ORCID Profile
0000-0002-6976-4645
Current Organisations
The University of Auckland
,
Asia University
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 11-2008
DOI: 10.1167/IOVS.08-1828
Abstract: To determine whether the distribution of naturally occurring myopia in Labrador Retrievers has a genetic component. Pedigree records of a large canine family were analyzed. Pure Labrador Retrievers, 1 to 8 years of age, free of ocular disease, and available for testing were studied. Refractive error was measured by cycloplegic retinoscopy in both eyes. The family included mating loops, and so an expectation maximization (EM) algorithm (multivar program, MORGAN software University of Washington, Seattle) was used to calculate log likelihoods of refractive error with environmental and additive genetic models. The fixed effects of coat color, sex, and litter size were also tested. In our s le of 116 dogs from this one family, the average spherical equivalent refraction (SER) was -0.41 D (range, -5.38 to +1.65 D, mean of both eyes, n = 116): 31% were myopic (SER or= +1.00 D). The significance of fixed and genetic effects was tested by comparing the full model (including genetic and all fixed effects) to models with one effect removed. Litter size and additive genetic effects were significant (P = 0.0013 and P = 0.000093, respectively), whereas sex and coat color were not. The overall variance in SER was accounted for approximately equally by additive genetic variance and residual/environmental variance. Narrow sense heritability of SER was 0.506. The distribution of refractive error within this family of Labrador Retrievers had a significant genetic component, but was also influenced by other factors (litter size, and undefined residual/environmental effects). The dog represents a unique model for the study of naturally occurring, heritable, high-prevalence, low-degree myopia.
Publisher: Informa UK Limited
Date: 27-03-2019
Publisher: Wiley
Date: 05-2013
DOI: 10.1111/OPO.12043
Publisher: American Physiological Society
Date: 12-1981
DOI: 10.1152/JN.1981.46.6.1192
Abstract: Potassium (K⁺) is an essential macronutrient of living cells and is the most abundant cation in the cytosol. K⁺ plays a role in several physiological processes that support plant growth and development. However, soil K⁺ availability is very low and variable, which leads to severe reductions in plant growth and yield. Various K⁺ shortage-activated signaling cascades exist. Among these, calcium signaling is the most important signaling system within plant cells. This review is focused on the possible roles of calcium signaling in plant responses to low-K⁺ stress. In plants, intracellular calcium levels are first altered in response to K⁺ deficiency, resulting in calcium signatures that exhibit temporal and spatial features. In addition, calcium channels located within the root epidermis and root hair zone can then be activated by hyperpolarization of plasma membrane (PM) in response to low-K⁺ stress. Afterward, calcium sensors, including calmodulin (CaM), CaM-like protein (CML), calcium-dependent protein kinase (CDPK), and calcineurin B-like protein (CBL), can act in the sensing of K⁺ deprivation. In particular, the important components regarding CBL/CBL-interacting protein kinase (CBL/CIPK) complexes-involved in plant responses to K⁺ deficiency are also discussed.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 13-01-2017
Abstract: The purpose of this study was to determine the relative roles of the sympathetic (SNS) and parasympathetic nervous system (PNS) in pupillary hippus. We used a paired-eye control study design with three cohorts receiving either 1.0% tropicamide (PNS antagonist) in light (TL), 1.0% tropicamide in dark (TD), or 10% phenylephrine (SNS) in light (PL), n = 12 in each. Each subject received one drop to the randomly determined treatment eye, while the other eye served as control. Bilateral measures of pupil size and dynamics were made over 2.6 seconds using an infrared eye-tracker s ling at 500 Hz. Measures were taken at baseline, then every 5 minutes for 40 minutes. Hippus, analyzed in both time and frequency domains, was compared between eyes and cohorts. Pupillary hippus with a distinct dominant frequency was present in all measures at baseline (mean: 0.62 Hz, SD: 0.213 Hz), and that frequency did not change in any group (P = 0.971). Hippus magnitude (treatment eye relative to control eye) decreased in the TL (-72.8 ± 4.7%, P < 0.0001) and TD (-71.3 ± 2.6%, P < 0.0001) groups, but did not change in the PL (+5.4 ± 13.7%, P = 0.173) group, despite PL pupils dilating to a proportion similar to TD. Pupillary hippus can be extinguished by antagonizing the PNS, whereas agonizing the SNS dilates the pupil without affecting hippus. This suggests that hippus originates from central PNS activity, and not from SNS activity, or oscillations in the balance between PNS and SNS at the pupil.
Publisher: Elsevier BV
Date: 06-2011
DOI: 10.1016/J.OPHTHA.2010.10.035
Abstract: To test the efficacy of an experimental Dual-Focus (DF) soft contact lens in reducing myopia progression. Prospective, randomized, paired-eye control, investigator-masked trial with cross-over. Forty children, 11-14 years old, with mean spherical equivalent refraction (SER) of -2.71 ± 1.10 diopters (D). Dual-Focus lenses had a central zone that corrected refractive error and concentric treatment zones that created 2.00 D of simultaneous myopic retinal defocus during distance and near viewing. Control was a single vision distance (SVD) lens with the same parameters but without treatment zones. Children wore a DF lens in 1 randomly assigned eye and an SVD lens in the fellow eye for 10 months (period 1). Lens assignment was then swapped between eyes, and lenses were worn for a further 10 months (period 2). Primary outcome was change in SER measured by cycloplegic autorefraction over 10 months. Secondary outcome was a change in axial eye length (AXL) measured by partial coherence interferometry over 10 months. Accommodation wearing DF lenses was assessed using an open-field autorefractor. In period 1, the mean change in SER with DF lenses (-0.44 ± 0.33 D) was less than with SVD lenses (-0.69 ± 0.38 D P < 0.001) mean increase in AXL was also less with DF lenses (0.11 ± 0.09 mm) than with SVD lenses (0.22 ± 0.10 mm P < 0.001). In 70% of the children, myopia progression was reduced by 30% or more in the eye wearing the DF lens relative to that wearing the SVD lens. Similar reductions in myopia progression and axial eye elongation were also observed with DF lens wear during period 2. Visual acuity and contrast sensitivity with DF lenses were not significantly different than with SVD lenses. Accommodation to a target at 40 cm was driven through the central distance-correction zone of the DF lens. Dual-Focus lenses provided normal acuity and contrast sensitivity and allowed accommodation to near targets. Myopia progression and eye elongation were reduced significantly in eyes wearing DF lenses. The data suggest that sustained myopic defocus, even when presented to the retina simultaneously with a clear image, can act to slow myopia progression without compromising visual function. Proprietary or commercial disclosure may be found after the references.
