What is diabetic retinopathy?
Diabetic retinopathy is an eye disease that can occur following long standing diabetes. In the early stages there may be no problem with the vision, which is why it is important to screen the eyes of people with diabetes so that early changes in the eye can be monitored and treatment can be arranged in good time.
The longer a person has diabetes, the more likely it is that diabetic retinopathy will develop. Retinopathy means a problem with the retina, the light-sensitive layer that lines the inside of the back part of the eye. If the sugar level in the blood is high for long periods of time this can affect the small blood vessels at the back of the eye. These blood vessels can become leaky, allowing fluid from the blood to spread into the retina, which can then stop the retina from working properly. These changes show up as spots of blood in the retina and also areas of exudate (yellow coloured areas of fatty deposits in the retina). Later, these blood vessels can become blocked, starving the retina of oxygen. The retina responds to the reduced oxygen supply by producing new blood vessels. However, these behave in an abnormal fashion, with uncontrolled growth leading to bleeding inside the eye. All these changes to the retina can lead to loss of vision. The sooner they are detected, the sooner treatment can be started and the less likely vision will be lost.
There are three types of diabetic retinopathy; non-proliferative retinopathy, maculopathy and proliferative retinopathy. They represent different stages of the same condition. It is possible to have more than one type at the same time.
The changes associated with this stage are dot and blot haemorrhages combined with yellow patches of exudate. The dot haemorrhages are the result of swellings in the wall of the small retinal blood vessels. The blot haemorrhages are due to bleeding into the retina from the leaky blood vessels. The yellow patches are the result of fats leaking from the blood out into the retina. These combined changes are called background retinopathy.
The macula is the part of the retina which is responsible for our central vision. If this area is affected by the non-proliferative changes mentioned above then it is possible that the vision will be reduced permanently unless treatment is started.
This refers to the growth of new blood vessels in response to the blockage of some vessels due to diabetes. These new blood vessels are fragile and grow in an uncontrolled manner. They can easily bleed into the jelly of the eye (vitreous haemorrhage) and if left untreated can even lead to new blood vessels blocking off the drainage pores at the front part of the eye causing glaucoma. With time, the new blood vessels can form scar tissue which can pull on the retina and lead to retinal detachment.
Diagnosis of diabetic retinopathy
Diabetic retinopathy is diagnosed by examining the appearance of the back of the eye (the retina). This can be done either by a diabetic specialist, an ophthalmologist or an optician at a routine eye test. Recently a country wide diabetic screening service has been set up. This entails taking a photograph of the back of the eye for all diabetics and then having these pictures examined by specially trained graders who are able to spot if someone is developing diabetic changes in the eye. Treatment is then organised with an ophthalmologist.
Treatment of diabetic retinopathy
Laser treatment is used for both maculopathy and proliferative retinopathy. It consists of shining a tiny beam of laser light onto the retina. There is usually no sensation of discomfort associated with this. The laser beam creates a small burn on the retina. This helps to dry up areas of fluid (in cases of maculopathy) or helps to stop the growth of new blood vessels in cases of proliferative retinopathy (after multiple laser burns have been used).
Surgery is used to remove the vitreous jelly if it is filled with blood. Surgery can also be used to remove scar tissue from the retina and laser treatment can also be applied to the retina at the same time.
Recently intravitreal injections have been used to treat diabetic maculopathy. Both anti VEGF (Avastin and Lucentis) medications and steroid injections have been used with promising results. These treatments are still being assessed to evaluate which medication is best suited for a particular problem.