Degradation of Photopic and Mesopic Contrast Sensitivity Function in High Myopes With Partial Posterior Vitreous Detachment.

Purpose: The purpose of this study was to evaluate the effects of posterior vitreous detachment (PVD) on visual quality in patients with high myopia, as well as investigate the associated factors of photopic and mesopic contrast sensitivity function (CSF) in high myopia. Methods: Visual quality was comprehensively assessed in patients with high myopia. Visual acuity, contrast sensitivity (CS) at four spatial frequencies (3, 6, 12, and 18 cycles per degree [c.p.d.]) under photopic and mesopic conditions, as well as the modulation transfer function cutoff value (MTFcutoff), the objective scatter index (OSI), the Strehl ratio (SR), and internal aberrations, were measured in this cross-sectional study. Results: This study included 94 eyes from 47 subjects with bilateral high myopia, including 23 eyes with complete PVD (cPVD), 21 eyes with partial PVD (pPVD), and 50 eyes without PVD (nPVD). There was no significant difference in visual quality between the cPVD group and the nPVD group. Whereas in eyes with pPVD, there was a degradation of overall photopic CSF (versus nPVD, P = 0.048), photopic CS at 3 c.p.d. (versus cPVD, P = 0.009 and versus nPVD, P = 0.032), photopic CS at 18 c.p.d. (versus nPVD, P = 0.033), overall mesopic CSF (versus nPVD, P = 0.033), and secondary astigmatism (versus cPVD, P = 0.044). Under photopic conditions, the factors affecting CSF were pPVD and SR, whereas the factors affecting mesopic CSF were pPVD, OSI, and ganglion cell-inner plexiform layer thickness. Conclusions: The pPVD impaired visual quality in patients with high myopia compared to nPVD or cPVD, and pPVD could be a factor explaining CSF at both photopic and mesopic illumination. Translational Relevance: Clinicians need to closely monitor patients with high myopia with pPVD due to the potential decline in visual quality and the development of vitreoretinal disorders.

castleCSF - A contrast sensitivity function of color, area, spatiotemporal frequency, luminance and eccentricity.

The contrast sensitivity function (CSF) is a fundamental visual model explaining our ability to detect small contrast patterns. CSFs found many applications in engineering, where they can be used to optimize a design for perceptual limits. To serve such a purpose, CSFs must explain possibly a complete set of stimulus parameters, such as spatial and temporal frequency, luminance, and others. Although numerous contrast sensitivity measurements can be found in the literature, none fully explains the complete space of stimulus parameters. Therefore, in this work, we first collect and consolidate contrast sensitivity measurements from 18 studies, which explain the sensitivity variation across the parameters of interest. Then, we build an analytical contrast sensitivity model that explains the data from all those studies. The proposed castleCSF model explains the sensitivity as the function of spatial and temporal frequencies, an arbitrary contrast modulation direction in the color space, mean luminance, and chromaticity of the background, eccentricity, and stimulus area. The proposed model uses the same set of parameters to explain the data from 18 studies with an error of 3.59 dB. The consolidated contrast sensitivity data and the code for the model are publicly available at https://github.com/gfxdisp/castleCSF/.

Aerial single target acuity of harbor seals (Phoca vitulina) for stationary and moving targets of varying contrast.

Harbor seals (Phoca vitulina) need to detect single objects for example when orienting to landmarks or hunting prey. The detection of single objects, described by the single target acuity (STA), cannot be deduced from formerly determined grating acuity (GA) as different mechanisms underlie STA and GA. Thus, we assessed STA for stationary and moving single targets with varying contrast in two harbor seals in a first approach in air. In a two-alternative-forced-choice discrimination task, the seals had to indicate whether the single target was presented in a left or right stimulus field on a monitor. The STA for full-contrast stationary targets was determined as 0.27 deg of visual angle for both experimental animals. Contrary to our expectations, neither adding motion nor reducing contrast had a strong impact on STA. Additionally, we also determined GA in the two harbor seals (1.2 and 1.1 cycles/deg or 0.42 and 0.45 deg for a single stripe of the grating at threshold) to be slightly inferior to STA. Our results are in good correspondence with contrast sensitivity and allow calculating viewing distances in the context of for example visual orientation.

