Impaired Visual Function in Posterior Vitreous Detachment Assessed With the Active-Learning Quantitative Contrast Sensitivity Function Test.

Introduction: To investigate whether there is visual function impairment in patients with posterior vitreous detachment (PVD) using the active-learning quantitative contrast sensitivity function test. Methods: In this cross-sectional study, contrast sensitivity was measured in eyes with PVD and eyes without PVD using the quantitative contrast sensitivity function algorithm on the Adaptive Sensory Technology platform. Outcomes included the area under the log contrast sensitivity function curve, contrast acuity, and contrast sensitivity thresholds at 1 to 18 cycles per degree (cpd). Snellen visual acuity (VA) was also measured. Mixed-effects multiple linear regression analyses were performed to evaluate the association between the presence of PVD and visual function, controlling for age and lens status. Results: The cohort comprised 232 healthy eyes of 205 participants; of these, 80 eyes of 69 patients had PVD. There was no significant association between VA and PVD presence. However, PVD was significantly associated with decreased contrast sensitivity thresholds at 1.5 cpd (ß, -0.058; P = .003) and 3 cpd (ß, -0.067; P = .004). Contrast sensitivity thresholds at lower (1 cpd) or higher (6, 12, 18 cpd) spatial frequencies did not significantly correlate with PVD presence. Even in the subgroup of symptomatic PVD eyes, VA was not significantly decreased, while quantitative contrast sensitivity function outcomes showed visual function deficits at low spatial frequencies (1.5 cpd and 3 cpd). Conclusions: Contrast sensitivity measured with the quantitative contrast sensitivity function test showed visual function deficits in eyes with PVD that would have been missed with VA testing alone. Incorporating this test in the retina clinic might offer a more comprehensive functional assessment of eyes with PVD, serving as an adjunct outcome metric in clinical decision-making.

Effect of brimonidine on visual indices in patients with acute optic neuritis: A single blind randomized clinical trial.

PURPOSE: This study investigates brimonidine's potential effect on visual functions, particularly contrast sensitivity (CS), an indicator of retinal ganglion cell function. METHODS: In this single-blind, randomized clinical trial, 60 patients (aged 23-56) with first-episode acute optic neuritis within seven days of symptom onset were randomly assigned to brimonidine or control groups. The intervention group received brimonidine three times daily for three months, while the control group received synthetic tears with the same dosage and frequency. Primary outcomes were changes in CS, visual acuity (VA), and color vision at one and three months post-treatment. Repeated measures ANOVA was used to assess statistically significant and partial eta squared (η2) values, mean differences, and clinically significance important were reported. RESULTS: All participants completed the study without complications. VA improved significantly in both groups by follow-up end (p < 0.001), with significant improvement from first to third month only in the brimonidine group (p < 0.001). The mean VA difference between groups was not statistically and clinically significant. CS showed statistically significant improvement within both groups (p < 0.001) and between groups (p < 0.001), with a large effect size (partial η2 = 0.28). The mean CS difference between groups (14.5) was clinically considerable. No significant changes in color vision were observed between groups (p = 0.96). CONCLUSION: Brimonidine significantly improved contrast sensitivity compared to placebo and was well-tolerated. Its neuroprotective effects suggest it may be beneficial in treating optic neuritis and preserving retinal ganglion cell function. TRIAL REGISTRATION: Prospectively registered at Iranian Clinical Trial Registration; Registration date 3 December 2022; Registration number: IRCT20221127056631N1.

The effect of femtosecond laser-assisted in situ keratomileusis on contrast sensitivity.

