Diabetic retinopathy is the most common diabetic eye disease and can be a leading cause of blindness in adults.
If you have been diagnosed with diabetes mellitus, your body may not use and store sugar properly. High blood sugar levels may cause damage to the blood vessels in the retina. The retina is 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.
What are the stages of diabetic retinopathy?
Diabetic retinopathy has four stages:
Mild Nonproliferative Retinopathy.At this earliest stage, microaneurysms occur. They are small areas of balloon-like swelling in the retina's tiny blood vessels.
Moderate Nonproliferative Retinopathy.As the disease progresses, some blood vessels that nourish the retina are blocked.
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.
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.
Many people with diabetes have mild NPDR, which may not affect their vision. Vision is affected as the result of macular edema (pronounced eh-DEEM-uh) and/or macular ischemia (pronounced ih-SKEE-mee-uh).
Macular edema is swelling or thickening of the macula, a small area in the center 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 vision continues to function.
Macular ischemia occurs when small blood vessels (capillaries) close and no longer provide enough blood supply for the macula to work properly.
PDR is present when abnormal new vessels (neovascularization) begin growing on the surface of the retina or optic nerve. The main cause of PDR is widespread closure of retinal blood vessels, preventing adequate blood flow. The retina responds by growing new blood vessels in an attempt to supply blood to the area where the original vessels closed.
Unfortunately, the new abnormal blood vessels do not work properly or supply the retina with normal blood flow. The new vessels are often accompanied by scar tissue that may cause wrinkling or detachment of the retina. PDR may cause more severe vision loss than NPDR because it can affect both central and peripheral vision. Proliferative diabetic retinopathy causes visual loss in the following ways:
Vitreous hemorrhage:The fragile new vessels may bleed into the vitreous
(clear, gel-like substance that fills the center of the eye). If the vitreous hemorrhage is small, a person might see only a few new, dark floaters. A very large hemorrhage might block out all vision.
It may take days, months, or even years to reabsorb the blood, depending on the amount of blood present. If the eye does not clear the vitreous blood adequately within a reasonable time, vitrectomy surgery may be recommended.
Vitreous hemorrhage alone does not cause permanent vision loss. When the blood clears vision may return to its former level unless the macula is damaged.
Tractional retinal detachment: When PDR is present, scar tissue associated with neovascularization can shrink, wrinkling and pulling the retina from its normal position. Macular wrinkling can cause visual distortion. More severe vision loss can occur if the macula or large areas of the retina are detached.
How are diabetic retinopathy and macular edema detected?
Diabetic retinopathy and macular edema are detected during a comprehensive eye exam that includes:
Visual acuity test.This eye chart test measures how well you see at various distances.
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.
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.
Always, the best treatment is prevention; however strict control of your blood sugar can significantly reduce the long-term risk of vision loss from diabetic retinopathy.
- Medical Treatment:In some cases, your ophthalmologist may choose to treat your macular edema with injections in your eye. These shots of medicine—called intravitreal injections—may be steroids or other medications designed to shrink the swelling of the macula or to help reduce neovascularization or the growing of the abnormal vessels.
- Laser surgery:Laser surgery is often recommended for people with macular edema, PDR.
- The main goal of treatment is to prevent further loss of vision. It is uncommon for people who have blurred vision from macular edema to recover completely normal vision, although some may experience partial improvement. A few people may see the laser spots near the center of their vision following treatment. The spots usually fade with time but may not disappear.
- For PDR, the laser is focused on all parts of the retina except the macula. This panretinal photocoagulation treatment causes abnormal new vessels to shrink and helps to prevent them from growing in the future. It also helps to decreases the chance of vitreous bleeding or retinal distortion will occur. Multiple laser treatments over time are some times necessary. Laser surgery does not cure diabetic retinopathy and does not always prevent further loss of vision.
- Vitrectomy:In advanced PDR, your ophthalmologist may recommend a vitrectomy. During this microsurgical procedure, which is performed in the operating room, the blood filled vitreous is removed and replaced with a clear solution. Your ophthalmologist may wait for several months to see if the blood clears on its own before performing a vitrectomy. Vitrectomy often prevents further bleeding by removing the abnormal vessels that caused the bleeding. If the retina is detached, it can be repaired during the vitrectomy surgery. Surgery should usually be done early because macular distortion or traction retinal detachment will cause permanent visual loss. The longer the macula is distorted or out of place, the more serious the vision loss will be. Vision loss is largely preventable.
If you have diabetes, it is important to know that today, with improved methods of diagnosis and treatment, a smaller percentage of people who develop retinopathy have serious vision problems. 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 sugar and visiting your ophthalmologist regularly.
When should I schedule an examination?
People with diabetes should schedule examinations at least once a year. More frequent medical eye examinations may be necessary after a diagnosis of diabetic retinopathy. Pregnant women with diabetes should schedule an appointment in the first trimester, because retinopathy can progress quickly during pregnancy. If you need to be examined for eyeglasses it is important that your blood sugar be consistently under control for several days when you see your ophthalmologist. Eyeglasses that work well when blood sugar is out of control will not work well when blood sugar is stable. Rapid changes in blood sugar can cause fluctuating vision in both eyes even if retinopathy is not present.
You should have your eyes checked promptly if you have visual changes that: affect either one or both eyes; last more than a few days; are not associated with a change in blood sugar. When you are first diagnosed with diabetes, you should have your eyes checked: within five years of the diagnosis if you 29 years old or younger; within a few months of the diagnosis if are 30 years old and older.