned to one of three point‐of‐care tools (online ‘Classification of Age‐related macular degeneration and Risk Assessment Tool’ (CARAT), paper CARAT, or ‘placebo’) to use when providing care to their subsequent 5–10 AMD patients. Participants self‐audited the compliance of their AMD care to best practice for these patients, and a similar number of consecutive patients seen prior to enrolment. Post‐intervention, participants retook the AMD knowledge MCQs and confidence survey. A total of 29 participants completed the study. At the study endpoint, clinical confidence relative to baseline improved with the paper CARAT, relative to placebo, for knowledge of AMD risk factors, asking patients about these factors and referring for medical retinal sub‐specialist care. There were no between‐group differences for the change in AMD knowledge scores. Considering record documentation for patients with any AMD severity, there were no significant between‐group differences for documenting patient risk factors, AMD severity, clinical examination techniques or management. In a sub‐analysis, the change from baseline in compliance for documenting discussions about patient smoking behaviours for early AMD patients was higher with use of the online CARAT relative to placebo ( p = 0.04). For patients with intermediate AMD, the change from baseline in documenting the risk of progression to late AMD was greater among practitioners who used the paper CARAT, relative to placebo ( p = 0.04). This study demonstrates that point‐of‐care clinical tools can improve practitioner confidence and aspects of the documentation of AMD clinical care by optometrists as assessed by self‐audit.
The Open Perimetry Initiative
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 06-04-2022
DOI: 10.1167/JOV.22.5.1
A perimetric test procedure that uses structural information
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 2015
Structure-function mapping: Variability and Conviction in tracing retinal nerve fiber bundles and comparison to a computational model
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 04-02-2014
Abstract: We evaluated variability and conviction in tracing paths of retinal nerve fiber bundles (RNFBs) in retinal images, and compared traced paths to a computational model that produces anatomically-customized structure-function maps. Ten retinal images were overlaid with 24-2 visual field locations. Eight clinicians and 6 naïve observers traced RNFBs from each location to the optic nerve head (ONH), recording their best estimate and certain range of insertion. Three clinicians and 2 naïve observers traced RNFBs in 3 images, 3 times, 7 to 19 days apart. The model predicted 10° ONH sectors relating to each location. Variability and repeatability in best estimates, certain range width, and differences between best estimates and model-predictions were evaluated. Median between-observer variability in best estimates was 27° (interquartile range [IQR] 20°-38°) for clinicians and 33° (IQR 22°-50°) for naïve observers. Median certain range width was 30° (IQR 14°-45°) for clinicians and 75° (IQR 45°-180°) for naïve observers. Median repeatability was 10° (IQR 5°-20°) for clinicians and 15° (IQR 10°-29°) for naïve observers. All measures were worse further from the ONH. Systematic differences between model predictions and best estimates were negligible median absolute differences were 17° (IQR 9°-30°) for clinicians and 20° (IQR 10°-36°) for naïve observers. Larger departures from the model coincided with greater variability in tracing. Concordance between the model and RNFB tracing was good, and greatest where tracing variability was lowest. When RNFB tracing is used for structure-function mapping, variability should be considered.
Older age results in difficulties separating auditory and visual signals in time.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 24-09-2014
DOI: 10.1167/14.11.13
Abstract: Previous research provides conflicting evidence regarding whether older adults have altered tolerance to timing differences between auditory and visual events. We examine the potential impact of age-related unisensory decline on audiovisual synchrony perception. Fifteen younger (21-32 years) and 13 older (60-72 years) adults participated. To assess unisensory sensitivity, visual Gabor contrast detection thresholds and auditory masked tone pip detection thresholds were measured. Four multisensory conditions were then tested: suprathreshold and near-threshold stimuli (based on in idual unisensory psychometric functions), each tested with a masked tone pip stimuli at 0.5 and 4 kHz sound frequencies. Two audiovisual pairs (one synchronous, the other asynchronous) were presented in a two-interval forced-choice procedure, with observers identifying the interval containing the asynchronous stimulus. Older adults required a larger physical asynchrony to perceive the stimuli as asynchronous, particularly for low frequency sounds. Our results demonstrate that the impact of age on audiovisual synchrony perception cannot be explained by decline in unisensory sensitivity alone.
