Purpose: To study the ability of the alternative classification of the Wisconsin Study to predict progression to retinopathy requiring laser treatment in patients with diabetes.
Methods: A total of 1585 diabetic patients were included in the study. Of them, 294 (19%) were diagnosed with diabetes before and 1291 (81%) after age 30 years. Retinopathy was diagnosed on fundus photographs using a modification of the Wisconsin scale, and graded into 6 levels according to the worse eye. The first visit during the study period was used to represent baseline examination. The time points for detection of proliferative retinopathy (PDR) and clinically significant macular oedema (CSME) were recorded during a mean follow-up time of 2.9 years.
Results: Progression to PDR and/or CSME was significantly related to increasing severity of retinopathy at baseline (p<0.001; test for trend). Fifty per cent of patients with severe non-proliferative retinopathy (NPDR) (level 51) at entry progressed within one year to PDR and/or CSME; the 3-year risk for such progression in patients with mild (level 31) and moderate NPDR (level 41) was 25 and 60%, respectively. The incidence of progression to PDR and to CSME was 0.95 and 2.3/100 person-years, respectively. Progression to PDR and/or CSME was furthermore associated with a higher level of glycosylated haemoglobin, longer duration of the diabetes and use of antihypertensive treatment.
Conclusion: Increasing severity of retinopathy as recorded by this modification of the alternative classification of the Wisconsin Study was significantly associated with increased risk of progression to retinopathy requiring treatment.