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BACKGROUND: Visual biomarkers of Parkinson's disease (PD) are attractive as the retina is an outpouching of the brain. Although inner retinal neurodegeneration in PD is well-established this has overlap with other neurodegenerative diseases and thus outer retinal (photoreceptor) measures warrant further investigation. OBJECTIVE: To examine in a cross-sectional study whether clinically implementable measures targeting outer retinal function and structure can differentiate PD from healthy ageing and whether these are sensitive to intraday levodopa (L-DOPA) dosing. METHODS: Centre-surround perceptual contrast suppression, macular visual field sensitivity, colour discrimination, light-adapted electroretinography and optical coherence tomography (OCT) were tested in PD participants (n = 16) and controls (n = 21). Electroretinography and OCT were conducted before and after midday L-DOPA in PD participants, or repeated after ∼2 hours in controls. RESULTS: PD participants had decreased center-surround contrast suppression (p < 0.01), reduced macular visual field sensitivity (p < 0.05), color vision impairment (p < 0.01) photoreceptor dysfunction (a-wave, p < 0.01) and photoreceptor neurodegeneration (outer nuclear layer thinning, p < 0.05), relative to controls. Effect size comparison between inner and outer retinal parameters showed that photoreceptor metrics were similarly robust in differentiating the PD group from age-matched controls as inner retinal changes. Electroretinography and OCT were unaffected by L-DOPA treatment or time. CONCLUSIONS: We show that outer retinal outcomes of photoreceptoral dysfunction (decreased cone function and impaired color vision) and degeneration (i.e., outer nuclear layer thinning) were equivalent to inner retinal metrics at differentiating PD from healthy age-matched adults. These findings suggest outer retinal metrics may serve as useful biomarkers for PD.

INTRODUCTION: Vision standards for driving are typically based on visual acuity, despite evidence that it is a poor predictor of driving safety and performance. However, visual motion perception is potentially relevant for driving, as the vehicle and surroundings are in motion. This study explored whether tests of central and mid-peripheral motion perception better predict performance on a hazard perception test (HPT), which is related to driving performance and crash risk, than visual acuity. Additionally, we explored whether age influences these associations, as healthy ageing impairs performance on some motion sensitivity tests. METHODS: Sixty-five visually healthy drivers (35 younger, mean age: 25.5; SD 4.3 years; 30 older adults, mean age: 71.0; SD 5.4 years) underwent a computer-based HPT, plus four different motion sensitivity tests both centrally and at 15° eccentricity. Motion tests included minimum displacement to identify motion direction (Dmin ), contrast detection threshold for a drifting Gabor (motion contrast), coherence threshold for a translational global motion stimulus and direction discrimination for a biological motion stimulus in the presence of noise. RESULTS: Overall, HPT reaction times were not significantly different between age groups (p = 0.40) nor were maximum HPT reaction times (p = 0.34). HPT response time was associated with motion contrast and Dmin centrally (r = 0.30, p = 0.02 and r = 0.28, p = 0.02, respectively) and with Dmin peripherally (r = 0.34, p = 0.005); these associations were not affected by age group. There was no significant association between binocular visual acuity and HPT response times (r = 0.02, p = 0.29). CONCLUSIONS: Some measures of motion sensitivity in central and mid-peripheral vision were associated with HPT response times, whereas binocular visual acuity was not. Peripheral testing did not show an advantage over central testing for visually healthy older drivers. Our findings add to the growing body of evi

PURPOSE: Center-surround contrast suppression-typically induced when a center pattern is surrounded by another pattern with similar spatial features-is considered a perceptual analogue of center-surround neurophysiology in the visual system. Surround suppression strength is altered in a range of brain conditions affecting young people (e.g., schizophrenia, depression, migraine) and is modulated by various neurotransmitters. The early teen years are associated with neurotransmitter changes in the human visual cortex, which could impact on excitation-inhibition balance and center-surround antagonistic effects. Hence, we predict that early adolescence is associated with perceptual changes in center-surround suppression. METHODS: In this cross-sectional study, we tested 196 students at every age from 10 to 17 years and 30 adults (aged 21-34 years) to capture the preteen, adolescent, and adult periods. Contrast discrimination thresholds were measured for a central, circular, vertical sinusoidal grating pattern (0.67° radius, 2 cyc/deg spatial frequency, 2 deg/s drift rate) with and without the surround (4° radius, otherwise same spatial properties as the center). Individual suppression strength was determined by comparing the perceived contrast of the target with and without the surround. RESULTS: After excluding unreliable data (7% of total), we found an effect of age on perceptual center-surround contrast suppression strength, F(8,201) = 2.30, P = 0.02, with weaker suppression in the youngest adolescents relative to adults (Bonferroni pairwise comparisons between adults vs 12-year-olds P = 0.01; adults vs 13-year-olds P = 0.002). CONCLUSIONS: Our data demonstrate different center-surround interactions in the visual system-a key building block for visual perception-in early adolescence relative to adulthood.

In healthy adults with normal vision, temporary deprivation of one eye's visual experience produces transient yet robust homeostatic plasticity effects, where the deprived eye becomes more dominant. This shift in ocular dominance is short-lived and compensatory. Previous work shows that monocular deprivation decreases resting state gamma aminobutyric acid (GABA; inhibitory neurotransmitter) levels in visual cortex, and that those with the greatest reduction in GABA have stronger shifts due to monocular deprivation. Components of the GABAergic system in visual cortex vary with age (early childhood, early teen years, ageing); hence if GABA is critical to homeostatic plasticity within the visual system, adolescence may be a key developmental period where differences in plasticity manifest. Here we measured short-term visual deprivation effects on binocular rivalry in 24 adolescents (aged 10-15 years) and 23 young adults (aged 20-25 years). Despite differences in baseline features of binocular rivalry (adolescents showed more mixed percept p < 0.001 and a tendency for faster switching p = 0.06 compared to adults), deprived eye dominance increased (p = 0.01) similarly for adolescents and adults after two hours of patching. Other aspects of binocular rivalry - time to first switch (heralding the onset of rivalry) and mixed percept - were unaltered by patching. These findings suggest that binocular rivalry after patching can be used as a behavioral proxy for experience-dependent visual cortical plasticity in adolescents in the same way as adults, and that homeostatic plasticity to compensate for temporarily reduced visual input is established and effective by adolescence.

The Open Perimetry Initiative was formed in 2010 with the aim of reducing barriers to clinical research with visual fields and perimetry. Our two principal tools are the Open Perimetry Interface (OPI) and the visualFields package with analytical tools. Both are fully open source. The OPI package contains a growing number of drivers for commercially available perimeters, head-mounted devices, and virtual reality headsets. The visualFields package contains tools for the analysis and visualization of visual field data, including methods to compute deviation values and probability maps. We introduce a new frontend, the opiApp, that provides tools for customization for visual field testing and can be used as a frontend to run the OPI. The app can be used on the Octopus 900 (Haag-Streit), the Compass (iCare), the AP 7000 (Kowa), and the IMO (CREWT) perimeters, with permission from the device manufacturers. The app can also be used on Android phones with virtual reality headsets via a new driver interface, the PhoneHMD, implemented on the OPI. The use of the tools provided by the OPI library is showcased with a custom static automated perimetry test for the full visual field (up to 50 degrees nasally and 80 degrees temporally) developed with the OPI driver for the Octopus 900 and using visualFields for statistical analysis. With more than 60 citations in clinical and translational science journals, this initiative has contributed significantly to expand research in perimetry. The continued support of researchers, clinicians, and industry are key in transforming perimetry research into an open science.

PURPOSE: Previous studies show that some visual field (VF) defects are detectable from visual search behavior; for example, when watching video. Here, we developed and tested a VF testing approach that measures the number of fixations to find targets on a background with spatial frequency content similar to natural scenes. METHODS: Twenty-one older controls and 20 people with glaucoma participated. Participants searched for a Gabor (6 c/°) that appeared in one of 25 possible locations within a 15° (visual angle) 1/f noise background (RMS contrast: 0.20). Procedure performance was assessed by calculating sensitivity and specificity for different combinations of control performance limits (p = 95%, 98%, 99%), number of target locations with fixations outside control performance limits (k = 0 to 25) and number of repeated target presentations (n = 1 to 20). RESULTS: Controls made a median of two to three fixations (twenty-fifth to seventy-fifth percentile: two to four) to locate the target depending on location. A VF was flagged "abnormal" when the number of fixations was greater than the p = 99% for k = 3 or more locations with n = 2 repeated presentations, giving 85% sensitivity and 95.2% specificity. The median test time for controls was 85.71 (twenty-fifth to seventy-fifth percentile: 66.49-113.53) seconds. CONCLUSION: Our prototype test demonstrated effective and efficient screening of abnormal areas in central vision. TRANSLATIONAL RELEVANCE: Visual search behavior can be used to detect central vision loss and may produce results that relate well to performance in natural visual environments.

