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THE PREVALENCE AND CAUSES OF IMPAIRED VISION IN DIABETICS

The prevalence of partial sight and legal blindness was studied in 533 diabetics traced by prescriptions on insulin and oral hypoglycaemic agents (OHA) on the island of Falster (44 498 inhabitants). The prevalence of insulin‐treated diabetics (30 September 1980) was 0.52 per 1000 inhabitants and 0.72 per 1000 inhabitants of OHA‐treated patients. In the insulin‐treated group 106 patients had an onset age of diabetes below 30 years. Legal blindness occurred in 7.9% of 227 investigated insulin‐treated and in 4.9% of 306 OHA‐treated patients. Thus, the overall frequency of blindness in these 533 investigated diabetics was 6.2%. Partial sight was found in 4.9% of insulin‐treated and in 10.5% of OHA‐treated diabetics. In the insulin‐treated patients partial sight and legal blindness was caused by retinopathy (background and proliferative) in 81.8% and 84.8% of patients, respectively. Retinopathy contributed to partial sight in 46.8% and legal blindness in 80% of OHA‐treated diabetics. Proliferative retinopathy and background retinopathy caused visual loss in 48.4% and 36.4%, respectively, of legal blind diabetics. In diabetics with partial sight, background retinopathy was a more frequent cause of impaired vision (44.2% of the patients) than proliferative retinopathy (9.3% of the patients). In 50% of OHA‐treated patients with partial sight maculopathy without diabetic retinopathy (senile maculopathy) was the cause of visual impairment in contrast to 1% of insulin‐treated patients with partial sight. The severity of visual impairment was significantly associated with the duration of diabetes (> 15 years), the current age (> 50 years) and age at onset of diabetes (> 30 years) in insulin‐treated group. Relation between duration of diabetes (> 5 years) current age (> 70 years) and a visual acuity 0.10 could be demonstrated in OHA‐treated patients. Impaired vision was more common among females in both the insulin‐ and OHA‐treated group. In the females no association appeared between the frequency of pregnancies and a visual acuity 0.33. In diabetics with nephropathy, gangrene or amputation impairment of vision occurred more frequently.