ORCID Profile
0000-0003-1850-0225
Current Organisation
University of New South Wales
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Sensory Processes, Perception and Performance | Psychology
Publisher: Frontiers Media SA
Date: 14-03-2014
Publisher: Elsevier BV
Date: 12-2019
DOI: 10.1016/J.AJO.2019.08.013
Abstract: To compare the visual fields results obtained using the Swedish interactive thresholding algorithm-Standard (SS) and the Swedish interactive thresholding algorithm-Faster (SFR) in normal subjects, glaucoma suspects, and patients with glaucoma and to quantify potential time-saving benefits of the SFR algorithm. Prospective, cross-sectional study. One randomly selected eye from 364 patients (77 normal subjects, 178 glaucoma suspects, and 109 patients with glaucoma) seen in a single institution underwent testing using both SS and SFR on the Humphrey Field Analyzer. Cumulative test time using each algorithm was compared after accounting for different rates of test reliability. Pointwise and cluster analysis was performed to determine whether there were systematic differences between algorithms. Using SFR had a greater rate of unreliable results (29.3%) compared with SS (7.7%, P < .0001). This was mainly because of high false positive rates and seeding point errors. However, modeled test times showed that using SFR could obtain a greater number of reliable results within a shorter period of time. SFR resulted in higher sensitivity values (on average 0.5 dB for patients with glaucoma) that was greater under conditions of field loss (<19 dB). Cluster analysis showed no systematic patterns of sensitivity differences between algorithms. After accounting for different rates of test reliability, SFR can result in significant time savings compared with SS. Clinicians should be cognizant of false positive rates and seeding point errors as common sources of error for SFR. Results between algorithms are not directly interchangeable, especially if there is a visual field deficit <19 dB.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2019
DOI: 10.1097/OPX.0000000000001432
Abstract: In our intermediate-tier glaucoma care clinic, we demonstrate fair to moderate agreement in gonioscopy examination between optometrists and ophthalmologists, but excellent agreement when considering open versus closed angles. We highlight the need for increased consistency in the evaluation and recording of angle status using gonioscopy. The consistency of gonioscopy results obtained by different clinicians is not known but is important in moving toward practice modalities such as telemedicine and collaborative care clinics. The purpose of this study was to evaluate the description and concordance of gonioscopy results among different practitioners. The medical records of 101 patients seen within a collaborative care glaucoma clinic who had undergone gonioscopic assessment by two clinicians (one optometrist and either one general ophthalmologist [n = 50] or one glaucoma specialist [n = 51]) were reviewed. The gonioscopy records were evaluated for their descriptions of deepest structure seen, trabecular pigmentation, iris configuration, and other features. These were compared between clinicians (optometrist vs. ophthalmologist) and against the final diagnosis. Overall, 51.9 and 59.8% of angles were graded identically in terms of deepest visible structure when comparing between optometrist versus general ophthalmologist and optometrist versus glaucoma specialist, respectively. The concordance increased when considering ±1 of the grade (67.4 and 78.5%, respectively), and agreement with the final diagnosis was high ( %). Variations in angle grading other than naming structures were observed (2.0, 30, and 3.9% for optometrist, general ophthalmologist, and glaucoma specialist, respectively). Most of the time, trabecular pigmentation or iris configuration was not described. Fair to moderate concordance in gonioscopy was achieved between optometrists and ophthalmologists in a collaborative care clinic in which there is consistent feedback and clinical review. To move toward unified medical records and a telemedicine model, improved consistency of record keeping and angle description is required.
Publisher: Elsevier BV
Date: 02-2020
DOI: 10.1016/J.CLAE.2019.10.135
Abstract: To report a case of reduced aniseikonia in a myopic axial anisometrope during orthokeratology (OK) lens wear. A 19-year-old female university student with myopic anisometropia presented for an OK lens fitting consultation. At baseline, perceptual interocular image size difference or aniseikonia of 1.45% was found, with a smaller image seen by the right eye compared to the left eye. The patient was fitted with a pair of OK lenses and interocular image size differences, subjective refraction and corneal topography were measured after 7, 14 and 47 days of overnight lens wear. Hyperopic shifts in central refraction and corresponding flattening of the central cornea was measured during OK treatment. Aniseikonia reduced after OK wear with the most significant change measured from baseline to day 7. Aniseikonia recorded after 7, 14 and 47 nights of lens wear was 0.05%, 0.35% and 0.85%, respectively. Although minimum differences in refractive error between eyes was reached after 47 days of OK, aniseikonia was greater than that measured after 7 and 14 days of OK. This case report demonstrates reduction in aniseikonia with OK lens wear in a myopic patient with axial anisometropia, although this effect was not sustained beyond 1 week of lens wear. As the impact of corneal curvature changes on aniseikonia is not well understood, future studies on the impact of OK on aniseikonia and associated asthenopia is required.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2015
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 02-04-2018
Abstract: To investigate the effect of stimulus size and disease status on the structure-function relationship within the central retina, we correlated the differential light sensitivity (DLS) with Goldmann stimulus size I to V (GI-V) and optical coherence tomography (OCT) derived in vivo ganglion cell count per stimulus area (GCc) within the macular area in normal subjects and patients with early glaucoma. Humphrey Field Analyzer 10-2 visual field data with GI through V and Spectralis OCT macular ganglion cell layer (GCL) thickness measurements were collected from normal and early glaucoma cohorts including 25 subjects each. GCc was calculated from GCL thickness data and correlated with DLSs for different stimulus sizes. Correlation coefficients attained with smaller stimulus size were higher compared to larger stimulus sizes in both normal (GI-GII: R2 = 0.41-0.43, GIII-GV: R2 = 0.16-0.41) and diseased cohorts (GI-GII: R2 = 0.33-0.41, GIII-GV: R2 = 0.19-0.36). Quadratic regression curves for combined GI to V data demonstrated high correlation (R2= 0.82-0.90) and differed less than 1 dB of visual sensitivity within the GCc range between cohorts. The established structure-function relationship was compatible with a histologically derived model correlation spanning the range predicted by stimulus sizes GI to GIII. Stimulus sizes within critical spatial summation area (GI-II) improved structure-function correlations in the central visual field. The structure-function relationship was identical in both normal and diseased cohort when GI to GV data were combined. Congruency of GI and GII structure-function correlation with those previously derived with GIII from more peripheral locations further suggests that the structure-function relationship is governed by the number of ganglion cell per stimulus area.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 10-2018
DOI: 10.1167/TVST.7.5.22
Publisher: Public Library of Science (PLoS)
Date: 03-03-2016
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 17-10-2012
DOI: 10.1167/12.11.10
Abstract: Cast shadows are ubiquitous in the visual scene and they inform greatly about the scene's three-dimensional spatial layout. In the present study we investigated the ability of the visual system to detect the structural form of cast shadows using Glass patterns consisting of local dot-pairs or dipoles oriented appropriately to convey global structure. "Cast shadow" Glass patterns were constructed by superimposing two opposite polarity (light-increment - the object - and light-decrement - the shadow) concentric Glass patterns and then spatially displacing the decrement pattern along a particular orientation conforming to the pattern's lighting direction. We determined the shadow detection threshold, which specifies the amount of structural difference between the object (increment Glass-pattern) and its respective shadow (decrement Glass-pattern), required for observers to detect the cast shadow. This was achieved by varying the ratio between local opposite-polarity dipole pairs that were appropriately aligned along the lighting direction (congruent dipole pairs), and dipole pairs that were randomly oriented (incongruent dipole pairs), and were therefore inconsistent with the pattern's lighting direction. We reported that thresholds were comparatively lower (i.e., the visual system is able to tolerate greater local pattern inconsistencies) for light-from-above patterns than for light-from-below patterns (Experiment 1), and detection is optimal for highly coherent patterns (Experiment 2) small spatial separations between opposite polarity (Experiment 3). Our findings demonstrated that the visual system is more sensitive to light-from-above configurations when detecting the form of cast shadows, and this detection process largely ignores local inconsistencies between the object and its respective shadow.
Publisher: Elsevier BV
Date: 2007
DOI: 10.1016/J.VISRES.2006.10.010
Abstract: Perception of global structure conveyed in static Glass patterns is difficult, though not impossible, when the constituent dipoles are formed by partnering opposite polarity dots. We investigate whether the addition of motion signals to opposite-polarity Glass patterns can act to restore the perception of global structure. The stimuli were concentric Glass patterns consisting of 200 dipoles concentrically orientated, or oriented at random orientations, placed on a grey background. For each dipole, one luminance-increment dot (Weber contrast of 1) was paired with another dot set to a contrast ranging between luminance increment and luminance decrement (i.e., a Weber contrast range of approximately -1 to 1). Dipoles were either stationary (Experiment 1), or randomly re-positioned at 17Hz (Experiment 2), on each frame transition. A two-interval forced-choice paradigm, in conjunction with an adaptive staircase, was used to obtain Glass-pattern detection thresholds. The task required observers to identify the interval that contained concentric Glass structure the other interval contained randomly orientated dipoles. Generally, lower global form thresholds were observed for dynamic and same-polarity Glass patterns than for static and opposite-polarity Glass patterns. In particular, for dynamic presentations improvement in sensitivity was more evident for opposite-polarity than for same-polarity Glass patterns. These findings suggest that motion plays an important role in the detection of global structure in dynamic Glass patterns.
Publisher: Elsevier BV
Date: 02-2023
Publisher: Informa UK Limited
Date: 20-02-2022
DOI: 10.1080/02699052.2022.2034188
Abstract: Traumatic brain injury (TBI) causes significant impact on visual system. This study reports the impact of TBI on the near point of convergence (NPC) measure in in iduals with mild TBI. A systematic review and meta-analysis were conducted for studies that quantified NPC changes in mild TBI. The relevant studies were searched using search engines such as PubMed, EMBASE, Medline and Google Scholar. Thirty studies fulfilled the criteria for systematic review while twelve studies were included in the meta-analysis from 444 patients with mild TBI and 881 controls. This study showed a large and significant impact of head injury on the clinical measure of NPC in patients with mild TBI with a combined effect size of 0.98(95% CI: 0.67-1.29) and significantly moderate heterogeneity (Q(18) = 60.84, This study demonstrated that NPC is largely affected by the impact of TBI. Given the ease with which it can be measured and without the need of specialists and dedicated equipment, NPC measure might provide a supplementary measure of oculomotor function in addition to less sensitive and more subjective questionnaires and personal reports.
