Random-Dot Stereopsis in Microstrabismic Children: Stimulus Size Matters

Binocular vision disorders in a geriatric population

Clinical relevance: A population-based epidemiological survey is important to help establish the frequency of binocular vision disorders in a geriatric population. Such data will be useful to clinicians and help guide diagnostic testing for this age group.Background: To determine the prevalence of binocular vision disorders and their associations with age and sex in the geriatric population.Methods: This report is a part of the Tehran Geriatric Eye study (TGES); a population-based cross-sectional study conducted on residents over 60 years of age in Tehran, Iran, using random stratified cluster sampling. A total of 165 clusters were selected (proportionally to size) from 22 strata of Tehran city. All participants underwent a complete ocular examination including the measurement of visual acuity, refraction, unilateral and alternating cover tests, and the Worth 4-dot suppression test. Strabismus was defined as the presence of constant unilateral or alternating esotropia or exotropia at either near (40 cm) or far (6 m). Distance and near exophoria were defined as more than 3^Δ and 9^Δ of exophoria at 6 m and 40 cm, respectively. Distance and near esophoria were defined as more than 1^Δ and any amount of esophoria at 6 m and 40 cm, respectively.Results: Statistical analysis was performed on the data of 2,227 participants. The mean age of the participants was 66.6 ± 5.4 years and 59.4% were female. The prevalence of distance exophoria, esophoria, and hyperphoria was 8.9%, 0.34%, and 0.29%, respectively. The prevalence of near exophoria, esophoria, and hyperphoria was 32.4%, 0.61%, and 0.37%, respectively. The prevalence of distance exotropia and esotropia was 1.3% and 0.63%, respectively. The prevalence of near exotropia and esotropia was 4.6% and 0.59%, respectively.Conclusion: Non-strabismic binocular vision disorders were prevalent in an elderly population. Exo deviations were more prevalent than eso deviations.

Measuring aniseikonia tolerance range for stereoacuity - a tool for the refractive surgeon

Objective

No method exists to measure aniseikonia tolerance in stereoacuity. The brain can compensate for 2%–3% aniseikonia (i.e. 2–3 dioptres of anisometropia) without impairing stereoacuity; however, a substantial proportion of anisometropic patients experience problems caused by disruptions of sensory fusion due to surgically induced aniseikonia. We hypothesized that individual differences in tolerance to aniseikonia exist and sought to develop a method to measure aniseikonia tolerance.

Methods

A total of 21 eye‐healthy phakic individuals older than 50 years of age and 11 patients awaiting clear lens extraction were included. Patients were tested with best corrected near and distance visual acuity, cover/uncover test, eye dominance test, stereoacuity threshold (TNO test), slit lamp examination and ocular coherence tomography. The stereoacuity threshold was determined with aniseikonia induced by different size lenses ranging from 1% to 9% magnification of both eyes in increments of 1%. The aniseikonia tolerance range (ATR) was defined as the percentage aniseikonia in which the stereoacuity threshold was maintained.

Results

We examined 32 patients with a median age of 65 (95% CI: 62–66 years), CDVA better than 6/7.5 (0.1 logMAR), and median near visual acuity better than 6/6 (0.0 logMAR). The median stereoacuity threshold was 60 arcsec (maximum 30, minimum 120). We observed large inter‐individual differences in ATR: 6/31 (19%) participants had an ATR of ≤1%, 1/31 (3%) had an ATR of 1‐5%, 7/31 (22%) had an ATR of 5‐10%, and 17/31 (54%) had an ATR of >10%.

Conclusion

We present a reliable method for measuring the amount of aniseikonia that a person can tolerate without impairing stereopsis. We report large inter‐individual differences in tolerance of aniseikonia.

Stimuli Characteristics and Psychophysical Requirements for Visual Training in Amblyopia: A Narrative Review

Active vision therapy using perceptual learning and/or dichoptic or binocular environments has shown its potential effectiveness in amblyopia, but some doubts remain about the type of stimuli and the mode and sequence of presentation that should be used. A search was performed in PubMed, obtaining 143 articles with information related to the stimuli used in amblyopia rehabilitation, as well as to the neural mechanisms implied in such therapeutic process. Visual deficits in amblyopia and their neural mechanisms associated are revised, including visual acuity loss, contrast sensitivity reduction and stereopsis impairment. Likewise, the most appropriate stimuli according to the literature that should be used for an efficient rehabilitation of the amblyopic eye are described in detail, including optotypes, Gabor’s patches, random-dot stimuli and Vernier’s stimuli. Finally, the properties of these stimuli that can be modified during the visual training are discussed, as well as the psychophysical method of their presentation and the type of environment used (perceptual learning, dichoptic stimulation or virtual reality). Vision therapy using all these revised concepts can be an effective option for treating amblyopia or accelerating the treatment period when combining with patching. It is essential to adapt the stimuli to the patient’s individual features in both monocular and binocular training.

Evidence-Based Clinical Practice Guideline: Comprehensive Pediatric Eye and Vision Examination

Republished with written permission granted from the American Optometric Association, October 2, 2020.

The tolerance of anisometropia

PURPOSE

This study examines aniseikonia, Aniseikonia tolerance range (ATR), anisometropia and patient-reported outcomes (PRO) in an anisometropic population compared with a non-anisometropic population. The relationship between anisometropia and aniseikonia is determined, and the correlations between aniseikonia, anisometropia and ATR versus PRO are described.

METHODS

One hundred and twenty-three patients with IOL-induced anisometropia ≥1 dioptre (D) (the anisometropic group) and 17 patients who had IOL-induced anisometropia <1 D (the control group) were included. Best corrected visual acuity, aniseikonia, ATR and stereoacuity were examined, and two questionnaires were completed: convergence insufficiency symptom survey (CISS) and Visual Function Questionnaire (VFQ-39).

RESULTS

One hundred and thirteen patients had anisometropia >1 and <3 D, and 10 patients had anisometropia >3 D. There was no difference in PRO between the control group and the anisometropic group (Mann-Whitney, p-values VFQ: 0.96, CISS: 0.06). There was no correlation between anisometropia and PRO (Spearman's rank correlation test p-values: VFQ: 0.54, CISS: 0.57). Patients with low ATR were more sensitive towards anisometropia and had lower PRO than patients with high ATR (Mann-Whitney, p-values: VFQ: 0.0008, CISS: 0.11). A large tolerance of aniseikonia was observed.

CONCLUSION

No correlation between PRO and anisometropia or aniseikonia was found. Patients with low ATR are at risk of visual complaints if they are exposed to IOL-induced anisometropia. ATR might be a future screening tool in cataract patients.

Visual dot interaction with short-term memory

Aim: Many neurodegenerative diseases have a memory component. Brain structures related to memory are affected by environmental stimuli, and it is difficult to dissociate effects of all behavior of neurons. Materials & methods: Here, visual cortex of mice was stimulated with gratings and dot, and an observation of neuronal activity before and after was made. Bandwidth, firing rate and orientation selectivity index were evaluated. Results: A primary communication between primary visual cortex and short-term memory appeared to show an interesting path to train cognitive circuitry and investigate the basics mechanisms of the neuronal learning. The findings also suggested the interplay between primary visual cortex and short-term plasticity. Conclusion: The properties inside a visual target shape the perception and affect the basic encoding. Using visual cortex, it may be possible to train the memory and improve the recovery of people with cognitive disabilities or memory deficit.