OBJECTIVE: This study aimed to determine whether the visual response to flickering checkerboard patterns measured using electroencephalography (EEG) relate to excitatory or inhibitory metabolite levels measured using ultra-high (7Tesla/7T) magnetic resonance spectroscopy (MRS). BACKGROUND: Electrophysiological studies have shown altered visual cortical response amplitudes and contrast gain responses to high contrast flickering patterns in people with migraine. These contrast response anomalies have been argued to represent an imbalance between cortical inhibition and excitation, however the specific mechanism has not been elucidated. METHODS: MRS-measured metabolite levels were obtained from the occipital cortex of 18 participants with migraine and 18 non-headache controls. EEG contrast gain response functions were collected on separate days from a subset of 10 participants with migraine and 12 non-headache controls. Case-control outcome measures were statistically compared between groups both before and after checkboard exposure. RESULTS: No significant difference in GABA and glutamate levels were found between groups nor checkerboard timepoint. Glucose levels were significantly reduced after checkerboard exposure in both participant groups. There was no metabolic signature in visual cortex in response to high-contrast flickering checkboards that distinguished those with migraine and without. There was also no correlation between MRS and EEG measurements in response to the flickering checkerboard. CONCLUSION: Our findings suggest that the mechanisms driving contrast-flickering stimulus aversion are not simplistically reflected by gross changes in metabolic activity in the primary visual cortex.

PURPOSE: To introduce a new method (ARBON) for decreasing the test time of psychophysical procedures and examine its application to perimetry. METHODS: ARBON runs in parallel with an existing psychophysical procedure injecting occasional responses of seen or unseen into that procedure. Using computer simulation to mimic human responses during perimetry, we assess the performance of ARBON relative to an underlying test procedure and a version of that procedure truncated to be faster. Simulations used 610 normal eyes (age 20 to 80 years) and 163 glaucoma eyes (median mean deviation = -1.81 dB, 5th percentile = +2.14 dB, 95th percentile = -22.55 dB). Outcome measures were number of presentations and mean absolute error in threshold estimation. We also examined the probability distribution of measured thresholds. RESULTS: ARBON and the Truncated procedure reduced presentations by 16% and 18%, respectively. Mean error was increased by 8% to 10% for the Truncated procedure but decreased by 5% to 7% for ARBON. The probability distributions of measured thresholds using ARBON overlapped with the Underlying procedure by over 80%, whereas the Truncated procedure overlapped by 50%. CONCLUSIONS: ARBON offers a principled method for reducing test time. ARBON can be added to any existing psychophysical procedure without requiring any change to the logic or parameters controlling the procedure, resulting in distributions of measured thresholds similar to those of the underlying procedure. TRANSLATIONAL RELEVANCE: ARBON can be added to a perimetry test procedure to speed up the test while largely preserving the distribution of returned sensitivities, thus producing normative data similar to the data for the original, underlying perimetric test.

Visual snow syndrome is a neurological condition characterized by a persistent visual disturbance, visual snow, in conjunction with additional visual symptoms. Cortical hyperexcitability is a potential pathophysiological mechanism, which could be explained by increased gain in neural responses to visual input. Alternatively, neural noise in the visual pathway could be abnormally elevated. We assessed these two potential competing neural mechanisms in our studies of visual contrast perception. Cortical hyperexcitation also occurs in migraine, which commonly co-occurs with visual snow syndrome. Therefore, to determine whether the effect of visual snow syndrome can be distinguished from interictal migraine, we recruited four participant groups: controls, migraine alone, visual snow syndrome alone and visual snow syndrome with migraine. In the first experiment, we estimated internal noise in 20 controls, 21 migraine participants and 32 visual snow syndrome participants (16 with migraine) using a luminance increment detection task. In the second experiment, we estimated neural contrast gain in 21 controls, 22 migraine participants and 35 visual snow syndrome participants (16 with migraine) using tasks assessing sensitivity to changes in contrast from a reference. Contrast gain and sensitivity were measured for the putative parvocellular and 'on' and 'off' magnocellular pathways, respectively. We found that luminance increment thresholds and internal noise estimates were normal in both visual snow syndrome and migraine. Contrast gain measures for putative parvocellular processing and contrast sensitivity for putative off magnocellular processing were abnormally increased in visual snow syndrome, regardless of migraine status. Therefore, our results indicate that visual snow syndrome is characterized by increased neural contrast gain but not abnormal neural noise within the targeted pathways.

OBJECTIVE: To assess the accuracy of probabilistic deep learning models to discriminate normal eyes and eyes with glaucoma from fundus photographs and visual fields. DESIGN: Algorithm development for discriminating normal and glaucoma eyes using data from multicenter, cross-sectional, case-control study. SUBJECTS AND PARTICIPANTS: Fundus photograph and visual field data from 1,655 eyes of 929 normal and glaucoma subjects to develop and test deep learning models and an independent group of 196 eyes of 98 normal and glaucoma patients to validate deep learning models. MAIN OUTCOME MEASURES: Accuracy and area under the receiver-operating characteristic curve (AUC). METHODS: Fundus photographs and OCT images were carefully examined by clinicians to identify glaucomatous optic neuropathy (GON). When GON was detected by the reader, the finding was further evaluated by another clinician. Three probabilistic deep convolutional neural network (CNN) models were developed using 1,655 fundus photographs, 1,655 visual fields, and 1,655 pairs of fundus photographs and visual fields collected from Compass instruments. Deep learning models were trained and tested using 80% of fundus photographs and visual fields for training set and 20% of the data for testing set. Models were further validated using an independent validation dataset. The performance of the probabilistic deep learning model was compared with that of the corresponding deterministic CNN model. RESULTS: The AUC of the deep learning model in detecting glaucoma from fundus photographs, visual fields, and combined modalities using development dataset were 0.90 (95% confidence interval: 0.89-0.92), 0.89 (0.88-0.91), and 0.94 (0.92-0.96), respectively. The AUC of the deep learning model in detecting glaucoma from fundus photographs, visual fields, and both modalities using the independent validation dataset were 0.94 (0.92-0.95), 0.98 (0.98-0.99), and 0.98 (0.98-0.99), respectively. The AUC of the deep learning model in det

PURPOSE: The purpose of this study was to determine the impact of glare, that simulated the effects of oncoming vehicle headlights, and age on different aspects of motion perception in central and peripheral vision. METHODS: Twenty younger (mean age = 25 years, range = 20-32 years) and 20 older (mean age = 70 years, range = 60-79 years) visually healthy adults completed four visual motion tasks. Stimuli were presented centrally and at 15 degrees horizontal eccentricity for 2 viewing conditions: glare (continuous, off-axis) versus no glare. Motion tasks included minimum Gabor contrast required to discriminate direction of motion, translational global motion coherence, minimum duration of a Gabor to determine direction of motion (2 different size Gabors to determine spatial surround suppression), and biological motion detection in noise. Intraocular straylight was also measured (C-Quant). RESULTS: Older adults had increased intraocular straylight compared with younger adults (P < 0.001). There was no significant effect of glare on motion thresholds in either group for motion contrast (P = 0.47), translational global motion (P = 0.13), biological motion (P = 0.18), or spatial surround suppression of motion (P = 0.29). Older adults had elevated thresholds for motion contrast (P < 0.001), biological motion (P < 0.001), and differences in surround suppression of motion (P = 0.04), relative to the younger group, for both the glare and no-glare conditions. CONCLUSIONS: Although older adults had elevated thresholds for some motion perception tasks, glare from a continuous off-axis light source did not further elevate these thresholds either in central or peripheral vision. TRANSLATIONAL RELEVANCE: A glare source that simulated the effect of oncoming headlights, did not impact motion perception measures relevant to driving.

