A clinical trial on phakic intraocular lens for the treatment of refractive amblyopia in children and adolescents.

Purpose: To analyze the demographics and clinical outcomes of posterior chamber phakic intraocular (IOL) implantation for refractive amblyopia in children and adolescents. Methods: A prospective interventional study was performed on children and adolescents with amblyopia at a tertiary eye care center from January 2021 to August 2022. Twenty-three eyes of 21 anisomyopic and isomyopic amblyopia patients operated for posterior chamber phakic IOL (Eyecryl phakic IOL) as a treatment for amblyopia were included in the study. Patient demographics, pre- and postoperative visual acuity, cycloplegic refraction, anterior and posterior segment examination, intraocular pressure, pachymetry, contrast sensitivity, endothelial count, and patient satisfaction scores were evaluated. Patients were followed up at day 1, 6 weeks, 3 months, and 1 year after surgery, and visual outcomes and complications were documented. Results: The mean age of patients was 14.16 ± 3.49 years (range: 10-19 years). The mean intraocular lens power was - 12.20 diopter spherical (DS) in 23 eyes and - 2.25 diopter cylindrical (DC) in four patients. The mean unaided distant visual acuity (UDVA) and best-corrected visual acuity (BCVA) were 1.39 ± 0.25 and 0.40 ± 0.21 preoperatively on the log of minimum angle of resolution (logMAR) chart. Postoperatively, the visual acuity improved by 2.6 lines in 3 months period and maintained till 1 year. Postsurgery, contrast sensitivity in the amblyopic eyes significantly improved, and the average endothelial loss recorded was 5.78% at 1 year, which was statistically insignificant. Patient satisfaction score was statistically significant, with 4.736/5 recorded on the Likert scale. Conclusion: Posterior chamber phakic IOL is a safe, effective, and alternative method for treating amblyopia patients who are noncompliant with glasses, contact lenses, and keratorefractive procedures.

The epidemiology and disease pattern of pediatric ocular morbidities in Western India: The National Institute of OphthalMology AmBlyopia StUdy in Indian Paediatric EyeS (NIMBUS) study report 1.

Purpose: To determine the pattern of pediatric ocular morbidities in western India. Methods: This was a retrospective longitudinal study that included all consecutive children aged ≤15 years who presented to the outpatient department of a tertiary eye center for the first time. Patient demographics, best-corrected visual acuity (BCVA), and ocular examination data were compiled. Subgroup analysis was also performed based on age group (years): ≤5, 5-10, and >10-15. Results: A total of 11,126 eyes of 5563 children were included in the study. The mean age of the study population was 5.15 (±3.32) years with males (57.07%) being predominant. Approximately half of the patients (50.19%) were under the age of 5 years, followed by those aged 5-10 years (45.1%) and >10-15 years (4.71%). Among the study eyes, the BCVA was ≥20/60 in 58.57%, indeterminable in 35.16%, and <20/60 in 6.71%. The commonest ocular morbidity noted was refractive error (28.97%) followed by allergic conjunctivitis (7.64%) and strabismus (4.95%) in the total study cohort and also after age stratification. Conclusion: Refractive error, allergic conjunctivitis, and strabismus are the major causes of ocular morbidity in pediatric eyes at a tertiary care center. Planning screening programs at the regional and national levels is crucial to decreasing the burden of eye disorders. These programs also need to have a suitable referral mechanism established and be smoothly connected to primary and secondary health-care centers. This will help to assure quality eye care delivery, while also reducing the strain of overworked tertiary centers.

Evaluation of retinal microcirculation alterations using optical coherence tomography angiography in patients with hyperopia ametropic amblyopia: A case-control study.

