Amblyopia and binocular vision

Binocular imbalance measured by SSVEP predicts impaired stereoacuity in amblyopia

Purpose

The current study aims to implement steady-state visual evoked potentials (SSVEPs) in quantifying the binocular imbalance of amblyopia and to assess the predictive value of SSVEP-derived indices for amblyopic stereoacuity.

Methods

We measure frequency-tagged SSVEP responses elicited by each eye (F1 = 6 Hz through the fellow eye; F2 = 7.5 Hz through the amblyopic eye) within a binocular rivalry paradigm among a cohort of anisometropic amblyopic observers (n = 29, mean age: 12 years). Binocular suppression was quantified by assessing the disparity in SSVEP amplitudes between the eyes, while the strength of interocular interaction was evaluated through the intermodulation response at F1+F2 = 13.5 Hz. Subsequent analyses explored the associations between these neural indices and relevant behavioral metrics in amblyopia.

Results

Results reveal a significant difference in SSVEP amplitudes elicited from the fellow eye and the amblyopic eye, with the former exhibiting notably higher responses. Moreover, the fellow eye demonstrated prolonged dominance duration compared to its amblyopic counterpart. Furthermore, a negative correlation between binocular suppression and interocular interaction was observed, with stereoacuity showing a significant correlation with binocular suppression. Utilizing stepwise mulptiple linear regression analysis, we established that a predictive model combining binocular suppression and visual acuity of the amblyopic eye provided the best prediction of stereoacuity.

Conclusions

These results highlight the potential of binocular suppression, as assessed by SSVEPs within a binocular rivalry paradigm, as a promising neural predictor of stereopsis in amblyopia.

Add-on perceptual learning on refractive amblyopia in children

AIM

To evaluate the visual outcomes of standard amblyopic treatment add-on training via perceptual learning in refractive amblyopic children and to identify the risk factors for treatment failure.

METHODS

Retrospective charts were reviewed in children with refractive amblyopia who received standard treatment and add-on Cambridge Visual Stimulator (CAM) training. The add-on CAM group that was enrolled had worn full-corrected glasses for at least 2mo before training. A control group received only the standard treatment. Treatment success was defined as best-corrected visual acuity (BCVA) ≥20/25. The age, sex, initial BCVA, refractive errors, sessions and duration of training, and final BCVA were recorded.

RESULTS

A total of 209 children (129 children in add-on CAM group and 80 children in control group) were enrolled. Seventy-six percent of unilateral and 87% of bilateral amblyopic children achieved treatment success. In children with unilateral or bilateral moderate amblyopia, the duration to reach BCVA ≥20/25 was significantly shorter in add-on CAM group than in control group. Poor initial BCVA (P<0.001) and high astigmatism (P=0.007) were risk factors for treatment failure after add-on CAM training. Age, sex, and types of refractive error were not associated with treatment success.

CONCLUSION

Add-on CAM training is an effective strategy for visual improvement and can shorten the treatment course when the effect of standard treatment is limited in amblyopic children.

Fluoxetine as a possible treatment for adult amblyopia: results of a double-blind, randomized, placebo-controlled trial

PURPOSE

To evaluate the effects of oral fluoxetine on visual acuity and visual-evoked potential (VEP) parameters in adults patching for amblyopia.

METHODS

In this randomized clinical trial, adults (>18 years of age) with anisometropic or strabismic amblyopia were assigned randomly to a treatment (fluoxetine) group or a placebo group. Standard treatments for amblyopia (glasses prescription and patching) were prescribed for 4 months for all patients beforehand. The first group received fluoxetine (20 mg per day) and the second group received a placebo for 3 months, both continuing patching. Visual acuity evaluation and VEP were performed before and after treatment.

RESULTS

A total of 55 participants were included: 29 in the fluoxetine group and 26 in the placebo group. Mean age was 27.2 ± 8.6 years (18-54). The mean logMAR visual acuity of the amblyopic eye improved by 0.20 ± 0.24 (0-0.8) in the fluoxetine group (P < 0.001) and by 0.08 ± 0.15 (0-0.7) in the placebo group (P = 0.01); mean logMAR improvement was significantly higher in the fluoxetine group than in the placebo group (P = 0.04). At the end of the study, mean visual acuity of the fluoxetine group (0.36 ± 0.21 log MAR) was better than the placebo group (0.43 ± 0.35 log MAR). Among the VEP parameters, N75 amplitude did not change significantly in either group relative to baseline, but the changes were statistically significantly different between the two groups (P = 0.05); N135 latency improved from baseline in the fluoxetine group (P = 0.03).

CONCLUSIONS

In our study cohort, fluoxetine treatment resulted in greater improvement in visual acuity than placebo during patching for adult amblyopia.

Using the visual cliff and pole descent assays to detect binocular disruption in mice

Amblyopia, a neurodevelopmental visual disorder characterized by impaired stereoacuity, is commonly modeled in animals using monocular deprivation (MD) during a critical period of visual development. Despite extensive research at the synaptic, cellular and circuit levels of analysis, reliable behavioral assays to study stereoscopic deficits in mice are limited. This study aimed to characterize the Visual Cliff Assay (VCA) and the Pole Descent Cliff Task (PDCT) in mice, and to evaluate their utility in detecting binocular dysfunction. Using these assays, we investigated the impact of clinically relevant manipulations of binocular vision, including monocular occlusion, pupillary dilation, and amblyopia induced by long-term MD. Our findings reveal that optimal performance in both the VCA and PDCT are dependent on balanced binocular input. However, deficits after MD in the VCA exhibited relatively small effect sizes (7-14%), requiring large sample sizes for statistical comparisons. In contrast, the PDCT demonstrated larger effect sizes (43-61%), allowing for reliable detection of binocular dysfunction with a smaller sample size. Both assays were validated using multiple monocular manipulations relevant to clinical paradigms, with the PDCT emerging as the preferred assay for detecting deficits in stereoscopic depth perception in mice. These findings provide a robust framework for using the VCA and PDCT in mechanistic and therapeutic studies in mice, offering insights into the neural mechanisms of binocular vision and potential interventions for amblyopia.

Leveraging neural plasticity for the treatment of amblyopia

Amblyopia is a form of visual cortical impairment that arises from abnormal visual experience early in life. Most often, amblyopia is a unilateral visual impairment that can develop as a result of strabismus, anisometropia, or a combination of these conditions that result in discordant binocular experience. Characterized by reduced visual acuity and impaired binocular function, amblyopia places a substantial burden on the developing child. Although frontline treatment with glasses and patching can improve visual acuity, residual amblyopia remains for most children. Newer binocular-based therapies can elicit rapid recovery of visual acuity and may also improve stereoacuity in some children. Nevertheless, for both treatment modalities full recovery is elusive, recurrence of amblyopia is common, and improvements are negligible when treatment is administered at older ages. Insights derived from animal models about the factors that govern neural plasticity have been leveraged to develop innovative treatments for amblyopia. These novel therapies exhibit efficacy to promote recovery, and some are effective even at ages when conventional treatments fail to yield benefit. Approaches for enhancing visual system plasticity and promoting recovery from amblyopia include altering the balance between excitatory and inhibitory mechanisms, reversing the accumulation of proteins that inhibit plasticity, and harnessing the principles of metaplasticity. Although these therapies have exhibited promising results in animal models, their safety and ability to remediate amblyopia need to be evaluated in humans.

High Magnesium Promotes the Recovery of Binocular Vision from Amblyopia via TRPM7

Abnormal visual experience during the critical period can cause deficits in visual function, such as amblyopia. High magnesium (Mg2+) supplementary can restore ocular dominance (OD) plasticity, which promotes the recovery of amblyopic eye acuity in adults. However, it remains unsolved whether Mg2+ could recover binocular vision in amblyopic adults and what the molecular mechanism is for the recovery. We found that in addition to the recovery of OD plasticity, binocular integration can be restored under the treatment of high Mg2+ in amblyopic mice. Behaviorally, Mg2+-treated amblyopic mice showed better depth perception. Moreover, the effect of high Mg2+ can be suppressed with transient receptor potential melastatin-like 7 (TRPM7) knockdown. Collectively, our results demonstrate that high Mg2+ could restore binocular visual functions from amblyopia. TRPM7 is required for the restoration of plasticity in the visual cortex after high Mg2+ treatment, which can provide possible clinical applications for future research and treatment of amblyopia.

Visual Performance of Children with Amblyopia after 6 Weeks of Home-Based Dichoptic Visual Training

OBJECTIVES

This study was aimed at analyzing the efficacy on the improvement of the visual function of a dichoptic online cloud-based platform for the treatment of amblyopia in anisometropic children.

METHODS

A quasi-experimental (pretest-post-test) study was conducted in 23 subjects with ages from 5 to 15 years old with anisometropic amblyopia combined with additional presence (2 subjects) or not (21 subjects) of microtropia. A total of 30 home-based training sessions of 30 min per session with Bynocs® platform were prescribed for 6 weeks.