PURPOSE: Age-related macular degeneration (AMD) is a leading cause of vision impairment. This randomised placebo-controlled trial investigated whether point-of-care tools can improve optometrists' AMD knowledge and/or care provision. METHODS: Australian optometrists (n = 31) completed a demographics survey and theoretical AMD case study multiple-choice questions (MCQs) to assess their confidence in AMD care provision and AMD knowledge. Participants were then randomly assigned to one of three point-of-care tools (online 'Classification of Age-related macular degeneration and Risk Assessment Tool' (CARAT), paper CARAT, or 'placebo') to use when providing care to their subsequent 5-10 AMD patients. Participants self-audited the compliance of their AMD care to best practice for these patients, and a similar number of consecutive patients seen prior to enrolment. Post-intervention, participants retook the AMD knowledge MCQs and confidence survey. RESULTS: A total of 29 participants completed the study. At the study endpoint, clinical confidence relative to baseline improved with the paper CARAT, relative to placebo, for knowledge of AMD risk factors, asking patients about these factors and referring for medical retinal sub-specialist care. There were no between-group differences for the change in AMD knowledge scores. Considering record documentation for patients with any AMD severity, there were no significant between-group differences for documenting patient risk factors, AMD severity, clinical examination techniques or management. In a sub-analysis, the change from baseline in compliance for documenting discussions about patient smoking behaviours for early AMD patients was higher with use of the online CARAT relative to placebo (p = 0.04). For patients with intermediate AMD, the change from baseline in documenting the risk of progression to late AMD was greater among practitioners who used the paper CARAT, relative to placebo (p = 0.04). CONCLUSIONS: This study demon

Occluding one eye for several hours alters visual experience. Specifically, occluding one eye shifts the balance of ocular dominance to favour the recently deprived eye, which can be measured using binocular rivalry. This ocular dominance shift demonstrates homeostatic neuroplasticity within the visual system and has been explored in detail in younger adults. Here we measure whether the strength and general features of neuroplasticity revealed by monocular patching are maintained in older adults. Thirty younger (18-35 years) and 30 older adults (60-81 years) participated. Binocular rivalry features were measured before and after 2 h of occlusion. Post-patching, perceptual dominance of the non-patched eye decreased (p < .001) in both age groups. The effect of occlusion on all features of binocular rivalry did not significantly differ between groups. The older visual system maintains the ability to rapidly adjust to changes in perceptual experience induced by eye occlusion. This preservation of neuroplasticity suggests that visual training methods designed to improve visual performance based on eye occlusion should maintain effectiveness into older age.

PURPOSE: To evaluate the ability of additional central testing locations to improve detection of macular visual field (VF) defects in glaucoma. DESIGN: Prospective cross-sectional study. PARTICIPANTS: Four hundred forty healthy people and 499 patients with glaucomatous optic neuropathy (GON) were tested with a fundus tracked perimeter (CMP; CenterVue) using a 24-2 grid with 12 additional macular locations (24-2+). METHODS: Glaucomatous optic neuropathy was identified based on expert evaluation of optic nerve head photographs and OCT scans, independently of the VF. We defined macular defects as locations with measurements outside the 5% and 2% normative limits on total deviation (TD) and pattern deviation (PD) maps within the VF central 10°. Classification was based on the total number of affected macular locations (overall detection) or the largest number of affected macular locations connected in a contiguous cluster (cluster detection). Criteria based on the number of locations and cluster size were used to obtain equivalent specificity between the 24-2 grid and the 24-2+ grids, calculated using false detections in the healthy cohort. Partial areas under the receiver operating characteristic curve (pAUCs) were also compared at specificities of 95% or more. MAIN OUTCOME MEASURES: Matched specificity comparison of the ability to detect glaucomatous macular defects between the 24-2 and 24-2+ grids. RESULTS: At matched specificity, cluster detection identified more macular defects with the 24-2+ grid compared with the 24-2 grid. For example, the mean increase in percentage of detection was 8% (95% confidence interval [CI], 5%-11%) and 10% (95% CI, 7%-13%) for 5% TD and PD maps, respectively, and 5% (95% CI, 2%-7%) and 6% (95% CI, 4%-8%) for the 2% TD and PD maps, respectively. Good agreement was found between the 2 grids. The improvement measured by pAUCs was also significant but generally small. The percentage of eyes with macular defects ranged from about 30% to 50%

PURPOSE: The purpose of this study was to isolate and quantify the effects of observer response criterion on perimetric sensitivity, response variability, and maximum response probability. METHODS: Twelve people with glaucoma were tested at three locations in the visual field (age = 47-77 years, mean deviation = -0.61 to -14.54 dB, test location Humphrey field analyzer [HFA] sensitivities = 1 to 30 dB). Frequency of seeing (FoS) curves were measured using a method of constant stimuli with two response paradigms: a "yes-no" paradigm similar to static automated perimetry and a criterion-free two interval forced choice (2IFC) paradigm. Comparison measures of sensitivity, maximum response probability, and response variability were derived from the fitted FoS curves. RESULTS: Sensitivity differences between the tasks varied widely (range = -11.3 dB to 21.6 dB) and did not correlate with visual field sensitivity nor whether the visual field location was in an area of steep sensitivity gradient within the visual field. Due to the wide variation in differences between the methods, there was no significant difference in mean sensitivity between the 2IFC task relative to the yes-no task, but a trend for higher sensitivity (mean = 1.9 dB, SD = 6.0 dB, P = 0.11). Response variability and maximum response probability did not differ between the tasks (P > 0.99 and 0.95, respectively). CONCLUSIONS: Perimetric sensitivity estimates are demonstrably altered by observer response criterion but the effect varies widely and unpredictably, even within a single test. Response bias should be considered a factor in perimetric test variability and when comparing sensitivities to nonperimetric data. TRANSLATIONAL RELEVANCE: The effect of response criterion on perimetric response variability varies widely and unpredictably, even within a single test.

PURPOSE: To explore the differential effects of age and eccentricity on the perception of motion at photopic and mesopic light levels. METHODS: Thirty-six visually normal participants (18 younger; mean age 25 years, range: 20-31) and (18 older; mean age 70 years, range: 60-79) underwent two testing sessions, one at photopic and one at mesopic light levels. In each session, motion perception was tested binocularly at two eccentricities (centrally, and peripherally at 15° rightwards and 5° superior to the horizontal) for four motion tasks: minimum contrast of a drifting Gabor to identify motion direction (motion contrast); translational global motion coherence; biological motion embedded in noise and the minimum duration of a high-contrast Gabor to determine the direction of motion, using two Gabor sizes to measure spatial surround suppression of motion. RESULTS: There was a significant main effect of light condition (higher thresholds in mesopic) for motion contrast (p < 0.001), translational global motion (p = 0.001) and biological motion (p < 0.001); a significant main effect of age (higher thresholds in older adults) for motion contrast (p < 0.001) and biological motion (p = 0.04) and a significant main effect of eccentricity (higher thresholds peripherally) for motion contrast (p < 0.001) and biological motion (p < 0.001). Additionally, we found a significant three-way interaction between light levels, age and eccentricity for translational global motion (similar increase in mesopic thresholds centrally for both groups, but a much larger deterioration in older adult's peripheral mesopic thresholds, p = 0.02). Finally, we found a two-way interaction between light condition and eccentricity for translational global motion (higher values in central mesopic relative to peripheral photopic, p = 0.001) and for biological motion (higher values in peripheral mesopic relative to central photopic, p < 0.001). CONCLUSIONS: For the majority of tasks assessed, motion percepti

Visual snow syndrome (VSS) is a complex, sensory processing disorder. We have previously shown that visual processing changes manifest in significantly faster eye movements toward a suddenly appearing visual stimulus and difficulty inhibiting an eye movement toward a non-target visual stimulus. We propose that these changes reflect poor attentional control and occur whether attention is directed exogenously by a suddenly appearing event, or endogenously as a function of manipulating expectation surrounding an upcoming event. Irrespective of how attention is captured, competing facilitatory and inhibitory processes prioritise sensory information that is important to us, filtering out that which is irrelevant. A well-known feature of this conflict is the alteration to behaviour that accompanies variation in the temporal relationship between competing sensory events that manipulate facilitatory and inhibitory processes. A classic example of this is the "Inhibition of Return" (IOR) phenomenon that describes the relative slowing of a response to a validly cued location compared to invalidly cued location with longer cue/target intervals. This study explored temporal changes in the allocation of attention using an ocular motor version of Posner's IOR paradigm, manipulating attention exogenously by varying the temporal relationship between a non-predictive visual cue and target stimulus. Forty participants with VSS (20 with migraine) and 20 controls participated. Saccades were generated to both validly cued and invalidly cued targets with 67, 150, 300, and 500 ms cue/target intervals. VSS participants demonstrated delayed onset of IOR. Unlike controls, who exhibited IOR with 300 and 500 ms cue/target intervals, VSS participants only exhibited IOR with 500 ms cue/target intervals. These findings provide further evidence that attention is impacted in VSS, manifesting in a distinct saccadic behavioural profile, and delayed onset of IOR. Whether IOR is perceived as the build-u

PURPOSE: Contemporary eye care increasingly recommends the use of advanced retinal imaging technology. Anecdotal evidence suggests that this equipment is widely available in primary eye care settings; however, knowledge regarding how optometrists use this equipment in the context of diabetic retinopathy (DR) is limited. This study aimed to obtain a current overview of optometrists' clinical practice behaviours in the detection, screening, diagnosis and management of patients with diabetes. METHODS: A cross-sectional survey was designed to evaluate optometrists' self-reported clinical practice patterns and perceptions, as well as the availability and impact of retinal imaging equipment specific to DR and diabetic macular oedema (DMO) on optometrists' clinical practice. The survey invited participation from all optometrists practising in Australia. RESULTS: One hundred and sixty-seven optometrists participated. Optometrists' self-reported confidence in assessing DR and DMO was high. Optometrists' referral patterns considered the severity of DR and DMO before initiating referral to secondary ophthalmology care. Nearly all optometrists (98.8%) indicated that they had some form of retinal imaging equipment available to them in clinical practice. An optical coherence tomography (OCT) device was available to 75.5% of optometrists. A significant association between having an OCT device in the practice and higher self-reported confidence levels in the assessment of DMO was found. CONCLUSIONS: Many optometrists are well equipped with sophisticated retinal imaging technology for the provision of high-quality eye care. Enhancing optometric training and education programmes can maximise the community benefit of access to this equipment and improve delivery of eye care in the community.