Given that there are controversial findings regarding vessel density in amblyopia, we quantified retinal microcirculation using optical coherence tomography angiography and compared it between hyperopic ametropic amblyopia eyes and age-matched control eyes. This case-control study was conducted from March 2021 to March 2022 at the Affiliated Eye Hospital of Nanchang University, Nanchang, China. Both groups included 72 eyes. Foveal avascular zone area, circularity and perimeter, perfusion density and vessel density of macular superficial retinal capillary plexus, macular thickness, macular volume, peripapillary retinal nerve fiber layer thickness, and ganglion cell-inner plexiform layer thickness were compared between hyperopia ametropic amblyopia eyes and age-matched control eyes. Additionally, best-corrected visual acuity, maximum corneal curvature, minimum corneal curvature, and anterior chamber depth were measured. In the hyperopia ametropic amblyopia eyes and control eyes, vessel density was 7.51 ± 2.13 and 9.91 ± 2.71 mm-1 in the central, 17.20 ± 1.38 and 18.25 ± 1.37 mm-1 in the inner, and 17.90 ± 0.88 and 18.43 ± 0.97 mm-1 in the full regions, respectively. The perfusion densities were 0.17 ± 0.06 and 0.23 ± 0.07 in the central, 0.41 ± 0.05 and 0.44 ± 0.03 in the inner, and 0.44 ± 0.03 and 0.46 ± 0.02 in the full regions, respectively. The central macular thicknesses of hyperopia ametropic amblyopia and control eyes were 240.04 ± 20.11 and 235.08 ± 24.41 µm, respectively. Foveal avascular zone perimeter and circularity (P < .043 and P = .001) significantly differed between the 2 groups. Hyperopia ametropic amblyopia eyes showed lower appreciably in vessel and perfusion densities, which could be one of the major pathophysiological mechanisms of hyperopia ametropic amblyopia and provide a new direction for the diagnosis and treatment of amblyopia.

Binocular treatment for amblyopic children: a review.

The narrative review was planned to investigate the efficiency of binocular treatment for amblyopic children, and to compare it with the standard methods. Literature search was conducted for articles in English language available on PubMed, Cochrane Library, Embase, Medline and PsycInfo databases as well as through bibliographies of peer-reviewed studies. Studies in the field of binocular treatment for amblyopia were included. Visual outcomes considered were visual acuity, types of amblyopia and stereoacuity. Studies on deprivation amblyopia, animal studies, literature review of amblyopia treatment, case reports, and trials targeting participants in whom previous amblyopia treatment had failed were excluded. Of the 40 studies found, 21(52.5%) met the inclusion criteria. Visual acuity and binocular function improved with binocular treatment for treating amblyopia in children by decreasing suppression depth extent and increasing stereopsis. Binocular treatment for amblyopic children was found to be an effective and fast process for the recovery of visual functions, especially in the critical time of visual development.

Microvasculature evaluation of anisometropic amblyopia children by Angio-OCT.

To compare and assess the choroidal and retinal microstructural vascularity in amblyopic eyes with the fellow eyes in anisometropic amblyopic children using angiography optical coherence tomography (Angio-OCT). Twenty-seven children (54 eyes; 5.59 ± 1.08 years old; 59.3% girls) were enrolled in this study. Choroidal thickness (CT) was measured with the use of the enhanced depth imaging mode in Angio-OCT. Parafoveal/peripapillary vascular density indices and the foveal avascular zone (FAZ) size were analyzed by MATLAB code programming on Angio-OCT images. The mean FAZ size of the amblyopic eyes were larger both in superficial and deep capillary plexus layer (SCPL/DCPL). Compared with the contralateral eyes (BCVA were normal), all the vascular density indices of SCPL and DCPL in the parafoveal and peripapillary zones were lower in the amblyopic eyes, however, the difference was insignificant (p > 0.05). No significant decrease was observed in four quadrants analyses of the amblyopic eyes (p > 0.05). Except for the measurement at 2000 µm and 1500 µm from the fovea in temple, CT in amblyopic eyes were significantly thicken than the fellow eyes (p < 0.05). Compared with the fellow eyes, the CT of certain areas were thicker in the amblyopic eyes. Though the FAZ size of the amblyopic eyes was larger in SCPL/DCPL layers, the retinal vascular density indices in SCPL/DCPL were lower in amblyopia eyes without statistical difference. Angio-OCT may be an effective way to evaluate the status of the choroidal and retinal vascular system in amblyopic children.

Amblyopic astigmatism characteristics and surgical outcomes in younger children with severe congenital ptosis after frontalis suspension surgery.