Publisher: Society for Neuroscience
Date: 06-1993
DOI: 10.1523/JNEUROSCI.13-06-02332.1993
Abstract: The roughness of standardized surfaces (embossed dot arrays or gratings) was compared by scanning them with the little finger of either hand while the ulnar nerve was cooled unilaterally at the elbow both hands remained warm. Across-hand comparison of roughness showed that a given surface felt smoother on the cooled side. When the surfaces were adjusted to feel equally rough, that on the cooled side would normally have felt appreciably rougher. The effect of the nerve cooling on axonal conduction was monitored during the psychophysical experiments by stimulating the ulnar nerve above the cooled region and recording the EMG of an ulnar-innervated hand muscle. During cooling, large myelinated axons remained unblocked, but prolongation of their absolute refractory period to 5–10 msec left them unable to transmit trains of impulses at high frequencies (Wedensky inhibition). By varying the length of nerve cooled and the cooling temperature, it was shown that the perceptual effects were not due to an increase in the normal temporal dispersion of impulses transmitted by different-sized afferents. The effect of increasing the absolute refractory period on the signals from the various types of cutaneous afferent was modeled mathematically, using earlier human single-fiber responses to dot arrays. It is concluded that the reduction of perceived roughness with nerve cooling is due to Wedensky inhibition, and that the percept of roughness is related to the local contrast in the afferent spatiotemporal image.
Publisher: Society for Neuroscience
Date: 03-1992
DOI: 10.1523/JNEUROSCI.12-03-00827.1992
Abstract: The spatial resolving capacities of the four classes of mechanoreceptive afferents innervating human fingerpad skin were investigated to determine which class sets the limit of tactile spatial resolution for scanning stimuli. The stimulus consisted of an array of embossed dots (0.7 mm diameter, 0.5 mm high) arranged in a tetragonal pattern with dot spacing decreasing linearly from 6.4 mm at one end of the array to 0.87 mm at the other. The pattern was wrapped around a drum and repeatedly scanned across the receptive field of single afferents by continuously rotating the drum. Responses to many closely spaced scans were obtained by imposing a lateral shift of the pattern between each revolution. Impulses were recorded microneurographically. Responses were plotted in raster form to produce a neural image of the pattern. Responses of rapidly and slowly adapting type I (FAI and SAI) afferents resolved dots down to a spacing of about 1.5 mm. Responses of type II (FAII and SAII) afferents resolved dots down to a spacing of about 3.5 mm. Variation in scanning speed (range, 20–90 mm/sec) and contact force (range, 0.4–1.0 N) had minimal effects on spatial resolution of all afferents. The response clusters associated with in idual widely spaced dots were used to investigate receptive field structure. FAI and SAI fields (mean areas, 6.1 and 4.8 mm2, respectively) each contained several zones of maximal sensitivity. FAI fields had five to eight such zones, whereas SAI fields had three to five such zones. As dot spacing decreased, neighboring dots interacted to affect the responses associated with the in idual zones within a field. Initially, one or more zones were deactivated, effectively reducing receptive field size and allowing representation of finer spatial detail than would be predicted from the overall area of the receptive field. At very close dot spacings responses were only obtained when more than one sensitive zone within a field were simultaneously activated by different dots.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 07-2001
DOI: 10.1097/00003226-200107000-00009
Abstract: To quantify the tear spreading velocity and stabilization time after blinks in healthy patients. Video recordings (magnification, x130) were made of the movements of naturally occurring particles in the tear film while patients blinked naturally. After each blink, tear spreading velocity was computed every 40 milliseconds from particle displacements determined from a frame-by-frame analysis of the records. After a blink, tears moved rapidly upward over the cornea. Forty milliseconds after passage of the lid, the velocity was 7.34 +/- 2.73 mm/s (mean +/- standard deviation, n = 20). The time to tear stabilization (i.e., zero velocity) was 1.05 +/- 0.30 seconds. The decay of spreading velocity with time was well described by a logarithmic function for all in idual patient data (R2 range, 0.88-0.99 n = 20). We have shown that initial velocity and stabilization time are independent descriptors of tear spreading. Meibomian gland expression markedly reduced initial velocity leaving a normal stabilization time, whereas inhalation of an irritant reduced stabilization time leaving a normal initial velocity. In a patient with Sjögren syndrome, punctal plugs rapidly restored initial velocity and stabilization time from near zero values to normal values. We provide normal values for two descriptors of tear spreading, namely initial velocity and time to stabilization. These values can be modified by manipulations that alter tear constituents. Consequently, these descriptors may provide a basis for quantitative, noninvasive tear assessment.