Visual search efficiency and functional visual cortical size in children with and without dyslexia
Publisher: Elsevier BV
Date: 05-2021
Advantages of terminating Zippy Estimation by Sequential Testing (ZEST) with dynamic criteria for white-on-white perimetry
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2005
A two-stage neural spiking model of visual contrast detection in perimetry
Publisher: Elsevier BV
Date: 08-2008
Impact of Victorian COVID-19 restrictions on emergency department presentations and hospital admissions for ophthalmic conditions
Publisher: Informa UK Limited
Date: 04-12-2023
Visual and auditory perceptual rivalry in migraine
Publisher: SAGE Publications
Date: 20-04-2011
Abstract: Introduction: Recent evidence demonstrates that perceptual rivalry rate can be modulated by perturbation of the serotonergic system. Specifically, pharmacologically lowering the availability of serotonin results in slower rivalry rates. As it has been suggested that brain serotonin is low during the interictal phase of migraine, we hypothesized that perceptual rivalry rates would be reduced in in iduals with migraine. Methods: Visual and auditory perceptual rivalry measures were obtained for a group of 30 participants with migraine (15 migraine with aura, 15 migraine without aura) and 20 non-headache control in iduals. Results: Our experiments reveal fewer perceptual rivalry switches within both visual and auditory domains for our migraine without aura group, while the with-aura group performed similarly to non-headache controls. Dividing the data by headache frequency rather than headache subtype classification revealed fewer perceptual switches in those with more frequent headaches. Conclusions: Our data provides further support for interictal differences in brain sensory reactivity in migraine, with the observed effects being in the same direction as those caused by pharmacologically reducing brain availability of serotonin in normal observers.
Short-term homeostatic visual neuroplasticity in adolescents after two hours of monocular deprivation
Publisher: Elsevier BV
Date: 06-2023
Observer-based rather than population-based confidence limits for determining probability of change in visual fields
Publisher: Elsevier BV
Date: 11-2005
DOI: 10.1016/J.VISRES.2005.08.012
Abstract: Determining confidence intervals on psychophysical thresholds is straight forward if the psychometric function is known. In clinical settings, however, there is only partial information about the psychometric function, hence confidence limits are usually derived from test-retest data collected from many subjects. In this paper, we introduce a computational technique for deriving confidence limits for an in idual's endpoint threshold using data typically obtained in a clinical setting, rather than a database of test-retest performance. The technique uses probabilistic analysis of all possible response sequences in a test procedure. We then extend this procedure to allow for levels of typical uncertainty in data measurement.
Response times across the visual field: Empirical observations and application to threshold determination
Publisher: Elsevier BV
Date: 08-2014
DOI: 10.1016/J.VISRES.2014.04.013
Abstract: This study aimed to determine if response times gathered during perimetry can be exploited within a thresholding algorithm to improve the speed and accuracy of the test. Frequency of seeing (FoS) curves were measured at 24 locations across the central 30° of the visual field of 10 subjects using a Method of Constant Stimuli, with response times recorded for each presentation. Spatial locations were interleaved, and built up over multiple 5-min blocks, in order to mimic the attentional conditions of clinical perimetry. FoS curves were fitted to each participant's data for each location, and response times derived as a function of distance-from-threshold normalised to the slope of each FoS curve. This data was then used to derive a function for the probability of observing response times given the distance-from-threshold, and to seed simulations of a new test procedure (BURTO) that exploited the probability function for stimulus placement. Test time and error were then simulated for patients with various false response rates. When compared with a ZEST algorithm, simulations revealed that BURTO was about one presentation per location faster than ZEST, on average, while sacrificing less precision and bias in threshold estimates than simply terminating the ZEST earlier. Despite response times varying considerably for a given in idual and their thresholds, response times can be exploited to reduce the number of presentations required in a visual field test without loss of accuracy.
Developing a Screening Tool for Areas of Abnormal Central Vision Using Visual Stimuli With Natural Scene Statistics
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 23-02-2022
DOI: 10.1167/TVST.11.2.34
Optic nerve tissue displacement during mild intraocular pressure elevation: its relationship to central corneal thickness and corneal hysteresis.
