Diabetes can affect the eyes in myriad of ways, but a recent study in the Journal of Ocular Pharmacology and Therapeutics reports diabetic patients who take insulin may have a small decrease in their lens thickness as a result of the medication. Specifically, the investigation found the glycosylated hemoglobin (HbA1C)-lowering glycemic effect of insulin was tied to the decrease in lens thickness.

The study, conducted by a team of Turkish researchers, evaluated the effects of insulin on ocular parameters in patients with type 2 diabetes who started insulin therapy.                   

Using an optical biometer and a refraction test, the investigators measured the patients’ ocular parameters at three months and after initiating insulin therapy. Additionally, the patients’ fasting blood glucose, HbA1C and blood lipid levels were measured at the same intervals.

The investigators found post-treatment HbA1C and fasting blood glucose levels (8.5% ± 2.5% and 188.1 ± 111.2mg/dL, respectively) were significantly lower than pretreatment levels (12% ± 1.4% and 325.3 ± 95.7mg/dL, respectively). Of note: a significant positive link was observed between the change in HbA1C and the change in lens thickness, in addition to a significant negative correlation between the change in fasting blood glucose and the change in the spherical equivalent refraction.

Insulin dose and treatment regimen type were not significantly correlated with ocular parameters, the researchers said.

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,” the researchers wrote in their study paper. 

Seven E, Yıldız S, Tekin S, et al. Effect of insulin therapy on ocular biometric parameters in diabetic patients. J Ocul Pharmacol Ther. October 23, 2019. [Epub ahead of print].