In primary visual cortex fMRI responses to chromatic and achromatic stimuli are interdependent and predict contrast detection thresholds.

Chromatic and achromatic signals in primary visual cortex have historically been considered independent of each other but have since shown evidence of interdependence. Here, we investigated the combination of two components of a stimulus; an achromatic dynamically changing check background and a chromatic (L-M or S cone) target grating. We found that combinations of chromatic and achromatic signals in primary visual cortex were interdependent, with the dynamic range of responses to chromatic contrast decreasing as achromatic contrast increased. A contrast detection threshold study also revealed interdependence of background and target, with increasing chromatic contrast detection thresholds as achromatic background contrast increased. A model that incorporated a normalising effect of achromatic contrast on chromatic responses, but not vice versa, best predicted our V1 data as well as behavioural thresholds. Further along the visual hierarchy, the dynamic range of chromatic responses was maintained when compared to achromatic responses, which became increasingly compressive.

Ocular parameters associated with visual performance of enhanced monofocal intraocular lens.

BACKGROUND: An enhanced monofocal intraocular lenses (IOLs) (Tecnis Eyhance ICB00 and Tecnis Eyhance Toric DIU) has been developed to enhance intermediate vision while avoiding the disadvantages of multifocal IOLs. Although many studies have demonstrated the improvement of intermediate visual acuity with enhanced monofocal IOLs, it is not known specifically for which patients these IOLs should be recommended or avoided. In this study, we aim to find out which ocular parameters affect vision performance and photic phenomenon of ICB00 or DIU at different distances. METHODS: Patients who underwent cataract surgery with ICB00 or DIU, performed by a single surgeon, were included. Before surgery, the patients' age, gender, axial length, anterior chamber depth, spherical aberration Z (4,0), vertical coma, horizontal coma, angle kappa (κ), angle alpha (α), and other ocular parameters were investigated. One month after surgery, uncorrected near visual acuity (UNVA at 40 cm), uncorrected intermediate visual acuity (UIVA at 66 cm), uncorrected distance logMAR visual acuity (UDVA), IOL decentration, and quality of vision (QoV) questionnaires were conducted. RESULTS: A total of 43 patients (58 eyes) were included. The results of the univariate linear regression analyses showed a negative correlation between spherical aberration and logMAR UNVA and UIVA (p = 0.003, ß=-0.51 and p = 0.018, ß=-0.23, respectively) and a positive correlation between angle α and logMAR UIVA (p = 0.036, ß = 0.19). Deeper anterior chamber depth (ACD) was associated with poorer total QoV (p = 0.018, ß = 14.43), particularly in glare, halo, blur, and fluctuation perception. A higher degree of IOL decentration tended to decrease UNVA and UIVA (Pearson correlation coefficient, r = 0.336 and r = 0.221, respectively); however, no significant effect was observed on UDVA (Pearson correlation coefficient, r = 0.042). CONCLUSIONS: In enhanced monofocal IOLs, a higher level of spherical aberration is associated with better performance in UNVA and UIVA, whereas a larger angle α has a negative impact. A deeper ACD negatively affects the QoV.

Exploring the impact of optical corrections on visual functions in myopia control-a scoping review.