BACKGROUND: To examine the astigmatism characteristics and surgical outcomes in patients with unilateral severe congenital ptosis following frontalis suspension surgery. METHODS: We included 53 congenital ptosis patients who underwent frontalis suspension surgery in Hunan Children's Hospital. Each patient underwent a refractive examination before and after surgery to assess astigmatism. We also evaluated the effects and complications associated with the procedure. RESULTS: Degree of astigmatism in ptotic and fellow eyes was - 1.45 ± 0.59 D and - 0.66 ± 0.51 D before surgery. Ratio of severe astigmatism in ptotic and fellow eyes was 51.3 and 12.8%. The fellow eyes presented with with-the-rule astigmatism (WR; 71.8%) and against-the-rule astigmatism (AR; 20.5%) types, with no cases of oblique astigmatism (OA). Ptotic eyes demonstrated higher frequencies of AR (59.0%) and OA (10.2%) than did fellow eyes. Furthermore, the former showed increased astigmatism, followed by a gradual decrease at the 6-month, before significantly decreasing at the 1-year postoperatively. The ratio of postoperative AR and OA astigmatism cases in ptotic eyes decreased to 35.9 and 7.7% 1 month postoperatively. However, there was a postoperative increase in the WR ratio from 30.8 to 56.4% after 1 month. Kaplan-Meier survival analysis showed a success rate of 81.4% at 6 months and 62.9% at 12 months which was influenced by the following complications: suture reaction, epithelial keratopathy, infection and granuloma, lid lag, and recurrence. CONCLUSION: Monocular congenital ptosis could develop severe astigmatism and higher frequency of AR or OA, early surgery may ameliorate astigmatic amblyopia.

Rapid Alternate Flicker Modulates Binocular Interaction in Adults With Abnormal Binocular Vision.

Purpose: The current understanding of binocular processing is primarily derived from static spatial visual perception: this leaves the role of temporal information unclear. In this study, we addressed this gap by testing the effect of alternating flicker on binocular information processing in adults with abnormal binocular vision. Our goal was to determine which temporal frequency optimally balanced input from both eyes. Methods: We took measurements in four groups of human adults: 10 normal adults with the individual's nondominant eye covered by a 2% neutral density filter (aged 25.60 ± 1.43 years, experiment 1), 9 nonamblyopic anisometropes (aged 24.33 ± 1.66 years, experiment 2), 7 amblyopes (aged 26.5 ± 1.64 years, experiment 3), and 7 treated amblyopes (aged 24 ± 3.21 years, experiment 4). The balance point (BP), where participants' two eyes are equally effective, was measured using a binocular orientation combination task at four spatial frequencies (SFs; 0.5-4 c/d) and five temporal frequencies (TFs; baseline and 4, 7, 10, and 15 Hz). Its log transformation |logBP| was taken into further analysis. Results: We observed clear U-shaped temporal tuning of the |logBP| for the entire range of TFs (that we measured: trough occurred at 7 Hz). This pattern occurred and was significant in all four groups (P < 0.001). In addition, the effect of SFs on |logBP| was significant in normal, amblyopic, and treated amblyopic groups (all P < 0.001) and was marginally significant in the nonamblyopic anisometropic group (P = 0.086). Conclusions: Alternating flicker around 7 Hz may be the optimal temporal frequency for balancing eyes in human adults with binocular imbalance.

Amblyopia and the whole child.

Amblyopia is a disorder of neurodevelopment that occurs when there is discordant binocular visual experience during the first years of life. While treatments are effective in improving visual acuity, there are significant individual differences in response to treatment that cannot be attributed solely to difference in adherence. In this considerable variability in response to treatment, we argue that treatment outcomes might be optimized by utilizing deep phenotyping of amblyopic deficits to guide alternative treatment choices. In addition, an understanding of the broader knock-on effects of amblyopia on developing visually-guided skills, self-perception, and quality of life will facilitate a whole person healthcare approach to amblyopia.

[Role of optical coherence tomography in unilateral amblyopia]. / Apport de la tomographie en cohérence optique dans l'amblyopie unilatérale.