Publisher: Wiley
Date: 19-06-2018
DOI: 10.1111/OPO.12568
Abstract: To determine the extent to which (1) optic nerve tissue is displaced following mild acute elevation of intraocular pressure, and (2) clinically accessible measures at the anterior eye can be used as a surrogate for such displacements. We imaged the optic disc of 21 healthy subjects before and after intraocular pressure (IOP) elevation of ~10 mmHg delivered by ophthalmodynamometry. Steady-state tissue displacement during IOP elevation was assessed axially from OCT data, and laterally from SLO data. Recovery from IOP elevation was assessed by tracking a single vertical B-scan through the cup centre. Anatomical structures were demarcated by three masked clinicians to determine lateral shifts for temporal cup edge and central disc vessels, and axial shifts of disc surface and anterior lamina cribrosa. Spatial maps of deformation were constructed within the demarcated cup and disc to assess within-tissue displacement. Measured displacements were correlated with corneal hysteresis, corneal thickness, and IOP. The temporal cup edge moved more temporally with higher baseline IOP (R Mild acute elevation of IOP produces large and rapidly reversible shifts in optic nerve tissue in young, healthy eyes. The resulting degree, direction and spatial distribution of cup movement are associated with IOP status and corneal thickness, but not corneal hysteresis.
Geometry of the Retinal Nerve Fibers From Emmetropia Through to High Myopia at Both the Temporal Raphe and Optic Nerve
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 21-11-2019
Abstract: The geometry of retinal nerve fibers may be altered with myopia, a known risk factor for glaucoma. Recent developments in high resolution imaging have enabled direct visualization of nerve fiber bundles at the temporal raphe with clinical hardware, providing evidence that this area is sensitive to glaucomatous damage. Here, we test the hypothesis that nerve fiber geometry is altered by myopia, both at the temporal raphe and surrounding the optic nerve head. Seventy-eight healthy in iduals participated, with refractive errors distributed between emmetropia and high myopia (+0 to -13 DS). Custom high-density OCT scans were used to visualize RFNL bundle trajectory at the temporal raphe. A standard clinical OCT protocol was used to assess papillary minimum rim width (MRW) and peripapillary retinal nerve fiber layer (RNFL) thickness. Measures of raphe shape-including position, orientation, and width-did not depend significantly on axial length. In 7.5% of subjects, the raphe was rotated sufficiently that inversion of structure-function mapping to visual field space is predicted in the nasal step region. Low concordance to ISNT and related rules was observed in myopia (e.g., for RNFL, 8% of high axial myopes compared with 67% of emmetropes). Greater robustness to refractive error was observed for the IT rule. High density OCT scans enabled visualization of marked interin idual variation in temporal raphe geometry however, these variations were not well predicted by degree of myopia as represented by axial length. That said, degree of myopia was associated with abnormal thickness profiles for the papillary and peripapillary nerve fiber layer.
MR-EYE: High-Resolution MRI of the Human Eye and Orbit at Ultrahigh Field (7T)
Publisher: Elsevier BV
Date: 02-2021
Spatial vision in older adults: perceptual changes and neural bases
Publisher: Wiley
Date: 17-05-2018
DOI: 10.1111/OPO.12565
Abstract: The number of older adults is rapidly increasing internationally, leading to a significant increase in research on how healthy ageing impacts vision. Most clinical assessments of spatial vision involve simple detection (letter acuity, grating contrast sensitivity, perimetry). However, most natural visual environments are more spatially complicated, requiring contrast discrimination, and the delineation of object boundaries and contours, which are typically present on non‐uniform backgrounds. In this review we discuss recent research that reports on the effects of normal ageing on these more complex visual functions, specifically in the context of recent neurophysiological studies. Recent research has concentrated on understanding the effects of healthy ageing on neural responses within the visual pathway in animal models. Such neurophysiological research has led to numerous, subsequently tested, hypotheses regarding the likely impact of healthy human ageing on specific aspects of spatial vision. Healthy normal ageing impacts significantly on spatial visual information processing from the retina through to visual cortex. Some human data validates that obtained from studies of animal physiology, however some findings indicate that rethinking of presumed neural substrates is required. Notably, not all spatial visual processes are altered by age. Healthy normal ageing impacts significantly on some spatial visual processes (in particular centre‐surround tasks), but leaves contrast discrimination, contrast adaptation, and orientation discrimination relatively intact. The study of older adult vision contributes to knowledge of the brain mechanisms altered by the ageing process, can provide practical information regarding visual environments that older adults may find challenging, and may lead to new methods of assessing visual performance in clinical environments.