Publisher: Elsevier BV
Date: 02-2007
DOI: 10.1016/J.VISRES.2006.11.003
Abstract: When the sinusoidal grating of a "Gabor pattern" is drifted, the apparent position of the pattern shifts in the direction of motion [De Valois, R. L., & De Valois, K. K. (1991). Vernier acuity with stationary moving Gabors. Vision Research, 31, 1619-1626]. We investigated the underlying cause of this illusion by determining whether the effect is a consequence of the internal motion shifting the perceived position of the whole pattern, or a consequence of a shift in the perceived location of the centroid (centre of mass) of the Gabor envelope. While each of these two possible distortions can account for a perceived positional offset, they give different predictions for the apparent size of the stimulus. A simple shift in perceived position results in no change in apparent size, while a centroid shift will likely result in either a decrease or an increase in the pattern's apparent size, depending on whether the trailing or leading edge of the Gabor stimulus is most affected by motion. We examined whether there is a change in the apparent size of Gabor patterns containing a range of grating motion speeds. We found that the perceived size of the pattern increased in the presence of motion as a function of speed, and is thus consistent with a centroid-shift explanation. We verified that this size change is a consequence of an increase in contrast at the leading edge, since the leading edge appears elongated relative to the trailing edge. We furthermore showed that the apparent-position shifts due to motion can be negated by displacing the centroid in the opposite direction to the motion.
Publisher: Elsevier BV
Date: 12-2002
DOI: 10.1016/S0042-6989(02)00384-X
Abstract: A primary task of the visual system is to extract the direction and speed of animate objects from the retinal image. We examined global speed processing by determining how local speeds are integrated and whether integration occurs across all speeds or within fixed speed ranges. The first experiment addressed how local motion signals are combined to determine the speed of an object in motion. Observers judged the speed of a moving cloud of dots that took a random walk in direction while the dots inside the cloud moved somewhat independently of the cloud itself. The apparent speed of the cloud of dots is found to change in proportion with the dot speed and is well predicted by calculating the average speed resulting from nearest neighbour matches across stimulus frames. The second experiment addressed whether local speeds are combined across all speeds or within fixed speed ranges for the detection of global motion. Global dot motion (GDM) stimuli that moved in a radial or rotational directions moving at a low speed of 1.2 degrees /s or a high speed of 9.6 degrees /s were used to measure the thresholds for detecting structured motion as a function of the speed of noise dots (0 degrees /s-10.8 degrees /s) added to the stimulus. With low-speed targets, only additional noise dots moving at low speeds interfered with signal detection. High-speed targets were only interfered with by dots moving at high speeds. This finding established the existence of at least two independent speed tuned systems in the range of speeds tested. Experiment 3 investigated how speed signals are combined within a system to determine the global speed. Using sectored radial GDM stimuli the perceived speed of the fastest dots was measured as a function of whether the speed of the dots in alternate sectors either activated the high or low-speed systems. Averaging only occurred when dots were all within the sensitivity range of the high-speed system, however, if alternate sectors activated separate speed systems, averaging did not occur. Thus local speeds are averaged, independent of direction, to derive a global speed estimate, but averaging only occurs within, and not across, speed tuned mechanisms.
Publisher: Frontiers Media SA
Date: 09-04-2019
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 29-12-2010
DOI: 10.1167/10.14.26
Abstract: When a number of visual elements are presented briefly one after the other at two separate locations, mislocalization occurs with elements perceived "jumping" evenly across the space between locations. This is the visual saltation illusion. We investigated whether saltation occurs in three-dimensional (3D) space. In separate experiments, observers judged the perceived positions of the first, second, and last elements for a sequence in which the first two elements were presented at one location, and the third was presented at a second location. If saltation occurred, only the second element was mislocalized to a position between the first and second locations. In Experiment 1, we observed 3D saltation, but only for conditions in which the stimulus was located away from the point of fixation. This effect was also observed when the two locations in depth have no lateral 2D separation (Experiment 2). In Experiment 3, we showed that a locally generated motion aftereffect between the two locations distorts the perceived position in depth of only the second element, which perceptually overlaps with the adapted region. Our results demonstrate the appearance of 3D saltation, and that the illusion represents a process in which higher cortical areas feed back to activate lower level inputs to achieve 3D perceptual "filling in."
Publisher: Public Library of Science (PLoS)
Date: 09-06-2022
DOI: 10.1371/JOURNAL.PONE.0268951
Abstract: We conducted a systematic review and meta-analysis to understand the impact of traumatic brain injury (TBI) on visual attention and whether different components and processes of visual attention (such as selective, sustained, ided, and covert orientation of visual attention) are affected following brain injury. A literature search between January 1980 to May 2021 was conducted using Medline, Scopus, PubMed, and Google Scholar databases was undertaken for studies that assessed visual attention using different tasks that target specific or multiple components of visual attention. Three hundred twenty-nine potentially relevant articles were identified, and 20 studies met our inclusion criteria. A total of 123 effect sizes (ES) were estimated from 20 studies that included 519 patients with TBI and 530 normal participants. The overall combined ES was statistically significant and large (ES = 0.92), but with high heterogeneity (Q = 614.83, p 0.0001, I 2 = 80.32%). Subgroup analysis showed that the impact of TBI severity, with the ES for moderate-severe TBI significantly higher than mild TBI (t (112) = 3.11, p = 0.002). Additionally, the component of visual attention was differentially affected by TBI (F (2, 120) = 10.25, p .0001) the ES for selective attention (ES = 1.13) and covert orientation of visual attention (ES = 1.14) were large, whilst for sustained attention, the ES was medium at 0.43. A subgroup analysis comparing outcome measures showed that reaction time (ES = 1.12) was significantly more affected compared to performance accuracy (ES = 0.43), F (1, 96) = 25.98, p .0001). Large and significant deficits in visual attention was found following TBI which can last for years after the initial injury. However, different components of visual attention were not affected to the same extent, with selective visual attention and orientation of visual attention most affected following TBI.
Publisher: Springer Science and Business Media LLC
Date: 10-09-2020
DOI: 10.1038/S41598-020-71627-1
Abstract: Current tests for assessing metamorphopsia do not account for confounders such as perceptual filling-in and spatial redundancy, which affect its sensitivity and repeatability. This proof-of-concept study aimed to assess the performance of a novel laboratory-based psychophysical test (Line Sag Test, LST) which addresses these issues for quantification of metamorphopsia in idiopathic epiretinal membranes. The LST quantifies perpendicular metamorphopsia at three eccentricities (3°, 6°, and 9°) along eight meridians (45° steps). Metamorphopsia was assessed using the LST and Amsler grid and the hit rates of both tests for detecting metamorphopsia were compared. Normal metamorphopsia scores using the LST did not differ significantly from 0 and fell within one step-size (p = 0.500). The LST detected significantly more cases of metamorphopsia than the Amsler grid (14/21 versus 3/21) (p = 0.003). Similarly, significantly more cases of visual distortions in asymptomatic iERMs were detected using the LST than the Amsler grid (11/18 versus 0/18) (p = 0.008). The LST has a higher hit rate compared to the Amsler grid (67% versus 14%). This work demonstrates a psychophysically-robust functional test addressing perceptual confounders is more sensitive for quantifying and localising metamorphopsia in macular disease, particularly in asymptomatic disease.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 23-02-2016
DOI: 10.1167/16.3.31
Abstract: In the present study we investigated the detectability of three-dimensional (3D) cocircular contours defined by binocular disparity and established the influence of a number of stimulus factors to their perception. In Experiment 1 we examined the depth range over which local elements are grouped in depth, and whether contour detectability systematically changed with the degree to which they are oriented in depth. We found that increasing the orientation of curved contours in depth improved detection performance. In Experiment 2, we examined the degree to which contour detection was disrupted by varying their continuity in depth by jittering the local depth position of contour elements. Detection performance declined with the increasing displacement of local contour elements in depth away from the depth orientation of the contour. Experiments 3 and 4 ascertained whether a detection advantage is afforded to 3D contours defined by local variations in luminance polarity and color. Local color and polarity differences can disrupt the two-dimensional grouping of local contour elements on the basis of similarity, but we tested whether continuity in depth facilitates grouping of contour elements differing in polarity and color. We found no detection advantage for 3D contours defined by local color and polarity variations, suggesting binocular disparity does not facilitate grouping in depth when local elements differ in color and polarity. These findings further suggest the visual system uses binocular disparity to detect contours, but is likely to involve systems tuned to luminance polarity and color.
Publisher: Informa UK Limited
Date: 17-02-2021
DOI: 10.1111/CXO.13135
Abstract: There is a significant unintended consequences of blue-blocking lenses on visual behaviour, particularly for the detection of colour. Optometrists need to be mindful of this when prescribing the appropriate blue-blocking lenses for in iduals who work in environments in which blue light is prevalent. The selective reduction in visible wavelengths transmitted through commercially available blue-blocking lenses is known to influence object appearance and luminance contrast, and also potentially object colour contrast. The present study investigated the effect of a number of commercially available blue-blocking lenses on colour contrast sensitivity in normal in iduals under low and high contrast stimulus conditions. Five healthy participants (one man and four women), aged between 23 and 39-years, were recruited for this study. Crizal Prevencia (Essilor), Blue Guardian (Opticare), and Blu-OLP (GenOp) lenses were examined in this study in comparison to a control lens (clear lens without blue-filtering coating). In Experiment 1, colour contrast thresholds were measured using a visual search colour detection task in which the colour (CIE Lu'v' red, green, blue and yellow) of the target circle stimulus (randomly located in an annulus of achromatic circles) was systematically reduced using a staircase procedure. As blue-blocking lenses selectively block blue light, in Experiment 2, colour contrast thresholds were specifically quantified for a range of short wavelengths near the attenuation transmittance range of the blue-blocking lenses tested. Experiments 1 and 2 showed that colour contrast was impaired only for blue colours, and this was most evident at low contrasts. Additionally, the blue-blocking lenses with lower transmittance profiles led to greater reductions in colour contrast sensitivity and shown to affect colour contrast thresholds. Our results suggest that while reducing blue light potentially minimises the harmful effect of blue hazard light, blue-blocking lenses can unintentionally reduce colour contrast sensitivity, particularly at low light levels.