RESULTS

Amblyopic eye logMAR visual acuity (VA) significantly improved from 0.28 ± 0.24 to 0.13 ± 0.20 after the 6-week treatment (p < 0.001). At baseline, 60.9% of participants had VA in amblyopic eye of 0.20 logMAR or worse, whereas this percentage decreased to 21.7% after treatment. Binocular function (BF) significantly improved from 2.82 ± 1.11 to 2.32 ± 0.94 (p < 0.001). Mean compliance was 92%, 87% and 93% at 2, 4 and 6 weeks of treatment, respectively.

CONCLUSIONS

In conclusion, home-based dichoptic training with the digital platform evaluated is an effective method to improve amblyopic VA and stereoacuity in children with anisometropic amblyopia combined or not with microtropia.

Spontaneous recovery from amblyopia following fellow eye vision loss: a systematic review and narrative synthesis

BACKGROUND

The effectiveness of traditional amblyopia therapies is largely restricted to childhood. However, spontaneous recovery in adulthood is possible following vision loss in the fellow eye due to enucleation, injury, or disease. The twofold purpose of this study was (1) to define the incidence of recovery and (2) to elucidate the clinical features associated with greater amblyopic eye gains.

METHODS

A systematic review of three databases yielded 24 reports containing 110 cases of patients ≥18 years old with unilateral amblyopia and vision-limiting fellow eye pathology.

RESULTS

Our analysis revealed that 25 of 42 of adult patients (59.5%) gained ≥2 logMAR lines in the amblyopic eye after fellow eye vision loss. The degree of improvement is clinically meaningful (median, 2.6 logMAR lines). Recovery occurs within 12 months of initial loss of fellow eye vision. Regression analysis demonstrated that younger age, worse baseline visual acuity in the amblyopic eye, and worse vision in the fellow eye independently conferred greater gains in amblyopic eye visual acuity. Recovery occurs across amblyopia types and fellow eye pathologies, although disease entities affecting fellow eye retinal ganglion cells demonstrate shorter latencies to recovery.

CONCLUSIONS

Amblyopia recovery after fellow eye injury demonstrates that the adult brain harbors the neuroplastic capacity for clinically meaningful recovery, which could potentially be harnessed by novel approaches to treat adults with amblyopia.

Deficits of the "Good" Eye in Amblyopia: Processing Geometric Properties

Purpose

Although fellow eyes of amblyopia are typically considered normal, recent studies have revealed impairments in certain aspects of vision. However, it remains unclear at which level of object processing these impairments occur. This study aims to investigate the functional level of visual perception impairment in the fellow eye of children and adults with amblyopia using the geometric functional hierarchy discrimination task based on Klein Mathematics methodology.

Methods

Seventy-six patients with amblyopia (40 children and 36 adults) and 77 age-matched healthy controls (40 children and 37 adults) were recruited for this study. The participants completed four sets of geometric hierarchies (in ascending order of stability: Euclidean, affine, projective, and topology) and one set of color discrimination tasks. They were instructed to rapidly and accurately select a distinct shape from the four quadrants.

Results

The participants' performance was evaluated using the inverse efficiency (IE) score (IE = response time (RT)/accuracy). The results of IEs show that the fellow eye of children with amblyopia exhibits normal topological processing, yet displays higher IEs in other geometric properties and color processing, suggesting impairments in these specific discrimination abilities. However, adults with amblyopia did not show deficits on any discrimination types compared with adult controls.

Conclusions

The lack of compromised topological processing suggests that amblyopia may not have inflicted any damage to the subcortical visual pathways. Furthermore, these deficits observed in the fellow eye tend to diminish significantly during adulthood, implying that amblyopia may potentially hinder the maturation process of the fellow eye.

Childhood amblyopia: A systematic review of recent management options

This study reviews the current information on treatment of childhood amblyopia, with the goal of improving visual functions. The authors searched various online databases including PubMed, Web of Science, ProQuest, Scopus, Google Scholar, Ebsco, and Medline. The articles, published between 2002 and 2023, included in this study were used to assess the different modalities for the management of different types of childhood amblyopia. The final systematic review included 41 studies from different countries, covering 4060 children with a mean age 6.8 ± 124 years. The findings showed that childhood amblyopia commonly treated through a systemic approach, i.e., starting with treatment of refractive errors with given optical adaptation time, followed by visually stimulating amblyopic eye by covering the dominant eye with patching, Atropine or Bangerter filters. Refractive adaptation period of 18-22 weeks has proven to show a significant improvement in visual acuity. It has been confirmed that 2 h patching is effective for the first time treated amblyopes, and if there is no improvement, increase the period to 6 h daily. Novel methods that improve binocular function such as dichoptic, perceptual training, video gaming, and drugs that facilitate visual neuroplasticity, are useful in the treatment of amblyopia that is not responsive to conventional therapy. The study concludes that significant evidence show that childhood amblyopia is treated through a systemic approach. Starting from correcting refractive errors with a period of optical adaptation, followed by patching therapy and atropine penalization. New methods that improve the binocular functions and medications that facilitate visual neuroplasticity have found to be useful in the treatment of amblyopia that is not responsive to conventional treatment.

Harnessing brain plasticity to improve binocular vision in amblyopia: An evidence-based update

Amblyopia is a developmental visual disorder resulting from atypical binocular experience in early childhood that leads to abnormal visual cortex development and vision impairment. Recovery from amblyopia requires significant visual cortex neuroplasticity, i.e. the ability of the central nervous system and its synaptic connections to adapt their structure and function. There is a high level of neuroplasticity in early development and, historically, neuroplastic responses to changes in visual experience were thought to be restricted to a "critical period" in early life. However, as our review now shows, the evidence is growing that plasticity of the adult visual system can also be harnessed to improve vision in amblyopia. Amblyopia treatment involves correcting refractive error to ensure clear and equal retinal image formation in both eyes, then, if necessary, promoting the use of the amblyopic eye by hindering or reducing visual input from the better eye through patching or pharmacologic therapy. Early treatment in children can lead to visual acuity gains and the development of binocular vision in some cases; however, many children do not respond to treatment, and many adults with amblyopia have historically been untreated or undertreated. Here we review the current evidence on how dichoptic training can be used as a novel binocular therapeutic approach to facilitate visual processing of input from the amblyopic eye and can simultaneously engage both eyes in a training task that requires binocular integration. It is a novel and promising treatment for amblyopia in both children and adults.

Unveiling Visual Acuity in 58,712 Four-Year-Olds: Standardized Assessment Defined Normative Visual Acuity Threshold

The purpose was to define the threshold of normal visual acuity (VA), mean monocular and binocular VA, and interocular difference in the uniform cohort of healthy four-year-old children. All the children were recruited from the Croatian National Registry of Early Amblyopia Detection database. LEA Symbols® inline optotypes were used for VA testing at near and distance, binocularly and monocularly. The pass cut-off level was set to ≤0.1 logMAR. The final sample consisted of 58,712 four-year-old children. In total, 83.78% of the children had unremarkable results, and 16.22% of the children were referred to examination. Of those, 92% of the children were referred due to binocular, and 8% of the children due to monocular causes. The children referred due to binocular causes demonstrated a VA of 0.3 ± 0.24, while the children referred due to monocular causes 0.6 ± 0.21. The ROC curve analysis defined the uniform cut-off value for a normative VA of 0.78. We analyzed the largest uniform cohort of 58,712 children, and have determined normative data for binocular and monocular VA tested with gold standard logMAR chart in four-year-old children. The results presented here established no reasoning to further utilize historical protocols in testing VA in preschool children aged ≥ 4 years.

Decreased scene-selective activity within the posterior intraparietal cortex in amblyopic adults

Amblyopia is a developmental disorder associated with reduced performance in visually guided tasks, including binocular navigation within natural environments. To help understand the underlying neurological disorder, we used fMRI to test the impact of amblyopia on the functional organization of scene-selective cortical areas, including the posterior intraparietal gyrus scene-selective (PIGS) area, a recently discovered region that responds selectively to ego-motion within naturalistic environments (Kennedy et al., 2024). Nineteen amblyopic adults (10 female) and thirty age-matched controls (12 female) participated in this study. Amblyopic participants spanned a wide range of amblyopia severity, based on their interocular visual acuity difference and stereoacuity. The visual function questionnaire (VFQ-39) was used to assess the participants' perception of their visual capabilities. Compared to controls, we found weaker scene-selective activity within the PIGS area in amblyopic individuals. By contrast, the level of scene-selective activity across the occipital place area (OPA), parahippocampal place area (PPA), and retrosplenial cortex (RSC)) remained comparable between amblyopic and control participants. The subjects' scores on "general vision" (VFQ-39 subscale) correlated with the level of scene-selective activity in PIGS. These results provide novel and direct evidence for amblyopia-related changes in scene-processing networks, thus enabling future studies to potentially link these changes across the spectrum of documented disabilities in amblyopia.