PURPOSE: Myopia is controlled optically with peripheral defocus spectacles, multifocal contact lenses, or orthokeratology lenses. However, it is unknown which optical correction will improve visual performance. This scoping review aimed to identify and summarize studies on various visual functions using optical corrections for myopia control. METHODS: To develop the search strategy, population (Myopia), concept (visual performance), and context (unrestricted race/region) were used. PubMed, SCOPUS, Cochrane Library, and Web of Science databases were searched using the keywords myopia, contrast sensitivity, high and low contrast visual acuity, stereopsis, and optical correction of myopia control. This scoping review protocol was registered in the Open Science Framework registry and followed the framework for scoping review outlined by the Joanna Briggs Institute. RESULTS: Eight studies (n = 8) met the inclusion criteria and were included in the review. Four were conducted in Europe, two were conducted in China, and one was conducted in Japan and Singapore. Five studies were randomized controlled trials, out of which three used contact lenses and two studies used peripheral defocus spectacles lenses. Studies ranged from one day to 2 years. Three studies that used orthokeratology lenses were prospective study designs. Among the studies that used orthokeratology lenses and contact lenses, two studies measured the contrast sensitivity function with CSV1000 (Vector Vision) under mesopic and photopic conditions, with and without glare. Two studies measured the central and peripheral contrast sensitivity using psychophysics experiments. High and low contrast visual acuity was measured using the Freiburg Vision Test (n = 1) and ETDRS charts (n = 3), and stereopsis was assessed using a random dot stereogram (n = 1). The studies showed a reduction in central and peripheral contrast sensitivity function and low contrast acuity when treated with multifocal contact lenses, orthokeratology lenses, and peripheral defocus lenses compared with single-vision lenses. CONCLUSION: This scoping review found a reduction in central and peripheral contrast sensitivity function, as well as low contrast visual acuity when using various optical corrections for myopia control, while high-contrast visual acuity remained the same. The impact of visual functions may not influence the effectiveness of myopia control. Eye care practitioners should provide awareness to the parent and patient population about the potential visual impact of recent designs for optical corrections of myopia control.

Visual Field Dependence Persists in Age-Related Central Visual Field Loss.

Purpose: To examine whether the age-related increase in visual field dependence persists in older adults with central field loss (CFL). Methods: Twenty individuals with CFL were grouped into participants with age-related binocular CFL (CFL, n = 9), age-related monocular CFL/relative scotomata (mCFL, n = 8), and CFL occurring at a young age (yCFL, n = 3). Seventeen controls were age-matched to the older CFL groups (OA) and three to the yCFL group (yOA). Participants judged the tilt direction of a rod presented at various orientations under conditions with and without a visual reference. Visual field dependence was determined as the difference in judgment bias between trials with and without the visual reference. Visual field dependence was examined between groups and relative to visual acuity and contrast sensitivity. Results: All older groups performed similarly without the visual reference. The CFL group showed greater visual field dependence than the OA group (Mann-Whitney U test; U = 39, P = 0.045). However, there was no group difference when considering all three older groups (Kruskal-Wallis ANOVA; H(2, N = 34) = 4.31, P = 0.116). Poorer contrast sensitivity correlated with greater visual field dependence (P = 0.017; ρ = -0.43). Conclusions: Visual field dependence persists in older adults with CFL and seems exacerbated in those with dense binocular scotomata. This could be attributed to the sensitivity of the spared peripheral retina to orientation and motion cues. The relationship with contrast sensitivity further suggests that a decline in visual function is associated with an increase in visual field dependence beyond the effects of normal aging. These observations can guide tailored care and rehabilitation in older adults with CFL.

Clinical report: Virtual reality enables comparable contrast sensitivity measurements to in-office testing (pilot study).