Publisher: University of Bern
Date: 31-08-2019
DOI: 10.16910/JEMR.12.2.6
Abstract: The ability to sight-read traditional staff notation is an important skill for all classically trained musicians. Up until now, however, most research has focused on pianists, by comparing experts and novices. Eye movement studies are a niche area of sight-reading research, focusing on eye-hand span and perceptual span of musicians, mostly pianists. Research into eye movement of non-piano sight-reading is limited. Studies into eye movement of woodwind sight-reading were conducted in the 1980s and early 2000s, highlighting the need for new research using modern equipment. This pilot study examined the eye movements of six woodwind (flute, clarinet) undergraduates of intermediate-to-advanced skill level during sight-reading of scores of increased difficulty. The data was analysed in relation to expertise level and task difficulty, focusing on numbers of fixations and fixation durations. The results show that as music ex les became more difficult the numbers of fixations increased and fixation durations decreased more experienced players with better sight-reading skills required less time to process musical notation and participants with better sight- reading skills utilised fewer fixations to acquire information visually. The findings confirm that the efficiency of eye movements is related to instrumental and sight-reading expertise, and that task difficulty affects eye movement strategies.
Publisher: Elsevier BV
Date: 07-2020
Publisher: Wiley
Date: 19-05-2016
DOI: 10.1111/OPO.12295
Abstract: To test the hypothesis that visual field assessment in ocular disease measured with target stimuli within or close to complete spatial summation results in larger threshold elevation compared to when measured with the standard Goldmann III target size. The hypothesis predicts a greater loss will be identified in ocular disease. Additionally, we sought to develop a theoretical framework that would allow comparisons of thresholds with disease progression when using different Goldmann targets. The Humphrey Field Analyser (HFA) 30-2 grid was used in 13 patients with early/established optic nerve disease using the current Goldmann III target size or a combination of the three smallest stimuli (target size I, II and III). We used data from control subjects at each of the visual field locations for the different target sizes to establish the number of failed points (events) for the patients with optic nerve disease, as well as global indices for mean deviation (MD) and pattern standard deviation (PSD). The 30-2 visual field testing using alternate target size stimuli showed that all 13 patients displayed more defects (events) compared to the standard Goldmann III target size. The median increase for events was seven additional failed points: (range 1-26). The global indices also increased when the new testing approach was used (MD -3.47 to -6.25 dB and PSD 4.32 to 6.63 dB). Spatial summation mapping showed an increase in critical area (Ac) in disease and overall increase in thresholds when smaller target stimuli were used. When compared to the current Goldmann III paradigm, the use of alternate sized targets within the 30-2 testing protocol revealed a greater loss in patients with optic nerve disease for both event analysis and global indices (MD and PSD). We therefore provide evidence in a clinical setting that target size is important in visual field testing.
Publisher: Wiley
Date: 23-11-2022
DOI: 10.1111/OPO.13065
Abstract: To analyse optical coherence tomography (OCT)‐derived inner nuclear layer (INL) and outer retinal complex (ORC) measurements relative to ganglion cell‐inner plexiform layer (GCIPL) measurements in glaucoma. Glaucoma participants ( n = 271) were categorised by 10‐2 visual field defect type. Differences in GCIPL, INL and ORC thickness were calculated between glaucoma and matched healthy eyes ( n = 548). Hierarchical cluster algorithms were applied to generate topographic patterns of retinal thickness change, with agreement between layers assessed using Cohen's kappa (κ). Differences in GCIPL, INL and ORC thickness within and outside GCIPL regions showing the greatest reductions and Spearman's correlations between layer pairs were compared with 10‐2 mean deviation (MD) and pattern standard deviation (PSD) to determine trends with glaucoma severity. Glaucoma participants with inferior and superior defects presented with concordant GCIPL and INL defects demonstrating mostly fair‐to‐moderate agreement (κ = 0.145–0.540), which was not observed in eyes with no or ring defects (κ = −0.067–0.230). Correlations ( r ) with MD and PSD were moderate and weak in GCIPL and INL thickness differences, respectively (GCIPL vs. MD r = 0.479, GCIPL vs. PSD r = −0.583, INL vs. MD r = 0.259, INL vs. PSD r = −0.187, p = .0001–0.002), and weak in GCIPL‐INL correlations (MD r = 0.175, p = 0.004 and PSD r = 0.154, p = 0.01). No consistent patterns in ORC thickness or correlations were observed. In glaucoma, concordant reductions in macular INL and GCIPL thickness can be observed, but reductions in ORC thickness appear unlikely. These findings suggest that trans‐synaptic retrograde degeneration may occur in glaucoma and could indicate the usefulness of INL thickness in evaluating glaucomatous damage.
Publisher: Elsevier BV
Date: 2008
DOI: 10.1016/J.VISRES.2007.10.019
Abstract: We investigated how different types of complex motion patterns interact in the perception of shape. We used global dot-motion stimuli which consisted of two superimposed groups of dots one group of dots moved along an ellipsoidal trajectory (target pattern), while the other group of dots was ided into quadrants with dots in alternating sectors moving in radial expanding and radial contracting directions (background pattern). In the first experiment, observers judged whether the major axis of an ellipsoidal motion pattern oriented at 45 degrees or -45 degrees from vertical lay to the right or to the left of a central vertical line. Ellipsoids with different aspect ratios, which controlled both the tilt (left or right of vertical) and the extent of ellipsoidal curvature, were presented to observers using method of constant stimuli. The appearance of the ellipsoidal target pattern was distorted in the presence of background motion. The aspect ratio of the target at which observers perceived the figure to be circular was approximately 0.86 (an aspect ratio of 1.0 indicates a circle), with the pattern's major axis lying in the two sectors that contained contracting motion. This finding may constitute evidence that background motion distorts the perception of space, resulting in a distorted target pattern. However, the distortion effect is limited to conditions for which the speed of the target pattern and background pattern was slow and high contrast, and for when dots forming the target and background patterns were of the same luminance polarity.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 04-09-2018
DOI: 10.1167/TVST.7.5.3
Publisher: Elsevier BV
Date: 06-2011
DOI: 10.1016/J.VISRES.2011.03.016
Abstract: Peripheral vision is characterized in part by poor spatial resolution and impaired visual performance, particularly when the object is surrounded by flanking elements, a phenomenon popularly known as "crowding". Crowding scales with eccentricity irrespective of the target size, both in terms of magnitude and spatial extent, which is determined by varying the target-flanker separation. However, the extent to which crowding depends upon the flanking stimuli parameters alone without separating target and flankers is poorly understood. In the present study, we investigated the effect of flanking stimulus parameters on crowding in orientation and contrast discrimination tasks using closely located "chain" lateral Gabor stimuli in order to enhance our understanding of the underlying mechanisms of crowding in peripheral vision. We found a strong configural effect on crowding in both orientation and contrast discrimination tasks, with reduced crowding when the flanker parameters enhanced the target salience and increased crowding when the flankers were perceptually grouped with the target. While in orientation discrimination crowding was dependent on eccentricity, and in contrast discrimination it was dependent on flanker contrast and eccentricity, crowding showed little dependence on the number of flankers in either task. We conclude that crowding in peripheral orientation and contrast discrimination is configuration specific, which can be reduced without alterations to the target-flanker separation and that crowding is a combination of low-level as well as high-level cortical processing.
Publisher: SAGE Publications
Date: 06-2020
Abstract: Visual processing expertise in musicians has traditionally focused on the difference between expert and non-expert music sight-readers. More generally, differences between musicians and non-musicians have been explored, often with a view to promoting the possible benefits of music training. However, as the definition of music sight-reading expertise varies widely and there is largely no accounting for visual processing expertise in other domains that may be present in non-musicians, interpretation of the results becomes challenging and conclusions may be misleading. Of greater value to the investigation of the visual processing benefits of formal music education would be the ability to definitively isolate those with visual processing expertise in the music sight-reading domain from those without. Only then would it be possible for meaningful comparisons to be made between both the expert and the non-expert music sight-readers and each of these groups, in turn, with non-musicians. The aim of the present study was to explore visual processing by measuring the Working Memory Capacity (WMC) and Rapid Automatized Naming (RAN) capabilities of piano music sight-readers. Participants were grouped as expert or non-expert music sight-readers and the results compared with the WMC and RAN results of non-musicians.
Publisher: Informa UK Limited
Date: 05-2020
DOI: 10.1111/CXO.12959
Abstract: Blue-blocking lenses (BBLs) are marketed as providing retinal protection from acute and cumulative exposure to blue light over time. The selective reduction in visible wavelengths transmitted through BBLs is known to influence the photosensitivity of retinal photoreceptors, which affects both visual and non-visual functions. This study measured the spectral transmittance of BBLs and evaluated their effect on blue perception, scotopic vision, circadian rhythm, and protection from photochemical retinal damage. Seven different types of BBLs from six manufacturers and untinted control lenses with three different powers (+2.00 D, -2.00 D and Plano) were evaluated. The whiteness index of BBLs used in this study was calculated using Commission International de l'Eclairage (CIE) Standard Illuminates D65, and CIE 1964 Standard with a 2° Observer. The protective qualities of BBLs and their effect on blue perception, scotopic vision, and circadian rhythm were evaluated based on their spectral transmittance, which was measured with a Cary 5,000 UV-Vis-NIR spectrophotometer. BBLs were found to reduce blue light (400-500 nm) by 6-43 per cent, providing significant protection from photochemical retinal damage compared to control lenses (p ≤ 0.05). All BBLs were capable of reducing the perception of blue colours, scotopic sensitivities and circadian sensitivities by 5-36 per cent, 5-24 per cent, and 4-27 per cent, respectively depending on the brand and power of the lens. BBLs can provide some protection to the human eye from photochemical retinal damage by reducing a portion of blue light that may affect visual and non-visual performances, such as those critical to scotopic vision, blue perception, and circadian rhythm.
