Effect of Insulin Therapy on Ocular Biometric Parameters in Diabetic Patients

To evaluate effects of insulin on ocular parameters in patients with type 2 diabetes mellitus who start insulin therapy. In this prospective study, ocular biometric parameters were obtained using optical biometer (Lenstar LS900^®; Haag-Streit AG) and refraction test (ARK-510A Auto refracto-keratometer; Nidek Co. Ltd, Aichi, Japan) before and at 3 months after initiating insulin therapy. In addition, patients' fasting blood glucose (FBG), glycosylated hemoglobin (HbA1C), and blood lipid levels were measured at the same time points. Pretreatment and post-treatment results were compared. In addition, associations between ocular parameters with initial dose and type of insulin treatment regimen, HbA1C, and FBG levels were evaluated. The patients' mean age was 51.2 ± 12.9 (18-73) years. Post-treatment HbA1C and FBG levels (8.5% ± 2.5% and 188.1 ± 111.2 mg/dL, respectively) were significantly lower than pretreatment values (12% ± 1.4% and 325.3 ± 95.7 mg/dL, respectively; P < 0.001 for both). There was a significant positive correlation between the change in HbA1C and the change in lens thickness (P = 0.03), and a significant negative correlation between the change in FBG and the change in the spherical equivalent refraction (P = 0.045). Insulin dose and treatment regimen type were not significantly correlated with ocular parameters (P > 0.05). HbA1C-lowering glycemic effect of insulin was correlated with a small decrease in lens thickness. Long-term, randomized controlled trials including larger patient numbers are needed to shed light on the long-term effects of insulin use and glycemic control on ocular parameters.