Key points • Dedicated eye imaging can be implemented at 7T to acquire high-resolution, high contrast-to-noise, and high signal-to-noise images in a feasible imaging time suitable for clinical use. • Simple, reproducible participant preparation techniques can be adopted to reduce the motion of the eye leading to a reduction in subsequent artefacts. • Sequences available at ultrahigh field can be used in current 7T clinical applications to visualize ocular structures otherwise impossible with other ophthalmic imaging.

Dyslexia is characterised by poor reading ability. Its aetiology is probably multifactorial, with abnormal visual processing playing an important role. Among adults with normal reading ability, there is a larger representation of central visual field in the primary visual cortex (V1) in those with more efficient visuospatial attention. In this study, we tested the hypothesis that poor reading ability in school-aged children (17 children with dyslexia, 14 control children with normal reading ability) is associated with deficits in visuospatial attention using a visual search task. We corroborated the psychophysical findings with neuroimaging, by measuring the functional size of V1 in response to a central 12° visual stimulus. Consistent with other literature, visual search was impaired and less efficient in the dyslexic children, particularly with more distractor elements in the search array (p=0.04). We also found atypical interhemispheric asymmetry in functional V1 size in the dyslexia group (p=0.02). Reading impaired children showed poorer visual search efficiency (p=0.01), needing more time per unit distractor (higher ms/item). Reading ability was also correlated with V1 size asymmetry (p=0.03), such that poorer readers showed less left hemisphere bias relative to the right hemisphere. Our findings support the view that dyslexic children have abnormal visuospatial attention and interhemispheric V1 asymmetry, relative to chronological age-matched peers, and that these factors may contribute to inter-individual variation in reading performance in children.

PURPOSE: The purpose of this study was to compare visual field results of the COMPASS fundus perimeter (CMP) and the Humphrey Field Analyzer (HFA) in the same eyes; to compare structure-function concordance between circumpapillary retinal nerve fiber layer (Cp-RNFL) profiles and the two perimetry results; and to evaluate whether differences between the two results reflect postulated advantages of real-time eye movement compensation during perimetry. METHODS: We retrospectively analyzed 24-2 visual field data measured with CMP and HFA together with Cp-RNFL optical coherence tomography (OCT) scan data from 95 eyes of 65 people with glaucoma. We defined visual field locations with total deviation (TD) less than -5 dB as defective. The CMP and HFA fields were compared on measures of: spatial extent (number of defective locations); depth (TD values); and sharpness of scotomata edges (maximum TD difference between defective locations and their neighbors). Structure-function concordance between Cp-RNFL profile and respective visual field was also compared. RESULTS: Compared to the HFA, scotomata measured by CMP were of reduced spatial extent (mean difference = -3.14 locations, p < 0.001), greater depth (median TD of CMP = -17 dB versus HFA = -13 dB, p = 0.029) and steeper edges (median of maximum TD difference of CMP = 10.6 dB versus HFA = 6 dB, p < 0.001). Structure-function concordance between Cp-RNFL profile and either visual field were comparable despite the reduced scotoma spatial extent measured by CMP. CONCLUSIONS: Glaucomatous visual fields measured by CMP displayed characteristics consistent with expected effects of using real-time eye movement compensation technology compared to the widely used HFA. TRANSLATIONAL RELEVANCE: Glaucomatous visual field defects measured by the CMP are more localized, deeper, and steeper than those of the HFA.

Purpose: We aimed to image the optic nerve, subarachnoid space and optic nerve sheath in emmetropes and myopes ultra-high field (7-Tesla) magnetic resonance imaging (MRI). We targeted the retrobulbar distance of approximately 3 mm behind the eyeball, an area of clinical interest because of optic nerve sheath distensibility and pressure-related enlargement. Methods: Eleven emmetropes (+0.75 to −0.50D, aged 20–41 years) and 10 myopes (−4.5 to −12D, aged 21–37 years) participated. Cross-sectional area of the optic nerve, subarachnoid space and optic nerve sheath at approximately 3 mm behind the eye were measured from two-dimensional T2-weighted coronal oblique MRI images obtained through the left optic nerve. Axial length of the left eye was measured from T2-weighted axial MRI images. In nine emmetropes and seven myopes, the optic nerve head was imaged with optical coherence tomography to compare retrobulbar and intraocular measures. Results: Retrobulbar optic nerve, subarachnoid space and optic nerve sheath dimensions differed between myopes and emmetropes. Myopes tended to have smaller optic nerve and subarachnoid space. Longer MRI-derived axial length was associated with smaller optic nerve area (P = 0.03). Bruch's membrane opening area did not predict retrobulbar optic nerve area (P = 0.48). Conclusions: This study demonstrates the feasibility of using 7-Tesla MRI to measure optic nerve, subarachnoid space, and optic nerve sheath dimensions behind the eye. In healthy adults, the retrobulbar optic nerve and subarachnoid space size are influenced by the degree of myopia. Translational Relevance: ultra-high field MRI is a practical tool for assessing the morphometry of the optic nerve and surrounding anatomy behind the eye.

The features of perceptual surround suppression vary with eccentricity, such that the suppression strength is increased for horizontally oriented stimuli relative to other orientations near the fovea, but is strongest for radially oriented stimuli more peripherally. Perceptual suppression also varies with age, which has been well-studied for central fixation. However, only limited data are available regarding perceptual suppression in older adults for nonfoveal vision, and none of those studies have taken orientation biases of contrast sensitivity into account. Here, we explored the effects of older age on the eccentricity dependency of orientation biases of perceptual suppression. We found increased perceptual suppression in older adults at both 6° and 15° eccentricities relative to younger adults. A main effect of the horizontal orientation bias was found at 6° and a main effect of the radial orientation bias was found at 15° in both groups. In summary, perceptual surround suppression of contrast is stronger for older adults compared with younger adults at 6° and 15° eccentricities, but retinotopic orientation anisotropies are maintained with age. This study provides new insight into parafoveal visual perception in older adults, which may be particularly important to understand the visual experience of those who depend on nonfoveal vision owing to common age-related eye diseases.

Visual snow syndrome (VSS) is a poorly understood neurological disorder that features a range of disabling sensory changes. Visual processing changes revealed previously in VSS appear consistent with poor attentional control, specifically, with difficulty controlling environmentally driven shifts of attention. This study sought to confirm this proposal by determining whether these changes were similarly evident where attention is internally driven. Sixty seven VSS patients and 37 controls completed two saccade tasks: the endogenously cued saccade task and saccadic Simon task. The endogenously cued saccade task correctly (valid trial) or incorrectly (invalid trial) pre-cues a target location using a centrally presented arrow. VSS patients generated significantly shorter saccade latencies for valid trials (p = 0.03), resulting in a greater magnitude cue effect (p = 0.02), i.e. the difference in latency between valid and invalid trials. The saccadic Simon task presents a peripheral cue which may be spatially congruent or incongruent with the subsequent target location. Latencies on this task were comparable for VSS patients and controls, with a normal Simon effect, i.e. shorter latencies for saccades to targets spatially congruent with the preceding cue. On both tasks, VSS patients generated more erroneous saccades than controls towards non-target locations (Endogenously cued saccade task: p = 0.02, saccadic Simon task: p = 0.04). These results demonstrate that cued shifts of attention differentially affect saccade generation in VSS patients. We propose that these changes are not due to impairment of frontally-mediated inhibitory control, but to heightened saccade-related activity in visual regions. These results contribute to a VSS ocular motor signature that may provide clinical utility as well as an objective measure of dysfunction to facilitate future research.