The benefits of femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for correcting vision, particularly in terms of spherical equivalent (SE) and visual acuity (VA), have gained broad recognition. Nevertheless, it has remained uncertain whether FS-LASIK has a positive impact on contrast sensitivity (CS). In this study, we measured CS on seven participants by the quick contrast sensitivity function (qCSF) and compared CS before and after the surgery at two time points (1 day and 7 days after) by the repeated measures analysis of variance (ANOVA). Then, we clarified the underlying mechanisms using the perceptual template model (PTM). Furthermore, we investigated the relationship among SE, VA, and CS employing the Pearson correlation test. We found that (1) CS exhibited significant improvements on postoperative day 1, with further enhancements observed up to postoperative day 7, (2) CS improvements were dependent on spatial frequency (SF) and external noise, (3) CS improvements were attributed to the reduction of internal noise and the enhancement of the perceptual template, (4) VA and SE demonstrated significant improvement post-surgery, and (5) no significant correlations were observed among SE, VA, and CS, possibly due to limitations in sample size and lighting conditions. These findings contribute to our comprehension of FS-LASIK and provide a great indicator for assessing the outcomes of visual surgery.

Association of contrast sensitivity with vessel density and functional parameters in different stages of glaucoma.

PURPOSE: To evaluate the association between contrast sensitivity (CS), vessel density (VD), and functional parameters in patients with glaucoma of varying severity. METHODS: Ninety-four eyes of 94 patients (57 men and 37 women, aged 56.52 ± 11.28 years) were divided into mild and moderate to advanced glaucoma groups. The mild glaucoma group was further subdivided based on the presence of central visual field defect (CVFD). Pearson's correlations were used to evaluate the associations between area under the log CS function (AULCSF), best-corrected visual acuity (BCVA), 10 - 2 visual field (VF), and structural parameters, including VD. The area under the receiver operating characteristic (AUROC) curve was calculated to detect abnormal CS (AULCSF < 1.2). RESULTS: In mild glaucoma without CVFD, AULCSF was associated with radial peripapillary capillary VD (γ = 0.597, P = 0.001), with an AUROC of 0.840 (P = 0.006) for detecting abnormal CS. In mild glaucoma with CVFD, AULCSF worsened and was associated with superficial parafoveal VD (γ = 0.569, P = 0.017) and macular whole image VD (γ = 0.632, P = 0.007), with AUROCs of 0.833 (P = 0.021) and 0.792 (P = 0.043), respectively. In moderate to advanced glaucoma, the relationship between AULCSF and the mean deviation of 10 - 2 VF and BCVA was more robust than that observed in structural measures. CONCLUSIONS: Decreased VD is linked to early CS impairment. Radial peripapillary capillary and macular VD can serve as indicators of CS function in the early stages of glaucoma. KEY  MESSAGES: What is known Contrast sensitivity loss has been reported in glaucoma patients but its relationship with glaucoma-related structural and functional changes in different glaucoma severity and central visual field defect (CVFD) remains elusive. What is new Decline in RPC peripapillary vessel density was associated with early impairment of contrast sensitivity in mild glaucoma without CVFD. Decline in macular vessel density and central 16 points of 10-2 visual field damage were associated with contrast sensitivity reduction in mild glaucoma with CVFD. Microvasculature change can serve as an indicator for abnormal contrast sensitivity.

A chart-based test of contrast sensitivity in noise: reference ranges, effects of age and optical abnormality.

CLINICAL RELEVANCE: Contrast sensitivity plays an important role in the comprehensive assessment of visual function; however, measurement with standard eye charts can be affected by age and optical abnormality. BACKGROUND: This study describes a novel chart-based test of letter contrast sensitivity (CS) in luminance noise (the Illinois Eye and Ear Noise CS test), defines normal reference ranges, estimates test-retest repeatability, and assesses the effects of age and simulated optical abnormalities. METHODS: Seventy-five individuals with normal visual function (age 18-85 years) participated. Subjects identified letter optotypes that spanned a broad contrast range (0.9% to 59.6%) printed in a book-based test. Letters were presented against a grey background (no-noise condition) and in luminance noise that consisted of light and dark checks (noise condition). A subset of 10 subjects repeated the test to define short-term variability and performed the test under three additional conditions: simulated cataract, +2.00D defocus, and low room illuminance. RESULTS: In the no-noise condition, CS was independent of age (mean log CS of 1.74) until approximately 54 years, and declined for older subjects (CS loss of 0.1 log unit/decade). CS measured in noise was independent of age across the range of ages tested (mean log CS of 0.91). The 95% limits of agreement for test-retest repeatability was 0.19 log units. Simulated cataract, +2.00D defocus, and reduced illumination significantly reduced CS in the no-noise condition (F = 102.6, p < 0.001), whereas these optical manipulations did not significantly affect CS in noise (F = 2.58, p = 0.074). CONCLUSIONS: Measurements of CS in luminance noise may be valuable, as these measures are largely independent of age and certain forms of optical degradation. CS measurements in noise may provide useful insight into visual function in patients who have combined neural and optical abnormality, as noise minimises CS loss from optical defects.

