Evaluation of Fusion and Stereopsis in Anisometropic Patients

Background Binocular vision has many important advantages on monocular vision as it helps in determination of the distance of an object, gives much greater depth of perception, and the ability to have stereopsis and view the world in three dimension (3D). There is an evidence that binocular vision is present in many patients with anisometropia even who have amblyopia but with grades lower than normal. Purpose This study evaluates the effect of anisometropia on BSV functions. Method sixty-four patients above 6 years with anisometropia equal to or more than 2.5D never had their vision corrected either by glasses or refractive surgeries or went on patching treatment, Anisometropic patients were devided into two groups amblyopic group (AA) and non-amblyopic group (NA) were examined for assessing their fusion by Worth four dot test and their stereopsis by fly test (Titmus stereo acuity test) by their best corrective glasses based on their cycloplegic refraction. Results Anisomyopes shows better stereopsis 62% of them and better fusion 65% of them than anisohypropes which had only 8% with good stereopsis and 32% with good fusion. However, antimetropes showed bad fusion and stereopsis as all of the five cases have amblyopia. Only 29.5% of anisomyopes have amblyopia but 68% of anisohypropes have amblyopia. As regard worth four dot test (P < 0.001), as 90.6% of cases with amblyopia had suppressed eye but only 9.4 % of this amblyopic cases had normal fusion. However, in patients without amblyopia 15.6% had suppressed eyes but 84.4% had normal fusion. As regard Titmus test there was statistically significant difference between both groups (P < 0.001), as 100 % of cases with amblyopia had bad stereo acuity but 28.1% of patients without amblyopia had defect in their stereo acuity. Conclusion Fusion and stereopsis as binocular single vision functions were significantly affected in AA patients with best-corrected anisometropic glasses than in NA patients.

Functional Outcomes and Reading Speeds following PRESBYOND LBV Using Nonlinear Aspheric Ablation Profiles Combined with Micro-Monovision

Purpose. To report the functional outcomes and reading speeds following PRESBYOND laser blended vision (LBV) using nonlinear aspheric ablation profiles with micro-monovision with the Carl Zeiss Meditec MEL 90 platform. Methods. Data have been collected retrospectively for all patients who underwent PRESBYOND LBV using the MEL 90 excimer laser. Postoperative binocular uncorrected distance and near visual acuity, stereo-acuity, contrast sensitivity, and reading performance were compared with pre-op values measured with patient’s progressive glasses. Mean follow-up was 6 ± 1.2 months. Results. Sixty eyes of 30 patients (mean age 50.47 ± 6.43 years) were included. Of these, 18 patients were hyperopic and 12 patients were myopic with mean SE of 1.28 ± 1.38 D and −2.84 ± 1.86 D, respectively. At 6 months, the mean binocular UDVA was ≥−0.03 ± 0.06 log MAR and the mean binocular UNVA was ≥0.22 ± 0.04 log MAR. The uncorrected reading speeds (words per minute) at the preferred reading distance of 46.17 cm, 60 cm, and 80 cm were significantly better ( p value <0.01), whereas the smallest letter size and reading acuities were comparable to the preoperative values ( p > 0.05 for all distances). Uncorrected contrast sensitivity log values showed mild reduction; however, this was not statistically significant for any spatial frequency. There was a significant reduction in post uncorrected stereopsis to 89.67 arc sec, compared with pre-op corrected stereopsis (50.67 arc sec); however, it recovered fully with near correction (53.33 arc sec, p > 0.05 compared with pre). Conclusion. PRESBYOND LBV resulted in significantly better reading speeds and satisfactory functional visual outcomes, without a permanent change in stereo-acuity and contrast sensitivity 6 months postoperatively.