Publisher: Wiley
Date: 13-05-2013
DOI: 10.1111/OPO.12069
Abstract: In children, time spent outdoors has a protective effect against myopia development. In animal models, bright light reduces the development of experimental myopia. This study investigates how an increase in daily light exposure, presented either continuously during the day or periodically at different times of day, influences the development of experimental myopia in the chick. Myopia was induced in Cobb Chicks (Gallus domesticus) by monocular deprivation (MD) of form vision with a translucent diffuser for 3 days (from 4 days of age) under a 12:12 light: dark cycle. MD control chicks were exposed to constant 300 lux (n = 11) during the light period. MD treatment groups received either constant 2000 lux (n = 11) during the light period or 300 lux for 10 h with a 2 h period of bright light (10 000 lux), either in the morning (n = 10), midday (n = 10) or evening (n = 10), giving the same total daily light exposure as the 2000 lux group. After 3 days of MD, refractive status, corneal curvature and axial eye dimensions were measured for all eyes under anaesthesia. Myopia in the constant 2000 lux group (-4.94 ± 1.21 D) was significantly less than in the 300 lux control group (-9.73 ± 0.96 D p = 0.022). However, compared to the 300 lux control group, 2 h periods of 10 000 lux did not produce significant effects on refraction when presented either in the morning (-9.98 ± 0.85 p = 1.00), midday (-8.00 ± 1.26 p = 0.80), or evening (-13.14 ± 1.16 D p = 0.20), although significantly less myopia was induced in the midday group compared to the evening group (p = 0.018). Orthogonal regression showed that myopia development was matched by changes in vitreous chamber depth (R(2) = 0.69 p < 0.0001). In chicks, an increase in daily light exposure continuously during the day is more effective at inhibiting myopia than adding an equivalent dose within a 2 h period of bright light. A weak time-of-day effect also appears to be present in the response to bright light exposure. Our results suggest that future light-based myopia therapies in humans may be more effective if light levels are increased over the whole day, rather than through short periods of bright light exposure.
Publisher: Springer Science and Business Media LLC
Date: 23-11-2017
DOI: 10.1038/S41598-017-16320-6
Abstract: Virtual Reality (VR) headsets create immersion by displaying images on screens placed very close to the eyes, which are viewed through high powered lenses. Here we investigate whether this viewing arrangement alters the binocular status of the eyes, and whether it is likely to provide a stimulus for myopia development. We compared binocular status after 40-minute trials in indoor and outdoor environments, in both real and virtual worlds. We also measured the change in thickness of the ocular choroid, to assess the likely presence of signals for ocular growth and myopia development. We found that changes in binocular posture at distance and near, gaze stability, litude of accommodation and stereopsis were not different after exposure to each of the 4 environments. Thus, we found no evidence that the VR optical arrangement had an adverse effect on the binocular status of the eyes in the short term. Choroidal thickness did not change after either real world trial, but there was a significant thickening (≈10 microns) after each VR trial (p 0.001). The choroidal thickening which we observed suggest that a VR headset may not be a myopiagenic stimulus, despite the very close viewing distances involved.
Publisher: American Physiological Society
Date: 12-1981
Publisher: Wiley
Date: 25-09-2018
DOI: 10.1002/JMRI.26323
Abstract: Quantifying blood perfusion in ocular tissues is challenging, partly because the majority of the blood is carried by the choroid, which is difficult to visualize because it is located between the retina and sclera. To evaluate the intra- and interday repeatability of MRI measures of chorio-retinal blood perfusion. Prospective, cross-sectional, observational study. Twenty young healthy adults (six male, age: 25 ± 5 years) scanned twice within a single session repeated at the same time of day on 2 days. Arterial spin labeling (ASL) MRI at 3.0T using pseudocontinuous ASL (PCASL) labeling scheme and a 3D turbo-gradient-spin-echo (TGSE) acquisition, including axial T Region-of-interest analysis for assessment of chorio-retinal blood perfusion. Intra- and interday repeatability of measures analyzed using intraclass correlation coefficients (ICC), Pearson's correlation analysis, paired t-tests, and Bland-Altman plots. The mean chorio-retinal perfusion was 77.86 (standard deviation [SD] = 29.80) ml/100ml/min. Perfusion measurements correlated strongly within a single session (r = 0.95, 95% confidence interval [CI] [0.880-0.980], P < 0.001) and between the two sessions based on a single run (r = 0.80 [0.582-0.913], P < 0.001), and two runs (r = 0.80 [0.479-0.918], P 0.05). Quantitative ASL-MRI measurements of chorio-retinal blood perfusion showed high intra- and interday repeatability. The ASL-MRI technique provides reliable measures of chorio-retinal perfusion in vivo. 1 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019 :966-974.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 03-2004
DOI: 10.1167/IOVS.03-0732
