ABSTRACT
Objective: This study aims to find the effect of monocularly induced myopic and hypermetropic astigmatism on stereopsis among ammetropes and emmetropes.
Methods: This comparative cross-sectional study was conducted at the General outdoor patient department (OPD) of Al-Shifa Trust Eye Hospital, Rawalpindi, Pakistan from October 2018 to January 2019. The study was conducted on 430 individuals aged between 10 to 35 years, emmetropic and with astigmatic refractive error of <4D at the axis of 900, 1800, 450, 1350, and <6D spherical refractive error. Subjects were divided into two groups of 215 individuals each. Both groups were induced with myopic and hypermetropic astigmatism using ±1 Dc and ±2 Dc at three axes; 45 º, 90 º, and 180º. Stereoacuity was measured by the Titmus Fly Stereo Test at the baseline and varying at degrees after induced astigmatism. ANOVA and paired t-tests were used for statistical analysis.
Results: The mean stereoacuity in emmetropes and ammetropes was respectively. On average, there was a significant decrease in stereoacuity with increased dioptric astigmatism power (p<0.0001). Stereoacuity was affected the most at 45º whilst least at 180 º among both emmetropes and ammetropes. However, monocularly-induced hypermetropic astigmatism caused more deterioration in stereoacuity than monocularly induced myopic astigmatism.
Conclusions: This study illustrates that monocularly induced myopic and hypermetropic astigmatism affects stereoacuity in emmetropes as well as ammetropes at all given degrees.
Keywords: Stereoacuity, emmetropia, ametropia, amblyopia, astigmatism