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Diabetic Retinopathy

If you have diabetes mellitus, your body does not use and store glucose properly.

Over time, diabetes can damage blood vessels in the retina, the nerve layer at the back of the eye that senses light and helps to send images to the brain.

The damage to retinal vessels is referred to as diabetic retinopathy.

Nonproliferative Diabetic Retinopathy (NPDR)

Nonproliferative diabetic retinopathy (NPDR), commonly known as ‘background retinopathy’, is an early stage of diabetic retinopathy.

In this stage, tiny blood vessels within the retina leak blood or fluid.  The leaking fluid causes the retina to swell or to form deposits called exudates.

Many people with diabetes have mild NPDR, which usually does not affect their vision.

When vision is affected, it is the result of macular edema or macular ischemia, or both.

Macular Edema & Ischemia

Macular edema is swelling or thickening of the macula, a small area in the centre of the retina that allows us to see fine details clearly.

The swelling is caused by fluid leaking from retinal blood vessels. It is the most common cause of visual loss in diabetes.

Vision loss may be mild to severe, but even in the worst cases, peripheral (side) vision continues to function.

Laser treatment can be used to help control vision loss from macular edema. Newer treatments are being investigated.

Macular ischemia occurs when small blood vessels (capillaries) close. Vision blurs because the macula no longer receives sufficient blood supply to work properly.

Unfortunately, there are no effective treatments for macular ischemia.

Proliferative Diabetic Retinopathy

Proliferative diabetic retinopathy (PDR) is a complication of diabetes caused by changes in the blood vessels of the eye.

If you have diabetes, your body does not use and store sugar properly.  High blood sugar levels create changes in the veins, arteries, and capillaries that carry blood throughout the body.  This includes the tiny blood vessels in the retina, the light-sensitive nerve layer in the back of the eye.

In PDR, the retinal blood vessels are so damaged they close off. In response, the retina grows new, fragile blood vessels.

Unfortunately, these new blood vessels are abnormal and grow on the surface of the retina, so they do not resupply the retina with blood.

Occasionally, these new blood vessels bleed and cause a vitreous hemorrhage.  Blood in the vitreous, the clear gel-like substance that fills the inside of the eye, blocks light rays from reaching the retina.

A small amount of blood will cause dark floaters, while a large hemorrhage might block all vision, leaving only light and dark perception.

The new blood vessels can also cause scar tissue to grow.  The scar tissue shrinks, wrinkling and pulling on the retina and distorting vision.  If the pulling is severe, the macula may detach from its normal position and cause vision loss.

Laser surgery may be used to shrink the abnormal blood vessels and reduce the risk of bleeding.  The body will usually absorb blood from a vitreous hemorrhage, but that can take days, months, or even years.

If the vitreous hemorrhage does not clear within a reasonable time, or if a retinal detachment is detected, an operation called a vitrectomy can be performed.

During a vitrectomy, the eye surgeon removes the hemorrhage and any scar tissue that has developed, and performs laser treatment to prevent new abnormal vessel growth.

People with PDR sometimes have no symptoms until it is too late to treat them. The retina may be badly injured before there is any change in vision.

There is considerable evidence to suggest that rigorous control of blood sugar decreases the chance of developing serious proliferative diabetic retinopathy.

A medical eye examination is the only way to discover any changes inside your eye.

If your ophthalmologist finds diabetic retinopathy, you may require a special test called fluorescein angiography or optical coherence tomography (OCT) to find out if you need treatment.

If you have diabetes, early detection of diabetic retinopathy is the best protection against loss of vision.

You can significantly lower your risk of vision loss by maintaining strict control of your blood glucose and visiting your ophthalmologist regularly.

People with diabetes should schedule examinations at least once a year.

Pregnant women with diabetes should schedule an appointment in their first trimester, because retinopathy can progress quickly during pregnancy.

More frequent medical eye examinations may be necessary after a diagnosis of diabetic retinopathy.