SIGNIFICANCE: Vision health disparities largely stem from inaccessibility to vision specialists. To improve patient access to vision tests and to expedite clinical workflows, it is important to assess the viability of virtual reality (VR) as a modality for evaluating contrast sensitivity. PURPOSE: This study aimed to assess the validity of a VR version of the Pelli-Robson contrast sensitivity test by comparing its results with those of the corresponding in-office test. METHODS: Twenty-eight participants (mean ± standard deviation age, 37.3 ± 20.5 years) with corrected vision were recruited for testing on a voluntary basis with randomized administration of the in-office test followed by the VR analog or vice versa. Nineteen participants took each test twice to assess test-retest consistency in each modality. Virtual reality tests were conducted on a commercial Pico Neo Eye 2 VR headset, which has a 4K screen resolution. The environment for both tests was controlled by the participant for location and lighting. RESULTS: Similar sensitivity scores were obtained between testing modalities in both the right (n = 28 participants; Wilcoxon match-paired signed rank [SR], p=0.7) and left eyes (n = 28 participants; Wilcoxon match-paired SR, p=0.7). In addition, similar test-retest scores were found for VR (n = 19 participants; Wilcoxon match-paired SR, p=1.0) or in-office (n = 19 participants; Wilcoxon match-paired SR, p=1.0) tests. Virtual reality Pelli-Robson results correlated well with in-office test results in variably diseased participants (n = 14 eyes from 7 participants, R2 = 0.93, p<0.0001). CONCLUSIONS: In this pilot trial, we demonstrated that VR Pelli-Robson measurements of corrected vision align with those of in-office modalities, suggesting that this may be a reliable method of implementing this test in a more interactive and accessible manner.

Evaluation of contrast sensitivity in visually impaired individuals using K-CS test. A novel smartphone-based contrast sensitivity test-Design and validation.

BACKGROUND: To describe the development and investigate the accuracy of a novel smartphone-based Contrast Sensitivity (CS) application, the K-CS test. METHODS: A total of 67 visually impaired and 50 normal participants were examined monocularly using the novel digital K-CS test and the Pelli-Robson (PR) chart. The K-CS test examines letter contrast sensitivity in logarithmic units, using eight levels of contrast from logCS = ~0,1 to logCS = ~2,1 at two spatial frequencies of 1.5 and 3 cycles per degree (cpd). The K-CS test was compared to the gold standard, PR test and intra-session test repeatability was also examined. RESULTS: The K-CS test in normally sighted was found to agree well with the PR, providing comparable mean scores in logCS (±SD) (K-CS = 1.908 ± 0.06 versus PR = 1.93 ± 0.05) at 1.5 cpd and mean (± SD) logCS at 3 cpd (K-CS = 1.83 ± 0.13 versus PR = 1.86 ± 0.07). The mean best corrected visual acuity of visually impaired participants was 0.67 LogMAR (SD = 0.21) and the K-CS was also found to agree well with the Pelli-Robson in this group, with an equivalent mean (±SD) logCS at 1.5 cpd: (K-CS = 1.19 ± 0.27, PR = 1.15 ± 0.31), 3 cpd: K-CS = 1.01 ± 0.33, PR = 0.94 ± 0.34. Regarding the intra-session test repeatability, both the K-CS test and the PR test showed good repeatability in terms of the 95% limits of agreement (LoA): K-CS = ±0.112 at 1.5 cpd and ±0.133 at 3 cpd, PR = ±0.143 at 1.5 cpd and ±0.183 in 3 cpd in visually impaired individuals. CONCLUSION: The K-CS test provides a quick assessment of the CS both in normally sighted and visually impaired individuals. The K-CS could serve as an alternative tool to assess contrast sensitivity function using a smartphone and provides results that agree well with the commonly used PR test.

Effects of binocular disparity on binocular luminance combination.

This study aimed to examine the effects of binocular disparity on binocular combination of brightness information coming from luminance increments and decrements. The point of subjective equality was determined by asking the observers to judge which stimulus appeared brighter-a bar stimulus with variable disparity or another stimulus with zero disparity. For the bar stimulus, the interocular luminance ratio was varied to trace an equal brightness curve. Binocular disparity had no effect on luminance increments presented on a gray or black background. In contrast, when luminance decrements were presented on a gray background, non-zero disparities elevated points of subjective equality for stimuli with interocular luminance differences. This means that the binocular brightness combination of the two monocular signals shifted from winner-take-all summation toward linear averaging. It has been argued that this effect may be caused by non-zero binocular disparities attenuating interocular suppression, which is deemed to operate normally with zero disparity.

