Diabetes Mellitus is the leading cause of blindness as a result of complications due to diabetic retinopathy. The metabolic status of the cornea is affected by changes in blood glucose levels. Metabolic stress due to hyperglycemia can alter central corneal thickness. Objective: To compares central corneal thickness (CCT) in diabetics and non-diabetic controls and evaluates the relation of CCT with glycemic status and severity of diabetic retinopathy. Methods: 180 subjects(93 diabetics and 87

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... -diabetics) attending or referred to the Department of Ophthalmology of a tertiary care hospital were included in the study.CCT was measured in all subjects using an ultrasonic pachymeter. Results: 93 patients were diabetic(Type 1 four and type 2 eighty-nine) of which 35 patients had no diabetic retinopathy,44 patients had non-proliferative diabetic retinopathy and 14 patients had proliferative diabetic retinopathy. Mean CCT in diabetics(563.11µm ±11.40µm)was found to be greater than non-diabetics (529.53±17.91µm)and the difference was statistically significant (p<0.0001). Mean CCT in type 1 and type 2 DM patients was 562±12.90µm and 562.59±9.44µm respectively. There were 35 diabetic patients with good metabolic control(HbA1C <7%) who had mean CCT 559.03±8.32µm.41 patients with poor metabolic control(HbA1C≥7) had a mean of CCT 565.04±9.94µm and the difference was statistically significant. Mean CCT in patients with no diabetic retinopathy, in patients with non-proliferative diabetic retinopathy and proliferative diabetic retinopathy was 558.81 ± 7.67um,563.81 ± 12.32 and 563.43 ± 9.70um respectively and the difference was not statistically significant. Conclusions: A significant correlation was found between an increase in CCT and diabetes, with the positive correlation between thick cornea and duration of diabetes, indicating that patients with thick corneas are more likely to be found in the advanced stage of the disease. Measuring CCT in diabetic patients should be mandatory in the workup of refractive surgery, for donor tissue evaluation before keratoplasty, glaucoma suspects, contact lens users etc. This may help to identify patients at higher risk of developing severe complications, enabling ophthalmologists to treat their disease more accurately.