PURPOSE: To compare the macular and papillary parameters on optical coherence tomography (OCT) between the amblyopic eye and the healthy eye in subjects with unilateral strabismic or anisometropic amblyopia. PATIENTS AND METHODS: This is a cross-sectional and comparative study carried out over two years, from April 1, 2019, to March 31, 2021. We included patients aged over 5years, followed for unilateral amblyopia, free of any neurological and/or ocular pathology. The evaluation of the macular and papillary parameters in the amblyopic and healthy eyes was performed with Swept-Source Optical Coherence Tomography (OCT-SS). The parameters were compared according to age group and type of amblyopia. RESULTS: We collected 50 patients, 29 children, and 21 adults, with a mean age of 19.8years. Amblyopia was secondary to anisometropia in 40 patients and strabismus in 10 patients. Analysis of macular tomographic parameters found no significant difference between amblyopic eyes and healthy eyes for mean macular thickness (P=0.86), central macular thickness (P=0.86), or mean macular volume (P=0.54). The mean retinal peripapillary fiber thickness (RNFL) was 107.48µm in the amblyopic eye and 103.8µm in the healthy eye, with a statistically significant difference (P<0.001). This significant thickening of the RNFL in amblyopic eyes was present in adults (P<0.001), children (P<0.001), anisometropic (P<0.001), and strabismic amblyopia (P=0.024). Analysis of the other optic nerve head parameters revealed no significant difference between amblyopic eyes and healthy eyes in terms of optic disc surface area (P=0.89), neuro-retinal annulus surface area (P=0.47), vertical (P=0.98) or horizontal (P=0.74) cup to disc ratio. CONCLUSION: Amblyopia is accompanied by thickening of the peripapillary retinal fibers without macular repercussions. However, larger prospective studies are needed to confirm these results.

Morphological changes of the retinal layers in the central macula in children with anisometropic amblyopia.

PURPOSE: The goal of this study was to evaluate the morphological characteristics of the retinal layers in the central macula in children with anisometropic amblyopia. METHODS: This comparative, observational, prospective study included 28 patients who were diagnosed with anisometropic amblyopia and 30 age- and sex-matched healthy controls. All children were evaluated using the automatic calculation software system available on spectral-domain optical coherence tomography (SD-OCT) for automated segmentation of the macula. RESULTS: Of the included patients, 18 (64.3%) were male and 10 (35.7%) were female, with a mean age of 10.3±3.4 years. Mean spherical equivalent and best-corrected visual acuity (BCVA) were 4.13±1.95 diopters and 0.707±0.36 logMAR, respectively. The mean axial length was significantly lower in amblyopic eyes compared to fellow eyes (22.1±0.34mm vs. 23.3±0.42mm, P<0.0001), and control eyes (22.1±0.34mm vs. 23.1±0.40mm, P<0.0001). The mean thickness of the outer nuclear layer was significantly lower in amblyopic eyes compared to fellow eyes (79.8±11.9µm vs. 86.8±7.9µm, P=0.007), and healthy controls (79.8±11.9µm vs. 87.4±10.5µm, P=0.012). CONCLUSION: The results of this study showed that there are quantitative differences in retinal microstructures of the macula in eyes with anisometropic amblyopia compared to fellow eyes and healthy controls. These findings suggest that anisometropic amblyopia may result in abnormal development of macular structure in the inner retinal layer. A detailed analysis of retinal layers may be able to provide a guide to the depth of amblyopia and visual prognosis.

Ocular and visual perceptive factors associated with treatment outcomes in patients with anisometropic amblyopia.

BACKGROUND: The aim of this observational study was to identify ocular and visual perceptive risk factors related to treatment results following refractive correction and patching in children with anisometropic amblyopia, who were between the ages of 4 to 14 years old. METHODS: One-hundred and two children with newly diagnosed anisometropic amblyopia were recruited. Successful treatment of amblyopia was defined as the final best corrected visual acuity (BCVA) better than or equal to 0.1 logMAR and amblyopic eye BCVA within 1 line of the sound eye BCVA by the end of the treatment period. BCVA, cycloplegic refraction, stereoacuity, perceptual eye position (PEP) and interocular suppression were measured. RESULTS: Of these patients, 45.10% achieved successful treatment of amblyopia after refractive correction and patching for 10.5 months. The mean age was not significantly different between patients who were successfully and unsuccessfully treated (5.50 ± 1.59 years vs 6.14 ± 2.19 years, respectively). Patients who failed treatment had significantly larger interocular difference of BCVA at the time of initial treatment (successful group: 0.33 ± 0.29 logMAR, unsuccessful group: 0.65 ± 0.35 logMAR) and after refractive adaptation (successful group: 0.15 ± 0.13 logMAR, unsuccessful group: 0.42 ± 0.35 logMAR). They also had higher spherical equivalent (SE) of amblyopic eyes (successful group: 3.08 ± 3.61 D, unsuccessful group: 5.27 ± 3.38 D), bigger interocular difference of SE (successful group: 0.94 ± 2.71 D, unsuccessful group: 3.09 ± 3.05 D), worse stereoacuity (successful group: 2.32 ± 0.37 log seconds of arc, unsuccessful group: 2.75 ± 0.32 log seconds of arc), larger vertical PEP deviation (successful group: 6.41 ± 6.08 pixel, unsuccessful group: 19.07 ± 24.96 pixel) and deeper interocular suppression (successful group: 21.7 ± 19.7%, unsuccessful group: 37.8 ± 27.1%) than those of successfully treated patients. The most influential treatment failure risk factors were larger vertical PEP deviation [adjusted odds ratio (OR) (95% confidence interval) 1.12 (1.02-1.22)] and worse stereoacuity [adjusted odds ratio (OR) (95% confidence interval) 7.72 (1.50-39.85)] in multiple logistic regression analysis. CONCLUSIONS: Larger vertical PEP deviation and worse stereoacuity were the most influential treatment failure risk factors in children with anisometropic amblyopia. The vertical PEP deviation and stereoacuity, which can reflect interocular interaction, may be useful in predicting the response to therapy.

