Central corneal thickness and related factors in an elderly American Chinese population

Background: To assess central corneal thickness and related factors in an elderly American Chinese population residing in San Francisco. Design: Cross-sectional community based study. Participants: American Chinese aged 40 years and older were enrolled using random cluster sampling and volunteer screening in the Chinatown district of San Francisco. Methods: The following data were obtained: central corneal thickness by ultrasound pachymetry, intraocular pressure by Goldmann applanation tonometry, axial length by A-scan biometry, refractive status and corneal curvature by autorefractor. History of systemic and ocular diseases was collected via standard questionnaire. Main Outcome Measures: Central corneal thickness. Results: Of 311 eligible subjects, 274 consented to study participation, and 228 phakic eyes were analyzed. Mean corneal thickness was 524.1 +/- 31.1 mu m, 545.5 +/- 30.9 mu m and 538.9 +/- 31.8 mu m in the sampling cluster, volunteer group and all subjects, respectively. A multiple linear regression model showed corneal thickness to be negatively associated with age (standardized regression coefficient [SRC] = -0.21; P = 0.016) and corneal curvature (SRC = -0.19; P = 0.018) but positively correlated with intraocular pressure (SRC = 0.20; P = 0.023). Conclusions: The distribution of central corneal thickness among this American Chinese population is similar to that reported in studies from East Asia. The independent factors associated with thinner corneas included older age, lower intraocular pressure and greater corneal curvature. While descendents of Chinese immigrants in America have, on average, thicker corneas than their ancestors, this phenomenon is potentially impacted by the level of intraocular pressure.