South African Eye Study (SAES): ethnic differences in central corneal thickness and intraocular pressure

Purpose Glaucoma is the leading cause of irreversible blindness worldwide. South Africa has a diverse population but there is a lack of published ethnic specific normative data. The purpose of the study is to determine the distribution of intraocular pressure (IOP) and central corneal thickness (CCT) values in a multi-ethnic South African population and to determine additional systemic and ocular factors that influence IOP and CCT. Patients and methods This cross-sectional study included a total of 402 participants with 706 eyes aged 18-94 years. Participants underwent a standardized interviewer-administered questionnaire for risk factor assessment followed by a full ophthalmic examination. The averages of six IOP readings were measured with an Icare PRO tonometer and CCT was measured with a Pentacam. Results The mean CCT readings in the African, Mixed ethnicity, and Caucasian participants were 514.77 +/- 31.86, 531.77 +/- 35.17, and 549.97 +/- 30.51 mu m (P < 0.001). The mean IOP in the African, Mixed ethnicity, and Caucasian participants were 15.51 +/- 2.49, 15.09 +/- 2.12, and 15.13 +/- 2.53 mm Hg (P=0.07). Africans had significantly higher IOP than Mixed ethnicity (P=0.034) and Caucasians (P=0.011). Hypertensives had a higher IOP (P=0.03). Age and pseudophakia were associated with a lower IOP (P < 0.001) and higher CCT (P < 0.001). There was a strongly positive correlation between CCT and IOP (beta=0.021; P < 0.001). Conclusions In the South African Eye Study (SAES), Africans had the thinnest corneas and highest IOP followed by Mixed ethnicity and Caucasians. Including systemic and ocular factors that influence IOP specific to each population and ethnic group, will lead to a more accurate clinical risk stratification in glaucoma management.