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Increased central corneal thickness may skew IOP measurements in diabetic eyes
J Glaucoma. 2010;19:613-616.
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Central corneal thickness was higher in diabetic patients than in nondiabetic patients, suggesting the potential for inflated IOP measurements in diabetic eyes, a study found.
"Thicker central corneas may lead to overestimation of the 'true' IOP in diabetic patients as evidenced in various studies reporting consistently higher IOPs in diabetics," the study authors said. "Thicker central cornea associated with diabetes mellitus should be taken into consideration while obtaining accurate intraocular pressure measurements in diabetics."
There were 245 eyes of 245 subjects in the study. The study group comprised 100 diabetic patients and was broken into three subsets: 29 patients with no diabetic retinopathy, 48 patients with mild to moderate nonproliferative diabetic retinopathy and 23 patients with proliferative diabetic retinopathy.
A control group comprised 145 nondiabetic subjects.
Mean central corneal thickness was 564 µm in the study group and 538 µm in the control group. The difference was statistically significant (P = .001).
Mean central corneal thickness was 582 µm in the proliferative diabetic retinopathy subset, 565 µm in the no retinopathy subset and 558 µm among patients with nonproliferative diabetic retinopathy. The difference was statistically insignificant.
Mean IOP was 15.1 mm Hg in the study group and 11.6 mm Hg in the control group (P = .001).
The impact of central corneal thickness on IOP measurement is widely recognized. In this study, patients with diabetes mellitus demonstrated slightly thicker corneas and higher IOP than the control group. Other studies evaluating the impact of diabetes mellitus on central cornea thickness have found variable results, and the biologic basis of corneal changes in diabetic eyes continues to be poorly understood. The possibility of fluctuating central corneal thicknesses based on the status of diabetic control exists, and the impact of potential corneal structural changes on IOP remains largely unknown. Based upon the amount of conflicting data and relatively minimal differences between diabetic and control eyes reported in the literature, the impact of diabetes mellitus on central corneal thickness may have rather limited clinical relevance in most patients.
– Steven D. Vold, MD
President and CEO,
Boozman-Hof Eye Clinic, P.A., Rogers , Ark.