ARC/Arg3.1 expression in the lateral geniculate body of monocular form deprivation amblyopic kittens.

PURPOSE: The present study compared the expression of activity-regulated cytoskeleton-associated protein (ARC/Arg3.1) in the lateral geniculate body between form deprivation amblyopia kittens and normal kittens to examine the significance of ARC/Arg3.1 in the lateral geniculate body in the pathogenesis of amblyopia. METHODS: Twenty kittens were randomly divided into an experimental group (n = 10) and a control group (n = 10). Black opaque covering cloth was used to cover the right eye of kittens in the experimental group. Pattern visual evoked potentials (PVEP) were detected weekly in all kittens. The expression of the ARC/Arg3.1 gene was detected by immunohistochemistry and in situ hybridization, and apoptosis of lateral geniculate body cells was detected by TUNEL. RESULTS: PVEP detection showed that at the age of 5 and 7 weeks, the latency of P100 in the right eye of the experimental group was higher than that of the other three groups (P < 0.05), and the amplitude of P100 was lower than that of the other three groups (P < 0.05). The expression of ARC/Arg3.1 protein (P < 0.05) and mRNA (P < 0.05) in the lateral geniculate body of the experimental group was significantly lower than that of the control group. The level of neuronal apoptosis in the experimental group was higher than that in the control group (P < 0.05). The expression of the ARC/Arg3.1 gene was negatively correlated with the apoptosis level of lateral geniculate body neurons. CONCLUSIONS: The expression of ARC/Arg3.1 is associated with monocular form deprivation amblyopia and apoptosis of lateral geniculate body cells.

Refractive errors and ocular findings in children and adolescents with mental disorders: a retrospective study.

BACKGROUND: An increasing prevalence of mental disorders (MDs) has been reported among children and adolescents. However, only few studies have conducted ocular examinations, including those on refractive status, in these groups of patients. Thus, the purpose of this study was to evaluate the refractive status and ocular findings in children and adolescents with MDs compared with matched controls with similar socioeconomic backgrounds. METHODS: A total of 178 participants with MDs and 200 controls were recruited between April 2021 and May 2022. All the children and adolescents underwent cycloplegic or noncycloplegic autorefraction and retinoscopy, slit-lamp biomicroscopy, and dilated fundus examinations. Ocular alignment was assessed using Hirschberg, Krimsky, or prism cover tests. The prevalence of refractive errors and ocular findings was the main outcome. RESULTS: Twenty-seven percent of patients with MDs and 8% of controls had ocular findings, the most common of which were conjunctivitis, keratitis, and trichiasis. For refractive status, 70% (124/178) of patients with MDs had myopia ≤-1.00 DS, and 2% (4/178) had hyperopia ≥+2.00 DS. In the control group, 70% (140/200) of patients had myopia ≤-1.00 DS, and 1% (2/200) had hyperopia ≥+2.00 DS. No differences were observed between the MD and control groups. However, the patients in the MD group (14.25±2.69 years) were significantly more susceptible to strabismus (P<0.05) and amblyopia (P<0.01) than those in the control group (13.65±3.04 years). There was a substantial difference between the two groups in the time spent on screen-based devices (P<0.001). Furthermore, mental retardation (OR=3.286, P<0.01), emotional disorders (OR=2.003, P<0.01), and adjustment disorders (OR=2.629, P<0.01) were associated with an increased risk of amblyopia. Depression (OR =1.362, P<0.01) and emotional disorders (OR=2.205, P<0.01) were associated with a higher prevalence of strabismus. CONCLUSION: Ophthalmological examinations should be performed in children and adolescents with MDs because MDs are associated with a high prevalence of refractive errors and ocular diseases. Detection and intervention of ocular and refractive findings in children and adolescents with MDs are necessary and effective in alleviating the economic burden in healthcare and improving individuals' quality of life.

