Photographic detection of retinopathy in insulin-treated diabetes. A population study in the city of Tartu, Estonia

Abstract

Purpose: To perform a cross-sectional baseline investigation of diabetic retinopathy prevalence and metabolic control.

Methods: Using a register of insulin-dependent diabetes mellitus in Tartu (pop. 104,791), 175 patients were invited to fundus photography; 149 (89%) participated, 99 of them diagnosed with diabetes before the age of thirty. Four Kodachrome 64 photographs per eye were taken with a Canon CR4 - 45NM camera through tropicamide-dilated pupils; slides were projected and systematically graded. Capillary blood samples (n = 132) for HbA1c determination were mailed on filter paper. Following cysteine buffer elution, Mono S ion exchange chromatography was performed (reference range 3.7 to 5.3%).

Results: Any diabetic retinopathy was found in 114 patients (76.5%; 95% confidence interval, CI, 70 to 83%); mild to moderate non-proliferative retinopathy in 59 (40%; 95% CI 32 to 48%); severe non-proliferative retinopathy in 29 (19.5%; 95% CI 13 to 26%); proliferative retinopathy in 26 (17%; 95% CI 11 to 24%); 47 patients (32%) needed laser photocoagulation. Vitreous haemorrhage was observed in 9 (6%) of subjects. In patients diagnosed with diabetes before the age of 30 years, prevalence of any retinopathy was 82% (95% CI 73 to 89%) and of proliferative retinopathy 23% (95% CI 15 to 33%). Median HbA1c was 9.7% for women and 8.6% for men (95% CI for difference 0.7 to 2.1%).

Conclusion: Retinopathy prevalences (76-82%) are the highest reported from population-based studies. Glycaemia levels were very high and should be gradually lowered. Methods capable of validation can be successfully introduced for population-based assessment of hyperglycaemia and retinopathy prevalences.