Impact of Glaucomatous Ganglion Cell Damage on Central Visual Function.

Glaucoma, a leading cause of irreversible blindness, is characterized by the progressive loss of retinal ganglion cells (RGCs) and subsequent visual field defects. RGCs, as the final output neurons of the retina, perform key computations underpinning human pattern vision, such as contrast coding. Conventionally, glaucoma has been associated with peripheral vision loss, and thus, relatively little attention has been paid to deficits in central vision. However, recent advancements in retinal imaging techniques have significantly bolstered research into glaucomatous damage of the macula, revealing that it is prevalent even in the early stages of glaucoma. Thus, it is an opportune time to explore how glaucomatous damage undermines the perceptual processes associated with central visual function. This review showcases recent studies addressing central dysfunction in the early and moderate stages of glaucoma. It further emphasizes the need to characterize glaucomatous damage in both central and peripheral vision, as they jointly affect an individual's everyday activities.

Dual and Multi-Target Cone-Beam X-ray Luminescence Computed Tomography Based on the DeepCB-XLCT Network.

BACKGROUND AND OBJECTIVE: Emerging as a hybrid imaging modality, cone-beam X-ray luminescence computed tomography (CB-XLCT) has been developed using X-ray-excitable nanoparticles. In contrast to conventional bio-optical imaging techniques like bioluminescence tomography (BLT) and fluorescence molecular tomography (FMT), CB-XLCT offers the advantage of greater imaging depth while significantly reducing interference from autofluorescence and background fluorescence, owing to its utilization of X-ray-excited nanoparticles. However, due to the intricate excitation process and extensive light scattering within biological tissues, the inverse problem of CB-XLCT is fundamentally ill-conditioned. METHODS: An end-to-end three-dimensional deep encoder-decoder network, termed DeepCB-XLCT, is introduced to improve the quality of CB-XLCT reconstructions. This network directly establishes a nonlinear mapping between the distribution of internal X-ray-excitable nanoparticles and the corresponding boundary fluorescent signals. To improve the fidelity of target shape restoration, the structural similarity loss (SSIM) was incorporated into the objective function of the DeepCB-XLCT network. Additionally, a loss term specifically for target regions was introduced to improve the network's emphasis on the areas of interest. As a result, the inaccuracies in reconstruction caused by the simplified linear model used in conventional methods can be effectively minimized by the proposed DeepCB-XLCT method. RESULTS AND CONCLUSIONS: Numerical simulations, phantom experiments, and in vivo experiments with two targets were performed, revealing that the DeepCB-XLCT network enhances reconstruction accuracy regarding contrast-to-noise ratio and shape similarity when compared to traditional methods. In addition, the findings from the XLCT tomographic images involving three targets demonstrate its potential for multi-target CB-XLCT imaging.

Influence of Visual Field on Visual Acuity and Contrast Sensitivity in Open-Angle Glaucoma Eyes with Monofocal and Extended Depth-of-Focus Intraocular Lenses.

