Diabetes is perhaps the most common systemic disease that involves the eye in the long run. It is, however, also true that if diabetes is strictly controlled with regular dieting, exercising and periodic check-ups under the guidance of a physician the eyes can remain healthy. Also, if no other ailment like hypertension or heart diseases, etc, exists, a diabetic can continue to have good eyesight for lifetime. Uncontrolled diabetes, associated with high blood pressure and general disorders, may affect the eye in the long run.

Uncontrolled diabetes of more than eight to ten years duration is said to affect the eye. The commonest manifestation in the eye is retinal haemorrhages, due to leaks of blood vessels. The second common condition is cataract and the third is a marked change in the spectacle power. All the three complications lead to loss of sight.

Diabetes is detected by blood tests for sugar-fasting blood sugar (empty stomach) and post prandial done two hours after meal. Urine examination for sugar is always necessary, glucose tolerance curve is another test done after giving glucose by mouth.

Remedy
Retinal haemorrhages are gradually progressive, if not taken care of in good time. Methods and drugs are available to control the leaks and haemorrhages. The most important breakthrough in recent times has been the use of laser beams to seal a haemorrhage. The machine is expensive (about Rs. 10 lakhs) and is available only in major eye institutions. It needs experts to handle it and to bring out the best results.

It is also noticed that a rise in the sugar level caused by diabetes produces a change in the refractive power in the eye. At times diabetes is detected by the appearance of this warning signal alone. Once the diabetes is controlled, the power of the spectacles can return to normal.
It is obvious that the sugar level of diabetes should be under strict control. The following help to do so:

1. Oral tablets, e.g. glibenclamide chlorpropamide metformin, gliclazide, etc.
2. Injections of Insulin
3. A strict controlled diet, i.e. controlling the total calorie intake. A diabetic's daily calorie intake should comprise 2000 calories.
4. Regular exercise, morning walk and yoga.

Care of Your Eyes
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 urination and changes in the body blood vessels are all characteristic of the disease. Diabetes may cause serious changes in kidney, heart, brain and the eyes as well. The presence of cataracts and glaucoma, occasional blurring and most important, changes in the blood vessels at the back of the eye may affect sight.

What is Diabetic Retinopathy
Diabetic retinopathy is a complication of diabetes that affects the eyes. It is caused by the deterioration of the blood vessels nourishing the retina at the back of the eye. The weakened blood vessels may leak fluid or blood, develop fragile brush like branches and become enlarged in certain places.
The retina is the part of the eye where light filtering 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 images sent to the brain become blurred.

The risk of developing diabetic retinopathy for patients who have had irregular control of diabetes for long time is high. About 60% of the people who have had diabetes for fifteen years or more have some blood vessels damaged in their eyes.

When diabetes develops at an early age, in childhood or teenage years it is known as juvenile diabetes. Juvenile diabetics are particularly likely to develop diabetic retinopathy at an early age. Only a small percentage of those who develop retinopathy however have serious problems with their vision and even smaller percentage become blind. In spite of this, diabetic retinopathy is a leading cause of blindness in adults.

There are two forms of diabetic retinopathy. In one form, background retinopathy, blood vessels within the retina change. Some vessels decrease in size and others enlarge and form balloon like sacs which obstruct the flow of blood through vessels. These vessels leak forming deposits called exudates and causing retina to swell.

Background retinopathy is considered at an early stage of diabetic retinopathy. Fortunately, sight is usually not seriously affected and the condition does not progress in about 80% of diabetic patients. In some cases, however the leaking fluid collects in the macula, the central portion of the retina which is responsible for central vision.

Straight ahead images, reading and close work may then become blurred and loss of central vision can result in legal blindness (i.e. blindness where you cannot perform any useful work for a livelihood). Background retinopathy is a warning sign and can progress to more serious, sight endangering stages.