Publisher: Public Library of Science (PLoS)
Date: 22-05-2013
Publisher: University of Bern
Date: 15-10-2016
DOI: 10.16910/JEMR.9.7.1
Abstract: Previous studies have shown that performance at a defined level of music sight reading for pianists (6th Grade) is predictive of eye movement patterns (Waters, 1998) and that such patterns resemble those of text reading experts (Furneaux & Land, 1999 Sloboda, 1974 Truitt, 1997 Wolf, 1976). However, little is known about how expertise might affect eye movement patterns when the score has been visually disrupted using notational features that are unexpected or outside conventional presentation.The current project examined the effect of altering features of the music score on eye movement patterns of expert and non-expert music sight readers. Participants sight read specifically composed musical excerpts, which were then re-presented with the bar-lines removed, altered inter-note spacing and unpredictable beaming directions. Fixation and saccade characteristics were measured and compared between the two performances. It was expected that expert music sight readers would be most affected when the score was disrupted as they would be less capable of grouping notes into familiar, single units for efficient visual processing. Expert sight readers performed significantly faster than non-experts in both conditions: p .0001. Saccadic latency increased significantly for experts in the disrupted condition: p=0.0259, while non-experts increased slightly, not reaching significance. This suggests that the disruption of visual expectation was sufficient to cause a lengthening of saccade programming in the experts - an indication of interference with the chunking process. The resultant EM patterns for the non-experts demonstrated heightened non-expert behaviours: increased fixations of shorter duration.
Publisher: Public Library of Science (PLoS)
Date: 16-05-2013
Publisher: SAGE Publications
Date: 2010
DOI: 10.1068/P5917
Abstract: The perceived motion direction of a moving Glass pattern is influenced by the orientation of the dot pairs (dipoles) that generate the pattern (Krekelberg et al, 2003 Nature424 674–677 Ross, 2004 Vision Research44 441–448). Here, we investigate how the motion vector and the dipole orientation of moving Glass patterns influence the perceived orientation of each. We employed 1 s movie presentations of sequences of linear Glass patterns, each consisting of 200 dot pairs. Signal pairs, aligned in a common orientation, moved in a common direction. The observer's task was to indicate either the perceived direction of motion, or the perceived dipole orientation of Glass patterns that consisted of either same-polarity dipoles, or opposite-polarity dipoles. Perceived orientation or motion direction was measured as a function of the angular difference between the orientation and the motion direction of the dipoles. We found that the apparent global direction of motion was attracted by approximately 4° towards the dipole orientation for small (15°, 23°) angular differences between dipole motion-direction and dipole orientation, regardless of dipole polarity. However, under the same stimulus conditions, the apparent global orientation was much less affected by the direction of motion, suggesting that motion and form interact asymmetrically. Global form influences global motion-direction perception more powerfully than global motion influences global form perception.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 19-04-2022
DOI: 10.1167/TVST.11.4.18
Publisher: Frontiers Media SA
Date: 20-07-2021
DOI: 10.3389/FNHUM.2021.675376
Abstract: Traumatic Brain Injury (TBI) is defined by changes in brain function resulting from external forces acting on the brain and is typically characterized by a host of physiological and functional changes such as cognitive deficits including attention problems. In the present study, we focused on the effect of TBI on the ability to allocate attention in vision (i.e., the use of endogenous and exogenous visual cues) by systematically reviewing previous literature on the topic. We conducted quantitative synthesis of 16 selected studies of visual attention following TBI, calculating 80 effect size estimates. The combined effect size was large (g = 0.79, p & 0.0001) with medium heterogeneity (I 2 = 68.39%). Subgroup analyses revealed an increase in deficit with moderate-to-severe and severe TBI as compared to mild TBI [ F (2, 76) = 24.14, p & 0.0001]. Task type was another key source of variability and subgroup analyses indicated that higher order attention processes were severely affected by TBI [ F (2, 77) = 5.66, p = 0.0051). Meta-regression analyses revealed significant improvement in visual attention deficit with time [p(mild) = 0.031, p(moderate-to-severe) = 0.002, p(severe) & 0.0001]. Taken together, these results demonstrate that visual attention is affected by TBI and that regular assessment of visual attention, using a systematic attention allocation task, may provide a useful clinical measure of cognitive impairment and change after TBI.
Publisher: Elsevier BV
Date: 05-2013
DOI: 10.1016/J.VISRES.2013.02.017
Abstract: In the kinetic Zollner illusion a stimulus moving over a background of oriented lines appears tilted away from the line orientation. This "motion-tilt" illusion is a powerful demonstration of how form information can influence the computation of motion, particularly in signaling motion direction. In the present study, using a random dot stereogram of the kinetic Zollner illusion, we examined whether and how the degree of motion tilt is affected when form and motion components of the illusion are separated in depth. In Experiment 1 we showed that increasing the depth separation (by increasing binocular disparity) between the moving stimulus and oriented lines attenuated the motion-tilt effect. Motion tilt induction was observed for depth separations of -18 to 18 arcmin in uncrossed and crossed directions, but not at larger separations. In Experiment 2 we showed that motion tilt induction in the kinetic Zollner illusion was also observed when multiple oriented planes were presented in conjunction with a moving stimulus. However, the direction and extent of the illusory motion tilt was determined by the nearest oriented plane. Collectively, these findings show that the interaction of form and motion is dependent on depth and is optimally tuned for a small range of separations.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 12-06-2012
DOI: 10.1167/12.6.19
Abstract: In classic geometric illusions such as the Zollner illusion, vertical lines superimposed on oriented background lines appear tilted in the direction opposite to the background. In kinetic forms of this illusion, an object moving over oriented background lines appears to follow a titled path, again in the direction opposite to the background. Existing literature does not proffer a complete explanation of the effect. Here, it is suggested that motion streaks underpin the illusion that the effect is a consequence of interactions between detectors tuned to the orientation of background lines and those sensing the motion streaks that arise from fast object motion. This account was examined in the present study by measuring motion-tilt induction under different conditions in which the strength or salience of motion streaks was attenuated: by varying object speed (Experiment 1), contrast (Experiment 2), and trajectory/length by changing the element life-time within the stimulus (Experiment 3). It was predicted that, as motion streaks become less available, background lines would less affect the perceived direction of motion. Consistent with this prediction, the results indicated that, with a reduction in object speed below that required to generate motion streaks (< 1.12°/s), Weber contrast (< 0.125) and motion streak length (two frames) reduced or extinguished the motion-tilt-induction effect. The findings of the present study are consistent with previous reports and computational models that directly combine form and motion information to provide an effective determinant of motion direction.
