Racial Differences in Retinal Vessel Geometric Characteristics: A Multi-Ethnic Study in Healthy Asians.

PURPOSE: To investigate potential racial/ethnic differences in retinal vascular geometric parameters in a multi-ethnic Asian population (Chinese, Malay and Indian) free of clinical diseases. METHODS: A series of retinal vascular parameters were measured from retinal photographs using a computer-assisted program following a standardized protocol. Healthy participants were defined as non- smokers, absence of diabetes mellitus, uncontrolled hypertension, obesity, stroke, heart disease, glaucoma and retinopathy. RESULTS: There were significant differences in measurements of retinal vascular caliber, tortuosity and fractal dimension among the three ethnic groups. In multivariate liner regression model controlling for age, gender, body mass index, systolic blood pressure, cholesterol, and glucose levels, Indians had largest arteriolar and venular calibers (arterioles [standard error: SE]: 158.94 µm [1.00]; venules: 228.26 µm [1.53]), followed by Malays (arterioles: 138.31 µm [0.74]; venules: 204.26 µm [1.13]), and then Chinese (arterioles: 131.20 µm [0.84]; venules: 195.09 µm [1.28]). Chinese had largest arteriolar and venular tortuosity (arterioles (×10(5)): 7.20 [0.08]; venules (×10(5)): 9.09 [0.10]), and venular fractal dimension (1.244 [0.003]). There were no statistically significant differences in other retinal vascular parameters after correcting multiple comparisons by the method of modified false discovery rate. CONCLUSIONS: We found that among ethnic groups comprising of healthy Chinese, Malay and Indians, there were statistically significant differences in several retinal parameters. There exist racial influence in retinal vascular parameters and other yet unknown or unmeasured environmental factor or lifestyle habits and genetic variations not related to race that may also contribute to these differences.