Optical and aberrometric evaluation of a new enhanced monofocal intraocular lens with isofocal optic design.

PURPOSE: To evaluate the optical and aberrometric outcomes of an enhanced monofocal intraocular lens (ISOPure) compared with those of a standard monofocal lens (MicroPure) having the same platform and material. METHODS: A prospective, comparative and randomised clinical study. A total of 28 eyes of 28 patients were randomly assigned to either group. Monocular visual acuity (VA) was measured at distance and intermediate under photopic and mesopic conditions. Aberrometry was analysed for 3.0-, 4.0-, 4.5- and 5.0 mm pupils. The contrast sensitivity defocus curve was measured for 3.0- and 4.5-mm pupils, while the modulation transfer function (MTF) and Strehl ratio (SR) were assessed with a double-pass system. All measurements were performed monocularly 3 months after surgery. RESULTS: No significant differences were found for distance VA. Under photopic conditions, intermediate VA was better with the ISOPure lens, while no significant differences were found between the lenses under mesopic conditions. Internal and total aberrations were higher for the ISOPure lens. No significant differences were found for corneal aberrations. Additionally, both the contrast sensitivity defocus curve and optical quality showed similar behaviour for each lens, with the MTF cut-off frequency exceeding 30 c/deg in both cases. CONCLUSION: The isofocal ISOPure lens enhanced intermediate VA without affecting distance VA under photopic conditions. Moreover, there were no significant differences in visual quality between the ISOPure and MicroPure lenses, despite the former exhibiting higher internal and total aberrations than the monofocal model.

Effect of decentration on the quality of vision in two aspheric posterior chamber intraocular lenses: A contralateral eye study.

PURPOSE: To perform an intraindividual comparison of the quality of vision and the effect of decentration between two aspheric intraocular lenses: aspheric balanced curve (ABC) design Vivinex iSert XY1 (Hoya Surgical Optics, Singapore) and anterior aspheric design Tecnis ZCB00 (Abbott Medical Optics, CA). SETTING: Tertiary Eye Care Centre. DESIGN: Prospective, randomized comparative study using a random number table. METHODS: Thirty patients were randomized to the implantation of Vivinex iSert XY1 in one eye and Tecnis ZCB00 in the contralateral eye. Then, 12 weeks postoperatively, a laser ray-tracing aberrometer was used to evaluate the visual Strehl ratio, higher-order aberrations (HOA), decentration of IOL from the visual axis and geometric axis, angle alpha, and angle kappa. Contrast sensitivity was measured using the functional visual analyzer. RESULTS: The visual internal Strehl ratio was higher ( P < 0.05) at all pupil sizes and the spherical aberrations values were lower ( P < 0.05) at larger pupil sizes (5 mm and 6 mm) in the Vivinex group. The mean decentration from the visual axis in the Vivinex group was significantly more than that in the Tecnis group ( P < 0.01). With an increase in angle alpha, there was a greater decline in the visual Strehl ratio for Tecnis; however, there was a statistically significant decline at 3 mm pupil size for Tecnis ZCB00 ( P = 0.028). The contrast sensitivity was similar for both IOLs. CONCLUSION: In comparison to an anterior aspheric design IOL, the ABC design IOL yielded better quality of vision, neutralized spherical aberrations to a larger extent, and provided a relatively superior quality of vision with decentration.

Applying Resampling and Visualization Methods in Factor Analysis to Model Human Spatial Vision.