Abstract: To investigate the change in axial eye dimensions resulting from stretching the sclera by acute elevation of intraocular pressure (IOP). IOP was increased to 100 mm Hg for 1 hour through an intravitreal cannula, while ocular component dimensions were monitored every 10 minutes with A-scan ultrasound in anesthetized animals (10 chicks and 10 tree shrews). In addition, immunocytochemical detection of alpha-smooth muscle actin (alpha-SMA) using a monoclonal antibody was conducted in the sclera of the tree shrew and the chick. In both species, axial eye length immediately and significantly (P < 0.0001) increased on elevation of IOP to 100 mm Hg: chick to 103.9%, tree shrew to 101.2% (mean percentage of original measured at 15 mm Hg). After 1 hour of maintained pressure, chick eyes showed a further significant increase in axial length (to 108.6%), but axial length of tree shrew eyes decreased (to 100.3%) to the point that it was not significantly different from the original value at 15 mm Hg. Immunocytochemical studies of age-matched tissue demonstrated the presence of alpha-SMA-containing fibroblasts (myofibroblasts) within tree shrew but not chick sclera. Elevation of IOP caused axial elongation of chick eyes, but a consistent reduction in axial length of tree shrew eyes. The presence of myofibroblasts, demonstrated in tree shrew but not chick sclera, suggests that the reduction in axial length of tree shrew eyes may have been caused by activation of a contractile mechanism involving scleral myofibroblasts. Such a mechanism may play a role in the regulation of eye size and refractive development.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 09-2016
DOI: 10.1097/OPX.0000000000000957
Abstract: A number of optical methods for slowing myopia progression have been tested and are now available. However, data on real-world use in clinical use is scarce. Here, we present a review of the clinical outcomes for patients attending a specialist myopia control clinic at The University of Auckland Optometry School, NZ. We report a comparative case series of 110 patients (aged 4–33 years, mean: 12.13 ± 4.58 years, 62% female) who attended the clinic between 2010 and 2014. Fifty-six were prescribed orthokeratology, 32 dual focus soft contact lenses, and 22 received advice only. Initial myopia, vitreous and axial eye length, previous myopia progression, age, number of myopic parents, and gender were not significantly different between orthokeratology and dual focus soft contact lens groups. Mean follow-up time for the orthokeratology and dual focus lens groups was the same (orthokeratology: 1.30 ± 0.88 years dual focus lens: 1.33 ± 0.80 years (p = 0.989)). There was a significant reduction in the annualized myopia progression in both groups (orthokeratology: −1.17 ± 0.55 to −0.09 ± 017 D/yr, p 0.001 dual focus soft contact lens: −1.15 ± 0.46 to −0.10 ± 0.23 D/yr, p 0.001). There was no difference between orthokeratology and dual focus lens treatment efficacy (p = 0.763), nor in axial or vitreous chamber length changes after treatment (p = 0.184). One adverse event was reported over the 4-year period. Both orthokeratology and dual focus soft contact lenses are effective strategies for targeting myopia progression in the clinic. We saw no significant difference in the efficacy of the two methods in this regard, and so we believe there are very few barriers for any contact lens practitioner to be actively promoting myopia control treatment to at-risk patients.
Publisher: Springer Science and Business Media LLC
Date: 24-11-2020
Publisher: Informa UK Limited
Date: 03-2020
DOI: 10.1111/CXO.12967
Publisher: Elsevier BV
Date: 09-2015
DOI: 10.1016/J.CUB.2015.07.073
Abstract: Eyes with refractive error have reduced visual acuity and are rarely found in the wild. Vertebrate eyes possess a visually guided emmetropisation process within the retina which detects the sign of defocus, and regulates eye growth to align the retina at the focal plane of the eye's optical components to avoid the development of refractive error, such as myopia, an increasing problem in humans. However, the vertebrate retina is complex, and it is not known which of the many classes of retinal neurons are involved. We investigated whether the camera-type eye of an invertebrate, the squid, displays visually guided emmetropisation, despite squid eyes having a simple photoreceptor-only retina. We exploited inherent longitudinal chromatic aberration (LCA) to create disparate focal lengths within squid eyes. We found that squid raised under orange light had proportionately longer eyes and more myopic refractions than those raised under blue light, and when switched between wavelengths, eye size and refractive status changed appropriately within a few days. This demonstrates that squid eye growth is visually guided, and suggests that the complex retina seen in vertebrates may not be required for emmetropisation.
Publisher: Acoustical Society of America (ASA)
Date: 1985
DOI: 10.1121/1.392262
Abstract: The neural mechanisms subserving the sense of touch set the limits for the acquisition of information regarding the spatial and temporal characteristics of stimuli impinging on the skin surface. The results of three different psychophysical experiments imply that the skin of the finger pad can resolve the elements of a stimulus separated by 0.9 mm when the stimulus is applied to the skin and held stationary. This resolution limit is only slightly improved (to about 0.7 mm) when movement between the stimulus and skin is allowed. Single-unit recordings from the three classes of primary mechanoreceptive afferents in anesthetized monkeys shows that only one class, the slowly adapting afferents, resolve spatial detail of stationary stimuli near the resolution limit. In addition, slow adaptors appear to resolve moving stimuli (e.g., Braille-dot patterns) more effectively than do the other two classes. However, these observations do not explain the extraordinary capacity of the finger-pad skin for discriminating between fine textures. Neurophysiological evidence suggests that information about such textures (i.e., surfaces with spatial details below the resolution limit) may be conveyed by a code based on the relative engagement of the three receptor populations.
