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Diabetic retinopathy is a complication of diabetes that affects the retina.
The retina is the layer at the back of the eye which is sensitive to light. For sight to take place, light must be able to pass to the retina. It passes through the cornea and lens at the front of the eye and through the vitreous, the jelly-like substance in the middle of the eye.
Diabetes can cause the tiny blood vessels in the retina to become leaky or blocked. The former can lead to swelling of the retina. The latter can result in the growth of new vessels that may bleed and fill the eye with blood (called vitreous haemorrhage), or may pull the retina away from the sclera or wall of the eye (called tractional retinal detachment). Each can cause loss of vision.
Retinopathy is usually classified according to its severity, which may differ in both eyes.
Background retinopathy
This is the earliest stage in the development of retinopathy, but is uncommon in patients who have had diabetes for less than 8-10 years. At this stage in the development of retinopathy, vision is normal and there is no threat to sight. However, the presence of diabetic changes of haemorrhage, abnormal blood vessels (microaneurysms) and fatty deposits (exudates) in the eye is a warning sign that more severe retinopathy may develop, and it alerts the doctor to plan more frequent follow up.
Maculopathy
Maculopathy occurs when the central area of the retina, where most of the light sensitive cells which give us our central vision (especially important for close activities such as reading), is affected.
Maculopathy can be exudative, with leakage of fluid, protein and fats into the retina, blurring, obscuring or distorting vision. Laser treatment and control of cholesterol and fats may be of some benefit.
Maculopathy can also be ischaemic, again with visual blurring. This form of maculopathy is untreatable: prevention by good control of diabetes and hypertension is the best management.
Proliferative retinopathy
This occurs when capillaries (tiny blood vessels) become blocked. This starves the retina of nutrients, in response to which new vessels grow. These new vessels are fragile, however, and can bleed into the vitreous. This gives rise to floaters (either dots or lines in your vision) that, if severe, cloud the vision or cause loss of vision. If vessels grow on the iris they cause an increase in the pressure in the eye and cause severe and painful glaucoma. The new vessels eventually produce scar tissue, which may result in a retinal detachment with severe loss of sight.