Optics and neural adaptation jointly limit human stereovision

Stereovision is the ability to perceive fine depth variations from small differences in the two eyes’ images. Using adaptive optics, we show that even minute optical aberrations that are not clinically correctable, and go unnoticed in everyday vision, can affect stereo acuity. Hence, the human binocular system is capable of using fine details that are not experienced in everyday vision. Interestingly, stereo acuity varied considerably across individuals even when they were provided identical perfect optics. We also found that individuals’ stereo acuity is better when viewing with their habitual optics rather than someone else’s (better) optics. Together, these findings suggest that the visual system compensates for habitual optical aberrations through neural adaptation and thereby optimizes stereovision uniquely for each individual. Thus, stereovision is limited by small optical aberrations and by neural adaptation to one’s own optics.

Fixational eye movements abnormalities and rate of visual acuity and stereoacuity improvement with part time patching

Residual amblyopia is seen in 40% of amblyopic patients treated with part-time patching. Amblyopic patients with infantile onset strabismus or anisometropia can develop fusion maldevelopment nystagmus syndrome (FMNS). The purpose of this study was to understand the effects of presence of FMNS and clinical subtype of amblyopia on visual acuity and stereo-acuity improvement in children treated with part-time patching. Forty amblyopic children who had fixation eye movement recordings and at least 12 months of follow-up after initiating part-time patching were included. We classified amblyopic subjects per the fixational eye movements characteristics into those without any nystagmus, those with FMNS and patients with nystagmus without any structural anomalies that do not meet the criteria of FMNS or idiopathic infantile nystagmus. We also classified the patients per the clinical type of amblyopia. Patching was continued until amblyopia was resolved or no visual acuity improvement was noted at two consecutive visits. Children with anisometropic amblyopia and without FMNS have a faster improvement and plateaued sooner. Regression was only seen in patients with strabismic/mixed amblyopia particularly those with FMNS. Patients with FMNS had improvement in visual acuity but poor stereopsis with part-time patching and required longer duration of treatment.

Seeing the World Like Never Before: Human stereovision through perfect optics

Stereovision is the ability to perceive fine depth variations from small differences in the two eyes’ images. Using adaptive optics, we show that even minute optical aberrations that are not clinically correctable, and go unnoticed in everyday vision, can affect stereo acuity. Hence, the human binocular system is capable of using unnaturally fine details that are not encountered in everyday vision. More importantly, stereoacuity was still considerably variable even with perfect optics. This variability can be attributed to neural adaptation. Our visual system tries to compensate for these aberrations through neural adaptation that optimizes stereovision when viewing stimuli through one’s habitual optics. However, the same adaptation becomes ineffective when the optics are changed, even if improved. Beyond optical imperfections, we show that stereovision is limited by neural adaptation to one’s own optics.Significance statementHumans, and animals with front-facing eyes, view the world from slightly different vantage points. This creates small differences in the left and right images that can be utilized for fine depth perception (stereovision). Retinal images are also subject to imperfections that are often different in the optics of the two eyes. Using advanced optical correction techniques, we show that even the smallest imperfections that escape clinical detection affect stereovision. We also find that neural processes become adapted to a person’s own optics. Hence, stereovision is directly impacted by the optics of the eyes, and indirectly via neural adaptation. Since the optics change over the lifespan, our results imply that the adult binocular system is adaptable with possibilities for binocular rehabilitation.

Efficacy of Vision Therapy Software (CureSee) in Amblyopia

A developmental disorder of spatial vision, Amblyopia is defined clinically as a decrease in visual acuity (VA) in one, or more often in both eyes, in the absence of a clear disorder or ocular disease Amblyopia is the most common cause of monocular vision loss in children [1]. Affected individuals exhibit stereo acuity impairment and abnormal binocular summation [2]. Binocular therapies designed to improve amblyopia by binocular stimulation are highly differentiated into perceptual learning and differential training. Objective • To determine the efficacy of Vision Therapy software (CureSee) in Amblyopia. • To compare Stereopsis findings before and after VT • To compare Visual Acuity before and after VT • To compare Vergence amplitude before and after VT. Methodology: 68 Amblyopic Subjects who are visiting Ahooja Eye & Dental Institute, Gurugram for eye examination and Amblyopia management were taken. Patients diagnosed with Amblyopia were included as well as Patients with Ocular surgery done within 2 months and Patients with any Ocular pathology were excluded. Verbal Consent was taken and selected patients were enrolled into CureSee Vision Therapy Software management for Amblyopia. Data is collected prior and post the use of CureSee Vision Therapy Software by patients and the collected data were decoded and tabulated using the Ms. Excel 2010 computer program and IBM Statistical Package for Social Sciences (SPSS) statistics version 23.0 was used for the analysis of data. Result and Conclusion: Visual Acuity improved significantly by 0.14 LogMar to the Median Values of Right Eye and by 0.60 LogMar to the Median Values of Left Eye. Stereopsis improved from 800 ± 520 sec of arc to 60 ± 60 sec of arc with P≤0.001. PFV and NFV also improved significantly after the use of Vision Therapy Software. Results conclude that Vision Therapy software is effective in improving Stereopsis, Visual Acuity and Vergence values in Amblyopic patients.

