Diabetic retinopathy is the most common diabetic eye disease (followed by cataract and glaucoma) which affects up to 80% of all diabetics who have had diabetes for 15 years or more, and a leading cause of blindness in American adults. It is caused by changes in the blood vessels of the retina (the thin light-sensitive membrane that covers the back of the eye). If diagnosed and treated promptly, blindness is usually preventable.

Signs and Symptoms of Diabetes Retinopathy

Diabetic retinopathy begins without any noticeable change in vision and without pain. Even macular edema, which may cause vision loss more rapidly, may not have any warning signs for some time. In general, however, a person with macular edema is likely to have blurred vision, making it hard to do things like read and drive. In some cases, the vision will get better or worse during the day.

To sum up, symptoms are:

Blurred vision
Spot, floaters and flashes
Sudden loss of vision

How does diabetic retinopathy cause vision loss?

Diabetic retinopathy is result of microvascular retinal changes. Hyperglycemia-induced pericyte death and thickening of the basement membrane lead to incompetence of the vascular walls. These damage change the formation of blood retinal barrier and also make retinal blood vessel become more permiable.

Small blood vessels – such as those in the eye – are especially vulnerable to poor blood glucose control. An overaccumulation of glucose and/or fructose damages the tiny blood vessels in the retina. During the initial stage, called nonproliferative diabetic retinopathy (NPDR), most people do not notice any changes in their vision.

Some people develop a condition called macular edema. It occurs when the damaged blood vessels leak fluid and lipids onto the macula, the part of the retina that lets us see detail. The fluid makes the macula swell, which blurs vision.

As the disease progresses, severe nonproliferative diabetic retinopathy enters an advanced, or proliferative, stage. The lack of oxygen in the retina causes fragile, new, blood vessels to grow along the retina and in the clear, gel-like vitreous that fills the inside of the eye. Without timely treatment, these new blood vessels can bleed, cloud vision, and destroy the retina. Fibrovascular proliferation can also cause tractional retinal detachment. The new blood vessels can also grow into the angle of the anterior chamber of the eye and cause Neovascular Glaucoma. Nonproliferative diabetic retinopathy shows up as cotton wool spots, or microvascular abnormalities or as superficial retinal hemorrhages. Even so, the advanced proliferative diabetic retinopathy (PDR) can remain asymptomatic for a very long time, and so should be monitored closely with regular checkups.

Stages of diabetic retinopathy

1) Mild Nonproliferative Retinopathy

At this earliest stage, microaneurysms occur. They are small areas of balloon-like swelling in the retina’s tiny blood vessels.

2) Moderate Nonproliferative Retinopathy

As the disease progresses, some blood vessels that nourish the retina are blocked.

3) Severe Nonproliferative Retinopathy

Many more blood vessels are blocked, depriving several areas of the retina with their blood supply. These areas of the retina send signals to the body to grow new blood vessels for nourishment.

4) Proliferative Retinopathy

At this advanced stage, 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, vitreous 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.

Detection and Diagnosis of Diabetes Retinopathy

Diabetic retinopathy and macular edema are detected during a comprehensive eye exam that includes:

1. Visual acuity test. This eye chart test measures how well you see at various distances.
2. Dilated eye exam. Drops are placed in your eyes to widen, or dilate, the pupils. This allows the eye care professional to see more of the inside of your eyes to check for signs of the disease. Your eye care professional uses a special magnifying lens to examine your retina and optic nerve for signs of damage and other eye problems. After the exam, your close-up vision may remain blurred for several hours.
3. Tonometry. An instrument measures the pressure inside the eye. Numbing drops may be applied to your eye for this test.

Your eye care professional checks your retina for early signs of the disease, including:

* Leaking blood vessels.
* Retinal swelling (macular edema).
* Pale, fatty deposits on the retina–signs of leaking blood vessels.
* Damaged nerve tissue.
* Any changes to the blood vessels.

If your eye care professional believes you need treatment for macular edema, he or she may suggest a fluorescein angiogram. In this test, a special dye is injected into your arm. Pictures are taken as the dye passes through the blood vessels in your retina. The test allows your eye care professional to identify any leaking blood vessels and recommend treatment.