Purpose: Studies have reported different numbers of spatial frequency channels for chromatic and achromatic vision. To resolve the difference, we performed factor analysis, a multivariate modeling technique, on population data of achromatic and chromatic sensitivity. In addition, we included resampling and visualization methods to evaluate models from factor analysis. These routines are complex but widely useful. Therefore we have archived our analysis routines by building smCSF, an open-source software package in R (https://smin95.github.io/dataviz/). Methods: Data of 103 normally-sighted adults were analyzed. They included blue-yellow, red-green, and achromatic contrast sensitivity. To obtain the confidence interval of relevant statistical parameters, factor analysis was performed using a resampling method. Then exploratory models were developed. We then performed model selections by fitting them against the empirical data and quantifying the quality of the fits. Results: During the exploratory factor analysis, different statistical tests supported different factor models. These could partially be reasons for why there have been conflicting reports. However, after the confirmatory analysis, we found that a model that included two spatial channels was adequate to approximate the chromatic sensitivity data, whereas that with three channels was so for the achromatic sensitivity data. Conclusions: Our findings provide novel insights about the spatial channels for chromatic and achromatic contrast sensitivity from population data. Also, the analysis and visualization routines have been archived in a computational package to boost the transparency and replicability of science.

Assessing perceptual chromatic equiluminance using a reflexive pupillary response.

Equiluminant stimuli help assess the integrity of colour perception and the relationship of colour to other visual features. As a result of individual variation, it is necessary to calibrate experimental visual stimuli to suit each individual's unique equiluminant ratio. Most traditional methods rely on training observers to report their subjective equiluminance point. Such paradigms cannot easily be implemented on pre-verbal or non-verbal observers. Here, we present a novel Pupil Frequency-Tagging Method (PFTM) for detecting a participant's unique equiluminance point without verbal instruction and with minimal training. PFTM analyses reflexive pupil oscillations induced by slow (< 2 Hz) temporal alternations between coloured stimuli. Two equiluminant stimuli will induce a similar pupil dilation response regardless of colour; therefore, an observer's equiluminant point can be identified as the luminance ratio between two colours for which the oscillatory amplitude of the pupil at the tagged frequency is minimal. We compared pupillometry-based equiluminance ratios to those obtained with two established techniques in humans: minimum flicker and minimum motion. In addition, we estimated the equiluminance point in non-human primates, demonstrating that this new technique can be successfully employed in non-verbal subjects.

Contrast response function estimation with nonparametric Bayesian active learning.

Multidimensional psychometric functions can typically be estimated nonparametrically for greater accuracy or parametrically for greater efficiency. By recasting the estimation problem from regression to classification, however, powerful machine learning tools can be leveraged to provide an adjustable balance between accuracy and efficiency. Contrast sensitivity functions (CSFs) are behaviorally estimated curves that provide insight into both peripheral and central visual function. Because estimation can be impractically long, current clinical workflows must make compromises such as limited sampling across spatial frequency or strong assumptions on CSF shape. This article describes the development of the machine learning contrast response function (MLCRF) estimator, which quantifies the expected probability of success in performing a contrast detection or discrimination task. A machine learning CSF can then be derived from the MLCRF. Using simulated eyes created from canonical CSF curves and actual human contrast response data, the accuracy and efficiency of the machine learning contrast sensitivity function (MLCSF) was evaluated to determine its potential utility for research and clinical applications. With stimuli selected randomly, the MLCSF estimator converged slowly toward ground truth. With optimal stimulus selection via Bayesian active learning, convergence was nearly an order of magnitude faster, requiring only tens of stimuli to achieve reasonable estimates. Inclusion of an informative prior provided no consistent advantage to the estimator as configured. MLCSF achieved efficiencies on par with quickCSF, a conventional parametric estimator, but with systematically higher accuracy. Because MLCSF design allows accuracy to be traded off against efficiency, it should be explored further to uncover its full potential.

Association of Contrast Sensitivity With Eye Disease and Vision-Related Quality of Life.

