By Dr Ananya Mandal, MD
Diabetic retinopathy is a complication that is seen in diabetic patients who have suffered from the disease for a long time. One of the major risk factors for diabetic retinopathy is a long duration of diabetes.
The condition is caused by persistently high blood sugar levels damaging the small thread-like blood vessels that supply the retina. The retina lies at the back of the eye and is a light sensitive membrane. It converts the light that enters into the eyes into electric signals which the optic nerve then carries to the brain. In turn, the brain interprets the signals and converts them into images. Diabetic retinopathy is a progressive condition and, once it is advanced, it can lead to complete loss of vision and sudden blindness.
In the initial stages, tiny swellings called microaneurysms form in the sides of blood vessels and as disease progresses, new blood vessels also form. Both these new blood vessels and the microaneurysms are liable to rupture, leaking blood into the retina.
The longer a person suffers from diabetes, the greater the risk of developing retinopathy. Nearly 90% of people who have had type 1 diabetes for over 10 years develop some extent of diabetic retinopathy. The proportion of those who have had type 2 diabetics for over 10 years but do not take insulin is 67% and among type 2 diabetics with a 10 year disease duration who do take insulin, the proportion is 79%.
Blood sugar level
The higher a person's blood sugar level is, the greater the risk of developing diabetic retinopathy. People with a persistently raised glycated hemoglobin level (which indicates blood glucose level) are at greater risk of developing diabetic retinopathy.
High blood pressure in itself is detrimental to the retinal blood vessels and can cause hypertensive retinopathy. Therefore, among people with both a raised blood sugar level and high blood pressure, the risk of diabetic retinopathy is greater still.
Smokers are at a greater risk of blood vessel disorders, including retinopathy.
Pregnant women with gestational diabetes are at a greater risk of developing diabetic retinopathy.
Reviewed by Sally Robertson, BSc
Last Updated: Nov 3, 2013