Epidemiology of diabetic retinopathy and maculopathy in Africa: a systematic review

Abstract

AimTo summarize findings from studies reporting the prevalence and incidence of diabetic retinopathy and diabetic maculopathy in African countries in light of the rising prevalence of diabetes mellitus.MethodsUsing a predefined search strategy, we systematically searched MEDLINE, EMBASE, Science Citation index and Conference Proceedings Citation index, African Index Medicus and the grey literature database ‘OpenSIGLE’ for studies published between January 1990 and February 2011. Included studies reported prevalence or incidence of diabetic retinopathy or diabetic maculopathy of subjects with diabetes resident in African countries.ResultsSixty-two studies from 21 countries were included: three population-based surveys; two cohort studies; five case–control studies; 32 diabetes clinic-based, nine eye clinic-based and 11 other hospital-based surveys. Included studies varied considerably in terms of patient selection, method of assessing the eye and retinopathy classification. In population-based studies, the reported prevalence range in patients with diabetes for diabetic retinopathy was 30.2 to 31.6%, proliferative diabetic retinopathy 0.9 to 1.3%, and any maculopathy 1.2 to 4.5%. In diabetes clinic-based surveys, the reported prevalence range for diabetic retinopathy was 7.0 to 62.4%, proliferative diabetic retinopathy 0 to 6.9%, and any maculopathy 1.2 to 31.1%. No obvious association between prevalence and income level of the country was detected.ConclusionsLarge, community-based cross-sectional and cohort studies are needed to investigate rates and determinants of prevalence of diabetic retinopathy, incidence and progression in Africa. Consensus is needed on the most appropriate methods of identification and classification of retinopathy for research and clinical practice. Estimates of prevalence of diabetic retinopathy, proliferative diabetic retinopathy and maculopathy are comparable with recent European and American studies.

Retinopathy in type 1 diabetes mellitus: Major differences between rural and urban dwellers in northwest Ethiopia

“…A report published in 1992 from the Ethiopian capital on a mixed urban/rural group of T1DM patients (mainly urban) reported that of the 11.5% of the total group for whom retinal examination was recorded, retinopathy was found in 21.7% of those with disease duration of 0-9 years [23]. A systematic review which included reports from 21 African countries on the prevalence of diabetic retinopathy and maculopathy was undertaken recently [3]. Most of the studies included in the report were set up for specific but disparate reasons making it difficult to compare them with the present study: thus, several did not differentiate between T1DM and T2DM, many investigated a small percentage of the total diabetic group or did not state the percentage assessed for retinopathy and maculopathy, and although rural groups were included in a few studies the outcomes for rural and urban groups were not reported separately [3].…”

“…A systematic review which included reports from 21 African countries on the prevalence of diabetic retinopathy and maculopathy was undertaken recently [3]. Most of the studies included in the report were set up for specific but disparate reasons making it difficult to compare them with the present study: thus, several did not differentiate between T1DM and T2DM, many investigated a small percentage of the total diabetic group or did not state the percentage assessed for retinopathy and maculopathy, and although rural groups were included in a few studies the outcomes for rural and urban groups were not reported separately [3]. In the major T1DM-only study an urban cohort (n=88) from Soweto (South Africa) has been followed from 1982, with the 20 year follow-up published in 2005; in 1982 their average age was 22 years and duration of diabetes was 3 years [24].…”

“…Diabetic retinopathy and associated maculopathy are due to microvascular disease in which there is endothelial dysfunction giving rise to leakage of fluid from the retinal capillaries into the perivascular space, retinal oedema, small haemorrhages, and collapse of the capillaries. The resultant retinal ischaemia is associated with the stimulation of growth factors such as VEGF and the development of new fragile blood vessels; this stage, proliferative retinopathy, poses great risks for major bleeds and retinal detachment resulting in significant visual impairment [3]. Hyperglycaemia is a major cause of diabetic retinopathy and stricter blood glucose control is associated with improved outcomes as first shown clearly in the Diabetes Control and Complications trial (DCCT) [4].…”

Prevalence and risk factors associated with retinopathy in diabetic patients at Parirenyatwa Hospital outpatients’ clinic in Harare, Zimbabwe

“…2 In Zimbabwe the last study on diabetic retinopathy was done two decades ago (October 1995 to April 1996) in which an overall prevalence of 27.5% was reported.…”

“…Without treatment 50% of patients with proliferative diabetic retinopathy become blind within 5 years. 2 Visual impairment and blindness in patients with proliferative diabetic retinopathy can be reduced by laser photocoagulation treatment and antivascular endothelial growth factor medicines.…”