Slow Binocular Reading in Amblyopic Children Is a Fellow Eye Deficit.

SIGNIFICANCE: Amblyopic children read 25% slower than their peers during binocular silent reading. PURPOSE: We compared binocular reading to fellow eye reading to determine whether slow reading in amblyopic children is due to binocular inhibition; that is, the amblyopic eye is interfering during binocular reading. METHODS: In a cross-sectional study, 38 children with amblyopia and 36 age-similar control children who completed grades 1 to 6 were enrolled. Children silently read grade-appropriate paragraphs during binocular reading and fellow eye reading while wearing ReadAlyzer eye-tracking goggles (Compevo AB, Stockholm, Sweden). Reading rate, number of forward saccades, number of regressive saccades, and fixation duration were analyzed between groups and between viewing conditions. We also examined whether sensory factors (amblyopia severity, stereoacuity, suppression) were related to slow reading. RESULTS: For amblyopic children, binocular reading versus fellow eye reading did not differ for reading rate (176 ± 60 vs. 173 ± 53 words per minute, P = .69), number of forward saccades (104 ± 35 vs. 97 ± 33 saccades/100 words, P = .18), number of regressive saccades (21 ± 15 vs. 22 ± 13 saccades/100 words, P = .75), or fixation duration (0.31 ± 0.06 vs. 0.32 ± 0.07 seconds, P = .44). As expected, amblyopic children had a slower reading rate and more forward saccades than control children during binocular reading and fellow eye reading. Slow reading was not related to any sensory factors. CONCLUSIONS: Binocular reading did not differ from fellow eye reading in amblyopic children. Thus, binocular inhibition is unlikely to play a role in slow binocular reading and is instead a fellow eye deficit that emerges from a disruption in binocular visual experience during development.

Effectiveness of the Spot Vision Screener using updated 2021 AAPOS guidelines.

PURPOSE: To evaluate the Spot Vision Screener according to updated 2021 AAPOS Vision Screening Committee guidelines for instrument-based pediatric vision screen validation. METHODS: As part of an IRB-approved ongoing prospective study, children were screened with the Spot prior to a complete examination. RESULTS: Spot screening was successful in 1,036 of 1,090 children (95%). Forty-eight percent of participants were referred for further screening using the Spot manufacturer guidelines, and 40% of all children were found to have a 2021 amblyopia risk factor or visually significant refractive error by gold standard examination. The Spot recommendation compared reasonably well to the 2021 criteria, with an overall sensitivity of 0.88 and a specificity of 0.78. Applying updated guidelines to the Spot for hyperopia, anisometropia, and astigmatism yielded moderate-to-poor sensitivity (0.27-0.77) but excellent specificity (>0.9). The area under the curve of the receiver operating characteristic analysis demonstrates overall good prediction performance for the Spot for each diagnosis-myopia, hyperopia, astigmatism, anisometropia (range, 0.87-0.97). Results of our study suggest increasing the instrument referral criterion for astigmatism from 1.5 D (manufacturer thresholds of the screener used in this study) to 2 D in older children. Decreasing the anisometropia cut-off from 1 D to 0.75 D would improve sensitivity from 0.59 to >0.8. CONCLUSIONS: In our study population, the overall predictive ability of the Spot is good, with a sensitivity of 0.88 and a specificity of 0.78. We recommend specific device refractive referral criteria to maximize screening effectiveness using the updated AAPOS guidelines.

Production of brain-derived neurotrophic factor gates plasticity in developing visual cortex.