Background: Visual Snow (VS) syndrome is believed to be due to aberrant central visual processing. Positron Emission Tomography (PET) brain imaging and visual evoked potential studies provide evidence for excessive neuronal activity in the medial temporal lobe, specifically the lingual gyrus, and suggest the VS syndrome is a hyperexcitability syndrome. These data provide the basis for consideration of repetitive transcranial magnetic stimulation (rTMS) as a potential treatment for the VS syndrome. Objective: To publish the study protocol for a pilot study underway at the University of Colorado School of Medicine to investigate the use of rTMS intervention to improve symptoms and visual dysfunction associated with VS. The study aims to determine the adverse events and drop-out rate, evaluate performance of outcome measures, including a novel VS symptom scale, and describe changes in outcomes associated with treatment. Methods and Design: Up to 10 participants meeting criteria for VS syndrome, age 19-65 years, will undergo an open-label intervention consisting of 10 rTMS sessions, occurring 5 days a week over a 2-week period. Participants will complete pre-treatment and post-treatment assessments that include: the Colorado Visual Snow Scale (CVSS), the National Eye Institute Visual Functional Questionnaire-25 (VFQ-25), the General Anxiety Disorder-7 scale (GAD-7), and three psychophysical visual processing tasks. Discussion: Knowledge gained from this pilot study will inform future study planning and provide valuable lessons for future investigation of rTMS for the VS syndrome. An overview of study proceedings thus far demonstrates recruitment challenges associated with the COVID-19 pandemic, and additional challenges that are unique to the VS syndrome and to treatment schedules associated with TMS. Registration: This study has been approved by the Colorado Multiple Institutional Review Board. ClinicalTrials.gov Identifier: NCT04925232.

Purpose: Maps are required to relate visual field locations to optic nerve head regions. We compare individualized structure-to-function mapping (CUSTOM-MAP) to a population-derived mapping schema (POP-MAP). Methods: Maps were compared for 118 eyes with glaucomatous field loss, circumpapillary retinal nerve fiber layer (cpRNFL) thickness measured using spectral domain optical coherence tomography (OCT), and two landmarks: the optic nerve head (ONH) position relative to the fovea and the temporal raphe angle. Locations with visual field damage (total deviation < -6 dB) were mapped to 30° ONH sectors centered on the angle given by each mapping schema. The concordance between damaged function and damaged structure was determined per location for various cpRNFL damage probability levels, with the number of concordant locations divided by the total number of damaged field locations providing a concordance ratio per eye. Results: For the strictest concordance criteria (minimum cpRNFL thickness < 1% of normal), CUSTOM-MAP had higher mean concordance ratio than POP-MAP (60.5% c.f. 57.0% paired Wilcoxon, P = 0.005), with CUSTOM-MAP having a higher ratio in 43 eyes and POP-MAP having a higher ratio in 21 eyes. For all cpRNFL probability levels <20% of normal, more locations concorded for CUSTOM-MAP than POP-MAP. Inspection of the spatial patterns of differences revealed that CUSTOM-MAP often performed better in the arcuate regions, whereas POP-MAP had benefits inferior to the macula. Conclusions: Anatomic parameters required for individualized structure-function mapping are readily measured with OCT and can provide improved concordance for some eyes. Translational Relevance: Personalizing structure-function mapping may improve concordance between these measures. We provide a web-based tool for creating customized maps.

Purpose Age‐related macular degeneration (AMD) is a major cause of vision loss. This study investigated whether performing clinical audit and receiving analytical performance feedback altered documentation of the AMD care provided by optometrists. Methods Australian optometrists were recruited and completed a survey about their demographics and confidence in AMD care, and a three‐month audit of their practice records using an AMD audit tool (termed the pre‐audit evaluation). After receiving analytical feedback, participants identified areas for improvement and re‐audited their practices after three months to analyse changes in performance (termed the post‐audit evaluation). Paired t‐tests and Wilcoxon signed‐rank tests, as appropriate, were used to compare pre‐ and post‐audit data. Results Twenty optometrists, most practising in Victoria, Australia, completed the study. Participants primarily worked in corporate practice and/or rural settings and had a range of optometric experience (2–40 years). At baseline, participants felt confident in their: knowledge of AMD risk factors (65%), advice to patients about these factors (55%) and management of earlier stages of AMD (55%). Each clinician completed (median [IQR]): 15 [IQR: 10–19] and 12 [IQR: 8–16] audits of unique patient records, pre‐ and post‐audit, respectively. Post‐audit, average record documentation (per optometrist) improved for asking about: AMD family history (94% to 100%, p = 0.03), smoking status (21% to 58%, p < 0.01), diet (11% to 29%, p < 0.01) and nutritional supplementation (20% to 51%, p < 0.01). For clinical examination, compliance with documenting pinhole visual acuity, performing an in‐office Amsler grid (upon indication) and using optical coherence tomography improved post‐audit (p < 0.05). Accuracy of severity documentation improved for earlier stages of AMD (p < 0.05). For earlier stages of AMD, documentation of counselling about modifiable risk factors significantly improved post‐audit (p < 0

Adult homeostatic visual plasticity can be induced by short-term patching, heralded by a shift in ocular dominance in favor of the deprived eye after monocular occlusion. The potential to boost visual neuroplasticity with environmental enrichment such as exercise has also been explored; however, the results are inconsistent, with some studies finding no additive effect of exercise. Studies to date have only considered the effect of patching alone or in combination with exercise. Whether exercise alone affects typical outcome measures of experimental estimates of short-term visual neuroplasticity is unknown. We therefore measured binocular rivalry in 20 healthy young adults (20-34 years old) at baseline and after three 2-hour interventions: patching (of the dominant eye) only, patching with exercise, and exercise only. Consistent with previous work, the patching interventions produced a shift in ocular dominance toward the deprived (dominant) eye. Mild- to moderate-intensity exercise in the absence of patching had several effects on binocular rivalry metrics, including a reduction in the dominant eye percept. The proportion of mixed percept and the time to first switch (onset rivalry) did not change from baseline across all interventions. Thus, we demonstrate that exercise alone can impact binocular rivalry outcomes measures. We did not observe a synergistic effect between patching and exercise in our data.

A key visual neuronal property that is mirrored in human behaviour is centre-surround contrast suppression, which is orientation-dependent. When a target is embedded in a high-contrast surround, the centre appears reduced in contrast, the magnitude of which depends on the relative orientation between centre and surround. Previous reports demonstrate changes in perceptual surround suppression with ageing; however, whether the orientation-dependency of surround suppression is impacted by ageing has not been explored. Here, we tested 18 younger (aged 19–33) and 18 older (aged 60–77) adults. Perceptual surround suppression was stronger for parallel than orthogonal stimuli; however contrary to previous work, here we found no difference in perceptual suppression strength between age-groups. In the same participants, we measured event-related potentials (ERPs) and conducted multivariate pattern analysis to confirm that parallel and orthogonal centre-surround stimuli elicit distinguishable brain activity, predominantly over occipital areas. Despite a delay in the first prominent ERP component (P1) in response to each pattern, older adults showed similar decoding of orientation information (i.e. distinguish between parallel and orthogonal centre-surround stimuli from 70 ms post-stimulus onset) as younger adults. This suggests that sufficient information to distinguish orientation in centre-surround stimuli becomes available to the older human brain as early as in younger adults.

PURPOSE: Altered visual processing of motion and contrast has been previously reported in people with migraine. One possible manifestation of this altered visual processing is increased self-reported susceptibility to visual illusions of contrast and motion. Here, we use the Fraser-Wilcox illusion to explore individual differences in motion illusion strength in people with and without migraine. The motion-inducing mechanisms of the Fraser-Wilcox illusion are purported to be contrast dependent. To better understand the mechanisms of the illusion, as well as visual processing anomalies in migraine, we explored whether migraine status, susceptibility to visual discomfort, contrast discrimination, or motion sensitivity are related to quantified motion illusion strength. METHODS: Thirty-six (16 with aura, 20 without aura) people with migraine and 20 headache-free controls participated. Outcome measures were motion illusion strength (the physical motion speed that counterbalanced the illusory motion), motion sensitivity, and contrast discrimination thresholds (measured for each contrast pair that formed part of the illusory motion stimulus). Typical daily visual discomfort was self-reported via questionnaire. RESULTS: Motion illusion strength was negatively correlated with contrast discrimination threshold (r = -0.271, P = 0.04) but was not associated with motion sensitivity or migraine status. People with migraine with aura reported experiencing visual discomfort more frequently than the control group (P = 0.001). Self-reported visual discomfort did not relate to quantified perceptual motion illusion strength. CONCLUSIONS: Individuals with better contrast discrimination tend to perceive faster illusory motion regardless of migraine status.

