Influence of Ocular Dominance on Anisometropic Myopia

During Binocular viewing, the preferential use of dominant eye because of its increased static ciliary muscle tone, might allow the dominant eye more myopic then non dominant eye in anisometropic myopia. However certain studies found that, there was no apparent association between ocular dominance and refraction. The present study was therefore conducted to analyze, the effect of ocular dominance on anisometropic myopia. This study was done at Physiology research laboratory, Thanjavur medical college, Thanjavur. 49 Medical students with anisometropic myopia were recruited. Refractive error was measured by autorefractometry. Ocular dominance was first tested by miles test and then VEPs (Visual Evoked Potentials) were performed by checker board pattern reversal stimuli system. Out of 49 Anisometropia, the dominant eye was more myopic in 27 (55.1%) subjects and the spherical equivalent refraction was not significant with non dominant eyes (p=0.6037). There were no significant differences in mean spherical equivalent refraction between dominant and non dominant eyes of < 0.5D (p= 0.9266) and in anisometropia of ≥0.5D (p= 0.9281). Among 35 non cross dominance anisometropia (Right handed right ocular dominance), the dominant eye was more myopic in 18(51.4%) subjects and it was not significant with non dominant eyes (p=0 .6622). Out of 14 cross dominance anisometropia (Right handed left ocular dominance) the dominant eye was more myopic in 9 (64.28%) subjects and it was not significant with non dominant eyes. (p= 0.4896). There was no significant effect of ocular dominance on anisometropic myopia. Further research is needed to evaluate the influence of ocular dominance on high anisometric myopia of ≥ 1.75D and also to determine the influence of cross and non cross ocular dominance on myopia to resolve the disparity existing in present studies.