We have previously shown that recovery of visual responses to a deprived eye during the critical period in mouse primary visual cortex requires phosphorylation of the TrkB receptor for BDNF [M. Kaneko, J. L. Hanover, P. M. England, M. P. Stryker, Nat. Neurosci. 11, 497-504 (2008)]. We have now studied the temporal relationship between the production of mature BDNF and the recovery of visual responses under several different conditions. Visual cortical responses to an eye whose vision has been occluded for several days during the critical period and is then re-opened recover rapidly during binocular vision or much more slowly following reverse occlusion, when the previously intact fellow eye is occluded in a model of "patch therapy" for amblyopia. The time to recovery of visual responses differed by more than 18 h between these two procedures, but in each, the production of mature BDNF preceded the physiological recovery. These findings suggest that a spurt of BDNF production is permissive for the growth of connections serving the deprived eye to restore visual responses. Attenuation of recovery of deprived-eye responses by interference with TrkB receptor activation or reduction of BDNF production by interference with homeostatic synaptic scaling had effects consistent with this suggestion.

Visual Crowding Reveals Field- and Axis-Specific Cortical Miswiring After Long-Term Axial Misalignment in Strabismic Patients Without Amblyopia.

Purpose: Inspired by physiological and neuroimaging findings that revealed squint-induced modification of cortical volume and visual receptive field in early visual areas, we hypothesized that strabismic eyes without amblyopia manifest an increase in critical spacing of visual crowding, an essential bottleneck on object recognition and reliable psychophysical index of cortical organization. Methods: We used real-time eye tracking to ensure gaze-contingent display and examined visual crowding in patients with horizontal concomitant strabismus (both esotropia and exotropia) but without amblyopia and age-matched normal controls. Results: Nineteen patients with exotropia (12 men, mean ± SD = 22.89 ± 7.82 years), 21 patients with esotropia (10 men, mean ± SD = 23.48 ± 6.95 years), and 14 age-matched normal controls (7 men, mean ± SD = 23.07 ± 1.07 years) participated in this study. We found that patients with strabismus without amblyopia showed significantly larger critical spacing with nasotemporal asymmetry in only the radial axis that related to the strabismus pattern, with exotropia exhibiting stronger temporal hemifield crowding and esotropia exhibiting stronger nasal hemifield crowding, in both the deviated and fixating eyes. Moreover, the magnitude of crowding change was related to the duration and degree of strabismic deviation. Conclusions: Using visual crowding as a psychophysical index of cortical organization, our study demonstrated significantly greater peripheral visual crowding with nasotemporal asymmetry in only the radial axis in patients with strabismus without amblyopia, indicating the existence of hemifield- and axis-specific miswiring of cortical processing in object recognition induced by long-term adaptation to ocular misalignment.

Evaluation of retinal function and morphology in isoametropic amblyopia.

Purpose: To observe the photoreceptor anomalies in cases of ametropic amblyopia. Methods: A prospective study with 25 isoametropic amblyopic children in the age group of 5-14 years and 25 age-matched controls was done. Examination included refraction, best-corrected visual acuity (BCVA), and color vision. Adaptive optics (AO) and multifocal electroretinogram (mf-ERG) were done to assess the anatomy and function of photoreceptors. The subgroup analysis of the improved and non-improved groups was done. Results: The mean cone density in cases and control in the superior, temporal, and nasal quadrants was respectively as follows (21640 ± 5713, 24040 ± 3386, P = 0.01) (19755 ± 6282, 21832 ± 2911, P = 0.03) (19897 ± 5418, 22171 ± 3660, P = 0.01) (20768 ± 4799, 22819 ± 3241, P = 0.01). The amplitude of N1 wave and P1 wave in cases was significantly low compared to the controls. Cases with subnormal color vision had reduced BCVA (0.55 ± 0.018) in comparison to the children with normal response (0.350 ± 0.014). Cone density was also significantly reduced in children with subnormal color vision. Sixteen out of 25 cases showed BCVA improvement with spectacles. Baseline cone density was found to be significantly higher in the improved group. There was no correlation between BCVA and AO parameters. Conclusion: Patients with ametropic amblyopia show subnormal photoreceptor properties than controls. Low cone density may be associated with defective color vision and poor prognosis in these cases.

Cost-effectiveness of Universal School- and Community-Based Vision Testing Strategies to Detect Amblyopia in Children in Ontario, Canada.

