Diabetes is commonly associated with high blood sugar. It develops when the pancreas does not produce enough insulin, or when the body cannot use insulin effectively.
However, its effects extend beyond the pancreas, kidneys and nerves. Prolonged exposure to elevated blood glucose can also damage the delicate blood vessels in the eyes that are responsible for maintaining healthy vision.
If blood sugar remains above the target range for a long time, it can lead to diabetic retinopathy (DR), a condition that affects the blood vessels supplying the retina, the light-sensitive layer at the back of the eye and is related to diabetes.
According to Dr Rilwan Adan, Head of Lions Diabetes Centre at Lions Hospital, persistently high blood sugar can weaken these small blood vessels, causing them to leak fluid or blood, become blocked or develop abnormal new vessels that are fragile and prone to bleeding.
"Diabetes and the eyes are closely connected because persistently high blood sugar can damage the small blood vessels that supply the retina, the light-sensitive layer at the back of the eye. Over time, this can lead to diabetic retinopathy, one of the major complications of diabetes," she explains.
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One of the most concerning aspects of diabetic retinopathy is that it can develop without obvious symptoms. A person may continue with daily activities, believing their eyes are healthy, while retinal damage progresses unnoticed. Unlike an eye infection or injury, the condition does not necessarily cause pain, redness or immediate changes in vision.
"What is worrying is that diabetic retinopathy can develop silently. A person may have significant damage to the retina without experiencing pain or noticing any change in their vision," Dr Adan says.
This makes routine eye examinations particularly important. People with Type 2 diabetes face an additional challenge because the condition can remain undiagnosed for months or years, allowing changes in the retina to develop before treatment begins.
As diabetic retinopathy advances, symptoms may include blurred or distorted vision, floating spots or dark specks, difficulty reading and areas of reduced or missing vision. Fluctuating blood sugar levels may also affect visual clarity.
Diabetes can cause diabetic macular oedema, in which fluid accumulates in the macula, the central part of the retina responsible for sharp, detailed vision. More advanced retinopathy can lead to bleeding inside the eye, abnormal blood vessel growth and, in severe cases, retinal detachment.
Dr Adan warns that a sudden increase in floaters, flashes of light or a curtain-like shadow across the field of vision requires urgent eye assessment, as these symptoms may signal a serious retinal problem.
The risk of diabetic retinopathy increases with the length of time a person has lived with diabetes, particularly when blood sugar is poorly controlled.
Managing the condition therefore involves more than taking medication or monitoring glucose levels. Blood pressure, cholesterol, nutrition, physical activity and regular medical reviews also matter.
Eye screening schedules depend on individual risk factors and examination findings. Some people require annual screening or more frequent reviews, while others may be advised to attend less often. Importantly, normal eyesight does not guarantee a healthy retina.
A comprehensive dilated eye examination or appropriate retinal screening can detect damage before symptoms appear.