Longitudinal study of a cohort of people with diabetes screened by the Exeter Diabetic Retinopathy Screening Programme

Purpose To evaluate the long-term outcome of a cohort of people with diabetes screened by the Exeter Diabetic Retinopathy Screening Programme. Method The cohort comprised of diabetic patients from nine market town General Practices around Exeter who first attended the diabetic retinopathy screening programme in 1992. Screening was carried out by a combination of dilated fundoscopy by a screening technician and a single 45degrees Polaroid photograph of each eye. The prevalence of diabetic retinopathy at the baseline, the incidence of sight threatening diabetic retinopathy (STDR) in the next two rounds of screenings, and the long-term visual outcome are described. Results The cohort consisted of 775 patients (104 Type I, 517 Type II non-insulin-requiring and 154 Type IIinsulin-requiring). The mean age was 72.1 years (15-100), with mean disease duration of 13.0 years (1-79). Baseline prevalence was as follows: background retinopathy: 21.4%, proliferative: 2.8%, clinically significant macular oedema: 6.1%. The incidence of proliferative disease was 2.20% and 2.25% respectively in the next two rounds of screening (P > 0.05, chi(2) test). The incidence of clinically significant macular oedema was also constant over next two rounds of screening, at 4.79% and 5.18% respectively (P > 0.05, chi(2) test). Ninety-five (12.3%) patients were deceased and a further 179 (23%) patients were lost to follow-up by the third round. Only two patients with newly diagnosed STDR suffered,deterioration of visual acuity to 6/60 or worse as a result of diabetic retinopathy. Conclusion The incidence of STDR remained constant throughout the period of screening, reflecting the chronic progressive nature of the disease. Significant numbers of patients were lost to follow-up. Screening seemed effective in preserving vision in those patients with newly diagnosed STDR.