Importance: Screening for amblyopia in primary care visits is recommended for young children, yet screening rates are poor. Although the prevalence of amblyopia is low (3%-5%) among young children, universal screening in schools and mandatory optometric examinations may improve vision care, but the cost-effectiveness of these vision testing strategies compared with the standard in primary care is unknown. Objective: To evaluate the relative cost-effectiveness of universal school screening and mandated optometric examinations compared with standard care vision screening in primary care visits in Toronto, Canada, with the aim of detecting and facilitating treatment of amblyopia and amblyopia risk factors from the Ontario government's perspective. Design, Setting, and Participants: An economic evaluation was conducted from July 2019 to May 2021 using a Markov model to compare 15-year costs and quality-adjusted life-years (QALYs) between school screening and optometric examination compared with primary care screening in Toronto, Canada. Parameters were derived from published literature, the Ontario Schedule of Benefits and Fees, and the Kindergarten Vision Testing Program. A hypothetical cohort of 25 000 children aged 3 to 5 years was simulated. It was assumed that children in the cohort had irreversible vision impairment if not diagnosed by an optometrist. In addition, incremental costs and outcomes of 0 were adjusted to favor the reference strategy. Vision testing programs were designed to detect amblyopia and amblyopia risk factors. Main Outcomes and Measures: For each strategy, the mean costs per child included the costs of screening, optometric examinations, and treatment. The mean health benefits (QALYs) gained were informed by the presence of vision impairment and the benefits of treatment. Incremental cost-effectiveness ratios were calculated for each alternative strategy relative to the standard primary care screening strategy as the additional cost required to achieve an additional QALY at a willingness-to-pay threshold of $50 000 Canadian dollars (CAD) ($37 690) per QALY gained. Results: School screening relative to primary care screening yielded cost savings of CAD $84.09 (95% CI, CAD $82.22-$85.95) (US $63.38 [95% CI, US $61.97-$64.78]) per child and an incremental gain of 0.0004 (95% CI, -0.0047 to 0.0055) QALYs per child. Optometric examinations relative to primary care screening yielded cost savings of CAD $74.47 (95% CI, CAD $72.90-$76.03) (US $56.13 [95% CI, $54.95-$57.30]) per child and an incremental gain of 0.0508 (95% CI, 0.0455-0.0561) QALYs per child. At a willingness-to-pay threshold of CAD $50 000 (US $37 690) per QALY gained, school screening and optometric examinations were cost-effective relative to primary care screening in only 20% and 29% of iterations, respectively. Conclusions and Relevance: In this study, because amblyopia prevalence is low among young children and most children in the hypothetical cohort had healthy vision, universal school screening and optometric examinations were not cost-effective relative to primary care screening for detecting amblyopia in young children in Toronto, Canada. The mean added health benefits of school screening and optometric examinations compared with primary care screening did not warrant the resources used.

Temporal synchrony discrimination is abnormal in dichoptic but not monocular visual processing in treated anisometropic amblyopes.

PURPOSE: To evaluate whether temporal synchrony processing deficits remain when normal visual acuity is restored in adults with unilateral anisometropic amblyopia. METHODS: We recruited 14 clinically treated anisometropic amblyopes (mean age 23.17 ± 2.53 years) with best-corrected visual acuity ≤ 0.1 logMAR and 15 age-matched emmetropes (mean age 24.40 ± 1.92 years) with normal vision to participate in our experiment. We presented two pairs of flicking Gaussian dots (1 Hz) as visual stimuli: one pair of dots was synchronous (reference), and the other pair of dots was asynchronous (signal). Subjects were asked to determine the position of the asynchronous pair. We applied the constant stimuli method to measure the temporal synchrony threshold under monocular and dichoptic viewing conditions. There were eight temporal phase lags in the asynchronous pair. The minimum degree of the temporal phase at which a participant can discriminate a signal pair is defined as the temporal synchrony threshold. RESULTS: Under monocular viewing conditions where both the reference and signal pairs were presented to one eye, the temporal synchrony thresholds of previous amblyopic eyes and fellow eyes were not significantly different (p = 0.15). Under dichoptic viewing conditions where both the reference and signal pairs were dichoptically presented to both eyes, the temporal synchrony threshold in the treated anisometropic amblyopes was significantly higher than that of the controls (119.34 ± 20.43 vs. 99.78 ± 16.60 ms, p = 0.009). There was no significant correlation between the monocular and dichoptic viewing conditions in the treated amblyopes (r = -0.22, p = 0.94). CONCLUSIONS: Temporal synchrony discrimination is abnormal under dichoptic but not under monocular visual stimulation in treated anisometropic amblyopes with normalised visual acuity.