Publisher: Society for Neuroscience
Date: 12-1990
DOI: 10.1523/JNEUROSCI.10-12-03823.1990
Abstract: Hypothetical neural codes underlying the sensation of tactile roughness were investigated in a combined psychophysical and neurophysiological study. The stimulus set consisted of plastic surfaces embossed with dot arrays of varying dot diameter and center-to-center spacing. Human subjects explored each surface with the pad of the index finger and reported their subjective sense of roughness magnitude. The same surfaces were scanned across the receptive fields of cutaneous mechanoreceptive afferents in monkeys while recording the evoked action potentials. Hypothetical neural codes for roughness magnitude were computed from the neural response patterns and tested for their ability to account for the psychophysical data. The psychophysical results showed that subjective roughness magnitude is an inverted U-shaped function of dot spacing that peaks near 3.0 mm spacing, and that increased dot diameter produces decreased roughness sensations at all dot spacings. Hypothetical neural codes that do not bear a consistent relationship to roughness magnitude across all of these stimulus conditions can be rejected as the code for roughness. Four types of neural codes were considered. They were based on (1) mean firing rate, (2) general variation in firing rate, (3) short-term temporal variation in firing rate, and (4) local spatial variation in firing rate. Mean firing rate failed to explain the psychophysical results: surfaces that evoked the same firing rate often evoked very different roughness judgments. In contrast, neural codes based on firing-rate variation, especially in slowly adapting afferents, account for the psychophysical results.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 25-10-2018
Abstract: To investigate changes in subfoveal choroidal thickness (SFCT) induced by retinal defocus in presbyopic adults. Thirty-seven healthy presbyopic subjects (age 57.74 ± 4.06 years) with low refractive errors (+0.08 ± 1.09 Diopters [D]) viewed a distant target (video movie at 6 m) for 60 minutes on two occasions while SFCT was monitored with optical coherence tomography every 20 minutes. On each occasion, both eyes were optimally corrected for distance: one eye acted as control, while the other (experimental) eye viewed through an additional ophthalmic lens: a +2.00 D lens imposing myopic defocus on one occasion and a -2.00 D lens imposing hyperopic defocus on the other occasion. Baseline SFCT was not different between experimental and control eyes (226 ± 72 μm vs. 232 ± 75 μm P = 0.28). Myopic defocus caused a significant (P < 0.001) increase in SFCT in the defocused eye by 20 minutes (and +10 ± 5-μm increase at 60 minutes: P < 0.001), while hyperopic defocus caused a significant decrease in SFCT by 20 minutes (and -10 ± 5-μm decrease at 60 minutes: P < 0.001) with no change in control eyes. In presbyopic subjects, imposed myopic retinal defocus caused thickening of SFCT, while hyperopic defocus caused thinning of SFCT. This implies that uncorrected presbyopia, which is associated with hyperopic retinal defocus for near objects and which is highly prevalent in the developing world, would likely be associated with choroidal thinning and possibly reduced choroidal blood flow with prolonged periods in a near visual environment.
Publisher: Wiley
Date: 15-05-2023
DOI: 10.1111/OPO.13163
Abstract: Dual‐focus contact lenses create two focal planes, one providing a clear retinal image while the other imposes myopic defocus on the retina to slow myopia progression. This study used global‐flash multifocal electroretinogram (gmfERG) response litudes to compare central versus peripheral retinal responses under dual‐focus conditions and to assess the optimal degree of myopic defocus compared with a single‐vision control lens. Twenty participants each underwent three gmfERG trials, wearing a spectacle correction over dual‐focus contact lenses with plano central power and peripheral secondary focal powers of either +2.00D, +4.00D or a plano single‐vision lens. We compared litudes and latencies of the gmfERG direct and induced components (DC and IC) within participants, between the three different contact lens powers and at different retinal eccentricities (gmfERG ring). We observed significant differences in the gmfERG responses between the single‐vision and dual‐focus contact lenses. Overall, DC litudes peaked between zero and +2.00D secondary power, while IC litudes were maximal between +2.00D and +4.00D. Compared with the single‐vision control, the greatest increase in DC and IC litudes while wearing dual‐focus lenses occurred within the central 10° of the retina. There was no interaction effect between gmfERG ring (eccentricity) and secondary power, and no difference in the latency of the gmfERG responses between different powers. We found that dual‐focus contact lenses with a +2.00D secondary power are close to that expected to induce the greatest increase in gmfERG responses relative to a single‐vision lens. Dual‐focus lenses produced the highest DC and IC response litudes relative to a single‐vision lens in the central 10° of the retina. This suggests that dual‐focus contact lenses slow myopia progression by modifying central rather than peripheral retinal activity.
Publisher: SAGE Publications
Date: 10-1983
DOI: 10.1068/P120615
Abstract: The perceived orientation of a raised letterform indenting the skin of the finger reverses (from normal to its mirror-image) when the letter is held in contact with the finger and both are rotated through 180° about the axis of the finger. Thus, though the pattern of stimulated skin receptors remains constant, the perceived orientation of the letter reverses. On the basis of this observation it is proposed that tactual perception of object form involves assignment of a spatial coordinate system within which the patterns of skin stimulation are interpreted. In experiments in which the orientations of letters and subjects are systematically varied within the environment, the occurrence or nonoccurrence of reversal in perceived orientation of letters has been used to investigate the origin of the proposed spatial coordinate system that is, whether it is assigned with respect to the observer (egocentrically) or with respect to the environment (geocentrically). The results indicate that the assignment of coordinates is determined by both egocentric and geocentric factors. It is proposed that the reversal phenomena observed in these experiments, and in experiments of others which involve drawing characters on the skin, are consistent with Gibson's proposal that it is object form which is directly perceived, but that this involves interpretation of the patterns of skin stimulation within a framework of spatial coordinates.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 03-2012
Publisher: Wiley
Date: 12-05-2012
DOI: 10.1111/J.1475-1313.2012.00912.X