PURPOSE: Visual fields (VF) are measured monocularly at a single depth, yet real-life activities require people to interact with objects binocularly at multiple depths. To better characterize visual functioning in clinical vision conditions such as glaucoma, analyzing visual impairment in a depth-dependent fashion is required. We developed a depth-dependent integrated VF (DD-IVF) simulation and demonstrated its usefulness by evaluating DD-IVF defects associated with 12 glaucomatous archetypes of 24-2 VF. METHODS: The 12 archetypes included typical variants of superior and inferior nasal steps, arcuate and altitudinal defects, temporal wedge, biarcuate, and intact VFs. DD-IVF simulation maps the monocular 24-2 VF archetypes to binocular ones as a function of depth by incorporating three parameters of fixation, object, and interpupillary distances. At each location and depth plane, sensitivities are linearly interpolated from corresponding locations in monocular VF and returned as the higher value of the two. RESULTS: The simulation produced 144 DD-IVFs for multiple depths from combinations of 12 glaucomatous archetypes. The DD-IVFs are included as a Shiny app in the binovisualfields package. The number of impaired locations in the DD-IVFs varied according to the overlap of VF loss between eyes. CONCLUSIONS: Our DD-IVF program revealed binocular functional visual defects associated with glaucomatous archetypes of the 24-2 pattern and is designed to do the same for empirically measured VFs. The comparison of identified visual impairments across depths may be informative for future empirical exploration of functional visual impairments in depth in glaucoma and other conditions leading to bilateral VF loss. TRANSLATIONAL RELEVANCE: Our DD-IVF program can reveal depth-dependent functional visual defects for clinical vision conditions where 24-2 test patterns are available.

BACKGROUND: Migraine is underdiagnosed and undertreated. Optometrists are primary eye care providers, who regularly encounter people with migraine as an incidental finding during routine eye examinations, or when patients present to rule out whether visual or ocular problems are contributing to headache symptoms. Knowledge and use of a migraine screening tool in optometric practice is, therefore, important to be able to identify and refer people with migraine for appropriate management. OBJECTIVE: We sought to investigate optometrists' current behaviors regarding screening for migraine, and to assess the effectiveness of an educational resource in promoting the use of a 3-item validated migraine screening questionnaire, the ID-Migraine. METHODS: We first conducted a cross-sectional study using a survey to assess optometrists' current knowledge and behaviors about migraine screening and willingness to participate in a pilot implementation program. Participants who provided their contact details were invited to watch an online educational resource about a validated migraine screening tool. After 6 weeks, these participants were invited to participate in a follow-up cohort study involving a survey to assess the effectiveness of the educational resource. RESULTS: Ninety-eight optometrists completed the initial survey as part of the cross-sectional study. We found that most optometrists actively asked patients about migraine (79/98 respondents, 81%) as part of routine eye examinations and self-rated themselves as confident in identifying migraine (71/98 respondents, 72%). However, the majority (90/98 respondents, 92%) were not aware of any validated migraine screening tools. Seventy-eight respondents provided their contact details to receive information about the subsequent cohort study. In response to the follow-up study survey (31/78 participants, 40%), 45% (14/31 respondents) of participants self-reported using the ID-Migraine tool after watching our educational video

The perception of motion is considered critical for performing everyday tasks, such as locomotion and driving, and relies on different levels of visual processing. However, it is unclear whether healthy aging differentially affects motion processing at specific levels of processing, or whether performance at central and peripheral spatial eccentricities is altered to the same extent. The aim of this study was to explore the effects of aging on hierarchically different components of motion processing: the minimum displacement of dots to perceive motion (Dmin), the minimum contrast and speed to determine the direction of motion, spatial surround suppression of motion, global motion coherence (translational and radial), and biological motion. We measured motion perception in both central vision and at 15° eccentricity, comparing performance in 20 older (60-79 years) and 20 younger (19-34 years) adults. Older adults had significantly elevated thresholds, relative to younger adults, for motion contrast, speed, Dmin, and biological motion. The differences between younger and older participants were of similar magnitude in central and peripheral vision, except for surround suppression of motion, which was weaker in central vision for the older group, but stronger in the periphery. Our findings demonstrate that the effects of aging are not uniform across all motion tasks. Whereas the performance of some tasks in the periphery can be predicted from the results in central vision, the effects of age on surround suppression of motion shows markedly different characteristics between central and peripheral vision.

Purpose: The Australian Reduced Range Extended Spatial Test (ARREST) approach was designed to improve visual field spatial resolution while maintaining a similar test duration to clinically used testing algorithms. ARREST does not completely threshold visual field locations with sensitivity < 17 dB, and uses the presentations saved to test new locations in areas of steep gradient within the visual field. Previous assessments of ARREST's performance have used computer simulation. In this study, we cross-sectionally assessed the performance of ARREST in people with visual field loss. Methods: We tested 23 people with glaucoma (mean age: 71 ± 8 years) with established visual field loss. Three visual field procedures were performed using the Open Perimetry Interface: cZEST and ARREST on the Octopus 900 perimeter (Haag-Streit AG, Switzerland), and a reference standard (best available estimate [BAE]) on the Compass perimeter (CenterVue SpA, Italy). ARREST was compared against the cZEST and the BAE. Results: On average, ARREST added seven new locations (range = 0-15) to a visual field test. There was no significant difference in the number of stimulus presentations between procedures (mean = 259 ± 25 [ARREST] vs. 261 ± 25 [cZEST], P = 0.78). In classifying threshold values < 17 dB, ARREST performed similarly when compared against BAE. Conclusions: This study provides empirical evidence to support conclusions from previous computer simulations that ARREST can be used to increase spatial sampling in regions of interest without increasing test time. Translational Relevance: ARREST is a new approach that augments current visual field testing procedures to provide better spatial description of visual field defects without increasing test duration.

Purpose : We exploit the improved spatial resolution and signal-to-noise gain of ultra high field (7T) magnetic resonance imaging (MRI) with a dedicated eye coil for more accurate morphometric measurements of the optic nerve ~2.5mm behind the globe. Methods : Coronal T2-weighted oblique images (TR=2000ms, TE=64ms, FOV=155mm, matrix=384 x 384, slice thickness=0.7mm, scan time=2’34”) through the optic nerve were obtained in 21 healthy adults (20-41 years, 11 emmetropes: +0.75 to -0.50D, 10 myopes: -4.5 to -12D) using a 7T Siemens Magnetom scanner (Erlangen, Germany) and 6-channel eye coil (MRI.TOOLS GmbH, Berlin, Germany). Horizontal and vertical outer diameter of the optic nerve, subarachnoid space (fluid gap) and optic sheath were measured by hand using biomedical imaging software (OsiriX, Pixmeo, Switzerland) (Figure). Significant motion artefacts were avoided with customised fixation and preparation techniques. Results : Horizontal and vertical measurements were similar so were averaged. Right and left eye diameters did not differ and were highly correlated (optic nerve: Pearson r=0.9, p<0.001; fluid gap: r=0.8, p<0.001; optic sheath: r=0.7, p<0.001); hence we report left eye data only. Optic nerve diameter (average of horizontal and vertical diameters) ranged from 2.8-4.1mm in emmetropes and 1.5-4.2mm in myopes and correlated with refractive error (Spearman r=0.46, p=0.04). Similarly, fluid gap diameter (emmetropes: 3.6-5.5mm, myopes: 2.5-5.6mm), but not optic sheath diameter (emmetropes: 4.5-6.8mm, myopes: 4.2-6.8mm), correlated with refractive error (r=0.47, p=0.03). Conclusions : Ultra high field MRI with thinner slices enables more accurate demarcation of the optic nerve, surrounding fluid/subarachnoid space and optic sheath without overlapping of neighbouring anatomy (minimal partial volume artefact). Our 7T MRI-derived normative measurements of optic nerve, fluid gap and sheath diameter are comparable with published reports in healthy observers obtained at

PURPOSE: Aging and glaucoma both result in contrast processing deficits. However, it is unclear the extent to which these functional deficits arise from retinal or post-retinal neuronal changes. This study aims to disentangle the effects of healthy human aging and glaucoma on retinal and post-retinal contrast processing using visual electrophysiology. METHODS: Steady-state pattern electroretinograms (PERG) and pattern visual evoked potentials (PVEP) were simultaneously recorded across a range of contrasts (0%, 4%, 9%, 18%, 39%, 73%, 97%; 0.8° diameter checks, 31° diameter checkerboard) in 13 glaucoma patients (67 ± 6 years), 15 older (63 ± 8 years) and 14 younger adults (27 ± 3 years). PERG and PVEP contrast response functions were fit with a linear and saturating hyperbolic model, respectively. PERG and PVEP magnitude, timing (phase), and model fit parameters (slope, semi-saturation constant) were compared between groups. RESULTS: PERG responses were reduced and delayed in older adults relative to younger adults, and further reduced and delayed in glaucoma patients across all contrasts. PVEP signals were also reduced and delayed in glaucoma patients, relative to age-similar (older) controls. However, despite having reduced PERG magnitudes, older adults did not demonstrate reduced PVEP magnitudes. CONCLUSIONS: Older adults with healthy vision demonstrate reduced magnitude and delayed timing in the PERG that is not reflected in the PVEP. In contrast, glaucoma produces functional deficits in both PERG and PVEP contrast response functions. Our results suggest that glaucomatous effects on contrast processing are not a simple extension of those that arise as part of the aging process.