Prevalence and characteristics of amblyopia, strabismus, and refractive errors among patients aged 3-16 years in Shanghai, China: a hospital-based population study

BACKGROUND

Functional visual impairments in children are primarily caused by amblyopia or strabismus. This study aimed to determine the prevalence and clinical profile of amblyopia and strabismus among individuals aged 3-16 years in Shanghai, China.

METHODS

From February 2023 to February 2024, this hospital-based, cross-sectional study included data of children who visited the Ophthalmology Department of Shanghai General Hospital. Comprehensive ocular examinations included visual acuity measurement after cycloplegic refraction, slit lamp examination, cover test, and dilated fundus examination. Descriptive statistics were performed to estimate the proportion and clinical characteristics of amblyopia and strabismus.

RESULTS

A total of 920 children were enrolled in our study. Among them, 223 (24.24%) children were identified as amblyopia. Unilateral amblyopia occupied 57.85%, and bilateral amblyopia occupied 42.15%. Most participants were within the age range of 5-10 years (75.97% for unilateral amblyopia, and 70.21% for bilateral amblyopia). Anisometropia was the primary cause of unilateral amblyopia (68.99%). Most amblyopic children have high hyperopia (38.76% for unilateral amblyopia, and 39.89% for bilateral amblyopia). 30 (3.26%) children were diagnosed with strabismus, and 19 (63.3%) of them were aged 5-10 years. Seven of the children had both strabismus and amblyopia.

CONCLUSION

The proportion of patients with amblyopia and strabismus was determined as 24.24% and 3.26% in our study. Anisometropia was the leading cause of unilateral amblyopia, whereas high hyperopia was a crucial refractive error in the amblyopic population. These findings shed light on further longitudinal studies targeting the age-related changes in amblyopia, strabismus and refraction errors. Therefore, efforts should be made to manage uncorrected refractive errors, amblyopia, and strabismus among children in Shanghai.

Patching in Children With Unilateral Congenital Cataract and Child Functioning and Parenting Stress

Importance

Parents may be concerned about the adverse outcomes of occlusion therapy in children treated for unilateral congenital cataract (UCC).

Objective

To determine whether occlusion therapy in children treated for UCC with poor visual outcomes is negatively associated with poorer child and/or family functioning.

Design, Setting, and Participants

This cohort study was conducted in 2023 using data collected between 2006 and 2016 in the Infant Aphakia Treatment Study (IATS). IATS participants with a visual acuity (VA) of 20/200 or worse were included. Statistical analysis was performed from July 2022 to October 2023.

Exposure

Caregivers reported the mean daily minutes of patching during the 12 months prior to the VA assessment at 4.5 years of age. Patching was categorized as minimal (<15 minutes per day), moderate (15 to <120 minutes per day), or extensive (≥120 minutes per day).

Main Outcome Measures

At 4.25 and 10.5 years of age, caregivers reported stress associated with the parenting role using the Parenting Stress Index and the Ocular Treatment Index and child behavior problems using the Achenbach Child Behavior Checklist. Motor skills were assessed at age 54 months using the Movement Assessment Battery for Children-Second Edition. Children completed the Harter Self-Perception Profile for Children at age 10.5 years. One-way analysis of variance and χ2 tests were used to compare outcomes by amount of patching.

Results

Patching data were available for 47 of 53 children (88.7%) with a VA of 20/200 or worse. Among these 47 children with patching data included in the study, 20 (42.5%) were female, 27 (57.5%) were male, 12 (25.5%) were reported to have been patched fewer than 15 minutes per day, 11 (23.4%) were patched 16 to 119 minutes per day, and 24 (51.1%) were patched at least 120 minutes per day. Parenting stress, child behavior problems, motor functioning, and child self-perception were similar in all groups. For example, after adjusting for gender and insurance status, there was a nonsignificant difference between mean stress scores of 11.0 (95% CI, -4.5 to 26.5) points for parents who reported minimal patching vs parents who reported patching at least 120 minutes per day, and there was no significant difference in children's report of their global self-worth (0.0 [95% CI, -0.4 to 0.3] points).

Conclusions and Relevance

Occlusion therapy was not negatively associated with family or child functioning. Although the sample size was limited, these results do not support changes to the current practice guidelines.

Binocular Home Treatment for Amblyopia: Gains Stable for One Year

PURPOSE

To report the long-term outcomes of a noninferiority randomized controlled trial (RCT) with a binocular eye-tracking-based home treatment (CureSight; NovaSight, Ltd.) in patients with amblyopia.

DESIGN

Prospective, multicenter, nonrandomized, long-term follow-up observational study of an RCT.

METHODS

Forty-three children 4 to <9 years of age with anisometropic, small-angle strabismic, or mixed-mechanism amblyopia were initially treated for 16 weeks (NCT05185076) with CureSight. In this planned observational follow-up study, 38 patients with no additional amblyopia treatment were evaluated at 12 weeks post-treatment, and 27 were evaluated at 1-year post-treatment. The main outcome measures were visual acuity (VA), stereoacuity, and amblyopia recurrence at 12- and 52-week post-treatment.

RESULTS

At 12-week post-treatment, improvement in amblyopic eye VA was maintained vs baseline (0.27 ± 0.14 logMAR, P< .0001), with no change vs the end-of-treatment visit (P > .05). At 1 year there was a partial reduction in the amblyopic eye VA gain of 0.085±0.1 logMAR compared to end-of-treatment (P = .001), but the residual gain of 0.20±0.14 logMAR compared to baseline was statistically significant (P < .0001). Gains in stereoacuity and binocular VA were maintained vs baseline at both 12-weeks and 1-year post-treatment (P < .0001), with no change vs end-of-treatment (P > .05). Amblyopia recurrence (a worsening of ≥2 logMAR levels compared with end-of-treatment) occurred in 2/38 patients at 12-weeks post-treatment (5.3%), and in 5/27 patients at 1-year post-treatment (20.4%).

CONCLUSIONS

VA and stereopsis gains following binocular treatment with CureSight were maintained at 1 year without additional treatment.

Fine visuomotor skills in amblyopia: a systematic review and meta-analysis

BACKGROUND

Amblyopia is characterised by reduced visual acuity, poor binocular sensory fusion, and impaired or absent stereoacuity. Understanding the extent to which amblyopia affects everyday task performance is important to quantifying the disease burden of amblyopia and can assist clinicians to understand patients' likely functional capability.

METHODS

A systematic literature search identified published studies comparing fine visuomotor performance in either children or adults with amblyopia and those with normal binocular vision. The included studies (22 studies involving 835 amblyopes and 561 controls) reported results of self-perception patient reported outcome measures, tests of motor proficiency and video recorded reaching and grasping. The outcomes of 17 studies were grouped into four meta-analyses, with pooled results reported as standardised mean difference (SMD) with corresponding 95% CI.

RESULTS

Regardless of the cause of amblyopia (anisometropia, strabismus, mixed, deprivation), significant reduction in self-perception of physical competence and athletic competence (SMD=-0.74, 95% CI -1.23 to -0.25, p=0.003); fine motor skills scores (SMD=-0.86, 95% CI -1.27 to -0.45, p<0.0001); speed of visually guided reaching and grasping movements (SMD=0.86, 95% CI 0.65 to 1.08, p<0.00001); and precision of temporal eye-hand coordination (SMD=0.75, 95% CI 0.26 to 1.25, p=0.003) occurred in amblyopes compared with those with normal visual development.

CONCLUSION

Reports of the impact of amblyopia on fine motor skills performance find poorer outcomes in participants with amblyopia compared with those with normal vision development. Consistency in the outcome measure used to assess the functional impact of amblyopia would be valuable for future studies.

Novel Quantitative Contrast Sensitivity Function Enhances the Prediction of Treatment Outcome and Recurrence in Amblyopia

Purpose

Although effective amblyopia treatments are available, treatment outcome is unpredictable, and the condition recurs in up to 25% of the patients. We aimed to evaluate whether a large-scale quantitative contrast sensitivity function (CSF) data source, coupled with machine learning (ML) algorithms, can predict amblyopia treatment response and recurrence in individuals.

Methods

Visual function measures from traditional chart vision acuity (VA) and novel CSF assessments were used as the main predictive variables in the models. Information from 58 potential predictors was extracted to predict treatment response and recurrence. Six ML methods were applied to construct models. The SHapley Additive exPlanations was used to explain the predictions.

Results

A total of 2559 consecutive records of 643 patients with amblyopia were eligible for modeling. Combining variables from VA and CSF assessments gave the highest accuracy for treatment response prediction, with the area under the receiver operating characteristic curve (AUC) of 0.863 and 0.815 for outcome predictions after 3 and 6 months, respectively. Variables from the VA assessment alone predicted the treatment response, with AUC values of 0.723 and 0.675 after 3 and 6 months, respectively. Variables from the CSF assessment gave rise to an AUC of 0.909 for recurrence prediction compared to 0.539 for VA assessment alone, and adding VA variables did not improve predictive performance. The interocular differences in CSF features are significant contributors to recurrence risk.