Abstract: Previous studies suggest that the refractive status of the peripheral retina can influence the development and progression of myopia. Our aim was to compare peripheral refractions in the same cohort of human eyes corrected with spectacle lenses vs soft contact lenses. Ten young adults with moderate to high myopia (-5.00 D to -8.00 D) were investigated. Open-field autorefraction was used to measure on- and off-axis refractions with the eyes in primary gaze, when uncorrected, and when corrected with spectacles and contact lenses. Measures were made every 5° out to 30° horizontally in nasal and temporal retina and analysed as power vectors (M, J(0) , and J(45)). Partial coherence interferometry measures of eye size were also made on-axis and off-axis at 10º and 20º in nasal and temporal retina. Subjects (mean age 24 range 19-29 years) had an average on-axis mean-sphere refraction of -6.33 ± 0.31 D (mean ± 1 S.E.) and an average axial eye length of 25.99 ± 0.20 mm. The average relative peripheral refraction (RPR) for all subjects across all eccentricities was hyperopic when uncorrected (+0.90 ± 0.14 D) and also when corrected with spectacles (+1.01 ± 0.13 D) but changed to a myopic RPR when corrected with contact lenses (-1.84 ± 0.61 D). There was a highly significant effect of correction on peripheral refraction (p < 0.0001). Peripheral J(0) astigmatism also became significantly more negative (less with-the-rule) on correction with contact lenses (p = 0.015), whereas J(45) astigmatism remained unchanged. On- and off- axis eye length measures indicated a relatively prolate eye shape. Correcting the on-axis refractive error in moderate to high myopia with conventional spherical spectacle lenses results in hyperopic defocus in the peripheral retina. Correcting the same eyes with conventional spherical soft contact lenses results in significant myopic defocus in the peripheral retina. These results corroborate the general findings of earlier studies and the predictions of optical modelling by others. If the refractive status of the peripheral retina does influence myopia progression, then these results suggest that myopia progression should be slower with conventional contact lens wear than with conventional spectacle wear. However, previous studies comparing myopia progression with conventional spectacles and conventional contact lenses have reported no such difference.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 10-2001
DOI: 10.1097/00006324-200110000-00009
Abstract: The validity of the Cup:Disc (C:D) ratio as a clinical measure depends on the level of agreement among observers. In this study, we investigated the effect of observer experience on interobserver and intraobserver agreement in C:D ratio estimation. Nine 3rd-year (Yr3) and nine 4th-year (Yr4) optometry students and nine optometrists (Opt), determined C:D ratios from 26 optic disc photographs viewed monoscopically and stereoscopically. Observer agreement was investigated using weighted kappa (Kw) analysis. Interobserver agreement was higher (p < 0.01) among optometrists than among 4th-year students and higher (p < 0.01) among 4th-year than among 3rd-year students (mean Kw: Opt = 0.61 Yr4 = 0.51 Yr3 = 0.39). Stereoscopic estimates of C:D ratios were higher (p < 0.0001) than monoscopic estimates, and interobserver agreement was higher (p < 0.001) when evaluating the vertical rather than the horizontal C:D ratio. Intraobserver agreement (mean Kw: Opt = 0.67 Yr4 = 0.66 Yr3 = 0.62) did not vary significantly (p = 0.78) with experience. The extent to which an observer reproducibly assesses the C:D ratio from optic disc photographs (intraobserver agreement) does not increase with experience. However, the agreement between different observers in assessing the C:D ratio (interobserver agreement) increases with experience.
Publisher: Elsevier BV
Date: 1988
DOI: 10.1016/0165-0270(88)90043-X
Abstract: A tactile stimulator is described that moves embossed or textured patterns tangentially across the skin. Patterns constructed by standard photoetching are mounted on the outer surface of a cylinder that rotates at a selected speed and is held in contact with the skin at a selected force. The stimulator operates in several modes to meet the different requirements of psychophysical and neurophysiological experiments. The features of note are (i) relatively small size and weight (ii) flexible automated control of drum contact with the skin, angular velocity, axial position, and contact force (iii) monitoring of drum angular and axial location to better than 10 micron accuracy (iv) construction with commercially available devices (v) electronic monitoring of skin contact and (vi) rapid drum changes (2 seconds) during psychophysical or neurophysiological experiments.
Publisher: Wiley
Date: 05-12-2019
DOI: 10.1111/OPO.12656
Abstract: Emmetropisation is essentially a visually guided, within‐eye process. We investigated differences in global‐flash multifocal electroretinogram (gmfERG) responses to naturally occurring differences in spherical and astigmatic defocus across the retina, which might provide a basis for guiding eye growth. Experiment 1: The gmfERG responses (direct, DC, and induced, IC, litudes and latencies) recorded simultaneously from six retinal areas (15° eccentricity, spaced at 60°, areas 3.2° 2 ) were correlated with the uncorrected retinal defocus measured at the six corresponding retinal locations in 20 adults with foveal refractive errors (−4.75 to +1.25D). No correcting lenses were used to avoid introduction of lens‐induced aberrations and magnification. Experiment 2 investigated the effect of superimposing astigmatic defocus (+2.00/−4.00D Jackson Cross Cylinder presented at four orientations) on gmfERG responses. Experiment 1: DC and IC response litudes were greater in retinal regions naturally exposed to more hyperopic spherical defocus (DC: rho = 0.26, p = 0.005 IC: rho = 0.29, p = 0.001), but response latencies were unaffected by sign or magnitude of spherical defocus (DC: p = 0.34 IC: p = 0.40). Response litudes and latencies were unaffected by astigmatic defocus. Experiment 2: Rotating the JCC axis to four different orientations had no effect on the gmfERG responses (DC litude, p = 0.39 DC latency, p = 0.10 IC litude, p = 0.51 IC latency, p = 0.64). The gmfERG responses from discrete retinal areas varied with the sign and magnitude of local spherical defocus, but we found no evidence that retinal responses were affected by astigmatic defocus. Therefore, local astigmatism is unlikely to provide cues for controlling eye growth, whereas differences in response to spherical defocus between different retinal regions could potentially provide cues for controlling eye growth in emmetropisation.
Publisher: Springer Science and Business Media LLC
Date: 27-10-2020
DOI: 10.1038/S41598-020-75342-9
Abstract: Atropine eye drops and myopic retinal defocus each slow progression of myopia (short-sight). They also cause thickening of the choroid, and it has been suggested that the thickening is a precursor for reduced eye growth and slowed myopia progression. We investigated whether choroidal thickening due to optical defocus would add to thickening due to atropine when both were applied simultaneously. Addition would suggest that combining the two clinical treatments may improve efficacy of myopia control. We studied 20 children receiving 0.3% atropine daily for myopia control, over a period of 6 months. We imposed short periods of retinal defocus (1 h of myopic or hyperopic defocus (± 2.00D)) both before, and after 1 week and 3 and 6 months of atropine treatment. Prior to atropine, myopic or hyperopic defocus caused significantly thicker or thinner choroids respectively (± 12 µm, p 0.001). After one week of atropine alone, thickness had increased (+ 21 µm SD 17 µm p 0.001), and it increased further (by + 13 µm SD 6 µm p 0.001) when exposed to myopic defocus. Atropine abolished choroidal thinning in response to hyperopic defocus. These effects remained the same after 3 and 6 months of atropine treatment. Our results show that additive effects of atropine and optical defocus are present at the level of the choroid, and suggest that combining optical and pharmaceutical treatments is likely to enhance efficacy of clinical myopia control.
