To investigate the relationship between central corneal thickness (CCT) and demographics, and determine whether CCT may be a substantial mediator of the relationships between glaucoma and its demographic risk factors.
This cross-sectional study included patients in the Kaiser Permanente Northern California health plan from January 1, 2007 to December 31, 2011 who were 40 years and older and had a documented CCT measurement (N=81,082). Those with any cornea-related diagnoses or a history of corneal refractive surgery were excluded. Demographic characteristics, including age, sex, and race/ethnicity, as well as clinical information including glaucoma-related diagnosis, diabetic status, CCT, and intraocular pressure were gathered from the electronic medical record.
Multivariate linear regression analysis indicated that female sex, increased age, and black race were significantly associated with thinner corneas. A subgroup analysis among Asians revealed that Chinese, Japanese, and Koreans had corneas 6 to 13 µm thicker than South and Southeast Asians, Filipinos, and Pacific Islanders for each diagnosis (P<0.001). In our population, 24.5% (N=19878) had some form of open-angle glaucoma; 21.9% (N=17,779) did not have any glaucoma-related diagnosis. Variation in CCT accounted for only 6.68% [95% confidence interval (CI), 6.14%-7.24%] of the increased risk of open-angle glaucoma seen with increasing age, but explained as much as 29.4% (95% CI, 27.0%-32.6%) of the increased risk of glaucoma seen among blacks, and 29.5% (95% CI, 23.5%-37.0%) of the increased risk of glaucoma seen among Hispanics.
CCT seems to explain a substantial portion of the increased risk of glaucoma seen among blacks and Hispanics.