Perceptual learning of contour integration is not compromised in the elderly
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 04-01-2013
DOI: 10.1167/13.1.5
Abstract: Older adults have decreased ability to extract visual contours from noisy backgrounds. The neural mechanisms underpinning the integration of local features into global shapes are key to human visual object perception. Our study demonstrates that older adults maintain plasticity in these mechanisms. We tested 15 younger (20-34 years) and 17 older (62-78 years) adults on six occasions. The first five sessions were conducted over several weeks, with 3-7 days between visits. The final session was 3 months after the fifth session. Contour processing was measured using closed contours (circles or ellipses) constructed of Gabor elements, embedded in noise (identical Gabors of random orientation). At visits one, five, and six, Glass pattern coherence thresholds were also measured to determine whether learning transferred to an alternate task requiring the extraction of shape signal from noise. Older adults improved in their ability to perform the contour tasks in a similar fashion to younger adults. Improvement was specific to the trained task and performance improvements were maintained over a 3-month period. Our results indicate that plasticity of the aging human visual system is maintained for contour integration.
Motion Processing Deficits in Migraine
Publisher: SAGE Publications
Date: 05-2004
DOI: 10.1111/J.1468-2982.2004.00679.X
Abstract: This study was designed to determine whether cortical motion processing abnormalities are present in in iduals with migraine. Performance was measured using a visual motion coherence task (motion coherence perimetry, MCP) thought to depend on the operation of cortical area V5. Motion coherence thresholds were measured using stimuli composed of moving dots at 17 locations in the central ± 20° of visual field. Pre-cortical visual function was also measured using frequency doubling perimetry (FDP) at the same 17 locations. Several migraine subjects demonstrated significant pre-cortical visual functional abnormalities, however, most subjects had normal visual fields measured with FDP. Abnormal MCP performance was measured in 15 of 19 migraine-with-aura subjects, and 11 of 17 migraine-without-aura subjects. A decreased ability to detect coherent motion may possibly be explained by an increase in baseline neuronal noise, such as would be consistent with the concept of cortical hyperexcitability in migraine.
The effects of ageing and visual field loss on pointing to visual targets.
Publisher: Public Library of Science (PLoS)
Date: 15-05-2019
The eye in migraine: a review of retinal imaging findings in migraine
Publisher: Informa UK Limited
Date: 19-09-2022
DOI: 10.1080/08164622.2021.1971045
Abstract: Migraine is a common headache disorder with neurovascular involvement. Because eyecare practitioners are likely to encounter people with migraine in their everyday practice, it is important to understand how migraine might impact on ocular health. In this narrative review, we provide an update on the latest ophthalmic imaging evidence for retinal involvement in migraine, derived from studies of retinal structure and retinal vascular perfusion using spectral domain and swept source optical coherence tomography (OCT) and OCT angiography. Combined structural OCT evidence from a recent meta-analysis indicates subtle and non-specific thinning of the peripapillary retinal nerve fibre layer (RNFL) in people with migraine, whereas there is little consistent evidence for structural abnormalities of the macular region. Recent advances in OCT angiography technology have also provided an opportunity to visualise microstructural damage and vascular dysregulation in the eyes of people with migraine. However, given that OCT and OCT angiography studies have been exclusively cross-sectional, it is not possible to demonstrate the causal effect of migraine events. Furthermore, the lack of common methodology (different ophthalmic imaging devices and analysis algorithms), and very limited datasets (small s les, heterogenous migraine groups), lead to an inability to make strong conclusions regarding the nature of altered retinal structure and vascular perfusion in migraine. Nevertheless, we discuss the clinical implications of such observations for eyecare practitioners and provide practical advice for the monitoring and management of patients with a history of migraine.