Certain perceptual measures have been proposed as indirect assays of brain neurochemical status in people with migraine. One such measure is binocular rivalry, however, previous studies have not measured rivalry characteristics and brain neurochemistry together in people with migraine. This study compared spectroscopy-measured levels of GABA and Glx (glutamine and glutamate complex) in visual cortex between 16 people with migraine and 16 non-headache controls, and assessed whether the concentration of these neurochemicals explains, at least partially, inter-individual variability in binocular rivalry perceptual measures. Mean Glx level was significantly reduced in migraineurs relative to controls, whereas mean occipital GABA levels were similar between groups. Neither GABA levels, nor Glx levels correlated with rivalry percept duration. Our results thus suggest that the previously suggested relationship between rivalry percept duration and GABAergic inhibitory neurotransmitter concentration in visual cortex is not strong enough to enable rivalry percept duration to be reliably assumed to be a surrogate for GABA concentration, at least in the context of healthy individuals and those that experience migraine.

PURPOSE: People enjoy supervision during visual field assessment, although resource demands often make this difficult. We evaluated outcomes and subjective experience of methods of receiving feedback during perimetry, with specific goals to compare a humanoid robot to a computerized voice in participants with minimal prior perimetric experience. Human feedback and no feedback also were compared. METHODS: Twenty-two younger (aged 21-31 years) and 18 older (aged 52-76 years) adults participated. Visual field tests were conducted using an Octopus 900, controlled with the Open Perimetry Interface. Participants underwent four tests with the following feedback conditions: (1) human, (2) humanoid robot, (3) computer speaker, and (4) no feedback, in random order. Feedback rules for the speaker and robot were identical, with the difference being a social interaction with the robot before the test. Quantitative perimetric performance compared mean sensitivity (dB), fixation losses, and false-positives. Subjective experience was collected via survey. RESULTS: There was no significant effect of feedback type on the quantitative measures. For younger adults, the human and robot were preferred to the computer speaker (P < 0.01). For older adults, the experience rating was similar for the speaker and robot. No feedback was the least preferred option of 77% younger and 50% older adults. CONCLUSIONS: During perimetry, a social robot was preferred to a computer speaker providing the same feedback, despite the robot not being visible during the test. Making visual field testing more enjoyable for patients and operators may improve compliance and attitude to perimetry, leading to improved clinical outcomes. TRANSLATIONAL RELEVANCE: Our data suggest that humanoid robots can replace some aspects of human interaction during perimetry and are preferable to receiving no human feedback.

Caffeine is a widely used psychostimulant that is associated with increased acetylcholine levels in mammalian brain and acetycholinesterase antagonism. Acetylcholine, a neuromodulator, plays an important role in the processing of visual information. One key example in human vision, thought to at least partly involve cholinergic neuromodulation, is perceptual surround suppression of contrast, whereby the perceived contrast of a pattern is altered by the presence of a neighbouring pattern. Perceptual surround suppression is weaker with pharmacological administration of donepezil (a centrally-acting acetylcholine enzyme inhibitor) in healthy human observers. Here, we test whether temporarily manipulating caffeine levels (from complete washout to a controlled dose of caffeine) has a similar effect on perceptual surround suppression in 21 healthy young adults (aged 20-24 years, 11 females). Neither ingestion of a caffeine pill nor placebo altered contrast judgments when the target pattern was presented on a uniform grey background ( p=0.54). With caffeine ingestion, perceptual surround suppression strength was reduced relative to baseline (prior to pill ingestion, p=0.003) and placebo ( p=0.029), irrespective of whether the surround was oriented parallel or orthogonal to the central target. While daily habitual caffeine consumption of low-to-moderate doses (<400 mg/day, estimated from a written questionnaire) is not predictive of performance, our study indicates that acute consumption of caffeine on the day of testing influences perceptual surround suppression strength. Perceptual surround suppression is predominantly attributed to inhibitory processes involving the major cortical inhibitory neurotransmitter, gamma-aminobutyric acid. Our results point to the involvement of other neuromodulators, possibly cholinergic, in perceptual surround suppression.

Within each sensory modality, age-related deficits in temporal perception contribute to the difficulties older adults experience when performing everyday tasks. Since perceptual experience is inherently multisensory, older adults also face the added challenge of appropriately integrating or segregating the auditory and visual cues present in our dynamic environment into coherent representations of distinct objects. As such, many studies have investigated how older adults perform when integrating temporal information across audition and vision. This review covers both direct judgments about temporal information (the sound-induced flash illusion, temporal order, perceived synchrony, and temporal rate discrimination) and judgments regarding stimuli containing temporal information (the audiovisual bounce effect and speech perception). Although an age-related increase in integration has been demonstrated on a variety of tasks, research specifically investigating the ability of older adults to integrate temporal auditory and visual cues has produced disparate results. In this short review, we explore what factors could underlie these divergent findings. We conclude that both task-specific differences and age-related sensory loss play a role in the reported disparity in age-related effects on the integration of auditory and visual temporal information.

PURPOSE: The number of older adults is rapidly increasing internationally, leading to a significant increase in research on how healthy ageing impacts vision. Most clinical assessments of spatial vision involve simple detection (letter acuity, grating contrast sensitivity, perimetry). However, most natural visual environments are more spatially complicated, requiring contrast discrimination, and the delineation of object boundaries and contours, which are typically present on non-uniform backgrounds. In this review we discuss recent research that reports on the effects of normal ageing on these more complex visual functions, specifically in the context of recent neurophysiological studies. RECENT FINDINGS: Recent research has concentrated on understanding the effects of healthy ageing on neural responses within the visual pathway in animal models. Such neurophysiological research has led to numerous, subsequently tested, hypotheses regarding the likely impact of healthy human ageing on specific aspects of spatial vision. SUMMARY: Healthy normal ageing impacts significantly on spatial visual information processing from the retina through to visual cortex. Some human data validates that obtained from studies of animal physiology, however some findings indicate that rethinking of presumed neural substrates is required. Notably, not all spatial visual processes are altered by age. Healthy normal ageing impacts significantly on some spatial visual processes (in particular centre-surround tasks), but leaves contrast discrimination, contrast adaptation, and orientation discrimination relatively intact. The study of older adult vision contributes to knowledge of the brain mechanisms altered by the ageing process, can provide practical information regarding visual environments that older adults may find challenging, and may lead to new methods of assessing visual performance in clinical environments.

PURPOSE: We determine the feasibility of using a home-based tablet device to monitor retinal sensitivity (RS) in intermediate age-related macular degeneration (iAMD), the benefits of weekly reminders, and the comparison with clinic-based results. METHODS: A customized test for tablets was designed to measure RS (within central 2°) in individuals with iAMD at weekly intervals in their home, with remote data collection. Half of the participants were randomized to receive weekly test reminders. Clinic-based microperimetric macular sensitivity results were compared to tablet results. Participation rates were analyzed at 2 months. RESULTS: Of 38 participants (mean age, 70.3 years) with iAMD enrolled in the study, 21 (55%) were using the tablet-based test at 2 months. Common reasons for inactivity were noncompatible devices (41.1%) or other technology access issues (35.3%). Participants with weekly reminders completed tests more regularly (6.6 ± 3.9 vs. 8.7 ± 4.1 days, P = 0.01), but weekly reminders showed no effect on participation rates (P = 0.69). Mean RS from the tablet device (25.03 ± 2.41 dB) was not significantly different from the clinic-based microperimetry performance (25.21 ± 2.20 dB; P = 0.58). CONCLUSIONS: Regular monitoring of retinal function on a tablet device in a home setting in individuals with iAMD is feasible with results comparable to those of clinic-based microperimetry. Weekly reminders resulted in more frequent testing. Seamless ability to access technology will be important for higher participation rates. TRANSLATIONAL RELEVANCE: The use of home-monitoring on a tablet-device is promising, but adequate support for an older cohort to take up technology is required if such a tool is to be useful for long-term home monitoring.

