Diabetes related eye conditions:
- The most serious eye condition associated with diabetes involves the network of blood vessels supplying the retina. This condition is called diabetic retinopathy.
- The unusual changes in blood sugar levels resulting from diabetes can affect the lens inside the eye, especially when diabetes is uncontrolled. This can result in blurring of vision which comes and goes over the day, depending on your blood sugar levels.
- A longer term effect of diabetes is that the lens of your eye can go cloudy, This is called a cataract.
Not everyone who has diabetes develops an eye complication. Of those that do, many people have a very mild form of retinopathy which may never progress to a sight threatening condition.
The most serious complication of diabetes for the eye is the development of diabetic retinopathy. Diabetes affects the tiny blood vessels of the eye and if they become blocked or leak then the retina and possibly your vision will be affected. The extent of these changes determines what type of diabetic retinopathy you have. Forty per cent of people with type 1 diabetes and twenty per cent with type 2 diabetes will develop some sort of diabetic retinopathy.
Background diabetic retinopathy
This is the most common type of diabetic retinopathy and many people who have had diabetes for some time will have this early type. The blood vessels in the retina are only very mildly affected, they may bulge slightly (microaneurysm) and may leak blood (haemorrhages) or fluid (exudates). As long as the macula is not affected, vision is normal and you will not be aware that anything is wrong. Your retinal screening test will keep a close check on these early changes and ensure that any signs of progression to more serious stages of retinopathy are detected early.
Maculopathy means that your macula is affected by retinopathy. If this happens, your central vision will be affected and you may find it difficult to see detail such as recognising people’s faces in the distance or seeing detail such as small print. Most maculopathy can be treated with laser with the aim of preserving as much vision as possible. The amount of central vision that is lost varies from person to person. However, the vision that allows you to get around at home and outside (peripheral vision) is not affected.
Proliferative diabetic retinopathy
If diabetic retinopathy progresses, it can cause the larger blood vessels in the retina to become blocked. These blockages can result in areas of the retina becoming starved of oxygen. This is called ischaemia. If this happens the eye is stimulated into growing new vessels, a process called neo-vascularisation. This is the proliferative stage of diabetic retinopathy, and is nature’s way of trying to repair the damage by growing a new blood supply to the oxygen starved area of your retina.
Unfortunately, these new blood vessels are weak, and grow in the wrong place – on the surface of the retina and into the vitreous gel. As a result, these blood vessels can bleed very easily which may result in large haemorrhages over the surface of the retina or into the vitreous gel. These types of haemorrhages can totally obscure the vision in the affected eye as light is blocked by the bleed. With time the blood can be reabsorbed and vision can improve.
Extensive haemorrhages can lead to scar tissue forming which pulls and distorts the retina. This type of advanced diabetic eye disease can result in the retina becoming detached with the risk of serious sight loss.
Only between 5 and 10 per cent of all diabetics develop proliferative retinopathy. It is more common in people with type 1 diabetes than type 2. Sixty per cent of type 1 diabetics show some signs of proliferative disease after having diabetes for 30 years.