Publisher: Public Library of Science (PLoS)
Date: 06-07-2016
Publisher: Elsevier BV
Date: 04-2010
DOI: 10.1016/J.VISRES.2010.02.005
Abstract: We investigate the influence of local motion in the retinal image plane on the perception of speed-in-depth. Observers judged the apparent speed-in-depth of a square plane of dynamic dots that moved towards the observer. Dots forming the surface of the plane underwent random-direction motion in the image plane. We examined the consequences of changing the dots' image-plane speed on the apparent speed of the stimulus as it traversed depth, where depth is signaled by stereomotion or looming. Results for both the stereomotion and looming conditions indicate that as the speed of random-direction motion in the image plane increases, the apparent speed-in-depth of the stimulus also increases. When stereomotion was used to signal motion-in-depth, the speed judgment is adequately modeled by the resultant of a vector sum of dot-speed in the image plane and speed-in-depth. However, when looming was used to define motion-in-depth, a different pattern of results was found - the apparent speed-in-depth is lower than the actual speed-in-depth, and the results are best predicted by simple averaging. Our results demonstrate that the integration of speed in the image plane and speed-in-depth, to determine object speed, is dependent on the type of cue used to signal motion-in-depth, and this difference is a consequence of the ways in which looming and stereomotion cue motion-in-depth. Looming is derived not at a local stage of motion analysis, but is available only via global integration of local velocities, and consequently global speed conforms to the average speed. Stereomotion, on the other hand, provides an effective cue for in iduating local velocities in depth.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 08-2008
DOI: 10.1167/8.11.20
Publisher: Informa UK Limited
Date: 27-03-2021
DOI: 10.1080/08164622.2021.1898276
Abstract: Wearing blue-blocking lenses (BBLs) in the evening hours may not be effective in improving sleep quality. Optometrists need to be informed in prescribing BBLs by highlighting the consequences of their wear to the circadian system. Excessive exposure to artificial light, particularly at short wavelengths, during the evening, may disrupt normal nocturnal melatonin production, which is a natural process of the circadian rhythm and affect sleep quality. Current BBLs have been designed to limit blue-light exposure and may offer a means to minimise disruption to the circadian system. The purpose of this study was to evaluate the impact of BBLs on a normal sleep-wake circadian rhythm. Seven different commercial brands of BBLs (Crizal Prevencia, Smart Blue Filter, Blu-OLP, Blue Control, UV++Blue Control, SeeCoat Blue UV and Blue Guardian) and powers (+2.00 D, -2.00 D and Plano) were evaluated by quantifying the degree to which they reduce light radiation from l s and electronic devices. In particular, the non-linear circadian index and the circadian stimulus was determined for various light sources to establish changes in melatonin production that occur while viewing through different BBLs. A large difference was shown in the effectiveness of different BBL brands in reducing the spectral sensitivity of the circadian system. The BBL brand was shown to selectively affect the non-linear circadian index and circadian stimulus, particularly with those with transmittance profiles that block the most blue light having the lowest effect on the suppression of nocturnal melatonin secretion. BBLs may not improve sleep quality, because they continue to allow the transmittance of blue light that may suppress nocturnal melatonin secretion and hence disrupt the normal sleep-wake circadian rhythm.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 15-10-2010
DOI: 10.1167/10.12.19
Abstract: The visual saltation illusion--illusory motion induced by presenting elements first to one peripheral location, then to another, in rapid and regular succession--belongs to a class of stimuli for which a difference exists between the physical and perceived positions of elements. Rather than being perceived at their physical location, elements are perceived as traveling smoothly across the area between the two locations. In separate experiments, we examined the distortion to the saltatory path caused by adaptation to an upward drifting grating presented between the two physically stimulated locations (where elements were nonetheless perceived), and at the first location of physical stimulation. Where adaptation occurred between the two sites of physical stimulation, the saltatory path was distorted as if elements had a physical origin at that location elements perceived as arising from the central location were subject to a motion aftereffect (MAE). Where motion adaptation overlapped the first site of physical stimulation, the saltatory path was affected only for those elements perceived as arising from the first location elements perceived at the central location (but physically presented at the first site of stimulation) were not subject to an MAE. Our results indicate that the impact of motion adaptation on position is dependent on the perceived, and not the physical, location of elements.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 03-06-2015
Abstract: To establish Ricco's critical area (Ac) using the 30-2 Humphrey visual field analyzer (HVFA) and thereby identify Goldmann test sizes that are within or outside complete spatial summation at all visual field testing locations. We also determined the suitability of using age normative data for different test sizes. Finally, by modifying current output measures (dB values), we provide a new method that allows comparison of contrast sensitivity when testing with different Goldmann test sizes within complete spatial summation. We used the HVFA in full threshold mode and measured thresholds for all five Goldmann test sizes in 12 observers. Normative data of Heijl et al. were used for age transformation and comparison. All the data converted to a 50-year-old equivalent lie within 1 SD of expected variance for all test locations of the 30-2 paradigm. We established Ac values at all locations of the 30-2 paradigm and showed a systematic increase in Ac as a function of increased visual field eccentricity, consistent with previous studies. Age does not appear to affect Ac or the slope of partial summation for a wide range of visual field eccentricities tested using the HVFA. By equating spatial summation, we propose a new metric, dB*, that returns a uniform sensitivity value for different test sizes that are operating within complete spatial summation (i.e., follow Ricco's law). We established that converting to age-equivalent thresholds and application of dB* principle advantageously allows comparison of data sets across age and test size at different locations of the visual field. By identifying the Ac across the visual field, it is now possible to systematically determine threshold changes across the 30-2 locations in ocular disease and further characterize the importance of testing within complete spatial summation in standard automated perimetry.
Publisher: Informa UK Limited
Date: 07-2017
DOI: 10.1111/CXO.12551
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 11-10-2022
Publisher: Elsevier BV
Date: 02-2012
DOI: 10.1016/J.VISRES.2012.01.004
Abstract: The visual system is able to infer three-dimensional (3D) shape from the surface shading-gradient of objects. Using Global Dot Motion (GDM) stimuli, we investigated the influence of shape from shading on the perception of coherent local and global motion. In Experiment 1, we report that the visual system is unable to detect the local motion of dots that undergo a change in 3D shape (convex to concave shape) from frame to frame. For this condition, GDM detection thresholds were approximately four times higher than when dots do not change shape. However, when shaded dots were perceptually two-dimensional (as with bipartite and horizontally shaded dots) GDM the visual system was able to detect the global motion regardless of a change in shading direction. Finally in Experiment 3, we demonstrated that the addition of noise dots interferes with the detection of global motion only when they have same 3D shape as signal dots. GDM detection thresholds were unaffected if additional noise dots were of the opposite 3D shape. The findings of the present study demonstrate that 3D shape from shading information impacts of GDM detection, particularly, that this depth form-cue is used as a basis for independent motion analysis at both local and global levels of processing.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 06-2011
DOI: 10.1167/11.7.1
Abstract: Detection and identification of objects are the most crucial goals of visual perception. We studied the role of luminance and chromatic information for object processing by comparing performance of familiar, meaningful object contours with those of novel, non-object contours. Comparisons were made between full-color and reduced-color object (or non-object) contours. Full-color stimuli contained both chromatic and luminance information, whereas luminance information was absent in the reduced-color stimuli. All stimuli were made equally salient by fixing them at multiples of discrimination threshold contrast. In a subsequent electroencephalographic experiment observers were asked to classify contours as objects or non-objects. An advantage in accuracy was found for full-color stimuli over the reduced-color stimuli but only if the contours depicted objects as opposed to non-objects. Event-related potentials revealed the neural correlate of this object-specific luminance advantage. The litude of the centro-occipital N1 component was modulated by stimulus class with the effect being driven by the presence of luminance information. We conclude that high-level discrimination processes in the cortex start relatively early and exhibit object-selective effects only in the presence of luminance information. This is consistent with the superiority of luminance in subserving object identification processes.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 13-10-2017
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 06-2009
DOI: 10.1167/9.6.5
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 15-08-2011
DOI: 10.1167/11.9.5
Abstract: Visual saltation is the illusory mislocalization that occurs when multiple elements are rapidly presented to two peripheral locations mislocalized elements appear to fill in the intermediate space. We investigated the influence of element orientation on the path of illusory saltatory motion. Experiment 1 showed that congruence in element orientation at the two locations (horizontal-horizontal or vertical-vertical) produced rectilinear saltation, while incongruent orientations (vertical-horizontal or horizontal-vertical) elicited curvilinear saltation consistent with rigid rotation around a common point. In curvilinear saltation, mislocalized elements were perceived with an intermediate orientation. Experiment 2 showed that the perceived shape of the motion path was directly dependent on the salience of orientation information. In Experiment 3, we showed that the circular path of curvilinear saltation (induced by orientation incongruence) is altered by background motion (wedge-shaped regions of inward and outward moving dots) that overlaps only with the inter-element space. An ellipsoid path, where the major axis corresponds to the mislocalized element overlapping with outward motion and the minor axis corresponds to the mislocalized element overlapping with inward motion, is produced. These findings reveal that the interpretation of visual saltation arises from high-level computations in which the percept is derived through an interaction of form and motion.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 07-06-2018
DOI: 10.1167/TVST.7.3.17
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 09-11-2016
DOI: 10.1167/16.14.5
Abstract: In the present study, we measured the extent of statokinetic dissociation (SKD) in normal observers and then equated the psychophysical tasks into a two-interval forced choice (2IFC) procedure. In Experiment 1, we used the Humphrey visual field analyzer in static perimetry and automated kinetic perimetry modes to measure contrast sensitivity thresholds and the Goldmann manual kinetic perimeter to measure isopters. This was carried out using a Goldmann size II target. Goldmann kinetic perimetry was performed manually with both inward (peripheral to center) and outward (center to periphery) directions of movement to deduce an "average" isopter. This revealed the presence of SKD when superimposed upon the map of static contrast threshold results. There was no evidence of any contribution of examiner technique or instrument-specific differences to SKD. In Experiment 2, we determined the psychometric curves plotting proportion seen as a function of stimulus eccentricity with static and kinetic stimuli with a 2IFC procedure and method of constant stimuli. In an additional experiment, we also showed that subjects were able to reliably discriminate whether a stimulus was static, moving inward, or moving outward, and hence, comparisons could be made between static and kinetic perimetry tasks. Overall, by making the task objective and reducing criterion bias, eccentricity thresholds were equated across static and kinetic perimetry methods hence, no evidence of SKD was seen. We suggest SKD is inherent to the differences in methodology of threshold measurement in conventional static and kinetic perimetry and in idual criterion bias.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 19-03-2014
DOI: 10.1167/14.3.25
Abstract: In the present study we examined whether the perception of depth from cast shadows is dependent on visual awareness using continuous flash suppression (CFS). As a direct measure of how the visual system infers depth from cast shadows, we examined the cast-shadow motion illusion originally reported by Kersten, Knill, Mamassian, and Bulthoff (1996), in which a moving cast shadow induces illusory motion in depth in a physically stationary object. In Experiment 1, we used a disparity defined probe to determine the stereo motion speed required to match the cast-shadow motion illusion for different cast shadow speeds (0°/s-1.6°/s) and different lighting directions. We found that configurations implying light from above produce more compelling illusory effects. We also found that increasing shadow speed monotonically increased the stereo motion speed required to match the illusory motion, which suggests that quantitative depth can be derived from cast shadows when they are in motion. In Experiment 2, we used CFS to suppress the cast shadow from visual awareness. Visual suppression of the cast shadow from awareness greatly diminished the perception of illusory motion in depth. In Experiment 3 we confirmed that while CFS suppresses the cast-shadow motion from awareness, it continues to be processed by the visual system sufficient to generate a significant motion after effect. The results of the present study suggest that cast shadows can greatly contribute to the perception of scene depth structure, through a process that is dependent on the conscious awareness of the cast shadow.