PURPOSE: To investigate contrast sensitivity (CS) as a screening tool to detect eye disease and assess its association with both eye disease and vision-related quality of life. DESIGN: Cross-sectional study. METHODS: Setting and population: Adults receiving care from a free clinic and a Federally Qualified Health Center in Michigan. MAIN OUTCOME MEASURES: Screening positive for eye disease and Visual Function Questionnaire (VFQ) score. OBSERVATION: Participants received a vision exam reviewed via telemedicine for disease, completed a demographic survey, and the 9-item VFQ. The ability of CS to predict eye disease was explored and area under the curve (AUC) is reported. Logistic and linear regression were used to investigate the continuous effect of CS on the probability of screening positive for eye disease and VFQ score, respectively, adjusting for age and visual acuity. RESULTS: 1159 included participants were, on average, 54.9 ± 14.5 years old, 62% identified as female, 34% as White, 54% as Black, 10% as Hispanic/Latino, and reported mean VFQ score of 79.7 ± 15.3. CS ranged from 0.00 to 1.95 log units (mean = 1.54 ± 0.24), 21% of eyes had glaucoma, 19% cataract, 6% DR, and 2% AMD. AUCs were 0.53 to 0.73. A 0.3 log unit decrease in better eye CS was associated with increased odds of glaucoma (odds ratio [OR] = 1.35, confidence interval [CI] = 1.09-1.67), cataract (OR = 1.35, CI = 1.05-1.72), DR (OR = 2.05, CI = 1.51-2.77), and AMD (OR = 2.08, CI = 1.10-3.91). A 0.3 log unit increase in better eye CS was associated with a 5.9 unit increase in VFQ. CONCLUSION: While CS alone is not sufficient to identify people with eye disease, it is an important measure of visual function that can add value to comprehensive eye screening.

Binocular Summation With Quantitative Contrast Sensitivity Function: A Novel Parameter to Evaluate Binocular Function in Intermittent Exotropia.

Purpose: Intermittent exotropia (IXT) is the most common form of strabismus. Surgery can potentially improve binocular function in patients with IXT. We aimed to evaluate binocular function using a novel parameter-binocular summation ratio (BSR), measured using quantitative contrast sensitivity function (CSF) in patients with IXT before and after surgery. Methods: Prospective study of 63 patients with IXT and 41 healthy controls were consecutively enrolled and underwent quantitative CSF testing binocularly and monocularly. BSR was calculated by dividing the CSF of the binocular value by the better monocular value. Forty-eight patients with IXT underwent strabismus surgery. BSR, stereoacuity, fusion ability, and strabismus questionnaires were assessed pre-operatively and 2 months postoperatively. Results: Sixty-three patients with IXT (median age = 9 years) compared with 41 healthy controls showed a worse mean BSR based on all CSF metrics at baseline (the area under the log CSF [AULCSF], spatial frequency [SF] cutoff, and contrast sensitivity at 1.0-18.0 cpd SF). All 48 patients with IXT showed successful alignment after surgery, and there were significant improvements in BSR based on the AULCSF, SF cutoff, and contrast sensitivity at 6.0, 12.0, and 18.0 cpd SF, respectively. The distance stereoacuity and fusion ability also improved after surgery, and a better BSR was associated with better stereoacuity and fusion. For strabismus questionnaires, the psychosocial subscale scores improved postoperatively, whereas the functional subscale scores did not change. Conclusions: BSR based on quantitative CSF can characterize binocular function across a range of spatial frequencies and can be used as a supplemental measurement for monitoring binocularity in patients with IXT in clinical settings.

Assessment of amblyopic children undergoing occlusion therapy by pattern visual evoked potentials and contrast sensitivity tests.

