Prevalence of diabetic retinopathy and visual impairment in patients with diabetes mellitus in Zambia through the implementation of a mobile diabetic retinopathy screening project in the Copperbelt province: A cross-sectional study

Aims: A paucity of literature exists on prevalence of diabetic retinopathy (DR) in sub-Saharan Africa. We aim to estimate the prevalence of DR and visual impairment in Zambia's Copperbelt province through a cross-sectional study. Methods: All patients with a diagnosis of diabetes mellitus attending a DR screening programme were eligible to participate. Fundus photographs were graded in accordance with the DR grading system used in the UK National Health service (NHS). Visual impairment data were collected from visual acuity measurements recorded using Snellen chart. Results: A total of 2689 patients were screened and of these, 2153 patients had a least one eye of gradable quality for analysis. Fifty-five per cent (1190/2153) of patients were male. Mean age was 56 (SD 11). Fifty-two per cent (1113/2153) showed evidence of diabetic retinopathy (DR). Thirty-six per cent of patients graded (779/2153) had sight threatening DR. Proliferative DR was found in 7% (14/208) of type 1 diabetics compared to 5% (42/921) type 2 diabetics (p = <0.001). Duration of diabetes, random blood glucose, systolic and diastolic BP, and use of insulin and oral hypoglycaemics were strongly associated with DR in univariate analysis. The associations of increased systolic BP, random blood glucose, duration of diabetes and insulin use with DR were maintained in multivariate analysis. Conclusion: We observed a high prevalence of sight threatening DR which is close to the upper range of estimates that currently exist on DR. This study represents further evidence of global health inequality and the scale of the epidemic which sub-Saharan African countries now face.