A Great Ocean of Truth Lay Undiscovered
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 06-2008
Age-related changes in auditory and visual interactions in temporal rate perception
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 12-2015
DOI: 10.1167/15.16.2
Customized, Automated Stimulus Location Choice for Assessment of Visual Field Defects
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 27-05-2014
Abstract: To introduce a perimetric algorithm (gradient-oriented automated natural neighbor approach [GOANNA]) that automatically chooses spatial test locations to improve characterization of visual field (VF) loss without increasing test times. Computer simulations were undertaken to assess the performance of GOANNA. GOANNA was run on a 3° grid of 150 locations, and was compared with a zippy estimation by sequential testing (ZEST) thresholding strategy for locations in the 24-2 test pattern, with the remaining 98 locations being interpolated. Simulations were seeded using empirical data from 23 eyes with glaucoma that were measured at all 150 locations. The performance of the procedures was assessed by comparing the output thresholds to the input thresholds (accuracy and precision) and by evaluating the number of presentations required for the procedure to terminate (efficiency). When collated across whole-fields, there was no significant difference in accuracy, precision, or efficiency between GOANNA and ZEST. However, GOANNA targeted presentations on scotoma borders hence it was more precise and accurate at locations where the sensitivity gradient within the VF was high. Compared with ZEST, GOANNA was marginally less precise in areas of the VF that had spatially uniform sensitivity, but improved accuracy and precision in regions surrounding scotoma edges. GOANNA provides a principled framework for automatic placement of additional test locations to provide spatially denser testing around the borders of VF loss.
Orientation-dependency of perceptual surround suppression and orientation decoding of centre-surround stimuli are preserved with healthy ageing.
Publisher: Elsevier BV
Date: 11-2020
Appearance of the frequency doubling stimulus in normal subjects and patients with glaucoma
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 03-2003
DOI: 10.1167/IOVS.01-1251
Abstract: To determine whether the spatial structure of the frequency doubling technology (FDT) perimetry stimulus is visible at detection-contrast threshold in normal observers and those with glaucoma and to assess its perceived spatial frequency at threshold and suprathreshold contrast. Three subject groups were assessed: 10 young normal observers (aged 50 years), and 10 subjects with glaucoma. Detection thresholds for centrally and eccentrically presented 10 degrees squares, 0.25-cyc/deg, 25-Hz counterphase flicker sine-wave gratings were obtained by using a yes-no staircase procedure. Eccentric locations were in areas of loss of FDT sensitivity (< or =21 degrees ) in subjects with glaucoma, or at 7 degrees or 21 degrees inferonasally in normal observers. Resolution-contrast thresholds were determined by a two-alternative, forced-choice staircase procedure in which subjects selected the orientation of the grating stimulus tilted at +/-45 degrees. Perceived spatial frequency was determined by having subjects alter the spatial frequency of a temporally interleaved stationary sine-wave grating to match the FDT stimulus. No significant difference was found between detection- and resolution-contrast thresholds, implying that spatial structure was visible at detection threshold. In general, subjects perceived the spatial structure to have a spatial frequency closer to doubled than to veridical, although the young normal subjects reported a lower apparent spatial frequency than older in iduals. When instructed as for clinical testing, subjects respond to the presence of the structure of the grating, and perceive the FDT stimulus to have a spatial frequency greater than its true spatial frequency. These findings were consistent across both normal observers and those with glaucoma, at both central and eccentric test locations.
Measurement error of visual field tests in glaucoma
Publisher: BMJ
Date: 2003
DOI: 10.1136/BJO.87.1.107
Abstract: Psychophysical strategies designed for clinical visual field testing produce rapid estimates of threshold with relatively few stimulus presentations and so represent a trade-off between test quality and efficiency. The aim of this study was to determine the measurement error of a staircase algorithm similar to full threshold with standard automated perimetry (SAP) and frequency doubling perimetry (FDP) in glaucoma patients. Seven patients with early open angle glaucoma (OAG) were prospectively recruited. All were experienced in laboratory based psychophysics. Three matched test locations were examined with SAP (externally driven Humphrey field analyser) and FDP (CRT) in a single arbitrarily selected eye of each subject. Each location was tested twice with a 4-2-2 dB staircase strategy, similar to full threshold, and then with the method of constant stimuli (MOCS). Accuracy (threshold estimation error) was quantified by determination of differences between "true" threshold measurements made by MOCS and single staircase threshold estimates. Precision (repeatability) was quantified by the differences between repeated staircase threshold estimates. Precision was relatively high for both tests, although higher for FDP than SAP at depressed sensitivity levels. The staircase strategy significantly underestimated threshold sensitivity for both test types, with the mean difference (95% CI) between staircase and MOCS thresholds being 4.48 dB (2.35 to 7.32) and 1.35 dB (0.56 to 1.73) for SAP and FDP respectively. Agreement levels (weighted kappa) between MOCS and staircase thresholds were found to be 0.48 for SAP and 0.85 for FDP. Although this "bias" appeared constant for FDP across all sensitivity levels, this was not the case for SAP where accuracy decreased at lower sensitivity levels. Estimations of threshold sensitivity made using staircase strategies common to clinical visual field test instrumentation are associated with varying degrees of measurement error according to visual field test type and sensitivity. In particular, SAP significantly overestimates the "true" level of sensitivity, particularly in damaged areas of the visual field, suggesting that clinical data of this type should be interpreted with caution.