Conclusions

Our models showed CSF data could enhance treatment response prediction and accurately predict amblyopia recurrence, which has the potential to guide amblyopia management by enabling patient-tailored decision making.

Associations between the cause of amblyopia and pre-treatment contrast sensitivity, stereoacuity, fixation, and nystagmus

Purpose

To explore the association between the cause of amblyopia and pre-treatment contrast sensitivity, stereoacuity, fixation and nystagmus.

Design

Retrospective cohort study.

Methods

A retrospective review was conducted for 3408 patients with amblyopia who had not yet started amblyopia treatment utilizing a large amblyopia patient database maintained at Zhongshan Ophthalmic Centre. Six amblyogenic factor subtypes were identified: anisometropia, isoametropia, strabismus, anisometropia and strabismus, monocular visual deprivation, and binocular visual deprivation amblyopia. Monocular best corrected visual acuity (BCVA), the contrast sensitivity function (CSF), fixation, and stereopsis were compared between the subtypes before and after propensity score matching (PSM) for age and sex.

Results

The two deprivation groups had poorer BCVA and CSF than the other groups. There were no systematic differences in CSF between the non-deprivation groups. Nystagmus was more common in the bilateral amblyopia groups compared to the monocular amblyopia groups. Eccentric fixation was uncommon with the exception of the anisometropia and strabismus group which had an eccentric fixation rate of 20%. Distance stereoacuity measured without monocular cues was absent for almost all patients. The results were consistent when analyzed using PSM.

Conclusion

Visual deprivation causes more severe amblyopia than other amblyogenic factors. For non-deprivation amblyopia subtypes, individual differences such as variation in the severity of the amblyogenic factor might be more important in determining pre-treatment vision than whether amblyopia was caused by refractive error, strabismus or both.

Motion-Defined Form Perception in Deprivation Amblyopia

Purpose

The purpose of this study was to assess motion-defined form perception, including the association with clinical and sensory factors that may drive performance, in each eye of children with deprivation amblyopia due to unilateral cataract.

Methods

Coherence thresholds for orientation discrimination of motion-defined form were measured using a staircase procedure in 30 children with deprivation amblyopia and 59 age-matched controls. Visual acuity, stereoacuity, fusion, and interocular suppression were also measured. Fixation stability and fellow-eye global motion thresholds were measured in a subset of children.

Results

Motion-defined form coherence thresholds were elevated in 90% of children with deprivation amblyopia when viewing with the amblyopic eye and in 40% when viewing with the fellow eye. The deficit was similar in children with a cataract that had been visually significant at birth (congenital) and in children for whom the cataract appeared later in infancy or childhood (developmental). Poorer motion-defined form perception in amblyopic eyes was associated with poorer visual acuity, poorer binocular function, greater interocular suppression, and the presence of nystagmus. Fellow-eye deficits were not associated with any of these factors, but a temporo-nasal asymmetry for global motion perception in favor of nasalward motion suggested a general disruption in motion perception.

Conclusions

Deficits in motion-defined form perception are common in children with deprivation amblyopia and may reflect a problem in motion processing that relies on binocular mechanisms.

Multifaceted Interactions of Stereoacuity, Inter-Ocular Suppression, and Fixation Eye Movement Abnormalities in Amblyopia and Strabismus

Purpose

Amblyopic and strabismus subjects experience inter-ocular suppression, impaired stereoacuity, and increased fixation instability. The purpose of the study was to investigate factors affecting suppression and stereoacuity and examine their relationship to fixation eye movement (FEM) abnormalities.

Methods

We recruited 14 controls and 46 amblyopic subjects (anisometropic = 18, strabismic = 14, and mixed = 14) and 11 subjects with strabismus without amblyopia. We utilized the dichoptic motion coherence test to quantify suppression, and stereoacuity was assessed using the Titmus Fly test. We recorded FEMs using high-resolution video-oculography and classified subjects that did not have nystagmus (n = 27) versus those with nystagmus (n = 32; fusion maldevelopment nystagmus [FMN], n = 10) and nystagmus that did not meet the criteria of FMN (n = 20). We also recorded FEMs under dichoptic viewing (DcV) at varied fellow eye (FE) contrasts and computed the amplitude and velocity of the fast and slow FEMs and vergence instability.

Results

Inter-ocular suppression and stereoacuity deficits were closely correlated with an amblyopic eye (AE), visual acuity, and strabismus angle. Subjects with nystagmus displayed more pronounced stereoacuity deficits than those without nystagmus. Strabismic subjects with and without amblyopia, who demonstrated a fixation switch at 100% FE contrast, had lower inter-ocular suppression than subjects lacking a fixation switch under DcV. Amplitude of fast FEMs and velocity of slow FEMs, and vergence instability were increased as the FE contrast was lowered in both amblyopic and strabismic subjects.

Conclusions

The current study highlights the intricate relationships between AE visual acuity, eye deviation, and FEM abnormalities on suppression and stereoacuity deficits and underscores the need to evaluate FEM abnormalities while assessing dichoptic treatment outcomes.

Cost-effectiveness of screening for amblyopia among kindergarten children in China

Objective

Current cost-effectiveness analyses of amblyopia screening are mainly from western countries. It remains unclear whether it is cost-effective to implement a preschool amblyopia screening programme in China. Our study aimed to evaluate the cost-effectiveness of a hypothetical kindergarten-based amblyopia screening versus non-screening among 3-year-old children.

Methods

We developed a decision tree combined with a Markov model to compare the cost and effectiveness of screening versus non-screening for 3-year-old children from a third-party payment perspective. The primary outcomes were quality-adjusted life years (QALYs) and the incremental cost-effectiveness ratio (ICER). Costs were obtained from expert opinions in different regions of China. Transition probabilities and health utilities were mainly based on published literature and open sources. Sensitivity analyses were performed to assess the impact of parameters' uncertainty on results.

Results

Base-case analysis demonstrated that the ICER of screening versus non-screening was $17,466/QALY, well below the WTP threshold ($38,223/QALY) for China. One-way sensitivity analysis showed that the prevalence of amblyopia, the transition probability per year from untreated amblyopia to healthy, and the discount rate were the top three factors. The likelihood of cost-effectiveness of screening compared with non-screening was 92.56%, according to probabilistic sensitivity analysis. Scenario analysis also indicated that ICER was lower than the WTP threshold even if the time horizon was shortened or the screening was delayed to the age of 4 or 5.

Conclusions

Amblyopia screening could be considered a cost-effective strategy compared to non-screening for 3-year-old children in China. Screening for children at the age of 4 or 5 may even yield better results.

Using high-resolution functional MRI to differentiate impacts of strabismic and anisometropic amblyopia on evoked ocular dominance activity in humans

We employed high-resolution functional MRI (fMRI) to distinguish the impacts of anisometropia and strabismus (the two most frequent causes of amblyopia) on the evoked ocular dominance (OD) response. Sixteen amblyopic participants (8 females), comprising 8 individuals with strabismus, 7 with anisometropia, 1 with deprivational amblyopia, along with 8 individuals with normal visual acuity (1 female), participated in this study for whom, we measured the difference between the response to stimulation of the two eyes, across early visual areas (V1-V4). In controls, as expected from the organization of OD columns, the evoked OD response formed a striped pattern that was mostly confined to V1. Compared to controls, the OD response in amblyopic participants formed larger fused patches that extended into downstream visual areas. Moreover, both anisometropic and strabismic participants showed stronger OD responses in V1, as well as in downstream visual areas V2-V4. Although this increase was most pronounced in V1, the correlation between the OD response level and the interocular visual acuity difference (measured behaviorally) was stronger in higher-level visual areas (V2-V4). Beyond these common effects, and despite similar densities of amblyopia between the anisometropic and strabismic participants, we found a greater increase in the size of V1 portion that responded preferentially to fellow eye stimulation in anisometropic compared to strabismic individuals. We also found a greater difference between the amplitudes of the response to binocular stimulation, in those regions that responded preferentially to the fellow vs. amblyopic eye, in anisometropic compared to strabismic subjects. In contrast, strabismic subjects demonstrated increased correlation between the OD responses evoked within V1 superficial and deep cortical depths, whereas anisometropic subjects did not. These results provide some of the first direct functional evidence for distinct impacts of strabismus and anisometropia on the mesoscale functional organization of the human visual system, thus extending what was inferred previously about amblyopia from animal models.

Binocular balance across spatial frequency in anisomyopia

Purpose

Anisomyopia is prevalent in myopia and studies have reported it exhibits impaired binocular function. We investigated the binocular balance across spatial frequency in adults with anisomyopia and compared it to in individuals with less differences in refractive error, and examined whether ocular characteristics can predict binocular balance in anisomyopia.

Methods

Fifteen anisomyopes, 15 isomyopes and 12 emmetropes were recruited. Binocular balance was quantitatively measured at 0.5, 1, 2 and 4 c/d. The first two groups of the observers were tested with and without optical correction with contact lenses. Emmetropes were tested without optical correction.