The second form is proliferative retinopathy. This begins in the same manner as background retinopathy with the addition of new blood vessel growth on the surface of the retina in the optic nerve. These fragile new blood vessels may rupture and bleed into the vitreous the clear gel like substance that rills the centre of the eye. If the leaking blood clouds the normally clear vitreous, light passing from the lens through the vitreous to the retina is blocked and images are distorted. Additionally, scar tissue forming from the mass of the ruptured blood vessels in the vitreous may tighten and pull on the retina, tugging it away and detaching it from the back of the eye. Blood vessels may even grow on the iris and cause a form of glaucoma. Severe loss of sight and even blindness may result from these conditions.

Cause and Symptoms
The cause of diabetic retinopathy is not completely understood, however it is known that diabetes weakens the small blood vessels in various areas of the body. Pregnancy and high blood pressure may worsen this condition in diabetic patients. 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 examination.

Detection and Diagnosis
A comprehensive medical eye examination by an ophthalmologist is the best protection against the progression of diabetic retinopathy. Diabetic patients should be aware of the risks of developing sight disturbances and should have their eyes examined regularly. (Non-diabetic patients should also have their eyes examined periodically because these examinations help to detect the presence of diabetes and other diseases). It is preventable if detected early.

To detect diabetic retinopathy, the ophthalmologist painlessly examines the interior of the eye using an instrument called ophthalmoscope. The interior of the eye may also be photographed to provide further information.

The diabetic retinopathy is noted, a second method of examination may be used by the ophthalmologist to see which blood vessels are bleeding or leaking fluid. First a fluorescent dye is injected into the patient’s arm. The dye travels through the bloodstream and passes into the blood vessels of the retina.
Photographs are taken rapidly of the eye as it leaks through the retina’s blood vessels. This technique called fluorescein angiography, is sometimes used by the ophthalmologist to determine, if further treatment is necessary.

Treatment
Once diabetic retinopathy is diagnosed, the ophthalmologist considers the patient’s age, history, lifestyle and the degree of damage to the retina deciding on the treatment or the continued monitoring of the progress of the disease. In many cases treatment is not needed; in others treatment is recommended to halt the

damage by diabetic retinopathy and sometimes to improve sight. Probably the most significant treatment is the use of ophthalmologic laser surgery to seal or photocoagulate the leaking blood vessels. This procedure focuses a powerful beam of laser light energy on to the damaged retina. Small bursts of the laser intense heat stop the bleeding by sealing leaking vessels and forming tiny scars inside the eye. These scars reduce abnormal blood vessel growth and help bond the retina to the back of eye. This treatment does not require admission in the hospital. It is an outdoor procedure, does not require an incision and may be performed in the ophthalmologist office. If diabetic retinopathy is detected early, photocoagulation by ophthalmologic laser surgery may stop continued damage. Even in advance stage of the disease, it can reduce the chance that a patient will have severe visual loss.

However, photocagulation 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 must be used. In this surgical procedure called vitrectomy, the blood filled vitreous is removed from the eye and replaced with a clear artifical solution. About 70% of vitrectomy patients notice improvement in sight. The ophthalmologists may recommend a vitrectomy soon after the vitreous becomes clouded by blood, or wait up to a year to see if the eye clears itself naturally. The timing for each patient depends on the extent of damage to the eye and the condition of the other eye. If, however diabetic retinopathy causes the retina to detach from the back of the eye severe sight loss or blindness can result unless surgery is performed immediately to reattach the retina. Successful treatment of diabetic retinopthy not only depends on its early detection with monitoring by an ophthalmologist, but also on the patient's attitude and self-care. All medications should be taken and a diet to control diabetes should be followed as directed (Table 1). Although physical activity presents few problems with background retinopathy it can increase bleeding in proliferative retinopathy. Exercise for patients with proliferative retinopathy should be moderate, and straining or leaning over with the head down should be avoided.

Who can Treat Diabetic Retinopathy?
Only an ophthalmologist can treat diabetic retinopathy. Some ophthalmologist specialize in the treatment of retinal diseases such as diabetic retinopathy.
Loss of vision is largely preventable. Early detection of diabetic retinopathy is the best protection against sight loss. Even when symptoms are not noticed, the diabetic patient should schedule an examination by an ophthalmologist at least once a year. Eye examinations should be scheduled more frequently after diabetic retinopathy is diagnosed. In most cases with careful monitoring the ophthalmologist can begin treatment before sight is affected.