Stereopsis Deficits in Parkinson’s Disease and Their Clinical Implications

Background: Parkinson's disease (PD) is not exclusively a motor disorder. Among non-motor features, PD patients possess sensory visual dysfunctions. Stereopsis deficit can significantly impact patients' motor performance. However, it is not routinely tested, and its significance is under-investigated. Studying stereopsis using reliable 3D stimuli may help determine its implications in disease status in PD.The objective of the study is to investigate stereopsis abnormalities in PD with reliable and more physiological tools, and their correlation with indicators of PD severity. Methods: Twenty-four healthy control and 20 PD participants were first evaluated for visual acuity, visual field, contrast acuity, and stereoperception with 2D and Titmus stereotests, followed by the assessment with the 3D active shutter system. The correlation between stereopsis and disease severity, Unified Parkinson’s disease rating scale motor scores (UPDRS-III), levodopa equivalent daily dose (LEDD), course of disease and cognitive status were evaluated using univariate regression models. Results: Screening visual tests did not reveal any differences between PD and control group. With the 3D active shutter system, PD patients demonstrated significantly worse stereopsis (i.e p=0.002, 26 seconds of arc). There was a trend that UPDRS-III and LEDD negatively correlate with the stereo acuity, suggesting poorer stereoperception is related to disease severity. Preserved cognitive function correlated with more intact stereo acuity. Conclusion: With more reliable and physiological tools, PD patients exhibit poorer stereopsis. These deficits reflected PD motor and cognitive status. How stereopsis relates to gait, fall risks and navigation warrants more investigations in the future.

Refractive Errors and Binocular Anomalies in Primary Schools in Uyoun Aljawa: A Small Urban Town in Saudi Arabia

AIM: To assess the prevalence of uncorrected refractive error (RE) and binocular vision (BV) anomalies in school-aged children in Uyoun Aljawa, a small urban town in Saudi Arabia. METHODS: This was a cross-sectional study of 417 students (aged 6&ndash;13 years old) conducted in two primary schools in Uyoun Aljawa from November 2019 to January 2020. All students underwent comprehensive eye examination that include: distance visual acuity (VA), Non- cycloplegic refraction, ocular alignment assessment with the cover test; Near Point of Convergence (NPC) evaluation, Near stereo-acuity with Titmus-fly Stereotest, and finally, colour vision was screened with Ishihara plates. RESULTS: A total of 417 male schoolchildren (mean age &plusmn; SD: 9.2 &plusmn; 1.9) were included. In this study, 78 (18.4%) students had reduced vision (VA of &le;6/9) of which only 21 (27%) students had spectacles at the time of the study and 19.2% had uncorrected RE (VA of &lt;6/18 and no corrections). Emmetropia was reported in 80.3% of children where hyperopia was the most common refractive error (8.9%) followed by myopia (7.7%), and simple astigmatism was reported only in 3.1%. Heterophoria was reported in 12.5% of the sample, 5.2% had convergence insufficiency, and 16.3% showed subnormal results in stereo-acuity and 11 cases had a colour vision deficiency. CONCLUSION: The results of this study reveal a high prevalence of RE and other BVA among schoolchildren in Uyoun Aljawa. Vision Screening programs of children for RE and BVA should be conducted at the community level and integrated into school health programmes.