Aging alters intraocular but not interocular foveal center surround contrast suppression
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 12-01-2017
DOI: 10.1167/17.1.16
Abstract: Numerous previous studies have shown that healthy aging results in increased foveal center surround contrast suppression when the center and surround patterns are presented to both eyes. The mechanistic cause of this observation is not well established. Neurophysiological and psychophysical studies have shown that different mechanisms of parafoveal center surround suppression can be tapped by manipulating viewing conditions to present the center and surround to the same eye (intraocular viewing) or to different eyes (interocular viewing), or by manipulating stimulus parameters such as duration. Here, we tested intraocular and interocular foveal center surround contrast suppression for stimuli of 40 ms and 200 ms duration in 18 younger and 18 older adults. For both groups, foveal intraocular center surround contrast suppression decreased with longer stimulus duration whereas interocular surround suppression did not, confirming contributions from separate mechanisms to these forms of suppression. Intraocular center surround contrast suppression was increased in older adults compared to younger adults however, interocular suppression was similar in both groups. Our results indicate that aging differentially affects distinct forms of suppression arising at various levels of the visual pathway.
Illusory Motion Perception Is Associated with Contrast Discrimination but Not Motion Sensitivity, Self-Reported Visual Discomfort, or Migraine Status
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 29-07-2020
DOI: 10.1167/IOVS.61.8.43
Enhanced structure–function relationship in glaucoma with an anatomically and geometrically accurate neuroretinal rim measurement
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 11-12-2015
Abstract: To evaluate the structure-function relationship between disc margin-based rim area (DM-RA) obtained with confocal scanning laser tomography (CSLT), Bruch's membrane opening-based horizontal rim width (BMO-HRW), minimum rim width (BMO-MRW), peripapillary retinal nerve fiber layer thickness (RNFLT) obtained with spectral-domain optical coherence tomography (SD-OCT), and visual field sensitivity. We examined 151 glaucoma patients with CSLT, SD-OCT, and standard automated perimetry on the same day. Optic nerve head (ONH) and RNFL with SD-OCT were acquired relative to a fixed coordinate system (acquired image frame [AIF]) and to the eye-specific fovea-BMO center (FoBMO) axis. Visual field locations were mapped to ONH and RNFL sectors with fixed Garway-Heath (VF(GH)) and patient-specific (VF(PS)) maps customized for various biometric parameters. Globally and sectorally, the structure-function relationships between DM-RA and VF(GH), BMO-HRW(AIF) and VF(GH), and BMO-HRW(FoBMO) and VF(PS) were equally weak. The R(2) for the relationship between DM-RA and VF(GH) ranged from 0.1% (inferonasal) to 11% (superotemporal) whereas that between BMO-HRW(AIF) and VF(GH) ranged from 0.1% (nasal) to 10% (superotemporal). Relatively stronger global and sectoral structure-function relationships with BMO-MRW(AIF) and with BMO-MRW(FoBMO) were obtained. The R(2) between BMO-MRW(AIF) and VF(GH) ranged from 5% (nasal) to 30% (superotemporal), whereas that between BMO-MRW(FoBMO) and VF(PS) ranged from 5% (nasal) to 25% (inferotemporal). The structure-function relationship with RNFLT was not significantly different from that with BMO-MRW, regardless of image acquisition method. The structure-function relationship was enhanced with BMO-MRW compared with the other neuroretinal rim measurements, due mainly to its geometrically accurate properties.