INTRODUCTION: The aim of this prospective and comparative study was to investigate the association of perimetry parameters on visual acuity and contrast sensitivity in primary open-angle glaucoma (POAG) eyes with diffractive extended depth-of-focus (EDoF) and monofocal intraocular lenses (IOLs). METHODS: In cataract eyes with medicinally controlled POAG with no defects in the central visual field and mean deviation (MD) values of - 10 dB or better, EDoF and monofocal IOLs with the same platform except for echelette optics for EDoF were implanted in 22 and 24 eyes, respectively. Corrected distance visual acuity (CDVA), contrast sensitivity at 3 to 18 cycles per degree (cpd), and automated perimetry using 30-2 and 10-2 Swedish Interactive Threshold Algorithm programs were examined 3 months postoperatively. The influences of perimetry parameters including MD, foveal sensitivity (FS), and the means of the central four points (central MD and central FS) on CDVA and contrast sensitivity were evaluated using linear and multiple regression analyses. RESULTS: In POAG eyes with EDoF IOLs, contrast sensitivities at 12 and 18 cpd were associated with 30-2 and 10-2 perimetry parameters. In POAG eyes with monofocal IOLs, associations of 30-2 parameters were found in CDVA and 3-cpd contrast sensitivity. CONCLUSIONS: The visual function of POAG eyes with EDoF IOLs was associated with perimetry parameters in high spatial frequency contrast sensitivity, which was different from that of POAG eyes with monofocal IOL. TRIAL REGISTRATION: Japan Registry for Clinical Research: jRCTs032200218.

The effect of sunglass filters on contrast sensitivity, monocular eye closure, and blinking rate in people with intermittent exotropia.

CLINICAL RELEVANCE: Transient monocular eye closure and photosensitivity under bright light have been reported in people with intermittent exotropia (IXT). The exact mechanism of these symptoms has not been established. BACKGROUND: This study examines the effect of sunglass filters on contrast sensitivity (CS), transient monocular eye closure, and blinking rate under bright light in people with IXT. METHODS: Forty participants with IXT and complaints of photosensitivity were included in the study. The binocular CS test was performed under mesopic and photopic conditions with and without glare, and with and without two filters with different grades of light transmission (filter 1: 44-80%; filter 2: 20-43% light transmittance). The effect of two filters on transient eye closure, contrast sensitivity, and blinking rate was assessed under bright light. Also, participants were divided into 3 groups based on their degree of control of fusion (good, fair, and poor control). RESULTS: The mean age of the participants was 12.0 years ± 8.0 (standard deviation) (range: 7-40 years). There was no significant difference between the age (p = 0.139), stereopsis (p = 0.134), as well as the near and far degree of deviation (p = 0.516, and p = 0.237) between the three groups of fusion control. Under mesopic conditions with glare, mean binocular CS was significantly higher with filters (p < 0.001). Without filters, 57.5% of the participants exhibited monocular eye closure under a photopic setting with additional glare. No participant showed eye closure using filter 2. People in the poor control group showed exodeviation before monocular eye closure (62.5% without filter and 12.5% with filter 1, p = 0.01). The blinking rate decreased from 36.0 ± 4.0 blinks per minute without filter to 21.0 ± 3.0 using filter 1, and 20.0 ± 3.0 with filter 2. CONCLUSION: In people with IXT, wearing sunglass filters of different transmittance reduces monocular eye closure and blinking rate under bright light. To improve these symptoms, sunglasses can be considered for IXT.

Visual impact of diffusion optic technology lenses for myopia control.