Previous studies have found evidence for reduced cortical inhibition in aging visual cortex. Reduced inhibition could plausibly increase the spatial area of excitation in receptive fields of older observers, as weaker inhibitory processes would allow the excitatory receptive field to dominate and be psychophysically measureable over larger areas. Here, we investigated aging effects on spatial summation of motion direction using the Battenberg summation method, which aims to control the influence of locally generated internal noise changes by holding overall display size constant. This method produces more accurate estimates of summation area than conventional methods that simply increase overall stimulus dimensions. Battenberg stimuli have a checkerboard arrangement, where check size (luminance-modulated drifting gratings alternating with mean luminance areas), but not display size, is varied and compared with performance for a full field stimulus to provide a measure of summation. Motion direction discrimination thresholds, where contrast was the dependent variable, were measured in 14 younger (24-34 years) and 14 older (62-76 years) adults. Older observers were less sensitive for all check sizes, but the relative sensitivity across sizes, also differed between groups. In the older adults, the full field stimulus offered smaller performance improvements compared to that for younger adults, specifically for the small checked Battenberg stimuli. This suggests aging impacts on short-range summation mechanisms, potentially underpinned by larger summation areas for the perception of small moving stimuli.

PURPOSE: Correctly classifying progression in moderate to advanced glaucoma is difficult. Pointwise visual field test-retest variability is high for sensitivities below approximately 20 dB; hence, reliably detecting progression requires many test repeats. We developed a testing approach that does not attempt to threshold accurately in areas with high variability, but instead expends presentations increasing spatial fidelity. METHODS: Our visual field procedure Australian Reduced Range Extended Spatial Test (ARREST; a variant of the Bayesian procedure Zippy Estimation by Sequential Testing [ZEST]) applies the following approach: once a location has an estimated sensitivity of <17 dB (a "defect"), it is checked that it is not an absolute defect (<0 dB, "blind"). Saved presentations are used to test extra locations that are located near the defect. Visual field deterioration events are either: (1) decreasing in the range of 40 to 17 dB, (2) decreasing from >17 dB to "defect", or (3) "defect" to blind. To test this approach we used an empirical database of progressing moderate-advanced 24-2 visual fields (121 eyes) that we "reverse engineered" to create visual field series that progressed from normal to the end observed field. ARREST and ZEST were run on these fields with test accuracy, presentation time, and ability to detect progression compared. RESULTS: With specificity for detecting progression matched at 95%, ZEST and ARREST showed similar sensitivity for detecting progression. However, ARREST used approximately 25% to 40% fewer test presentations to achieve this result in advanced visual field damage. ARREST spatially defined the visual field deficit with greater precision than ZEST due to the addition of non-24-2 locations. CONCLUSIONS: Spending time trying to accurately measure visual field locations that have high variability is not productive. Our simulations indicate that giving up attempting to quantify size III white-on-white sensitivities below 17 dB and

Background Several visual tasks have been proposed as indirect assays of the balance between cortical inhibition and excitation in migraine. This study aimed to determine whether daily measurement of performance on such tasks can reveal perceptual changes in the build up to migraine events. Methods Visual performance was measured daily at home in 16 non-headache controls and 18 individuals with migraine using a testing protocol on a portable tablet device. Observers performed two tasks: luminance increment detection in spatial luminance noise and centre surround contrast suppression. Results Luminance thresholds were reduced in migraine compared to control groups ( p < 0.05), but thresholds did not alter across the migraine cycle; while headache-free, centre-surround contrast suppression was stronger for the migraine group relative to controls ( p < 0.05). Surround suppression weakened at around 48 hours prior to a migraine attack and strengthened to approach their headache-free levels by 24 hours post-migraine (main effect of timing, p < 0.05). Conclusions Daily portable testing of vision enabled insight into perceptual performance in the lead up to migraine events, a time point that is typically difficult to capture experimentally. Perceptual surround suppression of contrast fluctuates during the migraine cycle, supporting the utility of this measure as an indirect, non-invasive assay of the balance between cortical inhibition and excitation.

BACKGROUND: Visual snow (VS) is a constant visual disturbance described as flickering dots occupying the entire visual field. Recently, it was characterized as the defining feature of a VS syndrome (VSS), which includes palinopsia, photophobia, photopsias, entoptic phenomena, nyctalopia, and tinnitus. Sixty percent of patients with VSS also experience migraine, with or without aura. This entity often is considered psychogenic in nature, to the detriment of the patient's best interests, but the high frequency of similar visual symptoms argues for an organic deficit. The purpose of this review is to clarify VSS as a true entity and elaborate the nature of individual symptoms and their relationship to each other. EVIDENCE ACQUISITION: The literature was reviewed with specific regard to the clinical presentation and psychophysical, neurophysiological, and functional imaging studies in patients with defined visual disturbances that comprise VSS. RESULTS: Consideration of the individual symptoms suggests that multiple factors are potentially involved in the development of VSS, including subcortical network malfunction and cortical hyperexcitation. Although there is substantial overlap between VSS and migraine syndromes in terms of co-occurring symptoms, both neurophysiological and neuroimaging studies provide substantial evidence of separate abnormalities of processing, supporting these as separate syndromes. CONCLUSIONS: VSS is likely associated with either hyperactive visual cortices or, alternatively, impaired processing of simultaneous afferent information projecting to cortex. VSS likely results from widespread disturbance of sensory processing resulting in sensory misperception. There may be a number of syndromes associated with impaired sensory processing resulting in sensory misperception, including migraine, persistent perceptual postural dizziness, and tinnitus, which overlap with VSS. Elucidation of abnormality in one defined syndrome may provide a path forward

PURPOSE: To determine the feasibility of a tablet-based application to detect changes in retinal sensitivity and correlations with underlying pathology in neovascular age-related macular degeneration (nAMD) eyes undergoing treatment and in at-risk fellow eyes. METHOD: Participants with nAMD in at least one eye were recruited, examined, and imaged using spectral-domain optical coherence tomography (SD-OCT). Retinal sensitivity was measured within the central 5° at 12 locations using a customized test delivered on an iPad. Test points were superimposed on SD-OCT locations to investigate structure/function relationships. RESULTS: Included in the study were 53 nAMD eyes and 21 at-risk fellow eyes. In nAMD eyes, the mean retinal sensitivity was 24.1 ± 1.8 dB with reduced retinal sensitivity associated with the presence of atrophy (P < 0.01), retinal pigment epithelium (RPE) disruption (P < 0.01), and absent ellipsoid zone (EZ) (P < 0.01), but not with the presence of subretinal fluid (P = 0.94) nor intraretinal fluid (P = 0.52). In at-risk eyes, the average retinal sensitivity was 28.8 ± 0.6 dB, with reduced sensitivity significantly associated with the presence of drusen, atrophy, RPE disruption, and absent EZ (P < 0.01). CONCLUSION: The tablet-based test of retinal sensitivity was able to be performed by an elderly cohort with nAMD. The ability to correlate differences in sensitivity with pathology is encouraging when considering using the tablet devices as a home monitoring tool with remote surveillance. Dual pathology often present with retinal fluid confounded our ability to correlate fluid with sensitivity. TRANSLATIONAL RELEVANCE: These findings highlight the potential of tablet-based devices in performing visual function measures as a home monitoring tool with remote surveillance for the earlier detection of nAMD.

PURPOSE: The purpose of this study was to study how, in midperipheral vision, aging affects visual processes that interfere with target detection (crowding and surround suppression) and to determine whether the performance on such tasks are related to visuospatial attention as measured by visual search. METHODS: We investigated the effect of aging on crowding and suppression in detection of a target in peripheral vision, using different types of flanking stimuli. Both thresholds were also obtained while varying the position of the flanker (placed inside or outside of target, relative to fixation). Crowding thresholds were also estimated with spatial uncertainty (jitter). Additionally, we included a visual search task comprising Gabor stimuli to investigate whether performance is related to top-down attention. Twenty young adults (age, 18-32 years; mean age, 26.1 years; 10 males) and 19 older adults (age, 60-74 years; mean age, 70.3 years; 10 males) participated in the study. RESULTS: Older adults showed more surround suppression than the young (F[1,37] = 4.21; P < 0.05), but crowding was unaffected by age. In the younger group, the position of the flanker influenced the strength of crowding, but not the strength of suppression (F[1,39] = 4.11; P < 0.05). Crowding was not affected by spatial jitter of the stimuli. Neither crowding nor surround suppression was predicted by attentional efficiency measured in the visual search task. There was also no significant correlation between crowding and surround suppression. CONCLUSIONS: We show that aging does not affect visual crowding but does increase surround suppression of contrast, suggesting that crowding and surround suppression may be distinct visual phenomena. Furthermore, strengths of crowding and surround suppression did not correlate with each other nor could they be predicted by efficiency of visual search.