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Note: All links within content go to MayoClinic.com

Diabetes affects your body from head to toes. This includes your eyes. The most common and most serious eye complication of diabetes is diabetic retinopathy, which may result in poor vision or even blindness.

"Retinopathy" is the medical term for damage to the tiny blood vessels (capillaries) that nourish the retina, the tissue at the back of your eye that captures light and relays information to your brain. These blood vessels are often affected by the high blood sugar levels associated with diabetes.

Nearly half of people with known diabetes have some degree of diabetic retinopathy. The longer you have diabetes, the more likely it is you'll develop diabetic retinopathy. Initially, most people with diabetic retinopathy experience only mild vision problems. But the condition can worsen and threaten your vision.

The threat of blindness is scary. But with early detection and treatment, the risk of severe vision loss from diabetic retinopathy is small. You can take steps to protect your sight if you have diabetes. These include a yearly eye examination and steps to keep your blood sugar, blood pressure and blood cholesterol under the best possible control.

In the early, most treatable stages of diabetic retinopathy, you usually experience no visual symptoms or pain. The disease can even progress to an advanced stage without any noticeable change in your vision.

Symptoms of diabetic retinopathy may include:

• "Spiders," "cobwebs" or tiny specks floating in your vision
• Dark streaks or a red film that blocks vision
• Vision loss or blurred vision
• A dark or empty spot in the center of your vision
• Poor night vision
• Difficulty adjusting from bright light to dim light

If you have diabetes, your body doesn't use sugar (glucose) properly. Sugar in your blood is vital to your health because it's a main source of energy for your body's cells. But too much sugar in your blood can cause damage throughout your body, including your kidneys, nerves, heart and eyes. Damage to the capillaries in your eyes occurs in diabetic retinopathy.

Diabetic retinopathy occurs in two types, usually affecting both eyes similarly:

• Nonproliferative diabetic retinopathy (NPDR). This type, also called background diabetic retinopathy, is an early stage of the disease. It's the most common type of retinopathy, and symptoms are often mild or nonexistent.

  In NPDR the walls of blood vessels in the retina weaken. Tiny bulges called microaneurysms (mi-kro-AN-u-riz-umz) protrude from the walls of the small vessels in the retina. Another term for these microaneurysms is "outpouchings." The microaneurysms may begin to leak, oozing fluid and blood into the retina. As NPDR progresses, other signs of damage appear. These include swelling or beading of some of the larger retinal veins and patches of swollen nerve fibers, which are called cotton-wool spots because they look like fluffy wisps of cotton.

  Mild NPDR may not affect your ability to see clearly. Vision problems from more severe NPDR are usually the result of swelling (edema) of the central part of the retina (macula) — a condition called diabetic macular edema (DME) — or the closing of capillaries, which reduces blood flow to the macula (macular ischemia). When the macula can't function properly, your central vision decreases.

• Proliferative diabetic retinopathy (PDR). This is the more advanced form of the disease. Retinopathy becomes proliferative when abnormal new blood vessels grow (proliferate) in the retina or the optic disc. The blood vessels also can grow into the vitreous, the clear, jelly-like substance that fills the center of your eyes.

  This abnormal growth generally follows the widespread closing of capillaries in the retina. The condition can cause vision loss affecting both your central and peripheral vision. The new blood vessels may leak blood into the vitreous, which clouds or even blocks your vision. Other complications include detachment of the retina due to scar tissue formation (traction retinal detachment) and a form of glaucoma associated with the growth of abnormal blood vessels on the iris, the colored portion of the eye surrounding the pupil (neovascular glaucoma).

Blurred vision in diabetes
Blurred vision can be brought on by rapid fluctuations in blood sugar. Prolonged periods of elevated blood sugar cause sugar and its breakdown products to accumulate in the lens. This accumulation sucks up water and makes the lens swell, resulting in nearsightedness — meaning distant objects appear blurry. The nearsightedness subsides once your blood sugar is brought under steady control.

Blurred vision can also be caused by macular swelling (edema), regardless of your blood sugar level. This is cause for greater concern because macular edema often develops in people with diabetic retinopathy. The swelling may fluctuate during the day, making your vision get better or worse. If blood vessels in your eye are hemorrhaging, you might notice spots floating in your field of vision. These small spots are often followed within a few days or weeks by larger spots or clouds, which are caused by more marked hemorrhaging.

Having diabetes puts you at risk of retinopathy, whether you have type 1 diabetes or type 2 diabetes. Your risk increases the longer you have the disease.

Other risk factors for diabetic retinopathy include:

• Poorly controlled blood sugar levels
• High blood pressure
• High blood cholesterol
• Pregnancy
• Hispanic or African-American heritage

A common misconception among people with diabetes is, "If I can see well, there's nothing wrong with my eyes." That's false confidence. If you have diabetes, you're at risk of diabetic retinopathy, even if you don't have any vision problems. The early detection of diabetic retinopathy is your best protection against vision loss. For this reason regular eye examinations are essential.

