Effect of glycemic control on refractive changes in diabetic patients with hyperglycemia

To investigate the effect of intensive glycemic control on hyperglycemia- induced changes in refraction, corneal topography, lenticular and corneal thickness in diabetic patients.

Eighteen diabetic patients with plasma glucose >300 mg/dl were enrolled in the study consecutively. Autorefraction, C-Scan corneal topography, Javal keratometry, corneal pachymetry and ultrasonic biometric measurements were carried out at presentation and after metabolic control of blood sugar (plasma glucose profile <200 mg/dl). One eye of each patient was selected randomly for statistical analysis.

Mean plasma glucose levels were 356.00 mg/dl before and 133.78 mg/dl after treatment. The median values of the autorefractometric measurements were - 0.125 D on admission and + 0.375 D at the second examination. The difference in the refraction was statistically significant (P = 0.022). Nine of 18 patients became hyperopic, 2 became myopic and 7 showed no change after treatment. There was a significant change in the corneal topographic keratometric measurements at the flattest corneal meridian after treatment (P = 0.037). After treatment no statistically significant changes were observed in the pachymetric corneal thickness, anterior chamber depth, biometric dioptric lens calculations and Javal keratometric data.

Hyperglycemia is the major cause of the transient refractive changes in diabetic patients. Following intensive medical treatment, a considerable number of patients tend to become more hyperopic compared with the hyperglycemic state. During the treatment period, changes in the corneal topographic parameters might be a potential source of error for keratorefractive and cataract surgery.