The influence of background diabetic retinopathy in the second eye on rates of progression of diabetic retinopathy between 2005 and 2010

Purpose: The Gloucestershire Diabetic Eye Screening Programme offers annual digital photographic screening for diabetic retinopathy to a countywide population of people with diabetes. This study was designed to investigate progression of diabetic retinopathy in this programme of the English NHS Diabetic Eye Screening Programme. Methods: Mydriatic digital retinal photographs of people with diabetes screened on at least 2 occasions between 2005 and 2010 were graded and included in this study if the classification at first screening was no DR (R0), background DR in one (R1a) or both eyes (R1b). Times to detection of referable diabetic retinopathy (RDR) comprising maculopathy (M1), preproliferative (R2) or proliferative retinopathy (R3) were analysed using survival models. Results: Data were available on 19 044 patients, 56% men, age at screening 66 (57–74) years (median, 25th, 75th centile). A total of 8.3% of those with R1a and 28.2% of those with R1b progressed to any RDR, hazard ratios 2.9 [2.5–3.3] and 11.3 [10.0–12.8]. Similarly 7.1% and 0.11% of those with R1a progressed to M1 and R3, hazard ratios 2.7 [2.3–3.2] and 1.6 [0.5–5.0], compared to 21.8% and 1.07% of those with R1b, hazard ratio 9.1 [7.8–10.4] and 15.0 [7.1–31.5]. Conclusions: The risk of progression is significantly higher for those with background DR in both eyes than those with background retinopathy in only one or in neither eye.