PURPOSE: To assess the visual impact of Diffusion Optics Technology™ 0.2 DOT lenses (SightGlass Vision Inc.) designed for myopia control on primary gaze. DOT spectacle lenses contain light scattering elements that scatter light as it passes through the lens which, in turn, reduces retinal image contrast. METHODS: Fifty-one children (12.2 ± 1.3, range 10-14 years; 51% females) were randomly assigned to wear DOT spectacle (n = 27) or single vision lenses (n = 24) across six investigational sites in North America. Binocular high- and low-contrast distant visual acuities, near visual acuity, reading speed, contrast sensitivity, stereoacuity and glare were assessed in primary gaze after at least 3 years of wear, with the study 95% powered in all metrics to detect significant differences between the groups. RESULTS: Mean binocular distance high-contrast (-0.09 ± 0.02 vs. -0.08 ± 0.02 logMAR, p = 0.81), low-contrast (0.05 ± 0.02 vs. 0.07 ± 0.02 logMAR, p = 0.52) and near visual acuity with glare sources (-0.06 ± 0.03 vs. -0.09 ± 0.03 logMAR, p = 0.32) were similar for DOT and single vision lens wearers, respectively. Contrast sensitivity was similar between children wearing DOT or single vision lenses across 11 of the 16 spatial frequencies (p > 0.05). Mean stereopsis was similar (p = 0.30) with the DOT lenses (33.2 ± 12.5″) and single vision lenses (38.1 ± 14.2″). Functional reading speed metrics were similar in both study groups, as was the objectively measured head tilt during reading (p > 0.05). The mean halo radius was 0.56° ± 0.17° with the DOT lenses compared with 0.50° ± 0.12° with single vision lenses (p = 0.02), but the statistically significant difference was smaller than the non-inferiority bound of 0.4°. CONCLUSION: Diffusion optics technology lenses provide a clinically equivalent visual experience to a standard single vision lens.

Comparison of visual quality after wavefront-guided LASIK in patients with different levels of preoperative total ocular higher-order aberrations: a retrospective study.

Purpose: To compare the visual quality after wavefront-guided femtosecond LASIK (WFG FS-LASIK) in patients with different levels of preoperative total ocular higher-order aberrations to guide clinical decision-making regarding patient selection and treatment strategies. Methods: This study included 112 right eyes of 112 patients who previously underwent WFG FS-LASIK for correcting myopia and myopic astigmatism. The patients were divided into two groups based on the mean values of preoperative total ocular HOAs (0.30 ± 0.09 µm): HOA ≤ 0.3 and > 0.3 groups. The visual acuity, manifest refraction, corneal Strehl ratio (SR), root mean square (RMS) of corneal and ocular aberrations, and area under the log contrast sensitivity function (AULCSF) of both groups were compared preoperatively and at 1, 3, 6, and 12 months postoperatively. Results: The induced ocular HOAs and coma (Δ = 1 mo - Preop) were significantly lower in the HOAs > 0.3 group than in the HOAs ≤ 0.3 group (ΔHOAs: 0.39 ± 0.19 vs. 0.29 ± 0.18 µm, t = 2.797, P = 0.006; Δ coma: 0.30 ± 0.19 vs. 0.20 ± 0.21 µm, t = 2.542, P = 0.012). In the HOAs > 0.3 group, ΔHOAs were negatively correlated with the preoperative ocular HOAs (r = -0.315, P = 0.019). In the HOAs ≤ 0.3 group, the regression equation for Δ HOAs = 0.098 + 0.053 |SE| (F = 21.756, P < 0.001). In the HOAs > 0.3 group, the regression equation for ΔHOAs = 0.534 - 1.081 HOAs + 0.038|Sphere| (F = 7.954, P = 0.001). The postoperative uncorrected distance visual acuity, spherical equivalent, corneal aberrations, SR and AULCSF of both groups were similar (all P > 0.05). Furthermore, the ocular aberrations were not significantly different between both groups at 3, 6, and 12 months postoperatively (all P > 0.05). In addition, compared with the preoperative period, the AULCSF of both groups were significantly increased in the postoperative period (all P < 0.05). Conclusions: The induced ocular HOAs and coma in HOAs > 0.3 group were lower. However, both groups achieved equivalent and excellent visual quality after WFG FS-LASIK. WFG FS-LASIK may provide significant visual benefits for a wider range of patients.

Visual contrast sensitivity is associated with community structure integrity in cognitively unimpaired older adults: the Brain Networks and Mobility (B-NET) Study.