The National Eye Institute recommends that if you have diabetes you should receive a comprehensive dilated eye exam at least once a year. In addition, if you have diabetes and become pregnant, you should have a comprehensive dilated eye exam as soon as possible. Additional exams may be recommended throughout your pregnancy.

See your eye doctor promptly if your vision becomes blurry, spotty or hazy. If diabetic retinopathy is found, the course of treatment depends on the severity of the condition and whether your vision is currently impaired or threatened by the retinal changes.

Your eye doctor will likely diagnose diabetic retinopathy, either nonproliferative or proliferative, if an eye examination reveals any of the following:

• Leaking blood vessels
• Retinal hemorrhage
• Swollen retina
• Fatty deposits (exudates) in the retina
• Areas of nerve fiber damage (cotton-wool spots)
• Changes in blood vessels, such as closures, beading or loops
• Microaneurysms
• Formation of new blood vessels (neovascularization)
• Vitreous hemorrhage
• Scar tissue formation with retinal detachment

As part of an eye examination, your doctor may include a diagnostic procedure called fluorescein angiography to identify leaking blood vessels.

In fluorescein angiography, your doctor injects a dye into a vein in your arm. The dye circulates through your eyes, making the blood vessels in your retina easy to identify. Your doctor can pinpoint areas where normal blood vessels have become closed or have broken down and are leaking fluid. A camera with special filters takes flash pictures every few seconds for several minutes, providing your doctor with useful images.

Your doctor also may request an optical coherence tomography (OCT) examination. This noninvasive imaging scan provides high resolution images of the retina that show, for example, the thickness of the retina and whether fluid has leaked into retinal tissue. OCT exams can be useful both as a diagnostic tool and as a way of monitoring treatment effectiveness.

The abnormal growth of new blood vessels in proliferative diabetic retinopathy doesn't resupply the retina with a normal blood flow. Instead, these abnormal vessels may produce other complications:

• Vitreous hemorrhage. The new blood vessels may bleed (hemorrhage) into the vitreous. If the amount of bleeding is small, you might see only a few dark spots or floaters. In more severe cases, blood can completely fill the vitreous cavity and block all of your vision. Vitreous hemorrhage by itself usually doesn't cause permanent vision loss. The blood often clears from the eye initially — within a few weeks or months — and your vision may return to its previous clarity, unless your retina is damaged.
• Traction retinal detachment. The new blood vessels, if not stopped early in their development, are accompanied by the growth of scar tissue. The scar tissue can shrink and pull the retina away from the back wall of the eye. This causes blank or blurred areas in your field of vision, even complete loss of vision in severe cases.
• Neovascular glaucoma. The proliferation of blood vessels in the retina and vitreous may be accompanied by the growth of abnormal new blood vessels on the iris. This can interfere with the normal flow of fluid out of your eye and cause pressure in your eye to build up. The result is neovascular glaucoma, a serious complication of diabetic retinopathy that can cause damage to your optic nerve and even destroy your eye.

If you have mild nonproliferative diabetic retinopathy, you may not require treatment right away. However, your eye doctor will want to closely monitor your retina. Proliferative diabetic retinopathy requires prompt surgical treatment.

The two main treatments for diabetic retinopathy are photocoagulation and vitrectomy. In many cases, these treatments are effective and slow or stop the progression of the disease for some time. But they're not a cure. Because diabetes continues to affect your body, you may experience further retinal damage and vision loss at a later time.

Photocoagulation
The goal of photocoagulation, also known as laser treatment, is to stop the leakage of blood and fluid in the retina and thus slow the progression of diabetic retinopathy and vision loss. The decision to use the procedure depends on the type of diabetic retinopathy you have, its severity and how well it may respond to treatment.

Your doctor may recommend photocoagulation if you have:

• Diabetic macular edema, a swelling that involves or threatens the center of the retina
• Severe nonproliferative diabetic retinopathy, especially if you have type 2 diabetes
• Proliferative diabetic retinopathy
• Neovascular glaucoma

In photocoagulation, a high-energy laser beam creates small burns in areas of the retina with abnormal blood vessels to help seal any leaks. The procedure takes place in your doctor's office or in an outpatient surgical center. Before surgery your eye doctor dilates your pupil and applies anesthetic drops to numb your eye. In some cases he or she numbs your eye more completely by injecting anesthetic around and behind your eye.

First, your chin and forehead are rested in an examination device called a slit lamp. This is a microscope that uses an intense line of light (slit) to allow your doctor to clearly view portions of your eye. Then, your doctor places a medical contact lens on your cornea — the layer of clear tissue at the front of your eye — to help focus laser light onto the sections of the retina to be treated. Fluorescein angiographic photographs may serve as maps to show where the laser burns should be placed. During the procedure you may see bright flashes from the short bursts of high-energy light.

To treat macular edema, the laser is focused on spots where blood vessels are leaking near the macula. The doctor makes "spot welds" to stop the leakage. If the leaks are small, the laser is applied directly to specific points where the leaks occur (focal laser treatment). If the leakage is widespread or diffuse, laser burns are applied in a grid pattern over a broad area (grid laser treatment).