Results

Binocular balance across spatial frequency in optically corrected anisomyopes and isomyopes, as well as emmetropes were found to be similar. Their binocular balance nevertheless still got worse as a function of spatial frequency. However, before optical correction, anisomyopes but not isomyopes showed significant imbalance at higher spatial frequencies. There was a significant correlation between the dependence on spatial frequency of binocular imbalance in uncorrected anisomyopia and interocular difference in visual acuity, and between the dependence and interocular difference in spherical equivalent refraction.

Conclusion

Anisomyopes had intact binocular balance following correction across spatial frequency compared to those in isomyopes and emmetropes. Their balance was weakly correlated with their refractive status after optical correction. However, their binocular balance before correction and binocular improvement following optical correction were strongly correlated with differences in ocular characteristics between eyes.

Impact of active vision therapy compared to conventional patching therapy on visual acuity and stereoacuity in children with amblyopia

PURPOSE

To compare improvements in visual acuity (VA) and stereoacuity between active vision therapy (AVT) and conventional patching therapy in children with amblyopia.

METHODS

This study included 65 children aged 5 to 16 years (mean age±SD, 11.00±3.29 years) with unilateral amblyopia. Among them, 31 children underwent active vision therapy (AVT group), and 34 children underwent conventional patching therapy (patching group). AVT group underwent three sequential phases of AVT: Monocular phase (pursuit, saccades, fixation, visuomotor, eye-hand coordination, and central peripheral activities), biocular phase (diplopia awareness, antisuppression, monocular fixation in a binocular field, accommodative activities, bilateral integration, and fine motor activities) and binocular phase (fusion and stereopsis). Patching group patched their fellow eyes as per guidelines by Pediatric Eye Disease Investigator Group. Best-corrected monocular VA and stereoacuity were measured at baseline and after three months of therapy in both groups.

RESULTS

There were significant improvements in the mean acuities in amblyopic eye (AE) in both AVT (0.32±0.11 logMAR, p <0.001) and patching groups (0.27±0.19 logMAR, p ˂ 0.001). However, there was no significant difference in mean acuity gains in AE between AVT and patching groups (p = 0.059). Mean gains in stereoacuities (log seconds of arc) were statistically significant in both AVT (0.81±0.34, p < 0.001) and patching groups (0.32±0.34, p < 0.001). The stereoacuity gain in the AVT group was significantly higher compared to patching group (p < 0.001).

CONCLUSION

Active vision therapy had a better impact than conventional patching therapy in terms of improvement of stereoacuity but not in terms of VA when used for treating children with amblyopia.

Ocular dominance in cataract surgery: research status and progress

Ocular dominance (OD), a commonly used concept in clinical practice, plays an important role in optometry and refractive surgery. With the development of refractive cataract surgery, the refractive function of the intraocular lens determines the achievement of the postoperative full range of vision based on the retinal defocus blur suppression and binocular monovision principle. Therefore, OD plays an important role in cataract surgery. OD is related to the visual formation of the cerebral cortex, and its plasticity suggests that visual experience can influence the visual system. Cataract surgery changes the visual experience and transforms the dominant eye, which confirms the plasticity of the visual system. Based on the concept and mechanism of OD, this review summarizes the application of OD in cataract surgery.

Effectiveness of a Novel Video Game Platform in the Treatment of Pediatric Amblyopia

PURPOSE

To test the non-inferiority of a novel game platform for the treatment of pediatric amblyopia compared to standard eye patching.

METHODS

Forty participants (ages 4 to 18 years) across seven optometric clinics in the United States diagnosed as having amblyopia associated with anisometropia were randomly assigned to either 12 weeks of eye patching therapy (n = 19) or Barron Vision (Barron Associates, Inc) video game treatment (n = 21). Participants in the eye patching group with best corrected visual acuity (BCVA) worse than 20/200 in their amblyopic eye were prescribed 6 hours of patching daily, whereas those whose BCVA was 20/200 (1.00 logarithm of the minimum angle of resolution [logMAR]) or better were instructed to patch for 2 hours daily. Participants in the video game group, irrespective of the severity of their amblyopia, were instructed to play four different 5-minute mini-games five times a week for a total of 20 minutes a day.

RESULTS

A mixed linear modeling analysis of before and after BCVA differences after 12 weeks showed the non-inferiority of video game treatment to eye patching using a 0.10 logMAR threshold while adjusting for the participant's age, sex, and baseline BCVA.

CONCLUSIONS

The results of the study suggest that a 12-week home-based video game vision therapy intervention can provide equivalent treatment outcomes to eye patching for amblyopia in children ages 5 to 18 years. Video game-based vision therapy may be a more acceptable and time-efficient alternative to existing approaches. By incorporating elements of perceptual learning, approaches such as Barron Vision video game treatment may have additional long-term therapeutic benefits and may improve treatment compliance. [J Pediatr Ophthalmol Strabismus. 2024;61(1):20-29.].

Chondroitinase as a therapeutic enzyme: Prospects and challenges

The chondroitinases (Chase) are bacterial lyases that specifically digest chondroitin sulfate and/or dermatan sulfate glycosaminoglycans via a β-elimination reaction and generate unsaturated disaccharides. In recent decades, these enzymes have attracted the attention of many researchers due to their potential applications in various aspects of medicine from the treatment of spinal cord injury to use as an analytical tool. In spite of this diverse spectrum, the application of Chase is faced with several limitations and challenges such as thermal instability and lack of a suitable delivery system. In the current review, we address potential therapeutic applications of Chase with emphasis on the challenges ahead. Then, we summarize the latest achievements to overcome the problems by considering the studies carried out in the field of enzyme engineering, drug delivery, and combination-based therapy.

Current Developments in the Management of Amblyopia with the Use of Perceptual Learning Techniques

Background and Objectives: Amblyopia is a neurodevelopmental disorder caused by interocular suppression of visual input, affecting visual acuity, stereopsis, contrast sensitivity, and other visual functions. Conventional treatment comprises occlusion of the sound eye. In recent years, novel therapies that deploy perceptual learning (PL) principles have been introduced. The purpose of this study is to assess the latest scientific data on this topic. Materials and Methods: For this purpose, we conducted a literature search for relevant studies published during the previous 4 years (2020-2023). Results: A plethora of visual perceptual learning protocols have been recently developed. Dichoptic video games, contrast rebalanced movies, and online perceptual training platforms are the main formats. Perceptual learning activates neuroplasticity, overcomes interocular suppression, and improves the visual impairments induced by amblyopia. Conclusions: This novel treatment is effective in both children and adults, as well as in patients non-responding to patching.

Artificial intelligence-based screening for amblyopia and its risk factors: comparison with four classic stereovision tests

Introduction

The development of costs-effective and sensitive screening solutions to prevent amblyopia and identify its risk factors (strabismus, refractive problems or mixed) is a significant priority of pediatric ophthalmology. The main objective of our study was to compare the classification performance of various vision screening tests, including classic, stereoacuity-based tests (Lang II, TNO, Stereo Fly, and Frisby), and non-stereoacuity-based, low-density static, dynamic, and noisy anaglyphic random dot stereograms. We determined whether the combination of non-stereoacuity-based tests integrated in the simplest artificial intelligence (AI) model could be an alternative method for vision screening.

Methods

Our study, conducted in Spain and Hungary, is a non-experimental, cross-sectional diagnostic test assessment focused on pediatric eye conditions. Using convenience sampling, we enrolled 423 children aged 3.6-14 years, diagnosed with amblyopia, strabismus, or refractive errors, and compared them to age-matched emmetropic controls. Comprehensive pediatric ophthalmologic examinations ascertained diagnoses. Participants used filter glasses for stereovision tests and red-green goggles for an AI-based test over their prescribed glasses. Sensitivity, specificity, and the area under the ROC curve (AUC) were our metrics, with sensitivity being the primary endpoint. AUCs were analyzed using DeLong's method, and binary classifications (pathologic vs. normal) were evaluated using McNemar's matched pair and Fisher's nonparametric tests.

Results

Four non-overlapping groups were studied: (1) amblyopia (n = 46), (2) amblyogenic (n = 55), (3) non-amblyogenic (n = 128), and (4) emmetropic (n = 194), and a fifth group that was a combination of the amblyopia and amblyogenic groups. Based on AUCs, the AI combination of non-stereoacuity-based tests showed significantly better performance 0.908, 95% CI: (0.829-0.958) for detecting amblyopia and its risk factors than most classical tests: Lang II: 0.704, (0.648-0.755), Stereo Fly: 0.780, (0.714-0.837), Frisby: 0.754 (0.688-0.812), p < 0.02, n = 91, DeLong's method). At the optimum ROC point, McNemar's test indicated significantly higher sensitivity in accord with AUCs. Moreover, the AI solution had significantly higher sensitivity than TNO (p = 0.046, N = 134, Fisher's test), as well, while the specificity did not differ.