Publisher: Public Library of Science (PLoS)
Date: 09-12-2019
Publisher: Springer Science and Business Media LLC
Date: 12-08-2019
DOI: 10.1038/S41598-019-48026-2
Abstract: Standard automated perimetry (SAP), the most common form of perimetry used in clinical practice, is associated with high test variability, impacting clinical decision making and efficiency. Contrast sensitivity isocontours (CSIs) may reduce test variability in SAP by identifying regions of the visual field with statistically similar patterns of change that can be analysed collectively and allow a point (disease)-to-CSI (normal) comparison in disease assessment as opposed to a point (disease)-to-point (normal) comparison. CSIs in the central visual field however have limited applicability as they have only been described using visual field test patterns with low, 6° spatial s ling. In this study, CSIs were determined within the central 20° visual field using the 10-2 test grid paradigm of the Humphrey Field Analyzer which has a high 2° s ling frequency. The number of CSIs detected in the central 20° visual field was greater than previously reported with low spatial s ling and stimulus size dependent: 6 CSIs for GI, 4 CSIs for GII and GIII, and 3 CSIs for GIV and GV. CSI number and distribution were preserved with age. Use of CSIs to assess visual function in age-related macular degeneration (AMD) found CSI guided analysis detected a significantly greater deviation in sensitivity of AMD eyes from normal compared to a standard clinical pointwise comparison (−1.40 ± 0.15 dB vs −0.96 ± 0.15 dB p 0.05). This work suggests detection of CSIs within the central 20° is dependent on s ling strategy and stimulus size and normative distribution limits of CSIs can indicate significant functional deficits in diseases affecting the central visual field such as AMD.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 11-2020
DOI: 10.1097/OPX.0000000000001601
Abstract: The selective reduction in visible wavelengths transmitted through commercially available blue-blocking lenses (BBLs) is known to influence the appearance and contrast detection of objects, particularly at low light levels. This influence may impair the human retinal receptor response time to dynamic light changes during photostress events. This study aimed to assess whether BBLs selectively affect photostress recovery times (PSRTs) for chromatic and achromatic stimuli of different Weber contrasts that were viewed on a dark black background. Photostress recovery times were measured in 12 younger participants (18 to 39 years old) with no history of ocular disease or abnormal vision. Photostress recovery times were evaluated for four brands of BBLs, which were compared with a control lens. In these experiments, after exposure to an intense light source for 5 seconds, the time taken to recover vision and correctly identify a computer-generated letter stimulus viewed under low and high luminance levels was determined, which means perception is likely to be governed by mesopic and photopic conditions. Across conditions, the letter stimulus was achromatic and chromatic and could differ in luminance contrast. Under photopic stimulus conditions, although reducing luminance contrast increased PSRTs, BBLs had no significant effect on PSRTs relative to control lens. However, under mesopic stimulus conditions, BBLs significantly affect PSRTs for both achromatic ( F 2.006,8.02 = 61.95, P .0001) and chromatic stimuli ( F 3,16 =139.01, P .0001), particularly for blue targets, which had considerably longer PSRTs (38.40 seconds). The brand of BBL was also shown to selectively affect PSRTs, with those with transmittance profiles that block the most blue light having longer PSRTs. The present study suggests that, although the color and contrast of the target stimuli affected recovery times, the difference in recovery times between different types of BBLs was noticed only under low-light-level stimulus conditions.
Publisher: SAGE Publications
Date: 10-01-2016
Abstract: Cast shadows have been shown to provide an effective ordinal cue to the depth position of objects. In the present study, two experiments investigated the effectiveness of cast shadows in facilitating the detection of spatial contours embedded in a field of randomly placed elements. In Experiment 1, the separation between the cast shadow and the contour was systematically increased to effectively signal different contour depth positions (relative to background elements), and this was repeated for patterns in which the lighting direction was above and from below. Increasing the shadow separation improved contour detection performance, but the degree to which sensitivity changed was dependent on the lighting direction. Patterns in which the light was from above were better detected than patterns in which the lighting direction was from below. This finding is consistent with the visual system assuming a “light-from-above rule” when processing cast shadows. In Experiment 2, we examined the degree to which changing the shape of the cast shadow (by randomly jittering the position of local cast shadow elements) affected the ability of the visual system to rely on the cast shadow to cue the depth position of the contour. Consistent with a coarse scale analysis, we find that cast shadows remained an effective depth cue even at large degrees of element jitter. Our findings demonstrate that cast shadows provide an effective means of signaling depth, which aids the process of contour integration, and this process is largely tolerant of local variations in lighting direction.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 03-12-2010
DOI: 10.1167/10.14.1
Abstract: To study the effect of blur adaptation on accommodative variability, accommodative responses and pupil diameters in myopes (n = 22) and emmetropes (n = 19) were continuously measured before, during, and after exposure to defocus blur. Accommodative and pupillary response measurements were made by an autorefractor during a monocular reading exercise. The text was presented on a computer screen at 33 cm viewing distance with a rapid serial visual presentation paradigm. After baseline testing and a 5-min rest, blur was induced by wearing either an optimally refractive lens, or a +1.0 DS or a +3.0 DS defocus lens. Responses were continuously measured during a 5-min period of adaptation. The lens was then removed, and measurements were again made during a 5-min post-adaptation period. After a second 5-min rest, a final post-adaptation period was measured. No significant change of baseline accommodative responses was found after the 5-min period of adaptation to the blurring lenses (p > 0.05). Compared to the pre-adaptation level, both refractive groups had similar and significant increases in accommodative variability right after blur adaptation to both defocus lenses. After the second rest period, the accommodative variability in both groups returned to the pre-adaptation level. The results indicate that blur adaptation has a short-term effect on the accommodative system to elevate instability of the accommodative response. Mechanisms underlying the increase in accommodative variability by blur adaptation and possible influences of the accommodation stability on myopia development were discussed.
Publisher: Springer Science and Business Media LLC
Date: 07-03-2016
DOI: 10.3758/S13414-016-1076-9
Abstract: Optic flow provides important information for the perception of self-motion and can be generated by both diffuse and specular reflectance. Previous self-motion research using virtual environments has primarily considered the properties of diffuse optic flow, but not of specular flow. We used graphical simulations to examine the extent to which visually induced self-motion (vection) is robust against the variations in optic flow generated by different surface optics. We found that specular flow alone was capable of generating vection that was equivalent in strength to that generated by diffuse flow (Exp. 1). To test whether this specularly induced vection depends on midlevel visual processing, we measured vection strengths under conditions in which the luminance polarity of specular highlights was inverted. We found that inverting the luminance of specular reflections impaired vection strength, as compared with the vection generated by conditions with ecologically correct diffuse and/or specular flow (Exp. 2). We also found these variations in vection strength were correlated with the perceived relief heights of the surfaces depicted in the image sequences. These findings together suggest that vection can be induced by pure specular flow and that it requires processing beyond the computation of retinal motion velocities-most likely, processes involved in the recovery of 3-D surface shape.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2018
DOI: 10.1097/OPX.0000000000001286
Abstract: We demonstrate that the visual field defects in patients with tilted disc syndrome can be reduced or eliminated by neutralizing the peripheral scotoma in the area of posterior retinal bowing, which may allow differentiation between a congenital anomaly and acquired pathology. Tilted disc syndrome is a congenital and unchanging condition that may present with visual field defects mimicking loss seen in neurological diseases, such as transsynaptic retrograde degeneration. Our purpose was to systematically investigate the ability of a neutralized peripheral refraction to eliminate refractive visual field defects seen in tilted disc syndrome. This was compared with the same technique performed on patients with neurological deficits. The Humphrey Field Analyzer was used to measure sensitivities across the 30-2 test grid in 14 patients with tilted disc syndrome using four refractive corrections: habitual near correction and with an additional −1.00, −2.00 or −3.00 D negative lens added as correction lenses. Peripheral refractive errors along the horizontal meridian were determined using peripheral retinoscopy and thus allowed calculation of residual peripheral refraction with different levels of refractive correction. Visual field defects were assessed qualitatively and quantitatively using sensitivities and probability scores in both patient groups. A smaller residual refractive error after the application of negative addition lenses correlated with improvement in visual field defects in terms of sensitivity and probability scores in patients with tilted disc syndrome. Patients with established neurological deficits (retrograde degeneration) showed improvement in sensitivities but not in probability scores. Neutralizing the refractive error at the region of posterior retinal bowing due to tilted disc syndrome reduces the apparent visual field defect. This may be a useful and rapid test to help differentiate between tilted disc syndrome and other pathological causes of visual field defects such as neurological deficits.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 24-11-2010
DOI: 10.1167/10.13.15
Abstract: We examined whether motion blur accompanying apparent motion (AM) affects the shape of a stimulus presented in the motion path. In a two-alternative forced-choice procedure, observers judged the shape of a Gaussian test stimulus flashed in the path of motion, relative to a reference stimulus, which was a circular Gaussian stimulus located away from the path of motion. In Experiment 1, we report that the test stimulus was affected by AM and its perceived width was wider than its actual width, and counteracting this distortion, shape discrimination thresholds coincided with a test stimulus that was physically "thinner" than the reference stimulus. Shape distortion correlated with the strength of AM (Experiment 2) and increased within the range of inter-stimulus intervals used to induce AM and with retinal eccentricity but was eliminated when the test stimulus was made "hard-edged" (Experiment 3) or when the stimulus does not overlap with the motion path (Experiment 4). In Experiment 5, we demonstrate that the effect is present for dichoptic presentations. These results can be accounted for by a process in which the neural representation of AM generated by higher cortical areas feedback to interfere with the coding of stimulus shape by units located along the trajectory of AM.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 23-03-2018
DOI: 10.1167/TVST.7.2.8
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 12-2013
Publisher: Frontiers Media SA
Date: 17-01-2017
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 28-06-2011
DOI: 10.1167/11.7.20
Abstract: Three-dimensional (3D) shape can be inferred from the surface shading gradient of objects. Using Glass patterns, we investigated the importance of shape-from-shading information to the perception of global form. We examined whether different 3D shapes inferred from shading affect the extraction of local dipole orientations (local analysis) and the integration of dipoles in the perception of Glass structure (global analysis). In Experiment 1, we showed that incongruence in shading between partner dots prevents the recovery of the dipole orientation: partner dots with different 3D shapes are not paired to recover the dipole orientation. However, when incongruent "bipartite" partner dots (that have the same contrast polarity as shaded dots, but are two-dimensional) were used, the visual system was able to extract the local dipole orientation and detect the global pattern (Experiment 2). In Experiment 3, we showed that additional noise dipoles affect the detection of Glass structure regardless of the 3D shape difference between signal and additional noise dipoles. This demonstrates that the visual system combines different oriented 3D dipoles to detect Glass structure. Our findings show that shape-from-shading information impacts on the ability to detect form structure but in different ways at local and global stages of processing.