Older adults with impairment in contrast sensitivity (CS), the ability to visually perceive differences in light and dark, are more likely to demonstrate limitations in mobility function, but the mechanisms underlying this relationship are poorly understood. We sought to determine if functional brain networks important to visual processing and mobility may help elucidate possible neural correlates of this relationship. This cross-sectional analysis utilized functional MRI both at rest and during a motor imagery (MI) task in 192 community-dwelling, cognitively-unimpaired older adults ≥ 70 years of age from the Brain Networks and Mobility study (B-NET). Brain networks were partitioned into network communities, groups of regions that are more interconnected with each other than the rest of the brain, the spatial consistency of the communities for multiple brain subnetworks was assessed. Lower baseline binocular CS was significantly associated with degraded sensorimotor network (SMN) community structure at rest. During the MI task, lower binocular CS was significantly associated with degraded community structure in both the visual (VN) and default mode network (DMN). These findings may suggest shared neural pathways for visual and mobility dysfunction that could be targeted in future studies.

Presaccadic Attention Enhances and Reshapes the Contrast Sensitivity Function Differentially around the Visual Field.

Contrast sensitivity (CS), which constrains human vision, decreases from fovea to periphery, from the horizontal to the vertical meridian, and from the lower vertical to the upper vertical meridian. It also depends on spatial frequency (SF), and the contrast sensitivity function (CSF) depicts this relation. To compensate for these visual constraints, we constantly make saccades and foveate on relevant objects in the scene. Already before saccade onset, presaccadic attention shifts to the saccade target and enhances perception. However, it is unknown whether and how it modulates the interplay between CS and SF, and if this effect varies around polar angle meridians. CS enhancement may result from a horizontal or vertical shift of the CSF, increase in bandwidth, or any combination. In addition, presaccadic attention could enhance CS similarly around the visual field, or it could benefit perception more at locations with poorer performance (i.e., vertical meridian). Here, we investigated these possibilities by extracting key attributes of the CSF of human observers. The results reveal that presaccadic attention (1) increases CS across SF, (2) increases the most preferred and the highest discernable SF, and (3) narrows the bandwidth. Therefore, presaccadic attention helps bridge the gap between presaccadic and postsaccadic input by increasing visibility at the saccade target. Counterintuitively, this CS enhancement was more pronounced where perception is better-along the horizontal than the vertical meridian-exacerbating polar angle asymmetries. Our results call for an investigation of the differential neural modulations underlying presaccadic perceptual changes for different saccade directions.

Neural Substrates for Early Data Reduction in Fast Vision: A Psychophysical Investigation.

To ensure survival, the visual system must rapidly extract the most important elements from a large stream of information. This necessity clashes with the computational limitations of the human brain, so a strong early data reduction is required to efficiently process information in fast vision. A theoretical early vision model, recently developed to preserve maximum information using minimal computational resources, allows efficient image data reduction by extracting simplified sketches containing only optimally informative, salient features. Here, we investigate the neural substrates of this mechanism for optimal encoding of information, possibly located in early visual structures. We adopted a flicker adaptation paradigm, which has been demonstrated to specifically impair the contrast sensitivity of the magnocellular pathway. We compared flicker-induced contrast threshold changes in three different tasks. The results indicate that, after adapting to a uniform flickering field, thresholds for image discrimination using briefly presented sketches increase. Similar threshold elevations occur for motion discrimination, a task typically targeting the magnocellular system. Instead, contrast thresholds for orientation discrimination, a task typically targeting the parvocellular system, do not change with flicker adaptation. The computation performed by this early data reduction mechanism seems thus consistent with magnocellular processing.

The Relationship between Clinical and Psychophysical Assessments of Visual Perceptual Disturbances in Individuals at Clinical High Risk for Psychosis: A Preliminary Study.