Treatment of Diabetes Retinopathy

There are three major treatments for diabetic retinopathy, which are very effective in reducing vision loss from this disease. In fact, even people with advanced retinopathy have a 90 percent chance of keeping their vision when they get treatment before the retina is severely damaged. Still, the best way of addressing diabetic retinopathy is to monitor it vigilantly and ensure that it does not happen in the first place by careful blood glucose control and limitation of dietary fructose.

These three treatments are laser surgery, injection of triamcinolone into the eye and vitrectomy. It is important to note that although these treatments are very successful, they do not cure diabetic retinopathy. Caution should be exercised in treatment with laser surgery since it causes a loss of retinal tissue. It is often more prudent to inject triamcinolone. In some patients it results in a marked increase of vision, especially if there is an edema of the macula.

Avoiding tobacco use and correction of associated hypertension are important therapeutic measures in the management of diabetic retinopathy.

Laser surgery

A type of laser surgery called panretinal photocoagulation, or PRP, is used to treat severe macular edema and proliferative retinopathy. The goal is to create 1 000 - 2 000 burns in the retina with the hope of reducing the retina’s oxygen demand, and hence the possibility of ischemia. In treating advanced diabetic retinopathy, the burns are used to destroy the abnormal blood vessels that form at the back of the eye.

Before the surgery, the ophthalmologist dilates the pupil and applies anesthetic drops to numb the eye. In some cases, the doctor also may numb the area behind the eye to prevent any discomfort. The lights in the office are also dimmed to aid in dilating the pupil. The patient sits facing the laser machine while the doctor holds a special lens to the eye. During the procedure, the patient may see flashes of light. These flashes may eventually
create an uncomfortable stinging sensation for the patient. After the laser treatment, patients should be advised not to drive for a few hours while the pupils are still dilated. Vision may remain a little blurry for the rest of the day, though there should not be much pain in the eye.

Scatter laser treatment

Rather than focus the light on a single spot, the eye care professional may make hundreds of small laser burns away from the center of the retina, a procedure called scatter laser treatment or panretinal photocoagulation. The treatment shrinks the abnormal blood vessels. Patients may lose some of their peripheral vision after this surgery, but the procedure saves the rest of the patient’s sight. Laser surgery may also slightly reduce colour and night vision.

A person with proliferative retinopathy will always be at risk for new bleeding as well as glaucoma, a complication from the new blood vessels. This means that multiple treatments may be required to protect vision.

Vitrectomy

Instead of laser surgery, some people need an eye operation called a vitrectomy to restore vision. A vitrectomy is performed when there is a lot of blood in the vitreous. It involves removing the cloudy vitreous and replacing it with a saline solution made up of salt and water. Because the vitreous is mostly water, there should be no change between the saline solution and the normal vitreous.

Studies show that people who have a vitrectomy soon after a large hemorrhage are more likely to protect their vision than someone who waits to have the operation. Early vitrectomy is especially effective in people with insulin-dependent diabetes, who may be at greater risk of blindness from a hemorrhage into the eye.

Vitrectomy is often done under local anesthesia. The doctor makes a tiny incision in the sclera, or white of the eye. Next, a small instrument is placed into the eye to remove the vitreous and insert the saline solution into the eye.

Patients may be able to return home soon after the vitrectomy, or may be asked to stay in the hospital overnight. After the operation, the eye will be red and sensitive, and patients usually need to wear an eyepatch for a few days or weeks to protect the eye. Medicated eye drops are also prescribed to protect against infection.

Preventionof Diabetes Retinopathy

Researchers have found that diabetic patients who are able to maintain appropriate blood sugar levels have fewer eye problems than those with poor control. Diet and exercise play important roles in the overall health of those with diabetes.

Diabetics can also greatly reduce the possibilities of eye complications by scheduling routine examinations with an ophthalmologist. Many problems can be treated with much greater success when caught early.

Sources: St. Lukes Eye, Wikipedia, National Eye Institute

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