Early glycaemic control for maintaining visual function in type 1 diabetes: The Oulu cohort study of diabetic retinopathy.

Purpose:: The purpose of this study was to evaluate the visual function and the ophthalmic status of young Finnish adults with long duration of type 1 diabetes in relation to the history of the metabolic control.
Methods:: A population-based cohort of children with type 1 diabetes examined in the Northern Ostrobothnia hospital district in 1989 (n = 216) was re-examined 18 years later. High-contrast visual acuity (best-corrected visual acuity), contrast sensitivity, refractive error, lens status, intraocular pressure, stage of diabetic retinopathy and received treatments were evaluated. The metabolic control was reflected by the mean of glycated haemoglobin A1 or glycated haemoglobin A1c values of the years 1983-1989 and 1992-2007, respectively.
Results:: In all, 96 men and 76 women age 30 ± 3 years with type 1 diabetes duration of 23 ± 4 years attended the re-evaluation. About 60% (103/172) had normal best-corrected visual acuity and 3% had low vision. Contrast sensitivity was abnormal in two-thirds. Half had myopia. Four patients had cataract surgery. Low childhood glycated haemoglobin A1 was indicative, and favourable glycated haemoglobin A1c during youth was a significant predictor of better contrast sensitivity and ocular state in adulthood.
Conclusion:: The majority of the patients have useful vision, although minor functional impairments are commonly detectable. Long duration of type 1 diabetes in association with non-optimal glycaemic control threatens visual function already at young adulthood. Thus, strong emphasis to control diabetes from onset is important in maintaining good visual function.