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 12-2010
DOI: 10.1167/IOVS.10-5387
Abstract: To examine the effect of induced myopia on scleral myofibroblast populations and in vivo ocular biomechanical compliance. One-week-old guinea pigs were monocularly deprived (MD) of form vision for 2 weeks. Ocular biomechanical compliance was measured in both eyes of anesthetized animals by increasing the intraocular pressure (IOP) to 50 mm Hg for 1 hour, while A-scan ultrasound measures were made every 10 minutes to investigate the change in axial length. The total cell population and myofibroblast subpopulation of the posterior 100° of the sclera was determined with immunohistochemical techniques. The vitreous chamber depth (VCD) of MD and contralateral control eyes showed significant elastic expansion on increasing the IOP, compared with that of the nonmanipulated normal eyes. The creep response of the VCD in response to increased IOP was initially greater in the normal eyes until eye length was similar to the MD and control eyes. An unexpectedly high proportion of the scleral cell population were myofibroblasts (63.7% ± 1.7%, average ± SEM n = 30). MD significantly decreased the total number of cells in the region between the optic nerve and 10° nasal (equivalent to myopic crescent location in humans) compared with the number in control or normal eyes, but no significant effect on myofibroblasts or the total number of cells was found elsewhere. A high proportion of scleral cells have contractile potential. This proportion is unaffected by MD. However, there is a significant difference in the in vivo elastic response of the sclera between MD and normal eyes, suggesting that factors other than number of cells have an effect on axial length.
Publisher: Springer US
Date: 2002
Publisher: Hindawi Limited
Date: 2018
DOI: 10.1155/2018/8528315
Abstract: Purpose . To investigate the effects of atropine on choroidal thinning induced by hyperopic retinal defocus. Methods . Ten young adults with myopia (−1.00 D to −5.00 D) viewed a video at 6 metres for 60 minutes on successive days. On day 1, one eye (control) was distance corrected with a contact lens the other (experimental) eye wore a contact lens imposing 2.00 D of hyperopic retinal defocus. Sub- and perifoveal choroidal thickness (SFCT, PFCT) were monitored with optical coherence tomography. On day 2, the procedure was repeated but the experimental eye had received one drop of 0.5% atropine 22 hours earlier. Results . On day 1, eyes exposed to hyperopic defocus developed progressively thinner choroids (SFCT (baseline) = 253 ± 32 μ m versus SFCT (40 mins) = 244 ± 31 μ m, p = 0.004 ), whereas SFCT and PFCT in control eyes did not change ( p 0.17 ). On day 2 (22 hours after instilling atropine), baseline SFCT and PFCT were not different to day 1 ( p 0.05 ) and hyperopic defocus failed to thin the choroid (max change in SFCT = +2 ± 2 μ m, p = 0.36 ). Conclusions . Atropine abolished choroidal thinning induced by hyperopic defocus without changing baseline choroidal thickness. The results suggest that atropine inhibits signals associated with hyperopic defocus, for ex le, from lag of accommodation during near work. This trial is registered with ACTRN12617001519347 .
Publisher: Springer Science and Business Media LLC
Date: 05-1983
DOI: 10.3758/BF03202952
Abstract: Public health strategies have focused largely on physical health. However, there is increasing recognition that raising mental health awareness and tackling stigma is crucial to reduce disease burden. National c aigns have had some success but tackling issues locally is particularly important. To assess the public's awareness and perception of the monthly BBC Cornwall mental health phone-in programmes that have run for 8.5 years in Cornwall, UK (population 530 000). A consultation, review and feedback process involving a multiagency forum of mental and public health professionals, people with lived experience and local National Health Service trust's media team was used to develop a brief questionnaire. This was offered to all attendees at two local pharmacies covering populations of 27 000 over a 2-week period. In total, 14% (95% CI 11.9-16.5) were aware of the radio show, 11% (95% CI 9.0-13.1) have listened and the majority (76%) of those who listened did so more than once. The estimated reach is 70 000 people in the local population, of whom approximately 60 000 listen regularly. The show is highly valued among respondents with modal and median scores of 4 out of 5. Local radio is a successful, cost-effective and impactful way to reach a significant proportion of the population and likely to raise awareness, reduce stigma and be well received. The format has been adopted in other regions thus demonstrating easy transferability. It could form an essential part of a public health strategy to improve a population's mental well-being. W.H. received support from the National Institute for Health Research (NIHR) Collaboration for Leadership in Applied Health Research and Care (CLAHRC) for the South West Peninsula UK. The views expressed in this publication are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health. L.R. and D.S. were involved in delivering the programmes but had no role in their evaluation.