The Detection of both Global Motion and Global Form Is Disrupted in Glaucoma
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 10-2005
DOI: 10.1167/IOVS.04-1406
Abstract: It is well known that glaucoma results in performance impairments on tasks processed early in the visual pathways. Glaucoma should also impair cortical visual processing because of reduced input from retinal ganglion cells and also possibly because of abnormal cortical function. This study was undertaken to assess whether cortically processed global percepts are disrupted in glaucoma in areas of visual field classified as normal by standard automated perimetry (SAP). Performance on global tasks (motion and form) was compared to measures of presumed precortical magnocellular and parvocellular function in the same in iduals. Fifteen control subjects and 12 patients with primary open-angle glaucoma participated. Testing was performed foveally and midperipherally (12.5 degrees). Contrast-discrimination thresholds were measured by using the steady-pedestal (magnocellular) and pulsed-pedestal (parvocellular) contrast-discrimination tasks of Pokorny and Smith. Global motion coherence and global form coherence thresholds were measured at high and low contrast. Patients with glaucoma demonstrated higher global motion and form-coherence thresholds than did control subjects for targets presented in the midperiphery (P < 0.05), but not foveally. Different in iduals performed poorly on the motion and form tasks. The subjects with the greatest presumed magnocellular and parvocellular loss were those with the largest deficits on the global motion and form tasks, respectively. Some subjects with glaucoma demonstrate profound impairments of global motion or global form integration in areas of visual field classified as normal by SAP. This finding implies that some people with glaucoma may have far greater difficulty with complex visual tasks (for ex le, navigation through the environment or face recognition) than is predicted by their visual field loss.
Visual Snow
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2018
DOI: 10.1097/WNO.0000000000000702
Abstract: Visual snow (VS) is a constant visual disturbance described as flickering dots occupying the entire visual field. Recently, it was characterized as the defining feature of a VS syndrome (VSS), which includes palinopsia, photophobia, photopsias, entoptic phenomena, nyctalopia, and tinnitus. Sixty percent of patients with VSS also experience migraine, with or without aura. This entity often is considered psychogenic in nature, to the detriment of the patient's best interests, but the high frequency of similar visual symptoms argues for an organic deficit. The purpose of this review is to clarify VSS as a true entity and elaborate the nature of in idual symptoms and their relationship to each other. The literature was reviewed with specific regard to the clinical presentation and psychophysical, neurophysiological, and functional imaging studies in patients with defined visual disturbances that comprise VSS. Consideration of the in idual symptoms suggests that multiple factors are potentially involved in the development of VSS, including subcortical network malfunction and cortical hyperexcitation. Although there is substantial overlap between VSS and migraine syndromes in terms of co-occurring symptoms, both neurophysiological and neuroimaging studies provide substantial evidence of separate abnormalities of processing, supporting these as separate syndromes. VSS is likely associated with either hyperactive visual cortices or, alternatively, impaired processing of simultaneous afferent information projecting to cortex. VSS likely results from widespread disturbance of sensory processing resulting in sensory misperception. There may be a number of syndromes associated with impaired sensory processing resulting in sensory misperception, including migraine, persistent perceptual postural dizziness, and tinnitus, which overlap with VSS. Elucidation of abnormality in one defined syndrome may provide a path forward for investigating all.
An overview of optometrists' diabetic retinopathy practice patterns - a cross-sectional survey.
Publisher: Wiley
Date: 08-03-2021
DOI: 10.1111/OPO.12798
Abstract: Contemporary eye care increasingly recommends the use of advanced retinal imaging technology. Anecdotal evidence suggests that this equipment is widely available in primary eye care settings however, knowledge regarding how optometrists use this equipment in the context of diabetic retinopathy (DR) is limited. This study aimed to obtain a current overview of optometrists' clinical practice behaviours in the detection, screening, diagnosis and management of patients with diabetes. A cross-sectional survey was designed to evaluate optometrists' self-reported clinical practice patterns and perceptions, as well as the availability and impact of retinal imaging equipment specific to DR and diabetic macular oedema (DMO) on optometrists' clinical practice. The survey invited participation from all optometrists practising in Australia. One hundred and sixty-seven optometrists participated. Optometrists' self-reported confidence in assessing DR and DMO was high. Optometrists' referral patterns considered the severity of DR and DMO before initiating referral to secondary ophthalmology care. Nearly all optometrists (98.8%) indicated that they had some form of retinal imaging equipment available to them in clinical practice. An optical coherence tomography (OCT) device was available to 75.5% of optometrists. A significant association between having an OCT device in the practice and higher self-reported confidence levels in the assessment of DMO was found. Many optometrists are well equipped with sophisticated retinal imaging technology for the provision of high-quality eye care. Enhancing optometric training and education programmes can maximise the community benefit of access to this equipment and improve delivery of eye care in the community.