This study investigated relations between a measure of early-stage visual function and self-reported visual anomalies in individuals at clinical high risk for psychosis (CHR-P). Eleven individuals at CHR identified via the Structured Interview for Psychosis-Risk Syndromes (SIPS) were recruited from a CHR-P research program in NYC. The sample was ~36% female, ranging from 16 to 33 years old (M = 23.90, SD = 6.14). Participants completed a contrast sensitivity task on an iPad with five spatial frequencies (0.41-13 cycles/degree) and completed the self-report Audio-Visual Abnormalities Questionnaire. Higher contrast sensitivity (better performance) to low spatial frequencies was associated with higher perceptual (r = 0.616, p = 0.044) and visual disturbances (r = 0.667, p = 0.025); lower contrast sensitivity to a middle spatial frequency was also associated with higher perceptual (r = -0.604, p = 0.049) and visual disturbances (r = -0.606, p = 0.048). This relation between the questionnaire and contrast sensitivity to low spatial frequency may be indicative of a reduction in lateral inhibition and "flooding" of environmental stimuli. The association with middle spatial frequencies, which play a critical role in face processing, may result in a range of perceptual abnormalities. These findings demonstrate that self-reported perceptual anomalies occur in these individuals and are linked to performance on a measure of early visual processing.

Psychophysics of neon color spreading: Chromatic and temporal factors are not limiting.

Neon color spreading (NCS) is an illusory color phenomenon that provides a dramatic example of surface completion and filling-in. Numerous studies have varied both spatial and temporal aspects of the neon-generating stimulus to explore variations in the strength of the effect. Here, we take a novel, parametric, low-level psychophysical approach to studying NCS in two experiments. In Experiment 1, we test the ability of both cone-isolating and equiluminant stimuli to generate neon color spreading for both increments and decrements in cone modulations. As expected, sensitivity was low to S(hort-wavelength) cone stimuli due to their poor spatial resolution, but sensitivity was similar for the other color directions. We show that when these differences in detection sensitivity are accounted for, the particular cone type, and the polarity (increment or decrement), make little difference in generating neon color spreading, with NCS visible at about twice detection threshold level in all cases. In Experiment 2, we use L-cone flicker modulations (reddish and greenish excursions around grey) to study sensitivity to NCS as a function of temporal frequency from 0.5 to 8 Hz. After accounting for detectability, the temporal contrast sensitivity functions for NCS are approximately constant or even increase over the studied frequency range. Therefore there is no evidence in this study that the processes underlying NCS are slower than the low-level processes of simple flicker detection. These results point to relatively fast mechanisms, not slow diffusion processes, as the substrate for NCS.

Quantitative patterns of visual impairment and recovery in children with brain injury.

Brain injury can cause many distinct types of visual impairment in children, but these deficits are difficult to quantify due to co-morbid deficits in communication and cognition. Clinicians must instead rely on low-resolution, subjective judgements of simple reactions to handheld stimuli, which limits treatment potential. We have developed an interactive assessment program called the Visual Ladder, which uses gaze-based responses to intuitive, game-like tasks to address the lack of broad-spectrum quantified data on the visual abilities of children with brain injury. Here, we present detailed metrics on eye movements, field asymmetries, contrast sensitivity, and other critical visual abilities measured longitudinally using the Ladder in hospitalized children with varying types and degrees of brain injury, many of whom were previously considered untestable. Our findings show which abilities are most likely to exhibit recovery and reveal how distinct patterns of task outcomes defined unique diagnostic clusters of visual impairment.

Can repetitive transcranial magnetic stimulation influence the visual cortex of adults with amblyopia? - systematic review.