Publisher: Public Library of Science (PLoS)
Date: 15-12-2014
Publisher: Elsevier BV
Date: 08-2005
DOI: 10.1016/J.VISRES.2005.02.019
Abstract: We investigated the role of disparity information in the detection of global form. Glass patterns, which allow insight into processing at both local and global stages of form analysis, were used as stimuli. We determined how detection of concentric Glass patterns is affected by a disparity difference introduced between partner dots forming local dipoles (Experiment 1), and how detection is affected by the addition of randomly oriented dot-pairs (noise dots) at crossed and uncrossed disparities (Experiment 2). The first experiment showed that detection thresholds increased when partner dots were separated in depth at disparities greater than approximately 17 min arc the second experiment showed that noise dots disrupted the detection of form if they were presented at disparities of between approximately +/-20 min arc from the Glass pattern's presentation depth plane. Our findings suggest that disparity information plays a role in the recovery of the image structure and, importantly, local and global form mechanisms were found to be selective for a small range of stereo-depths. We discuss the findings of our study in the light of current evidence indicating that a common neural substrate is responsible for the analysis of form and binocular disparity.
Publisher: Elsevier BV
Date: 03-2005
DOI: 10.1016/J.VISRES.2004.09.042
Abstract: The human visual system is adept at detecting global structure, or form, within a scene. The initial stage of post-retinal processing for all aspects of vision is fed by On- and Off-centre cells sensitive to centred luminance increments and decrements respectively. These cells provide input to two parallel pathways that process variations in local luminance (first-order pathway) and local contrast (second-order pathway). Here, we investigate the contribution of luminance and contrast information to global form detection, a stage between the extraction of local orientation and the recognition of objects. The underlying processes involve two stages. We find that signals in the On-, Off- and second-order pathways are segregated at both stages of processing. Surprisingly, the non-linear stage in the second-order form pathway is different from that in motion processing: the second-order form detectors show an asymmetry in sensitivity to increments and decrements that is not apparent in motion. A functional architecture for global form detection is proposed along with its possible neural substrates.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 20-06-2017
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 02-03-2018
DOI: 10.1167/TVST.7.2.1
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 16-05-2022
DOI: 10.1167/TVST.11.5.13
Publisher: Elsevier BV
Date: 12-2022
DOI: 10.1016/J.NEUROPSYCHOLOGIA.2022.108422
Abstract: Visual attentional deficits are frequently reported in patients with mild traumatic brain injury (TBI). In the present study, the ability to orient visual attention (i.e., the use of endogenous and exogenous visual cues) was investigated using a modified Posner visual search task, in which the participant was required to search for a target shape (radial frequency patterns) amongst distractor shapes. Participants were required to determine whether a target radial frequency pattern was present or absent from an array of distractors. Attention to the target location was cued using central or peripheral cueing procedures to investigate endogenous or exogenous attention allocation. Predictability was not manipulated between central and peripheral cues. Search difficulty was varied by systematically changing the radial frequency difference between target and distractors (and thereby shape difference), and cues could be valid or invalid in that they correctly or incorrectly indicated the position of the target shape. Both target discriminability (i.e., identifying the presence or absence of the target) and reaction times were measured. Thirteen patients with chronic mild TBI and 21 age-, sex-, and IQ -matched healthy controls participated in the study. For control participants, both discrimination accuracy and reaction times improved with visual search efficiency, and they were sensitive to the type of cue, with performance worst for cue invalid conditions than valid conditions. However, the results for TBI patients were strikingly different we find that discrimination accuracy slightly improved with visual search difficulty (compared to controls), but not reaction times, and TBI patients were largely insensitive to the type of visual cue, and did not show a selective deficit for central or peripheral cues, suggesting an impairment in both endogenous and exogenous visual attention. In conclusion, patients with mild TBI exhibit a poor ability to orient visual attention.
Publisher: Springer Science and Business Media LLC
Date: 12-08-2022
DOI: 10.1038/S41598-022-18163-2
Abstract: Difficulty in the ability to allocate and maintain visual attention is frequently reported by patients with traumatic brain injury (TBI). In the present study, we used a multiple object tracking (MOT) task to investigate the degree to which TBI affects the allocation and maintenance of visual attention to multiple moving targets. Fifteen adults with mild TBI and 20 control participants took part in this study. All participants were matched for age, gender, and IQ. The sensitivity and time taken to perform the MOT task were measured for different conditions in which the duration of the tracking, number of target, and distractor dots were systematically varied. When the number of target dots required to be tracked increased, sensitivity in correctly detecting them decreased for both groups but was significantly greater for patients with mild TBI. Similarly, increasing the number of distractor dots had a greater effect on reducing task sensitivity for patients with mild TBI than control participants. Finally, across all conditions, poorer detection performance was observed for patients with mild TBI when the tracking duration was longer compared to control participants. The present study showed that patients with mild TBI have greater deficits (compared to control participants) in their ability to maintain visual attention on tracking multiple moving objects, which was particularly hindered by increased tracking load and distraction.
Publisher: Informa UK Limited
Date: 18-06-2018
DOI: 10.1080/02699052.2018.1483030
Abstract: To conduct a review of literature and quantify the effect that traumatic brain injury (TBI) has on oculomotor functions (OM). A systematic review and meta-analysis was conducted from papers that objectively measured saccades and smooth-pursuit eye movements in mild and severe TBI. The overall impact of TBI on OM functions was moderate and significant with an effect size of 0.42 from 181 OM case-control comparisons. The heterogeneity, determined using the random effect model, was found to be significant (Q (180) = 367, p < 0.0001, I TBI often results in long-standing OM deficits. Experimental measures of OM assessment reflect neural integrity and may provide a sensitive and objective biomarker to detect OM deficits following TBI.
Publisher: Elsevier BV
Date: 05-2014
DOI: 10.1016/J.JNEUMETH.2014.02.012
Abstract: Current methods to measure eye-hand coordination (EHC) have been widely applied in research and practical fields. However, some aspects of the methods, such as subjectivity, high price, portability, and high appraisal contribute to difficulties in EHC testing. The test was developed on an Apple iPad(®) and involves tracing up to 13 shapes with a stylus pen. The time taken to complete each trace and the spatial accuracy of the tracing is automatically recorded. The difficulty level for each shape was evaluated theoretically based on the complexity and length of outline. Ten adults aged 31.5±7.8 years and five children aged 9.4±1.1 years with normal vision participated. In adults, the time taken to trace and number of errors significantly decreased from the first to the second attempt (p<0.05) but not thereafter, suggesting a learning effect with repeatability after a practice attempt. Time taken and number of errors in children were both higher in monocular than binocular viewing conditions (p=0.02 and p<0.01, respectively) while adults' performance was similar in both viewing conditions. Existing EHC tests are subjective in clinics and require higher skills and cost in research, and measure gross EHC. This novel test has been developed to address some of the limitations. The test is engaging for children and adults and is an objective method with potential for the assessment of fine EHC, suited to clinic-based and research use in ophthalmic or brain trauma settings, and in developmental disorders.
Publisher: SAGE Publications
Date: 16-04-2013
Abstract: Many treatments for anxiety utilize associative learning theory and involve mental imagery components. However, the roles associative learning and imagery play in anxiety disorders and their treatments are still largely unknown. Here we show that voluntary mental imagery can undergo associative learning in the same manner as normal sensory perception. After conditioning voluntary mental images with emotion-evoking stimuli, perceptual stimuli of the same content were found to produce the associated emotional response—indicating generalization from imagery to perception. This associative learning with imagery was found to be orientation selective and could not be accounted for by alternative, non-imagery-based interpretations of the data. These results support pictorial theories of mental imagery by indicating the interchangeability of imagery and perception in associative learning and demonstrate that voluntary mental images can drive associative learning, providing a mechanistic account of clinical practice involving mental imagery.
Publisher: Wiley
Date: 25-03-2023
DOI: 10.1111/OPO.13129
Abstract: To determine whether there are quantifiable structural or functional differences that can distinguish between high‐tension glaucoma (HTG intraocular pressure [IOP] 21 mm Hg) and low‐tension glaucoma (LTG IOP ≤ 21 mm Hg) at diagnosis. This was a retrospective, cross‐sectional study. Clinical results of one eye from 90 newly diagnosed HTG and 319 newly diagnosed LTG patients (117 with very‐low‐tension glaucoma [vLTG ≤15 mm Hg] and 202 with middling LTG [mLTG mm Hg, ≤21 mm Hg]) were extracted, which included relevant demographic covariates of glaucoma, quantitative optical coherence tomography (including the optic nerve head, retinal nerve fibre layer and ganglion cell‐inner plexiform layer) measurements and standard automated perimetry global metrics. We used binary logistic regression analysis to identify statistically significant clinical parameters distinguishing between phenotypic groups for inclusion in principal component (PC) (factor) analysis (PCA). The separability between each centroid for each cohort was calculated using the Euclidean distance ( d ( x , y )). The binary logistic regression comparing HTG and all LTG identified eight statistically significant clinical parameters. Subsequent PCA results included three PCs with an eigenvalue . PCs 1 and 2 accounted for 21.2% and 20.2% of the model, respectively, with a d( x , y ) = 0.468, indicating low separability between HTG and LTG. The analysis comparing vLTG, mLTG and HTG identified 15 significant clinical parameters, which were subsequently grouped into five PCs. PCs 1 and 2 accounted for 24.1% and 17.8%, respectively. The largest separation was observed between vLTG and HTG (d( x , y ) = 0.581), followed by vLTG and mLTG (d( x , y ) = 0.435) and lastly mLTG and HTG (d( x , y ) = 0.210). Conventional quantitative structural or functional parameters could not distinguish between pressure‐defined glaucoma phenotypes at the point of diagnosis and are therefore not contributory to separating cohorts. The overlap in findings highlights the heterogeneity of the primary open‐angle glaucoma clinical presentations among pressure‐defined groups at the cohort level.
