Race, iris pigmentation, and intraocular pressure

The association of intraocular pressure with age, sex, race, iris pigmentation, systemic blood pressure, and family income was evaluated using data from the Health and Nutrition Examination Survey of 1971-1972. In general, mean intraocular pressure was highest for blacks with brown irides and progressively lower for whites with brown irides, whites with neither brown nor blue irides, and whites with blue irides. Multilinear regression analysis showed positive associations of intraocular pressure with systolic blood pressure (p less than 0.0001), age (p less than 0.0001) and amount of iris pigmentation (p less than 0.0001). The association with iris pigmentation held for both a combined race/iris color variable and for iris color among white persons. When race rather than iris pigmentation was used in the regression equation, it was a weaker (p less than 0.03) but still significant risk factor for higher levels of intraocular pressure. Intraocular pressure was negatively associated with family income (p less than 0.004). Despite the significant associations, the proportion of variance in intraocular pressure that was explained by these variables was small (R2 = 0.06).