Amblyopia is the most frequent cause of monocular vision loss. Transcranial Magnetic Stimulation (TMS) has been used to improve several vision parameters of the amblyopic eye in adulthood. This study is relevant in order to evaluate TMS effects and to raise awareness of the need for further research. Transcranial Magnetic Stimulation (TMS) is a neuromodulation technique capable of changing cortical excitability. In the last decade, it has been used to improve visual parameters in amblyopic patients. The main goal of this systematic review is to evaluate the influence of TMS in the amblyopic eye, in the visual parameters of amblyopic patients. Searches were done in PubMed and Embase databases, and a combined search strategy was performed using the following Mesh, EMBASE, and keywords: 'Amblyopia', 'Transcranial Magnetic Stimulation', and 'theta burst stimulation'. This review included randomised controlled studies, descriptive cases, and clinical case studies with adult amblyopes. All articles that had any of the following characteristics were excluded: children or animal studies, reviews, pathologies other than amblyopia, and other techniques rather than repetitive TMS (rTMS), or Theta Burst Stimulation (TBS). A total of 42 articles were found, of which only four studies (46 amblyopes) meet the criteria above. Three of the articles found significant improvement after one session of continuous TBS (cTBS) in visual parameters like visual acuity, contrast sensitivity, suppressive imbalance, and stereoacuity. One study found a significant visual improvement with 10 Hz rTMS. Only one stimulation-related dropout was reported. The few existing studies found in this review seem to show that through the usage of high-frequency rTMS and cTBS, it is possible to re-balance the eyes of an adult amblyope. However, despite the promising results, further research with larger randomised double-blind studies is needed for a better understanding of this process.

Visual contrast sensitivity in clinical high risk and first episode psychosis.

BACKGROUND: Individuals at Clinical High Risk (CHR) for psychosis or in their First Episode (FE) of psychosis are in a pivotal time in adolescence or young adulthood when illness can greatly impact their functioning. Finding relevant biomarkers for psychosis in the early stages of illness can contribute to early diagnosis, therapeutic management and prediction of outcome. One such biomarker that has been studied in schizophrenia (SZ) is visual contrast sensitivity (VCS). VCS can be used to differentiate visual information processing function in the magnocellular versus parvocellular visual pathways. Few studies have assessed VCS in early psychosis. METHODS: Participants included CHR (n = 68), FE psychosis (n = 34) and Healthy Comparison (HC) (n = 63). All were clinically assessed and completed a VCS paradigm that involved near threshold luminance and chromatic stimuli. RESULTS: CHR and FE participants had lower VCS in the luminance condition (F[2166] = 3.42, p < 0.05) compared to HC. There was also a significant sex X group interaction (F[5163] = 4.3, p < 0.001) in the luminance condition (F[5163] = 4.3, p < 0.001) as FE males (p < 0.01) and CHR females (p < 0.01) had the greatest deficits compared to male and female HC participants respectively. VCS deficits in the luminance condition were associated with more thought disorder, slower processing speed, worse executive functioning and poor global functioning (r's 0.25-0.50, p < 0.05). CONCLUSION: This study supports the hypothesis that there are deficits in visual information processing, particularly in tasks that emphasize the magnocellular pathway, in patients experiencing early psychosis. VCS therefore has the potential to be used as a biomarker in this population.

Consequences of eye movements for spatial selectivity.

What determines spatial tuning in the visual system? Standard views rely on the assumption that spatial information is directly inherited from the relative position of photoreceptors and shaped by neuronal connectivity.1,2 However, human eyes are always in motion during fixation,3,4,5,6 so retinal neurons receive temporal modulations that depend on the interaction of the spatial structure of the stimulus with eye movements. It has long been hypothesized that these modulations might contribute to spatial encoding,7,8,9,10,11,12 a proposal supported by several recent observations.13,14,15,16 A fundamental, yet untested, consequence of this encoding strategy is that spatial tuning is not hard-wired in the visual system but critically depends on how the fixational motion of the eye shapes the temporal structure of the signals impinging onto the retina. Here we used high-resolution techniques for eye-tracking17 and gaze-contingent display control18 to quantitatively test this distinctive prediction. We examined how contrast sensitivity, a hallmark of spatial vision, is influenced by fixational motion, both during normal active fixation and when the spatiotemporal stimulus on the retina is altered to mimic changes in fixational control. We showed that visual sensitivity closely follows the strength of the luminance modulations delivered within a narrow temporal bandwidth, so changes in fixational motion have opposite visual effects at low and high spatial frequencies. By identifying a key role for oculomotor activity in spatial selectivity, these findings have important implications for the perceptual consequences of abnormal eye movements, the sources of perceptual variability, and the function of oculomotor control.