Diabetic Retinopathy Treatments — Focal Laser

Macular edema is treated with laser surgery.  This procedure is called focal laser treatment.

Your ophthalmologist places up to several hundred small laser burns in the areas of retinal leakage surrounding the macula. These burns slow the leakage of fluid and reduce the amount of fluid in the retina.

The surgery is usually completed in one session, although further treatment may be needed.

A patient may need focal laser surgery more than once to control the leaking fluid.  Focal laser treatment stabilizes vision.  In fact, focal laser treatment reduces the risk of vision loss by 50 percent.

In a small number of cases, if vision is lost, it can be improved.  Let your eye surgeon (ophthalmologist) know if you have vision loss.

Before the laser surgery, the technician will dilate your pupil and apply drops to numb the eye.  The area behind your eye also may be numbed to prevent discomfort.

The lights in the laser room will be dim.  As you sit facing the laser machine, your eye surgeon will hold a special lens to your eye.

During the procedure, you may see flashes of light.  These flashes eventually may create a stinging sensation that can be uncomfortable.

You will need someone to drive you home after surgery. Because your pupil will remain dilated for a few hours, you should bring a pair of sunglasses.
For the rest of the day, your vision will probably be a little blurry. Your ophthalmologist will make arrangement to check the effects of the laser, usually within about six weeks of treatment.

Diabetic Retinopathy Treatments — Pan-Retinal Photocoagulation

During the first three stages of diabetic retinopathy, no treatment is needed, unless you have macular edema.

To prevent progression of diabetic retinopathy, people with diabetes should control their levels of blood sugar, blood pressure, and blood cholesterol.

Proliferative retinopathy is treated with laser surgery.  This procedure is called pan-retinal photocoagulation or PRP, which helps to shrink the abnormal blood vessels.

Your doctor places 1,000 to 2,000 laser burns in the areas of the retina away from the macula, causing the abnormal blood vessels to shrink.

Because a high number of laser burns are necessary, two or more sessions usually are required to complete treatment.

Although you may notice some loss of your side vision, PRP can save the rest of your sight.

PRP may slightly reduce your colour vision and night vision.

PRP works better before the fragile, new blood vessels have started to bleed.  That is why it is important to have regular, comprehensive dilated eye exams.

Even if bleeding has started, PRP may still be possible, depending on the amount of bleeding.

If the bleeding in your eye is severe, you may need a surgical procedure called a vitrectomy.  During a vitrectomy, blood is removed from the center of your eye by a retinal specialist.

Diabetic Retinopathy Treatments — Anti-VEGF Drugs

Certain anti-vascular endothelial growth factor (anti-VEGF) treatments are approved for a condition known as “wet” age-related macular degeneration (AMD), in which abnormal blood vessels grow underneath the retina.

These unhealthy vessels leak blood and fluid that can swell and scar the macula (the central part of the retina), and vision loss may be rapid and severe.

Since anti-VEGF therapies have shown good potential for slowing vascular leakage and preventing vision loss associated with wet AMD, ophthalmologists are using them to treat other causes of macular edema.

If your ophthalmologist has diagnosed you with diabetic retinopathy, retinal venous occlusion, or other conditions, you may benefit from anti-VEGF treatment if other therapies are not producing the desired results or if your ophthalmologist thinks that anti-VEGF therapy is the best first course of action.

Treatment with the anti-VEGF drug is usually performed by injecting the medicine with a very fine needle into the back portion of your eye.

Your ophthalmologist will clean your eye to prevent infection and will administer an anesthetic into your eye to reduce pain.

Usually, patients receive multiple anti-VEGF injections over the course of many months.

There is a small risk of complications with anti-VEGF treatment, usually resulting from the injection itself. However, for most people, the benefits of this treatment outweigh the small risk of complications.

Information about eye conditions, disorders and treatments is presented courtesy of the Eye Physicians & Surgeons of Ontario.

Information about eye conditions, disorders and treatments is presented courtesy of the Eye Physicians & Surgeons of Ontario.