Improved visual function in IDDM patients with unchanged cumulative incidence of sight-threatening diabetic retinopathy

OBJECTlVE - To evaluate trends in visual acuity and the cumulative incidence of diabetic retinopathy in a clinic-based observational follow-up study: RESEARCH DESIGN AND METHODS - All patients visiting Hvidore Hospital in 1984 whose diagnosis of IDDM had been made before 41 years of age and between 1965 and 1979 (n = 356) were followed until 1994 or until their deaths. All patients were Caucasians and resided in Copenhagen. Patients were divided into three prevalence cohorts based on time of diabetes onset: group A, 1965-1969 (n = 113); group B, 1970-1974 (n = 130); and group C, 1975-1929 (n= 113). RESULTS - Fifteen years after diabetes onset, the visual acuity was significantly improved in patients with increasing calendar year of the disease onset. The median (interquartile range) visual acuity was 1.0 (0.8-1.0), 1.0 (0.9-1.0), and 1.0 (1.0-1.0) in groups A, B, and C, respectively (P < 0.01 overall; P = 0.28 for group A vs. group B; and P < 0.01 for group a vs. group C) with 60, 66, and 93 having a visual acuity of 1.0 in groups A, B, and C, respectively. The cumulative incidence (+/-SEM), expressed as a percentage and calculated according to the life-table method, of proliferative retinopathy, maculopathy, and laser-treated retinopathy 15 years after onset of diabetes were, respectively, 13 +/- 3, 11 +/- 3, and 12 +/- 3 in group A; 16 +/- 3, 12 +/- 3, and 21 +/- 4 in group B; 11 +/- 3, 5 +/- 2, and 12 +/- 3 in group C, respectively (NS). The development of proliferative retinopathy was associated with the degree of retinopathy and albuminuria at baseline and the mean HbA(1c) during follow-up. CONCLUSIONS - The study revealed an improvement in visual acuity with increasing calendar year of diabetes onset bur an unchanged cumulative incidence of diabetic retinopathy.