Patients’ Views of Visual Field Testing and Priorities for Research Development and Translation into Practice
Publisher: Elsevier BV
Date: 05-2021
DOI: 10.1016/J.OGLA.2021.10.003
Abstract: Information regarding the views of patients, on visual field testing is limited, and no information exists regarding their preferences for test developments. This study aimed to increase knowledge of patients' experiences of visual field assessment and to explore their opinions and priorities regarding current areas of research and development. Online questionnaire with purposive s ling design. Adults who regularly undergo visual field tests in Australia who report having glaucoma or being at glaucomatous risk. An anonymous survey, implemented using the Qualtrics webtool, with both closed- and-open ended questions designed to explore opinions regarding visual field testing, visit attendance for perimetry, as well as priorities for developments. The survey assessed 3 domains: (1) opinions regarding test duration and visit frequency, (2) subjective experience, and (3) perspectives on future developments. One hundred fifty-two complete survey responses were obtained. The median age of participants was 66 years (interquartile range [IQR], 60-72 years). Most participants (70%) had experience of undergoing more than 11 visual field tests. Participants recalled that they completed visual field tests in median of 6 minutes (IQR, 5-8 minutes) and were willing to accept additional time (median, 5 minutes IQR, 3-6 minutes) to obtain more information. Participants were prepared to increase both the number of visual field tests per eye and the frequency of visual field tests (median, 3 visits per year IQR, 2-4 visits per year) to gain more information about their visual status. Regarding future developments, the most preferred option was "similar test times but an increase in the level of information about my visual field," which ranked significantly higher than all other options, including "shorter test times that maintain the currently available level of information about my visual field." Our study confirms, in a different population and health care system, previous research reporting patient perspectives on visual field assessment. We further revealed that health care consumers show a strong preference for accurate information about their vision and report being prepared to undergo longer visual field tests or more visual field tests to achieve that outcome.
The effect of normal aging on closed contour shape discrimination
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 2010
DOI: 10.1167/10.2.1
Ageing elevates peripheral spatial suppression of motion regardless of divided attention
Publisher: Wiley
Date: 20-02-2020
DOI: 10.1111/OPO.12674
Abstract: It is more difficult to perceive the direction of motion of larger, high contrast patterns than smaller, low contrast patterns due to spatial suppression. Spatial suppression of motion is considered important to the segmentation of moving objects in the visual environment. Previous studies have shown that such spatial suppression of motion is reduced in older adults in central vision, to the extent that older adults can have better sensitivity than younger adults for foveally presented stimuli. Our study was designed to explore whether spatial suppression of motion is similarly reduced for older adults in parafoveal regions and whether ided attention impacts on suppression strength because attention is known to impact on spatial interactions. Twenty younger (19–34 years) and 18 older (61–77 years) adults completed a single task, where observers identified the direction of a drifting Gabor patch of variable size (σ of the Gaussian envelope = 0.5, 1, 2, 3, 4°) presented at 10 degrees of visual angle while observing a central fixation marker, and a dual task, where observers were required to ide their attention across two stimuli, the peripheral drifting Gabor patch and a central rapid serial visual presentation (RSVP) stream. Older adults showed increased spatial suppression of motion relative to younger adults for both tasks (main effect of group: p 0.001). Dividing attention elevated thresholds for both age groups to a similar extent (main effect of attention: p = 0.002), but did not specifically alter spatial interactions (group x attention interaction: p = 0.13). Older adults require significantly longer than younger adults to correctly identify stimulus motion, and demonstrate increased spatial suppression of motion, in peripheral vision. When considered alongside previous evidence for reduced suppression for central fixation, our study provides evidence for substantial differences between foveal and parafoveal mechanisms of spatial suppression.
Audiovisual Temporal Perception in Aging: The Role of Multisensory Integration and Age-Related Sensory Loss.
Publisher: Frontiers Media SA
Date: 09-05-2018
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End Date: 12-2022
Amount: $406,258.00
Funder: Australian Research Council
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