Abstract
Aim: The aim of this study was to explore possible associations between stereoacuity and refractive, accommodative and vergence anomalies.Methods: The study design was cross-sectional and comprised data from 1056 high school children aged between 13 and 18 years; mean age and standard deviation were 15.89 ± 1.58 years. Using a multi-stage random cluster sampling, participants were selected from 13 high schools out of a sample frame of 60 schools in the municipality concerned. In the final sample, 403 (38%) were males and 653 (62%) females. Refractive errors, heterophoria, near point of convergence, fusional vergences and accommodative functions (amplitude, facility, response and relative) were evaluated. Stereoacuity was evaluated using the Randot stereotest and recorded in seconds of arc where reduced stereoacuity was defined as worse than 40 s arc.Results: Overall, the mean stereoacuities (in seconds of arc) of the children with anomalies were the following: those with refractive errors (52.6 ± 36.9), with accommodative anomalies (53.1 ± 34.1) and with vergence anomalies (48.29 ± 31.1). The mean stereoacuity of those with vergence anomalies was significantly better than that of those with either refractive errors or accommodative anomalies (p = 0.02). In the refractive error category, only anisometropia had significantly reduced mean stereoacuity compared to emmetropia (Mann–Whitney U: p = 0.01). The mean stereoacuity of cases of accommodative anomalies was significantly reduced compared to those without such anomalies (Mann–Whitney U: p = 0.01). Similarly, the mean stereoacuity of cases with vergence anomalies was significantly reduced compared to those without vergence anomalies (p = 0.02).Conclusion: Refractive errors, accommodative or vergence anomalies are more likely to have reduced mean stereoacuity than cases without such anomalies. Refractive errors or accommodative anomalies had significantly more reduced stereoacuity than vergence anomalies. These findings suggest that the Randot stereotest could be used to identify those with such anomalies, and this study extends knowledge regarding the possible use of stereoacuity as a useful tool to screen for binocular anomalies.
Highlights
IntroductionStereopsis, described as binocular visual depth perception based on retinal rivalry, is one of the parameters used to evaluate the interactions of the accommodative and vergence systems.[1,2] Stereoacuity is the clinical measure of stereoscopic threshold derived from the minimum disparity that results in the appreciation of depth and it is an indicator of binocularity.[1,2] Accommodative anomalies are disorders of the eye’s focussing mechanism that result in an inappropriate response to a particular visual demand and are classified into accommodative insufficiency (AI), accommodative excess (AE) and accommodative infacility (AIF).[3,4] Near point vergence anomalies are disorders of binocular vision that cause an inability to sustain comfortable bifoveal fixation[5] and include convergence insufficiency (CI), convergence excess (CE) and fusional vergence dysfunction (FVD).[5]The refractive error, accommodative and vergence mechanisms are all part of the visual efficiency system.[3]
Data for near distance results are reported and data for most variables were not normally distributed and participants analysed had normal near visual acuity (VA)
Refractive error, accommodative or vergence anomalies were more likely to present with reduced stereoacuity than cases without the respective anomaly
Summary
Stereopsis, described as binocular visual depth perception based on retinal rivalry, is one of the parameters used to evaluate the interactions of the accommodative and vergence systems.[1,2] Stereoacuity is the clinical measure of stereoscopic threshold derived from the minimum disparity that results in the appreciation of depth and it is an indicator of binocularity.[1,2] Accommodative anomalies are disorders of the eye’s focussing mechanism that result in an inappropriate response to a particular visual demand and are classified into accommodative insufficiency (AI), accommodative excess (AE) and accommodative infacility (AIF).[3,4] Near point vergence anomalies are disorders of binocular vision that cause an inability to sustain comfortable bifoveal fixation[5] and include convergence insufficiency (CI), convergence excess (CE) and fusional vergence dysfunction (FVD).[5]The refractive error, accommodative and vergence mechanisms are all part of the visual efficiency system.[3].
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