3. Epidemiology of diabetic retinopathy:
Screening and prevention of blindness
Einar Stefánsson (Reykjavík)
The prevalence of diabetic retinopathy is highly variable. The overall prevalence of retinopathy
in diabetic populations has been reported anywhere from 12 to 88 % in different countries.
Similarly, the reported crude prevalence of proliferative diabetic retinopathy and diabetic
macular edema varies between different studies.
Duration and type of diabetes: As the prevalence of diabetic retinopathy is highly dependent
on the duration of diabetes, the crude prevalence provides limited information. For example in
the Icelandic type 1 diabetic population in 1994, the overall prevalence of any diabetic
retinopathy was 52 %, proliferative retinopathy was 13 % and macular edema 8 %. At the
same time 30 % of diabetic patients with duration of diabetes less than 20 years had retinopathy
and only 1 and 2 % respectively had proliferative retinopathy and macular edema, respectively. These numbers were
86 %, 33 % and 22 % for patients with diabetes for more than 20 years.
Type 2 diabetes patients tend to develop diabetic retinopathy sooner after onset than type 1 and are more likely to develop
macular edema and less likely to develop proliferative retinopathy.
Glycemic and blood pressure control: The DCCT showed a dramatic difference in the incidence of retinopathy between
those with conventional and intensive glycemic control. The UKPDS showed that blood pressure reduction lowers the incidence
of retinopathy in type 2 diabetic patients.
Vision: The variability in the prevalence of blindness is even greater than for retinopathy. Here the variable prevalence of
diabetic retinopathy is amplified by the variable delivery of screening and preventive treatment in various countries. Legal
blindness had been reported as high as 7.7 % in type 1 with 9.3 % partially sighted, and 6 and 13 % for type 2. In other
regions with systemic screening the prevalence of diabetic blindness is in many cases below 1 %.
Conclusion: We should see the variable prevalence of vision loss and diabetic retinopathy as an opportunity for the prevention
of blindness. The public health planning and health care delivery in the countries that have the lowest blindness rates
must be established in all countries.