Shortly after laser treatment, you can usually return home, but you won't be able to drive, so make sure to arrange for a ride. Your vision will be blurry for about a day. Even when laser surgery is successful in sealing the leaks, new areas of leakage may appear later. For this reason you'll have follow-up visits and, if necessary, additional laser treatments.

Immediately following laser surgery to treat macular edema, small spots caused by the laser burns may appear in your visual field. The spots generally fade and disappear with time. If you had blurred vision from macular edema before surgery, you may not recover completely normal vision.

Panretinal photocoagulation
For proliferative diabetic retinopathy, doctors use a form of laser surgery called panretinal or scatter photocoagulation. With this technique the entire retina except the macula is treated with scattered laser burns. The treatment causes the abnormal new blood vessels to shrink and disappear. Thus it reduces the chances of a vitreous hemorrhage and traction retinal detachment. Panretinal photocoagulation is usually done in two or more sessions.

You may notice some loss of peripheral vision afterward. Panretinal photocoagulation is a trade-off. Some of your side vision is sacrificed to save as much of your central vision as possible. You may also notice difficulties with your night vision.

Vitrectomy
A vitreous hemorrhage may clear up on its own. But if the hemorrhage is massive and doesn't clear, a vitrectomy may help to restore your sight and may allow the application of needed laser treatment.

In this procedure your surgeon uses delicate instruments to remove the blood-filled vitreous. A vitreous cutter cuts the tissue and removes it, piece by piece, from your eye. The tissue that is removed is replaced with a balanced salt solution to maintain the normal shape and pressure of the eye. A light probe illuminates the inside of the eye. The surgeon performs the procedure while looking through a microscope suspended over the eye. In this way the vitreous blood is removed to re-establish clear vision.

A vitrectomy is also used to remove scar tissue when it begins to pull the retina away from the wall of the eye. This allows a detached retina to settle back and flatten out. Your eye doctor may decide not to operate on a retina detached by scar tissue if the detachment is located away from the macula and doesn't appear to be progressing.

During a vitrectomy the surgeon may also use a laser probe to perform panretinal photocoagulation. This can help prevent renewed growth of abnormal blood vessels, bleeding and scar tissue formation.

Vitrectomy can be performed under local or general anesthesia. Sometimes it is necessary to inject a bubble of expandable gas into the eye cavity. As the gas bubble expands, it pushes on the retina and helps it reattach. You may be required to remain in a face-down position for several days until the gas bubble spontaneously goes away. Your eye will be red, swollen and sensitive to light for some time after surgery. For a short time afterward, you'll need to wear an eye patch and apply medicated eyedrops to help the healing. Full recovery may take weeks.

You can take steps to slow the progression of diabetic retinopathy:

• Control your blood sugar. Tight control of blood sugar slows the onset and progression of retinopathy and lessens the need for surgery. Tight control means keeping your blood sugar levels as close to normal as possible. Ideally, this means levels between 90 and 130 milligrams per deciliter (mg/dL) before meals and less than 180 mg/dL two hours after starting a meal — with a glycosylated hemoglobin A1C level less than 6 percent. A glycosylated hemoglobin A1C test, also called a glycated hemoglobin test, reflects your average blood sugar level for the two- to three-month period before the test. Your doctor uses it to determine how well you're managing your blood sugar.

  Tight control isn't possible for everyone, including some older adults, young children and people with cardiovascular disease. Talk to your doctor, your endocrinologist or diabetes educator about the best blood sugar control goals and management plan for you. A management plan frequently involves taking insulin or other medications, monitoring blood sugar levels, following a healthy eating plan, getting regular exercise and maintaining a healthy weight. It may take some time before the benefits of lowering your blood sugar are realized. And remember that better control lowers but doesn't eliminate your risk of developing retinopathy.

• Keep an eye on vision changes. In addition to getting an annual eye exam, be alert to any sudden changes in your vision. Have your eyes checked promptly if you experience vision changes that last more than a few days or aren't associated with a change in blood sugar, or if your vision becomes blurry, spotty or hazy.
• Keep your blood pressure down. Tight blood pressure control slows the progression of diabetic retinopathy. To reduce your blood pressure, you may need to make lifestyle changes and take medications.
• Control your cholesterol. Total blood cholesterol levels above 240 mg/dL are associated with a significantly increased risk of vision loss. As with high blood pressure, treatments to improve your blood cholesterol may include lifestyle changes and medications.
• Stop smoking. Smoking is especially bad for people with diabetes because it promotes the closure of blood vessels.
• Control stress. Stress can cause swings in blood sugar levels in people with diabetes. Stress may affect your ability to control your blood sugar. For example, you may be too busy to exercise or eat a good meal. Stress hormones also can directly affect your blood sugar levels, causing them to rise or fall. Don't hesitate to seek help from a counselor, therapist or support group to control your stress. Relaxation techniques such as meditation also may be helpful.