Discussion

The combination of multiple tests utilizing anaglyphic random dot stereograms with varying parameters (density, noise, dynamism) in AI leads to the most advanced and sensitive screening test for identifying amblyopia and amblyogenic conditions compared to all the other tests studied.

Reduced perception-action dissociation in children with amblyopia

The functional distinction between vision-for-perception and vision-for-action is a key aspect of understanding the primate visual system. While this dissociation has been well-established in adulthood, its development and dependence on typical visual experience remain unclear. To address these questions, we examined two groups of children: typically developed children and those with amblyopia, who presumably have a sub-optimal visual experience. The Ponzo illusion, known to impact perception but not visuomotor behaviors across age groups, was employed to assess the extent of dissociation. Participants engaged in two tasks involving the Ponzo illusion: a grasping task (vision-for-action) and a manual estimation task (vision-for-perception), with objects placed on the "close" and "far" surfaces of the illusion. Typically developed children displayed grasping movements that were unaffected by the illusion, as their grasping apertures were scaled based on object size, independent of its location. In contrast, children with amblyopia exhibited a clear susceptibility to the illusion, showing larger apertures for objects placed on the 'far' surface of the illusion, and smaller apertures for objects placed on the 'close' surface. Interestingly, both groups of children demonstrated similar susceptibility to the illusion during the perceptual task, with objects placed on the far surface being perceived as longer compared to objects placed on the close surface. These findings shed light on the impact of atypical visual development on the emergence of the dissociation between perception and action, highlighting the crucial role of typical visual experience in establishing this distinction.

Treating amblyopia using altered reality enhances the fine-scale functional correlations in early visual areas

Amblyopia is a developmental visual disorder that causes substantial visual deficits. Studies using resting-state functional magnetic resonance imaging have disclosed abnormal brain functional connectivity (FC) both across long-range cortical sites and within the visual cortex in amblyopes, which is considered to be related to impaired visual functions. However, little work has examined whether restoring the vision of amblyopes accompanies with an improvement of FC. Here in adult amblyopes and healthy participants, we compared their brain FC before and after an altered-reality adaptation training. Before the training, the voxel-wise FCs of amblyopia patients were substantially weaker than those of healthy control participants both within and across the early visual areas. After the training, visual acuities improved in amblyopes but not in the control participants. The effect kept strengthening in the subsequent month without further adaptation. Importantly, we observed enhanced voxel-wise FC both within and across the early visual areas of amblyopes. Moreover, the enhancement continued for at least 1 month. These results suggest that the effective treatment can improve both the amblyopes' vision and functional connections in the visual cortex.

Amblyopia-A novel virtual round table to explore the caregiver perspective

PURPOSE

A survey aimed to capture the caregiver's perspective on the impact of amblyopia and its treatment on the child and family, as well as caregivers' views on the design and feasibility of clinical trials investigating dichoptic binocular therapies for amblyopia.

METHODS

Parents of amblyopic children, patient advocates and healthcare professionals took part in a moderated, structured discussion on a novel virtual advisory-board platform.

RESULTS

Seven parents of children with amblyopia, two patient organisation representatives, one ophthalmologist and one optometrist participated in the survey. A total of 645 posts were entered on the platform over a 14-day period in September 2021. There was widespread agreement that the management of amblyopia poses more of a burden on the child and family than the condition itself, with treatment burden accentuated when treatment is unsuccessful. Parents expressed uncertainty and frustration in relation to the duration of patching, success of patching and alternative treatment options, and felt there was inadequate readily available, easy-to-understand information on the condition. Parents reported that a new treatment for amblyopia, such as dichoptic binocular therapy using video games, should be safe, non-invasive and engaging compared with an eye patch. Treating at home, potentially for a shorter treatment duration, and with an entertaining game were the main reasons parents would join a clinical study with this type of novel therapy. However, due to a limited critical period treatment window, parents would feel more comfortable joining a clinical trial if traditional therapies were offered in conjunction with those under investigation.

CONCLUSION

Patient perspectives and the role of caregivers in the acceptance of any interventional treatments are increasingly recognised. Understanding how amblyopia and its treatment impacts a child and family should be an important premise to guide therapy and evaluate treatment value, both in clinical trials and in routine medical practice.

Deficits in Reach Planning and On-Line Grasp Control in Adults With Amblyopia

Purpose

Adults with amblyopia exhibit impairments when reaching to grasp three-dimensional objects. We examined whether their deficits derive from problems with feedforward planning of these prehension movements or in using visual feedback to control them on-line.

Methods

Twenty-one adults with mild to severe anisometropic and/or strabismic amblyopia and reduced binocularity participated, along with 21 normally sighted age- and gender-matched controls. Subjects used their preferred hand to reach for, precision grasp, and then lift cylindrical table-top objects (two sizes, two distances) using binocular, dominant eye, or amblyopic/non-sighting eye vision just to plan their movements during a 1-second task preview with vision then occluded so feedback was absent or to plan and execute them (i.e., with visual feedback fully available). Kinematic and error measures of the timing and accuracy of the reach and grasp were quantified by view and feedback and compared by ANOVA.

Results

The amblyopic adults performed generally worse than controls across all three views in both feedback conditions. With vision for planning only, their movement initiation and duration times were significantly increased, as were their initial reach times and error rates, especially when using the amblyopic eye alone, whatever its visual acuity loss. These relative planning deficits were only partially rectified with visual feedback available on-line. Relative grasp planning deficits were less evident in the amblyopia group, who instead produced significantly increased grip times and errors under binocular and amblyopic eye visual feedback conditions, although the subgroup with unmeasurable stereovision also formed wider (inaccurate) grasps across all conditions.

Conclusions

Adults with amblyopia seem to have problems constructing reliable internal spatial representations for the feedforward planning of prehension, particularly with their affected eye and mainly affecting their reach, with additional deficits in on-line grasp control related to poor binocularity.

Low-Voltage Haze Tuning with Cellulose-Network Liquid Crystal Gels

Being key components of the building envelope, glazing products with tunable optical properties are in great demand because of their potential for boosting energy efficiency and privacy features while enabling the main function of allowing natural light indoors. However, windows and skylights with electric switching of haze and transparency are rare and often require high voltages or electric currents, as well as not fully meet the stringent technical requirements for glazing applications. Here, by introducing a predesigned gel material we describe an approach dubbed "Haze-Switch" that involves low-voltage tuning of the haze coefficient in a broad range of 2-90% while maintaining high visible-range optical transmittance. The approach is based on a nanocellulose fiber gel network infiltrated by a nematic liquid crystal, which can be switched between polydomain and monodomain spatial patterns of optical axis via a dielectric coupling between the nematic domains and the applied external electric field. By utilizing a nanocellulose network of nanofibers ∼10 nm in diameter we achieve <10 V dielectric switching and <2% haze in the clear state, as needed for applications in window products. We characterize physical properties relevant to window and smart glass technologies, like the color rendering index, haze coefficient, and switching times, demonstrating that our material and envisaged products can meet the stringent requirements of the glass industry, including applications such as privacy windows, skylights, sunroofs, and daylighting.

The Suppressive Basis of Ocular Dominance Changes Induced by Short-Term Monocular Deprivation in Normal and Amblyopic Adults

Purpose

We aimed to study the effect of short-term monocular deprivation on the suppressive interocular interactions in normals and amblyopes by using a dichoptic masking paradigm.

Methods

Nine adults with anisometropic or mixed amblyopia and 10 control adults participated in our study. The contrast sensitivity in discriminating a target Gabor dichoptically masked was measured before and after 2 hours of monocular deprivation. The mask consisted of bandpass-filtered noise. Both the target and the mask were horizontally oriented at the spatial frequency of 1.31 cpd. Deprivation was achieved using an opaque patch on the amblyopic eye of amblyopes and the dominant eye of controls.

Results

Results were similar in both controls and amblyopes. After 2 hours of monocular deprivation, the previously patched eye showed a significant increase in contrast sensitivity under dichoptic masking, which also suggested reduced suppressive effect from the nonpatched eye. Meanwhile, the contrast sensitivity of the nonpatched eye remained almost unchanged under dichoptic masking.

Conclusions

We demonstrate that the ocular dominance changes induced by short-term monocular deprivation-namely, the strengthening of the deprived eye's contribution-are associated with the unilateral and asymmetric changes in suppressive interaction. The suppression from the nondeprived eye is reduced after short-term monocular deprivation. This provides a better understanding of how inverse patching (patching of the amblyopic eye) could, by reducing the suppressive drive from the normally sighted (nondeprived) eye, form the basis of a new treatment for the binocular deficit in amblyopia.

