Comparative corneal topography and refractive variable in monozygotic and dizygotic twin Original Reearch Article

PURPOE: To invetigate the role of heredity in determining corneal hape, axial length, and overall refractive error. METHOD: Twenty monozygotic and 19 dizygotic twin pair, age 12 to 73 year, were enrolled in the tudy. Zygoity wa determined by phyical imilarity and by repone to quetion adapted from urvey. Two twin pair were excluded becaue of undetermined zygoity and one pair becaue of keratoconu (both ibling). Refractive error wa determined by an automated refractor. Manifet refraction wa alo recorded, a well a cycloplegic refraction in ubject under age 18 year. Corneal topography data and manual keratometer reading were alo obtained. Axial length were determined by A-can ultraound. Data were analyzed by tudent t tet only in the right eye. Left-eye data were comparable for all variable. REULT: Mean intrapair difference in refractive error (pherical equivalent) wa le for monozygotic than for dizygotic twin (RE: 0.41 v 1.53; P = .001). Mean intrapair difference in axial length wa le for monozygotic twin (RE: 0.39 v 0.76 mm; P = .031). Corneal topography data (power and meridian) in all zone (3, 5, and 7 mm) alo howed maller mean difference among monozygotic pair than dizygotic, but the difference wa tatitically ignificant only for the 5-mm zone. In addition, mot Holladay Diagnotic ummary variable that were tudied did not how any tatitically ignificant difference. CONCLUION: Axial length and overall refractive error have a ignificant genetic bai. Corneal topography data appear to have other overriding determining factor for everal of the variable tudied.