Publisher: MDPI AG
Date: 24-01-2021
DOI: 10.3390/JCM10030447
Abstract: We conducted a prospective, paired-eye, investigator masked study in 30 children with myopia (−1.25 D to −4.00 D age 10 to 14 years) to test the efficacy of a novel multifocal orthokeratology (MOK) lens compared to conventional orthokeratology (OK) in slowing axial eye growth. The MOK lens molded a center-distance, multifocal surface onto the anterior cornea, with a concentric treatment zone power of +2.50 D. Children wore an MOK lens in one eye and a conventional OK lens in the fellow eye nightly for 18 months. Eye growth was monitored with non-contact ocular biometry. Over 18 months, MOK-treated eyes showed significantly less axial expansion than OK-treated eyes (axial length change: MOK 0.173 mm less than OK p 0.01), and inner axial length (posterior cornea to anterior sclera change: MOK 0.156 mm less than OK, p 0.01). The reduced elongation was constant across different baseline progression rates (range −0.50 D/year to −2.00 D/year). Visual acuity was less in MOK vs. OK-treated eyes (e.g., at six months, MOK: 0.09 ± 0.01 vs. OK: 0.02 ± 0.01 logMAR p = 0.01). We conclude that MOK lenses significantly reduce eye growth compared to conventional OK lenses over 18 months.
Publisher: Proceedings of the National Academy of Sciences
Date: 02-1988
Abstract: Embossed letters, used previously in pattern recognition experiments in humans, were used to study the spatial patterns of neural activity evoked in peripheral fibers and cortical neurons in areas 3b and 1 of the primary somatosensory cortex of alert rhesus (Macaca mulatta) monkeys. The object was to investigate the representation and transformation of spatial information during the early stages of peripheral and cortical neural processing. Our method consisted of sweeping each letter of the alphabet across the skin repeatedly and constructing a two-dimensional plot (called a spatial event plot) of the action potentials evoked in afferent fibers and cortical neurons. By using this method, slowly and rapidly adapting primary afferents were shown to transmit isomorphic neural images of the letters. Although the slowly adapting images were more spatially acute, both populations conveyed images of sufficient quality to account for human psychophysical performance. In the cortical areas studied, the slowly adapting neurons of area 3b stood out for the acuity, complexity, and variety of their responses. Some of the spatial event plots for these neurons were isomorphic and at least as acute as those obtained from any primary afferent. Others were highly structured but nonisomorphic. The quality and variety of responses in area 3b slowly adapting neurons suggest that they play an important role in the processing of information underlying tactual pattern recognition. The rapidly adapting neurons of area 3b and all types of neurons in area 1 yield much less structured and differentiated responses.
Publisher: Wiley
Date: 24-05-2015
DOI: 10.1111/OPO.12218
Abstract: To describe the time-course and litude of changes to sub-foveal choroidal thickness (SFCT) induced by imposed hyperopic and myopic retinal defocus and to compare the responses in emmetropic and myopic subjects. Twelve East Asian subjects (age: 18-34 years six were emmetropic and six had myopia between -2.00 and -5.00 dioptres (D)) viewed a distant target (video movie at 6 m) for 60 min on two separate occasions while optical coherence tomography (OCT) images of the choroid were taken in both eyes every 5 min to monitor SFCT. On each occasion, one eye was optimally corrected for distance with a contact lens while the other eye wore a contact lens imposing either 2.00 D hyperopic or 2.00 D myopic retinal defocus. Baseline SFCT in myopic eyes (mean ± S.D.): 256 ± 42 μm was significantly less than in emmetropic eyes (423 ± 62 μm p < 0.01) and was correlated with magnitude of myopia (-39 μm per dioptre of myopia, R(2) = 0.67: p < 0.01). Repeated measures anova (General Linear Model) analysis revealed that in both subject groups, 2.00 D of myopic defocus caused a rapid increase in SFCT in the defocussed eye (significant by 10 min, increasing to approximately 20 μm within 60 min: p < 0.01), with little change in the control eye. In contrast, 2.00 D of hyperopic defocus caused a decrease in SFCT in the experimental eye (significant by 20-35 min. SFCT decreased by approximately 20 μm within 60 min: p < 0.01) with little change in the control eye. Small but significant changes in SFCT (5-8%) were caused by retinal defocus. SFCT increased within 10 min of exposure to 2.00 D of monocular myopic defocus, but decreased more slowly in response to 2.00 D of monocular hyperopic defocus. In our relatively small s le we could detect no difference in the magnitude of changes to SFCT caused by defocus in myopic eyes compared to emmetropic eyes.
Publisher: BMJ
Date: 09-2005
Publisher: Association for Research in Vision and Ophthalmology (ARVO)
Date: 14-01-2019
Abstract: To investigate the action of atropine on global flash multifocal electroretinogram (gmfERG) responses to retinal defocus. gmfERG recordings were made monocularly in 19 healthy adults under three lens-imposed defocus conditions (2 diopters myopic, 2 diopters hyperopic, and no defocus) before and 24 hours after instillation of 1 drop of 0.1% atropine. Signals reflecting activity from the outer and inner retina (direct [DC] and induced [IC] components respectively) were analyzed. Responses were grouped into either a central (0°-6°) or peripheral (6°-24°) retinal zone. The gmfERG responses were compared relative to the no defocus, no atropine condition. Within the central zone, atropine had no effect on the litudes and peak times of DC or IC responses to defocus. For IC responses in the peripheral zone, there was a significant interaction effect of atropine and defocus (F2,36 = 6.050, P = 0.011) with greater post-atropine litudes under myopic defocus (mean increase = 15.5%, 95% confidence interval [CI] = 5.6%-25.4%, P = 0.004). Atropine also had a significant main effect of increasing IC peak times (F1,18 = 9.722, P = 0.006). For DC responses, atropine had a significant main effect of increasing DC litudes (F1,18 = 7.821, P = 0.012) and peak times (F1,18 = 15.406, P = 0.001) regardless of sign of defocus. Our results imply that atropine acts in the inner layers of the peripheral retina to affect neuronal responses to myopic defocus, raising the possibility that atropine may potentiate the effects of myopic defocus in inhibiting eye growth.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United States of America
No related grants have been discovered for John Phillips.