Association of ocular dominance and anisometropic myopia

PURPOSE: To determine the association between ocular dominance and degree of myopia in patients with anisometropia. METHODS: Fifty-five subjects with anisometropic myopia were recruited. None of them had amblyopia. Refractive error and axial length were measured in each subject. Ocular dominance was determined using the hole-in-the-card test and convergence near-point test. RESULTS: There was a threshold level of anisometropia (1.75 D) beyond which the dominant eye was always more myopic than the nondominant eye. Of the 33 subjects with anisometropia of < or =1.75 D, the dominant eye was more myopic in 17 (51.5%) subjects. Dominant eyes, determined by the hole-in-the-card test, had a significantly greater myopic spherical equivalent (-5.27 +/- 2.45 D) than nondominant eyes (-3.94 +/- 3.10 D; P < 0.001). Dominant eyes also had a longer axial length than nondominant eyes (25.15 +/- 0.96 mm vs. 24.69 +/- 1.17 mm, respectively; P < 0.001). The difference was more evident in those subjects with higher anisometropia (>1.75 D), but was not significant in those with lower anisometropia (< or =1.75 D). Similar results were obtained using the convergence near-point test. CONCLUSIONS: The present study shows that the dominant eye has a greater degree of myopia than the nondominant eye in subjects with anisometropic myopia. Taking ocular dominance into account in the design of randomized clinical trails to assess the efficacy of myopia interventions may provide useful information.