IMPORTANCE Thicker or thinner central corneas may lead to either overestimation or underestimation of intraocular pressure, which is the most important causal and treatable risk factor for glaucoma. However, the findings on the associations between diabetes, random glucose, and glycated hemoglobin A(1c) (HbA(1c)) with central corneal thickness (CCT) are conflicting. OBJECTIVE To evaluate the associations between diabetes, random glucose, and HbA(1c) with CCT in a multiethnic Asian population. DESIGN, SETTING, AND PARTICIPANTS Cross-sectional analysis of the Singapore Epidemiology of Eye Diseases (SEED) Study conducted from 2004 to 2011. A total of 10 033 Chinese, Malay, and Indian individuals 40 years or older residing in Singapore were recruited. Participants with incomplete information on diabetes status (448 participants), prior refractive or cataract surgery (1940 eyes), and corneal edema or dystrophy (29 eyes) were excluded. Ameta-analysis was conducted to estimate the overall association of diabetes with CCT. EXPOSURES Standardized clinical examinations and interviewer-administered questionnaire to collect information about demographic, systemic, and ocular factors. MAIN OUTCOMES AND MEASURES Measurement of CCT using ultrasound pachymetry. RESULTS A total of 8846 adults (mean [SD] age, 57.9 [9.9] years; 4447 women [50.3%]) (17 201 eyes) were included in the final analyses. The CCT profile was similar among participants with and without diabetes (mean [SD] CCT, 545.3 [33.7] mu mvs 544.8 [33.9] mu m; P=.39). Following adjustments of age, sex, ethnicity, corneal curvature, axial length, and body mass index, CCT was a mean (SD) of 4.9 (0.8) mu m (95% CI, 3.3-6.5 mu m) thicker in patients with diabetes than those without diabetes. Multivariable analyses also showed that thicker CCT was associated with higher random glucose (per 10mg/dL [to convert to mmol/L, multiply by 0.0555], beta=0.3; 95% CI, 0.2-0.4) and higher HbA(1c) (per percentage, beta=1.5; 95% CI, 1.0-2.1) (all P<.001). These associations were significant in the subgroup with diabetes but not in the subgroup without diabetes. Ameta-analysis including 12 previous population-and clinical-based studies showed that CCT was 12.8 mu m (95% CI, 8.2-17.5 mu m) thicker in eyes of patients with diabetes. CONCLUSIONS AND RELEVANCE These findings suggest that diabetes and hyperglycemia were associated with thicker CCT. This study provides useful information on the interpretation of intraocular pressure in patients with diabetes.