Purpose
Sub-Saharan Africa faces an epidemic of diabetes; epidemiological data on diabetic retinopathy (DR) from this region is sparse. We performed the first prospective cohort study of DR in this region. We report progression of retinopathy and associations with clinical and biochemical variables in people with diabetes in Southern Malawi.
Methods
Subjects were systematically sampled from two hospital-based diabetes clinics providing primary diabetes care. Clinical examination and biochemical testing was performed to assess visual acuity, glycaemic control, systolic BP, HIV status, urine albumin-creatinine ratio, hemoglobin and serum lipid levels. Retinopathy was graded using modified Wisconsin grading using 4-field mydriatic photography: dual grading with arbitration at an accredited reading centre. Sight-threatening diabetic retinopathy (STDR) was defined as moderate preproliferative retinopathy or worse, exudates within one disc diameter of the foveal centre or clinically significant macular edema.
Results
Of 357 subjects recruited 295 were assessed at 24 months; 28 were confirmed dead (90.5% follow-up). At baseline 13.4% subjects were HIV-positive and 15.1% had anaemia. At 24 months rates of progression were: 2 step (or greater) 58/293 (19.8%); STDR 23/225 (10.2%). Cumulative incidence of STDR for subjects with Level 10 (no retinopathy), Level 20 (background) and Level 30 DR at baseline were 2.7% (95% CI 0.1-5.3), 27.3% (16.4-38.2) and 25.0% (0-67.4), respectively. In multivariate logistic analysis 2 step progression of DR was associated with HbA1c (OR 1.27, 95%CI 1.12-1.45), baseline grade of DR (1.39, 1.02-1.91) and HIV infection (OR 0.16, 0.03-0.78). During the course of the study 85 persons required laser photocoagulation. 17 subjects (5.8%) lost ≥15 ETDRS letters.
Conclusions
This study provides critical baseline information on progression of retinopathy and visual impairment in patents attending mixed urban and rural diabetes clinics. Progression to STDR from no retinopathy and background DR occurred approximately 3 and 2.5 times more frequently than reported in recent European studies, respectively. The negative association of HIV infection with DR progression is a new finding. Our results highlight the urgent need for provision of services for retinopathy detection and management to avoid a large burden of vision loss.