Diabetic eye disease is one of the most common causes of blindness in the 45 - 65 age group. Initially, the retina might appear normal but the patient describes non-specific visual disturbance. Colour vision might be affected.

At a later stage, blood and protein can leak out of abnormal blood vessels in the retina forming haemorrhages and exudates. This is called non-proliferative diabetic retinopathy (NPDR) or in the past, background diabetic retinopathy (BDR). The vision might still be normal. At this stage, no treatment is required, but regular follow up is essential. The leakage of protein can become more severe and the macula (part of the retina responsible for central vision) can be threatened. This is called diabetic maculopathy. Laser treatment can halves the risk of further deterioration.

On the other hand, abnormal vessels can be formed. They are more fragile and can bleed easily. This is called proliferative diabetic retinopathy (PDR). At this point, laser treatment is extremely important. If the abnormal new vessels bleed, it can cause a vitreous haemorrhage (bleeding into the jelly inside the eye) and the vision would become hazy, like seeing through a fog. Sometimes, it would clear by itself but surgery might be required. More importantly, extensive new vessels formation can generate a scarring response leading to tractional retinal detachment (TRD). Visual prognosis is very poor with TRD despite surgery.

In summary, early diabetic eye diseases might not cause any symptoms so screening is very important. Once a year for most people is required. When it is established, laser therapy can be useful. Once it gets out of hand, visual prognosis is very poor.