Diabetic retinopathy

Epidemiology

1. Prevalence of retinopathy

Diabetic retinopathy is the commonest cause of blindness in the 

population of working age in developed nations and is of increasing 

importance in developing nations2,3. The prevalence of retinopathy 

varies with the age of onset of diabetes and the duration of the 

disease: in younger patients (below 30 years of age) the prevalence 

of retinopathy is minimal during the first 5 years but increases to 

greater than 95% after 15 years of diabetes4. in contrast, in patients 

whose onset of diabetes occurs after the age of 30, up to 20% may 

have signs of retinopathy on presentation with the prevalence in this 

group rising more slowly to approach 60% after 15 years of diabetes5.

.

In an insulin-treated subset of older-onset (>30 years) diabetic 

patients, 30% have signs of retinopathy at diagnosis, rising to over 

80% after 25 years of diabetes. More recent data on patients with 

non-insulin dependent diabetes mellitus (NIDDM) as part of the 

UK Prospective Diabetes Survey (UKPDS) indicate that the prevalence 

of retinopathy at diagnosis is 38%, using a single microaneurysm as 

evidence of retinopathy6. 

.

As a general statement, therefore, the prevalence of DR of any

severity in the diabetic population as a whole is approximately 30%7.

.

1.2 Prevalence of sight-threatening retinopathy

Most cases of DR are non-sight threatening. However, the pre-

valence of progressive retinopathy with risk of visual impairment is 

approximately 10%8. 

.

Accurate figures for the prevalence of  blindness (defined as 

VA <3/60 in the better eye) in the UK are not yet available. In the 

Wisconsin epidemiologic studies, the prevalence of proliferative 

retinopathy was 60% after 25 years of diabetes in younger diabetic 

patients, but in older diabetics it varied from 20 to 30% depending 

on whether they were insulin-treated or not. In contrast, diabetic 

macular oedema in 11% of younger diabetics and in 4% to 7% of 

older depending on their insulin requirement. Despite the lower 

overall rate of sight-threatening retinopathy in older patients, the 

prevalence of visual disability is greater in this group due to the much 

larger numbers of patients with NIDDM9. More recent data has shown 

that the incidence of macular oedema over a 10 year period was 20% 

in young diabetics, 25% in older age diabetics taking insulin and 14% 

in non-insulin-taking older diabetics. In addition, there appeared to be 

a correlation between incidence of macular oedema and poor diabetic 

control (see later)10.

.

The prevalence of blindness due to DR has thus been estimated to be 

approximately 5% (range 3-7%)11 and may be as high as 8%1. The 

annual incidence of new cases of sight-threatening retinopathy in 

the UK has been estimated to be approximately 1.2% of diabetics12. 

In order to eliminate this, screening programmes aimed a the diabetic 

population at risk of sight-threatening retinopathy, are presently being 

developed. Pilot studies indicate that 2.5-3% per annum of the screened 

population would require referral to an ophthalmologist.