Diabetes mellitus is a condition which impairs the body's ability to use and store sugar. Elevated blood sugar levels, excessive thirst with an increase in urine excretion, and changes in the body's blood vessels are all characteristic of the disease. Diabetes may cause serious changes in the eyes as well. Conditions like cataracts, glaucoma, and most importantly, changes in the blood vessels of the retina may all seriously affect sight.

What is diabetic retinopathy?

Diabetic retinopathy is caused by deterioration of the blood vessels nourishing the retina, the light-sensing nerve layer inside the eye. These weakened blood vessels may leak fluid or blood, become enlarged or develop fragile branches.
The risk of diabetic retinopathy increases with time. Nearly 80% of patients with diabetes of 15 years or longer duration, will have some degree of retinopathy. Fortunately, a smaller percentage will develop visually threatening complications. However, diabetics are 25 times more prone to blindness than nondiabetics.
There are 2 forms of diabetic retinopathy. The first is called background retinopathy. In this form, blood vessels develop narrowings and dilatations, impairing blood flow and causing leakage of fluid which accumulate in the retina. This usually does not cause symptoms if the macula, or central part of the retina, is unaffected. In such patients, no specific treatment is required other than regular check-ups. However, if fluid collects near or in the macula, vision can become severely impaired.
The second form is called proliferative retinopathy. This starts off as background retinopathy, but then fragile blood vessel branches grow on the surface of the retina and into the vitreous gel, leading to recurrent bleeding, which obscures clear vision. Additionally, the bleeding leads to scar tissue formation in the vitreous gel, eventually causing contraction and detachment of the retina. Blood vessels may even grow on the iris, causing a severe form of glaucoma. Severe loss of sight and even blindness may result from these conditions.

Detection and diagnosis

Detailed examination of the eyes by an ophthalmologist is required to diagnose diabetic retinopathy. Even if no visual symptoms are present, diabetics should have their eyes examined regularly. Even in other patients, examination of the eyes can often give clues to the existence of possible diabetes.
If signs of diabetic retinopathy are noticed, a special method of examination is used to study the blood vessels. The inside of the eye is photographed while a dye is injected into a vein on the hand or arm. This procedure is called retinal angiography, and it is used to determine the extent of retinopathy, and to plan treatment, if indicated.

Treatment

Many stages of background retinopathy can just be followed up. In some cases where the progression of retinopathy is rapid, where fluid collects in the macula or where fragile new blood vessels grow, laser photocoagulation is required to halt the process. The leaking vessels are sealed, and often retinopathy can be stopped altogether. This procedure is done in the ophthalmologist's office and does not require anaesthesia or surgical incision. Sometimes, repeated application of laser treatment is necessary to achieve stability.
If there is bleeding inside the vitreous gel or if there is a threat of retinal detachment, surgery is required. This operation is called a vitrectomy, and entails removal of the blood-filled vitreous gel, sometimes with cutting of contracting membranes and repair of retinal detachment. Laser treatment is often applied during the operation as well.

Successful treatment of diabetic retinopathy not only depends on early detection and treatment by an ophthalmologist, but also on the patient's attitude and self-care. Strict discipline with diet and medication and optimal sugar control should be attempted. Pregnancy can worsen diabetic retinopathy, and special care should be taken if you are diabetic and wish to fall pregnant. High blood pressure can also worsen retinopathy and should be controlled optimally. Cigarette smoking is probably the worst thing a diabetic could do, as this has a very dramatic impact on the prognosis of retinopathy, with a more rapid disease progression and high risk of blindness.

Visual loss is largely preventable, and even if no symptoms are present, every diabetic should schedule an annual visit with an ophthalmologist. If retinopathy is already diagnosed, more frequent check-ups are required.
It is important to select an ophthalmologist with an interest in retinal conditions, as subtle changes can easily be overlooked, and experience in retinal examination reduces the chances of this happening.