Risk of recurrence after cessation of dichoptic, binocular treatment of amblyopia

Contrast-rebalanced dichoptic games and videos have been shown to be an effective treatment for childhood amblyopia. Whether the visual acuity gains achieved with these binocular treatments are long-lasting has not been determined. In this prospective cohort study of 100 consecutive amblyopic children who improved by ≥0.2 logMAR or obtained ≤0.2 logMAR amblyopic eye visual acuity during a binocular treatment clinical trial, risk of recurrence was 24% (95% CI, 16%-35%) at up to 3 years' follow-up according to Kaplan-Meier survival analysis, which accounts for censored, truncated, and missing data. Risk of recurrence was similar among children who required additional treatment for residual amblyopia after 4-8 weeks of dichoptic treatment (n = 62 [19%]; 95% CI, 10%-34%) and those who did not (n = 38 [32%]; 95% CI, 18%-52%; P = 0.12). There was no association between recurrence and age, visual acuity at the end of binocular treatment, stereoacuity, or ocular alignment. In a secondary analysis to compare rates of recurrence with published data, risk of recurrence in the subset of children who had no additional treatment for residual amblyopia (28%) was similar to the reported recurrence after cessation of successful patching and atropine (24%) at 12 months. Children with successful binocular treatment of amblyopia require monitoring for recurrence of amblyopia.

A role for ocular dominance in binocular integration

Neurons in the primate primary visual cortex (V1) combine left- and right-eye information to form a binocular output. Controversy surrounds whether ocular dominance, the preference of these neurons for one eye over the other, is functionally relevant. Here, we demonstrate that ocular dominance impacts gain control during binocular combination. We recorded V1 spiking activity while monkeys passively viewed grating stimuli. Gratings were either presented to one eye (monocular), both eyes with the same contrasts (binocular balanced), or both eyes with different contrasts (binocular imbalanced). We found that contrast placed in a neuron's dominant eye was weighted more strongly than contrast placed in a neuron's non-dominant eye. This asymmetry covaried with neurons' ocular dominance. We then tested whether accounting for ocular dominance within divisive normalization improves the fit to neural data. We found that ocular dominance significantly improved model performance, with interocular normalization providing the best fits. These findings suggest that V1 ocular dominance is relevant for response normalization during binocular stimulation.

Refining Clinical Quantification of Depth of Suppression in Amblyopia through Synoptophore Measurement

BACKGROUND

Amblyopia is associated with unbalanced suppression between the two eyes. Existing clinical measures of suppression, such as the Worth 4 Dot test, provide qualitative information about suppression but cannot precisely quantify it. The Synoptophore, a well-established instrument in binocular vision clinics, has historically been used to gauge suppression qualitatively as well but has the capability to quantify suppression. We extended the capability of the Synoptophore through the development of a systematic protocol of illumination manipulation to quantify suppression in amblyopia.

METHODS

Twenty-six previously treated adult amblyopes underwent our protocol on the Synoptophore to measure the illumination balance needed to obtain fusion responses. Separately, these same amblyopes were tested with Worth 4 Dot as it is classically performed in the United States, utilizing different test distances and room illuminations to qualify the suppression response.

RESULTS

Smaller, more central targets revealed larger magnitudes of suppression for both the Synoptophore and Worth 4 Dot tests (Synoptophore: χ25,26 = 25.538, p < 0.001; Worth 4 Dot: χ23,26 = 39.020, p < 0.001). There was a significant correlation between the two tests for depth of suppression measurements (rΤ > 0.345, p < 0.036), with more sensitivity measured by the Synoptophore, as suppression could be graded on a quantitative scale. Strabismic amblyopes demonstrated more suppression than non-strabismic amblyopes (z > 2.410, p < 0.016). Additionally, depth of suppression was correlated with interocular difference in both visual acuity (rΤ = 0.604, p < 0.001) and stereoacuity (rΤ = 0.488, p = 0.001).

CONCLUSIONS

We extended the utility of the Synoptophore by measuring its illuminance outputs and developing a suppression testing protocol that compared favorably with Worth 4 Dot (clinic standard) while improving upon the latter through more sensitive quantification of suppression.

Amblyopic stereo vision is efficient but noisy

People with amblyopia demonstrate a reduced ability to judge depth using stereopsis. Our understanding of this deficit is limited, as standard clinical stereo tests may not be suited to give a quantitative account of the residual stereo ability in amblyopia. In this study we used a stereo test designed specifically for that purpose. Participants identified the location of a disparity-defined odd-one-out target within a random-dot display. We tested 29 amblyopic (3 strabismic, 17 anisometropic, 9 mixed) participants and 17 control participants. We obtained stereoacuity thresholds from 59% of our amblyopic participants. There was a factor of two difference between the median stereoacuity of our amblyopic (103 arcsec) and control (56 arcsec) groups. We used the equivalent noise method to evaluate the role of equivalent internal noise and processing efficiency in amblyopic stereopsis. Using the linear amplifier model (LAM), we determined the threshold difference was due to a greater equivalent internal noise in the amblyopic group (238 vs 135 arcsec), with no significant difference in processing efficiency. A multiple linear regression determined 56% of the stereoacuity variance within the amblyopic group was predicted by the two LAM parameters, with equivalent internal noise predicting 46% alone. Analysis of control group data aligned with our previous work, finding that trade-offs between equivalent internal noise and efficiency play a greater role. Our results allow a better understanding of what is limiting amblyopic performance in our task. We find this to be a reduced quality of disparity signals in the input to the task-specific processing.

Cortical Reorganization After Optical Alignment in Strabismic Patients Outside of Critical Period

PURPOSE

To measure visual crowding, an essential bottleneck on object recognition and reliable psychophysical index of cortex organization, in older children and adults with horizontal concomitant strabismus before and after strabismus surgery.

METHODS

Using real-time eye tracking to ensure gaze-contingent display, we examined the peripheral visual crowding effects in older children and adults with horizontal concomitant strabismus but without amblyopia before and after strabismus surgery. Patients were asked to discriminate the orientation of the central tumbling E target letter with flankers arranged along the radial or tangential axis in the nasal or temporal hemifield at different eccentricities (5° or 10°). The critical spacing value, which is the minimum space between the target and the flankers required for correct discrimination, was obtained for comparisons before and after strabismus surgery.

RESULTS

Twelve individuals with exotropia (6 males, 21.75 ± 7.29 years, mean ± SD) and 15 individuals with esotropia (6 males, 24.13 ± 5.96 years) participated in this study. We found that strabismic individuals showed significantly larger critical spacing with nasotemporal asymmetry along the radial axis that related to the strabismus pattern, with exotropes exhibiting stronger temporal field crowding and esotropes exhibiting stronger nasal field crowding before surgical alignment. After surgery, the critical spacing was reduced and rebalanced between the nasal and temporal hemifields. Furthermore, the postoperative recovery of stereopsis was associated with the extent of nasotemporal balance of critical spacing.

CONCLUSIONS

We find that optical realignment (i.e., strabismus surgery) can normalize the enlarged visual crowding effects, a reliable psychophysical index of cortical organization, in the peripheral visual field of older children and adults with strabismus and rebalance the nasotemporal asymmetry of crowding, promoting the recovery of postoperative stereopsis. Our results indicated a potential of experience-dependent cortical organization after axial alignment even for individuals who are out of the critical period of visual development, illuminating the capacity and limitations of optics on sensory plasticity and emphasizing the importance of ocular correction for clinical practice.

Contour integration deficits at high spatial frequencies in children treated for anisometropic amblyopia

Purpose

This study was conducted to reexamine the question of whether children treated for anisometropic amblyopia have contour integration deficits. To do so, we used psychophysical methods that require global contour processing while minimizing the influence of low-level deficits: visibility, shape perception, and positional uncertainty.

Methods

Thirteen children with anisometropic amblyopia (age: 10.1 ± 1.8 years) and thirteen visually normal children (age: 10.8 ± 2.0 years) participated in this study. The stimuli were closed figures made up of Gabor patches either in noise or on a blank field. The contrast thresholds to detect a circular contour on a blank field, as well as the thresholds of aspect ratio and contour element number to discriminate a circular or elliptical contour in noise, were measured at Gabor spatial frequencies of 1.5, 3, and 6 cpd for amblyopic eyes (AEs), fellow eyes (FEs), and normal control eyes. Visual acuities and contrast sensitivity functions for AEs and FEs and the Randot stereoacuity were measured before testing.

Results

The AEs showed contrast deficits and degraded shape perception compared to the FEs at higher spatial frequencies (6 cpd). When the influence of abnormal contrast sensitivity and shape perception were minimized, the AEs showed contour integration deficits at spatial frequencies 3 and 6 cpd. These deficits were not related to basic losses in contrast sensitivity and acuity, stereoacuity, and visual crowding. Besides, no significant difference was found between the fellow eyes of the amblyopic children and the normal control eyes in the performance of contour integration.

Conclusion

After eliminating or compensating for the low-level deficits, children treated for anisometropic amblyopia still show contour integration deficits, primarily at higher spatial frequencies, which might reflect the deficits in global processing caused by amblyopia. Contour integration deficits are likely independent of spatial vision deficits. Refractive correction and/or occlusion therapies may not be sufficient to fully restore contour integration deficits, which indicates the need for the development of clinical treatments to recover these deficits.

