Diabetic retinopathy is a complication of diabetes which affects the back of the eye or the retina.
The retina is the part of the eye where light passing through the lens is focused. The focused light or images are then carried to the brain by the optic nerve. When leaking blood or fluid damages or scars the retina, the image sent to the brain becomes blurred.
It is known that diabetes weakens small blood vessels in various parts of the body. In the eye, these weakened vessels may leak blood or fluid. Pregnancy and high blood pressure may worsen the condition in diabetic patients.
The risk of developing diabetic retinopathy is high when a patient has had diabetes for a long time. About 60% of patients having diabetes for 15 years or more, will have some blood vessel damage in their eyes and a small percentage of these will progress to have serious problems with vision. An even smaller percentage may become blind, and because diabetes itself is fairly common, diabetic retinopathy has become the leading cause of new blindness in South Africa – a trend similar to that in developed countries. Is it said that the diabetic is 25 times more prone to blindness that the non-diabetic. Early detection and treatment reduces the sight threatening complication considerably.
Eye disorders that may be associated with Diabetes:
- Transient blurring of vision occurs in many diabetics because of changes in the lens of the eye, brought about by alteration in the blood sugar levels. Careful control of blood sugar will prevent this ocular problem.
- Paralysis of the nerves controlling the eye movements may occur in middle-aged diabetics and cause double vision. This very often recovers completely without treatment within three months.
- Cataract (cloudiness of the lens of the eye) is five times more common in diabetics and occur at an earlier age that would normally be expected. Once the cataract reduces vision sufficiently to interfere with normal lifestyle, an operation can be done to remove the cataract.
- The risk of glaucoma (a high eye pressure) is twice as likely than in non- diabetics. Early diagnoses and therapy is essential to prevent visual loss.
Forms of Diabetic Retinopathy
This is considered an early stage of diabetic retinopathy and most patients will remain in this category all their lives. The examining doctor sees evidence of damaged blood vessels, small haemorrhages, fatty deposits, fluid and balloon-like outpouchings of the vessel wall.
Though gradual blurring of vision may occur, sight is usually unaffected by background retinopathy and changes in the eye can go unnoticed unless detected by a medical eye examination.
In some cases, however, the leakage affects the macula – the part of the retina responsible for central vision and sight will thus be impaired. Background retinopathy is therefore a warning sign and can progress to a more serious, sight threatening stage.
This develops from background retinopathy. In an attempt to nourish the retina, new blood vessels grow (proliferate) on the surface of the retina and optic nerve. These immature, fragile vessels may rupture and bleed into the vitreous cavity producing sudden loss of vision as the light rays are blocked from reaching the retina.
In addition, scar tissue formed from the ruptured blood vessels can contract and pull on the retina; detaching it. This results in loss of function. New vessels can also grow on the iris and cause a form of glaucoma, which itself can lead to blindness.
When bleeding occurs in the proliferative retinopathy, the patient has hazy vision or complete loss of sight. Though there is no pain, this severe form of diabetic retinopathy requires immediate medical attention.
In the past the value of good control of diabetes was not considered to be important. Many recent studies, however, have shown that good control especially in the early stages can prevent or delay the appearance of retinal disease or slow down the progression of early background retinopathy.
Unfortunately, by the time serious retinopathy is present, good control may not influence the course of the retinal disease. Good diabetic control should be an initial goal in all patients. Blood pressure should be controlled optimally as well.
Probably the most significant treatment is the use of ophthalmologic laser to seal or photocoagulate the leaking blood vessels. This procedure focuses a powerful beam of laser light onto the damaged retina. Small bursts of the laser energy seal leaking vessels and form tiny scars inside the eye. The scars reduce new vessel growth and cause existing ones to shrink and close. If diabetic retinopathy is detected early, photocoagulation by ophthalmologic laser may stop continued eye damage. Even in advanced stage of the disease, it can reduce the chance that a patient will have severe vision loss.
However, photocoagulation cannot be used in all patients. Depending on the location and extent of diabetic retinopathy and if the vitreous is too clouded with blood another treatment may be used. In a surgical procedure called a vitrectomy, the blood-filled vitreous is removed from the eye and replaced with a clear, artificial solution. Most vitrectomy patients notice an improvement in sight.
The ophthalmologist may recommend a vitrectomy soon after the vitreous becomes clouded by blood, or wait to see if the eye clears itself, naturally. The timing for each patient depends on the extent of damage to the eye and to the condition of the other eye. If however, diabetic retinopathy causes the retina to detach, sever sight loss or blindness can result unless surgery is performed immediately to re-attach the retina. Once advanced complications have occurred the prognosis for vision is very poor.
Detection of diabetic retinopathy involves a painless examination of the interior of the eye. For further information your ophthalmologist may want to photograph the retina or perform fluorescein angiography.
The latter involves injection of fluorescein dye into a vein in the arm. Photographs are then taken as the dye is carried through the blood vessels of the eye, showing areas of leakage or poor blood flow.
Successful treatment depends on how early detection and patient co-operation. Diabetics should be aware of the risks of developing visual problems by:
- Having regular yearly eye check up’s
- Taking their medication and following a diet as directed to control their diabetes
- Making sure their high blood pressure is well controlled