The effect of diabetes on the eye is called diabetic retinopathy. Diabetic retinopathy is a common complication of diabetes, it may not have any symptoms or may not affect sight in the early stages but, as the condition progresses, eventually the sight will be affected. When the condition is caught early, treatment is effective at reducing or preventing damage to sight.
Diabetic related sight loss is thought to be the most common form of blindness in people of working age in the developed world. In about 10% of cases, diabetic macular oedema (DME) may occur where blood vessels leak their contents into the macular region of the retina and this may cause a more rapid form of vision loss.
What are the symptoms of diabetic retinopathy?
The earliest phase of diabetic retinopathy is known as ‘background diabetic retinopathy’. Often there are no symptoms in the early stages of the disease, nor is there any pain. In this phase, the arteries in the retina become weakened and leak, forming small haemorrhages. These leaking vessels often lead to swelling or oedema in the retina. As the disease progresses, some blood vessels that nourish the retina become blocked, over time worsening and depriving several areas of the retina with their blood supply.
In advanced diabetic retinopathy the signals sent by the retina for nourishment trigger the growth of new blood vessels. This condition is called proliferative retinopathy. These new blood vessels are abnormal and fragile. They grow along the retina and along the surface of the clear gel that fills the inside of the eye. By themselves, these blood vessels do not cause symptoms or vision loss. However, they have thin, fragile walls. If they leak blood, severe vision loss and even blindness can result.
A condition known as diabetic macular oedema occurs when blood leaks into the centre of the retina, known as the macula, the part of the eye where sharp, straight-ahead vision occurs. The fluid makes the macula swell, blurring vision. This can occur at any stage of diabetic retinopathy, although it is more likely to occur as the disease progresses.
Some countries run regular and effective retina screening where diabetic retinopathy can be diagnosed early and effectively treated. This is unfortunately not the case in all countries.
What treatments are available?
Prevention of diabetic retinopathy is the most important step to take for anyone with diabetes. Researchers have found that diabetic patients who are able to maintain appropriate blood sugar and blood pressure levels have fewer eye problems than those with poor control. Diet and exercise play important roles in the overall health of people with diabetes.
People with diabetes can also greatly reduce the possibilities of eye complications by going to their routine examinations with an eye doctor and taking part in the national screening programme. Many problems can be treated with much greater success when caught early.
Diabetic retinopathy is treated in many ways depending on the stage of the disease and the specific problem that requires attention. The doctor relies on several tests to monitor the progression of the disease and to make decisions for the appropriate treatment. Laser eye surgery called pan retinal photocoagulation (PRP) is one treatment choice to prevent the blood vessels from leaking, or to get rid of the growth of abnormal, fragile vessels. A new class of drugs have recently become available to treat macular oedema and they are often used in conjunction with the laser therapy. These are anti-VEGF (Vascular Endothelial Growth Factor) drugs and they target the substance in the body which is responsible for the development of blood vessels. In diabetic macular oedema, too much VEGF is produced in the eye, and these drugs block the production of these new, abnormal vessels.
Vitrectomy is another surgery commonly needed for diabetic patients who suffer a vitreous haemorrhage (bleeding in the gel-like substance that fills the centre of the eye). During a vitrectomy, the retina surgeon carefully removes blood, fibrous tissue and vitreous from the eye, relieving traction on the retina and preventing retinal detachment. If retinal detachments or tears occur, they are often sealed with laser surgery. Retinal detachment requires surgical treatment to reattach the retina to the back of the eye. The prognosis for visual recovery is dependent on the severity of the detachment.