The Relationship between Fixation Stability and Retinal Structural Parameters in Children with Anisometropic, Strabismic and Mixed Amblyopia

(1) Background: Amblyopia is an ocular condition leading to structural and functional changes. The relationship between these changes is complex and remains poorly understood. (2) Methods: Participants included 31 children aged 5 to 9 years with strabismic (n = 9), anisometropic (n = 16) and mixed (n = 6) unilateral amblyopia, and 14 age-matched non-amblyopic children. The 95% and 63% Bivariate Contour Ellipse Area (BCEA), axial length, Foveal Avascular Zone (FAZ) area, center macular thickness and volume were assessed. The relationship between these parameters was explored. (3) Results: Statistically significant differences were found among the four groups in best corrected distance visual acuity (BCVA) (p < 0.001), BCEA 95% (p = 0.002) and BCEA 63% (p = 0.002), but not in the FAZ area, central macular thickness, central macular volume and axial length. Eyes with amblyopia had poorer BCVA and larger fixation instability than controls. Inter-ocular differences were more significant in patients with strabismic amblyopia, particularly in BCVA (p = 0.003), central macular thickness (p < 0.001) and central macular volume (p = 0.002). In amblyopic eyes, BCEA 95% and 63% were correlated with BCVA, but not with the FAZ area. (4) Conclusion: Amblyopia is associated with a reduction in fixation stability and BCVA, although there is a general lack of correlation with structural changes, suggesting a complex interaction between anatomy and function in amblyopia.

Use and Costs of Instrument-Based Vision Screening for US Children Aged 12 to 36 Months

This cohort study examines patterns and out-of-pocket costs of instrument-based screening among children 12 to 36 months.

Characteristics and predictive factors of visual function improvements after monocular perceptual learning in amblyopia

Monocular perceptual learning has shown promising performance in restoring visual function in amblyopes beyond the critical period in the laboratory. However, the treatment outcome is variable and indeterminate in actual clinical and neuroscientific practice. We aimed to explore the efficacy of monocular perceptual learning in the clinical setting. By combining continuous monitoring of perceptual learning and clinical measurements, we evaluated the efficacy and characteristics of visual acuity and contrast sensitivity function improvement and further explored the individualized effect after perceptual learning. Amblyopes (average age:17 ± 7 years old) were trained in a monocular two-alternative forced choice identification task at the 50% contrast threshold of the amblyopic eye for 10-15 days. We found that monocular perceptual learning improves both visual acuity and contrast sensitivity function in amblyopia. The broader activation of spatial contrast sensitivity, with a significant improvement in lower spatial frequencies, contributed to improving visual acuity. Visual acuity changes in the early stage can predict the endpoint treatment outcomes. Our results confirm the efficacy of monocular perceptual learning and suggest potential predictors of training outcomes to assist in the future management of clinical intervention and vision neuroscience research in amblyopia beyond the critical period of visual plasticity.

Bifocal use in hyperopic anisometropic amblyopia treated with atropine: a proof-of-concept randomized trial

OBJECTIVES

To investigate the effect of bifocal wearing in the amblyopic eye when atropine is used in the sound eye for the treatment of hyperopic anisometropic amblyopia.

METHODS

Children 4-8 years old were randomly assigned to bifocal + atropine (n = 16) or only atropine (control, n = 19) groups of treatment in a proof-of-concept study. Measurements included visual acuity (logMAR), prism and cover test, stereoacuity (Randot preschool or Randot circles), contrast sensitivity (MARS test), accommodation (Grand Seiko WAM5500 and dynamic retinoscopy), retinoscopic and subjective refraction, before starting treatment and at 6 months, except accommodation, which was remeasured at 9-11 months. Main outcome measure was change in logMAR lines of visual acuity, and secondary outcome measures were change in stereoacuity and contrast sensitivity in the amblyopic eye, at 6 months.

RESULTS

Improvement in visual acuity of the amblyopic eye was significantly better (p = 0.04) in the atropine plus bifocal (3.3 ± 0.9 logMAR lines) than in the atropine only group (2.6 ± 0.8 logMAR lines), whereas change in stereoacuity and contrast sensitivity was not significantly different between the two groups. Differences in accommodative gain, which was impaired in the amblyopic compared to the sound eye, before treatment, decreased after treatment, in the atropine group (0.62 ± 0.16 vs 0.79 ± 0.2, p = 0.3), and atropine + bifocal group (0.69 ± 0.15 vs 0.82 ± 0.2, p = 0.4).

CONCLUSIONS

Use of bifocal lens add in the amblyopic eye of children with hyperopic anisometropic amblyopia, treated by atropine penalization, is beneficial in the follow-up period of 6 months.

Characteristics and Related Parameters of Quick Contrast Sensitivity Function in Chinese Ametropia Children

PURPOSE

To investigate the characteristics of quick contrast sensitivity function (qCSF) and its related parameters in Chinese ametropia children.

METHODS

This case series study enrolled 106 eyes of 53 children (male/female=29/24, age: 9.04±2.06 years). Examinations included manifest refraction, axial length, corneal curvature, and monocular and binocular qCSF readings without refractive correction (area under log CSF [AULCSF], CSF acuity, and contrast sensitivity [CS] at 1.0 to 18.0 cpd). The subjects were divided into groups according to age and refractive parameters for analysis.

RESULTS

The mean spherical equivalent (SE), AULCSF, and CSF acuity of the test eyes were -0.94±1.53 D, 0.44±0.33, and 8.50±5.97 cpd, respectively. In the monocular qCSF comparison, the refraction sphere (RS) was the major factor correlated with qCSF readings (B=0.186, P =0.009 for AULCSF; B=0.543, P =0.019 for CSF acuity; generalized linear model). The three groups stratified by RS/SE (<-1.00D, -1.00D to 0D, and >0D) showed significant differences in CS at medium spatial frequencies (3.0 and 6.0 cpd; all P <0.05). In the low RS/SE group (within -1 to 0 D), the CS at 12.0 cpd was significantly lower than that in the hyperopia group (all P <0.05). Binocular qCSF readings were significantly correlated with those of the eyes with lower RS (all P <0.05).

CONCLUSION

RS and SE are the major contributing factors of qCSF without refractive correction in children. The CS at medium spatial frequencies decrease significantly as the RS/SE increase. In low myopia children, the CS at medium and high spatial frequencies are significantly decreased, providing practical value in visual function screening in children.

Recovery from Amblyopia in Adulthood: A Meta-Analysis

Purpose

The effectiveness of traditional amblyopia therapies is largely restricted to childhood. However, recovery in adulthood is possible following removal or vision-limiting disease of the fellow eye. Study of this phenomenon is currently limited to isolated case reports and a few case series, with reported incidence ranging from 19-77% 1-5 . We set out to accomplish two distinct goals: (1) define the incidence of clinically meaningful recovery and (2) elucidate the clinical features associated with greater amblyopic eye gains.

Methods

A systematic review of 3 literature databases yielded 23 reports containing 109 cases of patients ≥18 years old with unilateral amblyopia and vision-limiting fellow eye pathology.

Results

Study 1 revealed 25/42 (59.5%) of adult patients gained ≥2 logMAR lines in the amblyopia eye after FE vision loss. The overall degree of improvement is clinically meaningful (median 2.6 logMAR lines). Study 2 showed that for cases with amblyopic eye visual acuity improvement, recovery occurs within 12 months of initial loss of fellow eye vision. Regression analysis revealed that younger age, worse baseline acuity in the amblyopic eye, and worse vision in the fellow eye independently conferred greater gains in amblyopic eye visual acuity. Recovery occurs across amblyopia types and fellow eye pathologies, although disease entities affecting fellow eye retinal ganglion cells demonstrate shorter latencies to recovery.

Conclusions

Amblyopia recovery after fellow eye injury demonstrates that the adult brain harbors the neuroplastic capacity for clinically meaningful recovery, which could potentially be harnessed by novel approaches to treat adults with amblyopia.

Characterizing amblyopic perception under non-rivalrous viewing conditions

Current assessments of interocular interactions in amblyopia often use rivalrous stimuli, with conflicting stimuli in each eye, which does not reflect vision under typical circumstances. Here we measure interocular interactions in observers with amblyopia, strabismus with equal vision, and controls using a non-rivalrous stimulus. Observers used a joystick to continuously report the perceived binocular contrast of dichoptic grating stimuli, identical except that the stimulus was contrast-modulated independently in each eye over time. Consistent with previous studies, a model predicting the time-course of perceived contrast found increased amblyopic eye attenuation, and reduced contrast normalization of the fellow eye by the amblyopic eye, in amblyopic participants compared to controls. However, these suppressive interocular effects were weaker than those found in previous studies, suggesting that rivalrous stimuli may overestimate the effects of amblyopia on interocular interactions during naturalistic viewing conditions.