Background: Amblyopia is a case where one or less commonly, both eyes have impaired visual performance, even with the best optical correction and no visible disease of the visual system. Objectives: To assess contrast sensitivity tests (CST) and pattern visual evoked potentials (PVEP) results in amblyopic children who have already started occlusion therapy for durations ranging from 6 to 12 months. Methods: This cross-sectional study was conducted on 200 eyes of 50 patients with monocular amblyopia and 50 age and sex matched controls. Both patients and controls underwent ophthalmological assessment, PVEP, and CST. Results: There was no statistically significant difference in the results of P100 latencies of qualitative PVEP in amblyopic eyes compared to non-amblyopic eyes and control eyes, while the qualitative CST showed a highly statistically significant difference, being affected in 98% of amblyopic eyes compared to unaffected eyes (4%) and control eyes (4%). The maximum contrast level and minimal contrast level of quantitative CST were significantly lower in amblyopic eyes compared to non-amblyopic and control eyes. The cutoff value of maximal contrast level at mean frequencies of 2.5 ± 0.9 Hz, and a range of (1.1-4.1) for amblyopic eyes is ≤21 dB, while the cutoff value of minimal contrast level at mean frequencies of 13.4 ± 2.6 Hz, and a range of (6.7-18) for amblyopic eyes is ≤12 dB. Conclusion: Detection of amblyopia by CST is a noninvasive and easy procedure, which represents a promising tool to support the diagnosis of amblyopia.

Effects of grating stimulation on vision in individuals with amblyopia: a systematic review and meta-analysis.

PURPOSE: To investigate the effects of Cambridge Stimulator with grating element stimulation on visual acuity (VA), grating acuity (GA), and contrast sensitivity (CS) in patients with amblyopia. METHODS: Three electronic databases (PubMed, Embase, and Cochrane Library) were searched for studies published from January 1970 to November 2022. The searched studies were reviewed and extracted independently by two authors. The included studies were evaluated by the Cochrane risk of bias. A meta-analysis calculating Hedges' g effect-size metric with 95% confidence intervals using random-effects DerSimonian-Laird model was employed. Heterogeneity was estimated using I2 statistics. Outcomes of interest included VA, GA, and CS. RESULTS: A total of 1221 studies were identified. Twenty-four studies including 900 subjects met the inclusion criteria. The outcome measure of all visual indexes (VA: Hedges' g of - 0.43, 95% CI = - 0.81 to - 0.05, I2 = 86%, p = 0.02; GA: Hedges' g of 3.79, 95% CI = 1.05 to 6.54, I2 = 98%, p = 0.01; CS: Hedges' g of 0.64, 95% CI = 0.19 to 1.09, I2 = 41%, p = 0.00) significantly favored in the grating group. CONCLUSIONS: Grating stimulation may be a positive help for visual functions in patients with amblyopia. The effects of grating stimulation on VA and CS appear to be opposite. This study is registered with www.crd.york.ac.uk/prospero/ (CRD42022366259).

Featural Representation and Internal Noise Underlie the Eccentricity Effect in Contrast Sensitivity.

Human visual performance for basic visual dimensions (e.g., contrast sensitivity and acuity) peaks at the fovea and decreases with eccentricity. The eccentricity effect is related to the larger visual cortical surface area corresponding to the fovea, but it is unknown if differential feature tuning contributes to this eccentricity effect. Here, we investigated two system-level computations underlying the eccentricity effect: featural representation (tuning) and internal noise. Observers (both sexes) detected a Gabor embedded in filtered white noise which appeared at the fovea or one of four perifoveal locations. We used psychophysical reverse correlation to estimate the weights assigned by the visual system to a range of orientations and spatial frequencies (SFs) in noisy stimuli, which are conventionally interpreted as perceptual sensitivity to the corresponding features. We found higher sensitivity to task-relevant orientations and SFs at the fovea than that at the perifovea, and no difference in selectivity for either orientation or SF. Concurrently, we measured response consistency using a double-pass method, which allowed us to infer the level of internal noise by implementing a noisy observer model. We found lower internal noise at the fovea than that at the perifovea. Finally, individual variability in contrast sensitivity correlated with sensitivity to and selectivity for task-relevant features as well as with internal noise. Moreover, the behavioral eccentricity effect mainly reflects the foveal advantage in orientation sensitivity compared with other computations. These findings suggest that the eccentricity effect stems from a better representation of task-relevant features and lower internal noise at the fovea than that at the perifovea.