Is poor glycaemic control in diabetic patients a risk factor of myopia?

Purpose: As a consequence of an increasing prevalence of short-sightedness (myopia) in countries that have adopted western dietary patterns, it has been hypothesized that hyperglycaemia and hyperinsulinaemia induce myopia. The purpose of this study was to evaluate the relation between glycosylated haemoglobin (HbA(1c)), insulin dosage and myopia in diabetic patients. Methods: All type 1 diabetic patients aged 16-26 years [mean age 22.0, standard deviation (SD) 2.9] attending the eye clinic at Steno Diabetes Center, Copenhagen, in 1995-1997 were included in the study (n = 393). The following data were collected from the medical records from baseline to 2005: age at diabetes onset, age at baseline, sex, weight, HbA(1c), insulin dosage, refractive error, visual acuity and ocular diabetes complications. Results: The prevalence of myopia [spherical equivalent (SE) <= -0.5 D] was 53.3% [95% confidence interval (CI) +/- 5.29] at baseline. We followed 252 patients for 7.1 years (SD 2.2). In a logistic regression analysis, age at baseline [odds ratio (OR) 0.90 (95% CI 0.82; 0.99), P = 0.031], duration of diabetes at baseline [OR 0.95 (95% CI 0.91; 0.99), P = 0.047] and HbA(1c) [OR 1.26 (95% CI 1.03; 1.47), P = 0.022] were associated with myopia. The relative risk of a myopic shift was 1.7 (95% CI 1.28; 2.26) in patients aged 16-21 years and 1.6 (95% CI 1.19; 2.14) in patients with HbA(1c) above 8.8%. Insulin dosage was not related to myopia. Conclusion: The prevalence of myopia in diabetic patients is considerably higher than in the background Danish population. Poor metabolic control of glucose is a suggested risk factor of myopia. The study suggests that myopia may be regarded as a complication of hyperglycaemia in diabetes.