Diabetes Complications: Eyes
Long standing diabetes can produce characteristic changes in the retina (the innermost layer of the eye, on which an image is formed). These changes are due to involvement of blood vessels (capillaries) of the retina. The walls of the capillaries of the retina get weakened giving rise to small pouches, which look like small red dots, on an examination of the retina. The capillaries are leaky and blood or its constituents may ooze from the fragile blood vessels or from these pouches; small white patches consisting of fat may appear in the retina. The veins of the retina are dilated.
Capillaries may close in some areas of the retina, resulting in cutting off of oxygen supply. As a compensatory mechanism, new minute blood vessels proliferate from the retina and extend into the jelly like material inside the eyeball, called the vitreous. These fragile blood vessels may bleed making the normally clear vitreous hazy. The haziness of the vitreous obstructs the light passing through the vitreous and impairs vision. A scar tissue may be formed along the fragile blood vessels and may pull the retina and detach it from the underlying layer. This scar tissue distorts the inner architecture of the eyeball. Diabetes is a leading cause of blindness in developed countries.
Swelling of the macula (the most sensitive part of the retina) can occur in diabetes, leading to rapid deterioration of vision.
Whether vision is affected or not depends on the position of retinal changes. Peripheral retinal changes do not impair vision. But a swelling or bleeding into a strategic part like macula reduces the vision markedly. Vision can improve when the blood is absorbed and the swelling of the macula respolves.
Young persons, with uncontrolled diabetes may develop temporary opacity of lens which can clear up when diabetes is controlled. The common cataract, of 'old age', occurs earlier in diabetics than in the general population. This cataract progresses faster in diabetics than in nondiabetics.
Diabetes may affect the nerves which supply the muscles that help the eyeball to turn. Weakness of these muscles gives rise to squint and double vision. This eye complication of diabetes fortunately always clears up with the passage of time.
The patient is often unable to read, when a previously elevated blood glucose level is brought to normal, due to change in the shape of lens. The refraction (for the glasses) should be tested about six weeks after the blood glucose level is stabilised.
In type 1 diabetes eyes should be tested, initially, within three to five years of diagnosis, once the person is ten years or older and subsequently every year. In type 2 diabetes, eyes should be tested at the time of diagnosis and later at least once every year. The eyes should be tested by an ophthalmologist (eye specialist) and not by an optician. Photographing the retina after injecting fluorescin dye is a valuable investigation.
The blood glucose level should be maintained between 80-100 mg/dl (fasting) and 100-140 mg/dl (post meal). High blood pressure should be controlled and blood lipids maintained within normal range. Tobacco should not be consumed in any form.
In laser treatment, a laser beam is thrown either on selected areas of or scattered over retina, to seal fine blood vessels and to prevent leakage from them.
Diabetics with a retinal disease should refrain from jumping, straining and doing a shirsasana. Those who have undergone laser treatment should not lift weight over 2 1/4 kg.
Vitreoretinal surgery is useful in clearing blood from vitreous, removing scar tissue and reattaching the retina.
Cataract surgery can be carried out successfully in diabetics as in non-diabetics. Diabetes, of course, has to be controlled properly before and after the operation. Lens implantation can be carried out in diabetics. The steroids that may be given after cataract surgery to reduce inflammation of the eye, increase blood glucose level, necessitating an increase in dosage of medication.
A diabetic with double vision may have to wear a patch before one eye to mask one image.
Loss of vision is a shattering experience for the patient who then needs lot of support. Aids like special insulin syringes, tablet dispenser, a trained dog have proved to be a great boon to blind diabetics.