Publisher: Public Library of Science (PLoS)
Date: 05-2015
Publisher: Wiley
Date: 17-02-2017
DOI: 10.1111/OPO.12355
Abstract: Goldmann size V ( GV ) test stimuli are less variable with a greater dynamic range and have been proposed for measuring contrast sensitivity instead of size III ( GIII ). Since GIII and GV operate within partial summation, we hypothesise that actual GV ( aGV ) thresholds could predict GIII ( pGIII ) thresholds, facilitating comparisons between actual GIII ( aGIII ) thresholds with pGIII thresholds derived from smaller GV variances. We test the suitability of GV for detecting visual field ( VF ) loss in patients with early glaucoma, and examine eccentricity‐dependent effects of number and depth of defects. We also hypothesise that stimuli operating within complete spatial summation (‘spatially equated stimuli’) would detect more and deeper defects. Sixty normal subjects and 20 glaucoma patients underwent VF testing on the Humphrey Field Analyzer using GI ‐V sized stimuli on the 30‐2 test grid in full threshold mode. Point‐wise partial summation slope values were generated from GI ‐V thresholds, and we subsequently derived pGIII thresholds using aGV . Difference plots between actual GIII ( aGIII ) and pGIII thresholds were used to compare the amount of discordance. In glaucoma patients, the number of ‘events’ (points below the 95% lower limit of normal), defect depth and global indices were compared between stimuli. 90.5% of pGIII and aGIII points were within ±3 dB of each other in normal subjects. In the glaucoma cohort, there was less concordance (63.2% within ±3 dB ), decreasing with increasing eccentricity. GIII found more defects compared to GV ‐derived thresholds, but only at outermost test locations. Greater defect depth was found using aGIII compared to aGV and pGIII , which increased with eccentricity. Global indices revealed more severe loss when using GIII compared to GV . Spatially equated stimuli detected the greatest number of ‘events’ and largest defect depth. Whilst GV may be used to reliably predict GIII values in normal subjects, there was less concordance in glaucoma patients. Similarities in ‘event’ detection and defect depth in the central VF were consistent with the fact that GIII and GV operate within partial summation in this region. Eccentricity‐dependent effects in ‘events’ and defect depth were congruent with changes in spatial summation across the VF and the increase in critical area with disease. The spatially equated test stimuli showed the greatest number of defective locations and larger sensitivity loss.
Publisher: Elsevier BV
Date: 12-2019
Publisher: Frontiers Media SA
Date: 10-07-2019
Publisher: Springer Science and Business Media LLC
Date: 26-02-2001
Abstract: The human visual system contains a functional sub-system that is specialized to extract image motion. The sensitivities of neurons change as one moves higher in the pathway. Initially cells collect responses from small retinal areas but later those local signals are combined to extract global motion either frontoparallel or radial motion relative to the center of the visual field. This sequence of processing is conducted in parallel by pathways sensitive to the motion of either the first- or second-order luminance statistics of the image. Previously it had been shown that these two pathways were independent at the level at which local motion signals and frontoparallel global motion signals are extracted. In this study independence is tested during the extraction of radial global motion a process strongly associated with cortical area MST (or V6) and the next logical level in the motion pathway. We find that the two pathways do provide independent estimates of radial motion and are, therefore, independent at all levels of the motion pathway that have been tested to date.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 12-01-2015
DOI: 10.1167/15.1.6
Abstract: In the present study, we measured the extent of spatial summation in the detection of image contrast within the central 40° visual field. Contrast detection thresholds (in 28 observers) were measured for a spot of light of 10 different sizes [area: 0.03-1.92(°)(2)] at different retinal meridians (0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°) and eccentricities (0°, 5°, 10°, 15°, and 20°). Contrast detection thresholds were significantly affected by the size of the stimulus with sensitivity improving with stimulus size consistent with Ricco's law. Summation curves were similar across different spatial meridians, but the extent of spatial summation increased with retinal eccentricity consistent with previous reports. The size of the stimulus was also shown to affect contrast detection thresholds in the periphery. In particular, contrast detection thresholds decreased more rapidly with increasing eccentricity for a smaller target than a larger one. This difference in performance is accounted for by the accompanying change in Ac with eccentricity. In Experiment 2, we show that spatial uncertainty affected contrast detection, particularly at eccentric locations greater than 5°, such that cueing the location of the stimulus improved contrast thresholds. Spatial uncertainty improved overall performance but did not affect the estimates of the critical areas of summation. The results of the present study indicate that, due to spatial summation, detection performance is highly dependent on the size of the stimulus, its eccentric location, and spatial uncertainty. Future perimetric methodologies must consider these factors to improve detection sensitivity.
Publisher: Frontiers Media SA
Date: 13-03-2015
Publisher: Elsevier BV
Date: 2007
DOI: 10.1016/J.VISRES.2006.09.004
Abstract: Motion signals contained within a stationary object projected on the fronto-parallel plane shift the object's apparent spatial position in the direction of the motion [see De Valois, R. L., & De Valois, K. K. (1991). Vernier acuity with stationary moving Gabors. Vision Research, 31(9), 1619-1626]. We report an analogous apparent position shift of three-dimensional objects that contain local elements that move in depth. Our stimulus was a transparent three-dimensional cylinder defined by 150 limited-lifetime dots, oriented such that it was end on and its tangent plane was circular. Dots moved in depth by changes in their binocular disparities. In the first experiment, observers judged the positions of the near and far ends of the cylinder, by moving marker lines in depth, for different dot speeds. The results showed that when dots moved towards the observer, the perceived location of the two ends of the cylinder appeared closer in depth. When dots moved away from the observer, the opposite effect was produced. Additionally, the amount of apparent position shift produced was dependent on dot speed, with faster speeds producing larger positional offsets. However, we found in the second experiment that when the cylinder contained randomly moving dots, or when the cylinder contained equal amounts of dots moving towards and away from the observer, positional shifts were very much reduced, or abolished. Our findings suggest that motion signals can induce a misperception of position in depth that is similar manner to that produced by motion within an object in the two-dimensional image plane.
Publisher: Informa UK Limited
Date: 07-2018
DOI: 10.1111/CXO.12657
Abstract: Despite evidence that amblyopia can often be treated by optical treatment alone, many practitioners still do not use an optical-correction-only phase in amblyopia treatment and some investigators omit this important step in their research. This paper aims to systematically review the evidence for the optical treatment of strabismic, refractive and combined-mechanism amblyopia and to quantify the evidence via a meta-analysis. A search of online databases MEDLINE, EMBASE, PsycInfo, the Cochrane Library, and bibliographies of review papers, along with subsequent personal communication, resulted in 29 papers that met our inclusion criteria, with 20 providing sufficient data for the calculation of effect sizes. A meta-analysis was performed to determine effect sizes and the heterogeneity thereof. Meta-regression was used to evaluate the contribution of the possible moderating factors of age, duration of optical correction, and initial visual acuity to the heterogeneity of the studies. In addition, effect sizes were analysed in subgroups based on amblyopia aetiology, that is refractive or strabismic or combined, and also in the fellow eyes. No evidence of publication bias in the included studies was found using a Galbraith plot. Optical treatment of amblyopia resulted in a large positive effect size of 1.07 (±0.49, 95 per cent confidence limits) on visual acuity, although the heterogeneity was significant (Q = 597.05, I Effect sizes were always moderate to large, whether participants were younger or older children, or whether the aetiology was refractive or strabismic. Thus, optical treatment of amblyopia should be considered prior to other treatment in those with refractive error. Improved acuity before initiating other treatment would presumably make occlusion or penalisation less onerous and may improve compliance with further treatment.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 07-05-2014
DOI: 10.1167/14.5.5
Abstract: Previous research has shown that adding lateral viewpoint changes to visual displays simulating self-motion in depth can increase the strength of linear vection. We performed experiments to determine whether these vection increases are caused by reduced adaptation to retinal motion, rather than increased motion parallax in the visual display. In Experiment 1, we added increasing litudes of sinusoidal angular viewpoint oscillation around the viewing axis (up to 94.2°/s) to radial flow simulating self-motion in depth. We found that angular viewpoint oscillation systematically reduced the onset latencies and increased the overall strength of vection in depth, compared with pure radial flow. In Experiment 2, we compared vection strength between radial flow displays with either added angular oscillation or continuous spiral rotation of equivalent peak velocity around the viewing axis (62.8°/s), and found that angular viewpoint oscillation generated the strongest vection. In Experiment 3, we found that pure radial flow with or without continuous spiral rotation produced radial motion aftereffects that lasted longer than that produced by radial flow with angular viewpoint oscillation. These findings support the view that the way viewpoint oscillation increases vection does not critically depend on motion parallax, but rather, on a changing pattern of retinal motion that serves to reduce visual adaptation and sustain sensitivity to optic flow.
Publisher: Elsevier BV
Date: 02-2006
DOI: 10.1016/J.VISRES.2005.05.002
Abstract: The extent to which local speeds at different depths are averaged to determine global speed was determined using a version of the Global Dot Motion (GDM) stimulus. Judgments of the apparent speed of fast moving dots (4.05-10.53 deg/s) in the presence of slow moving dots (4.05 deg/s) were measured using GDM stimuli which simulated radially expanding motion, and which confined slow and fast speed dots exclusively to alternating wedge shaped sectors. The presence of slow moving dots in the stimulus reduced the apparent speed of high-speed dots in a manner consistent with speed averaging. However with increases in depth, produced by a difference in binocular disparity between dots in alternating sectors, speed averaging became less effective, and the relationship between speed and disparity resembled a tuning function. We discuss our results in light of research that clarifies the functional properties of global motion mechanisms in the primate cortex.
Start Date: 01-2011
End Date: 08-2015
Amount: $110,000.00
Funder: Australian Research Council
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