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Y-F Shih, W-L Chen, J-F Fung, F-R Hu, I-J Wang; Comparative Corneal Topography, Corneal Thickness and Refractive Variables in Monozygotic and Dizygotic Twins . Invest. Ophthalmol. Vis. Sci. 2002;43(13):176.
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Purpose: To investigate the role of heredity in determining corneal shape, thickness, axial length and overall refractive error. Methods: 48 mnozygotic and 39 dizygote twin pairs, age 18 to 47 years, were enrolled in the study. Refractive error was determined by an automated refractometer. Manifest refraction was also recorded, as well as cycloplegic refraction in subjects under 18 years. Anterior corneal topographic pattern was obtained with Orbscan II and TMS-I. Posterior corneal topographic pattern was obtained with Orbscan II. Corneal thickness was obtained with Orbscan II and ultrasound pachymetry. Axial lengths were determined by A-scan ultrasound. Data were analyzed by Student t test only in the right eye. Left-eye data were comparable for all variables. Results: Mean intrapair difference in refractive error (spherical equivalent) was less for monzygotic than for dizygtic twin. (RE: 0.45 vs 1.64; p=0.001). Mean intrapair difference in axial difference in axial length was less for monozygotic twin (RE: 0.24 vs 0.58 mm;P=0.001). There was no significant intrapair difference in corneal thickness (RE: 4.8µm vs 5.2 µm, P≷0.05) Anterior corneal topographic pattern data (power and meridian) in all zones (3,5,7 mm), anterior and posterior elevation map also showed small differences among monozygotic pairs than dizygotic twins. Conclusion: Corneal topography data, axial length and overall refractive error have a significant genetic basis. There was no significant genetic bases for corneal thickness.
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