Information about Diabetic Retinopathy
What is diabetic retinopathy?
Diabetic retinopathy is a disorder of major public health importance, and one of the major causes of visual loss which cannot be corrected with glasses. The condition is due to damage to the small blood vessels that nourish the retina, the light-sensitive tissue that lines the back of the eye. There are often no symptoms in the early stages of diabetic retinopathy. Therefore, vision may not be affected until the disease becomes severe. There are four levels of diabetic retinopathy which include:
1. Mild Nonproliferative Diabetic Retinopathy
At this earliest stage, microaneurysms occur. Microaneurysms are small areas of balloon-like swelling in the retina's blood vessels.
2. Moderate Nonproliferative Diabetic Retinopathy
As the disease progresses, some blood vessels that nourish the retina are blocked. Leakage into the retina may appear and may affect vision (diabetic macular edema, see below)
3. Severe Nonproliferative Diabetic Retinopathy
Many more blood vessels are blocked, depriving several areas of the retina of blood supply. These areas of the retina send signals to the body to grow new blood vessels for nourishment.
4. Proliferative Diabetic Retinopathy
At this advanced stage, the signals sent by the retina for nourishment trigger the growth of new blood vessels. 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. The vessels sometimes can bleed into the middle cavity of the eye (vitreous) or be accompanied by scar tissue which can cause the retina to detach from the back wall of the eye. These complications of proliferative diabetic retinopathy, if left untreated, can cause severe vision loss.
The first two levels of this retinopathy (mild and moderate), may be monitored by a health care provider who is skilled at diagnosis and management of the retina and can monitor for progression to more advanced levels (severe nonproliferative or proliferative retinopathy). The follow-up can be influenced by the presence or absence of macular edema (described below). While some cases of severe nonproliferative or proliferative diabetic retinopathy are followed carefully, others may receive injections in the eye. The injections of anti-VEGF medications can result in regression the retinopathy including new vessels. Steroids are also sometimes used. Laser treatment to the peripheral parts of the retina also reduces the chance of developing severe vision loss from blood collecting in the middle cavity of the eye or from scar tissue detaching from the back wall of the eye. This laser treatment may be given in one or several sessions
What is macular edema?
Independent of these levels of diabetic retinopathy, an additional cause of vision loss from diabetes can be macular edema. Macular edema can develop at any level of retinopathy. Macular edema is the term used for swelling in the small central part of the retina used for sharp straight-ahead vision. Sometimes, when diabetes weakens the blood vessels nourishing the retina, some of the blood vessels become leaky. Excess fluid and lipids (fatty materials) leak from the blood vessels into the retina, causing the retina to become thickened or swollen. This swelling of the central part of the retina can lead to decreased vision. When the leakage reaches a certain level injections of anti-VEGF medications, steroids, or focal laser treatments may be used.
Macular edema and the various levels of diabetic retinopathy 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. 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.
How is macular edema treated?
If your eye care professional believes you need treatment for macular edema, he or she may suggest simple pictures of the back of the eye, an optical coherence tomogram (OCT) or a fluorescein angiogram or any combination of the above. An OCT measures the thickness of the center of the retina and can detect abnormal features of the retina not readily apparent by other examinations or images. In fluorescein angiography, a special dye (not iodine) is injected into your arm or hand. Pictures (not x-rays) are taken as the dye passes through the blood vessels in your retina. The test allows your eye care professional to identify leaking blood vessels and may facilitate treatment.
The primary treatment for diabetic macular edema in most cases is injection into the vitreous of the eye of anti-VEGF medications. This is a safe and effective treatment in most patients. Multiple shots separated by one month or more may be required. There are three drugs widely used for this purpose: Avastin, Lucentis, and Eylea. They are all very effective, but in some circumstances one drug is favored over the others. This will be discussed with your retinal specialist. If the anti-VEGF shots are not effective, laser treatment can be added. When treating your eye with laser photocoagulation, your doctor places from a few, up to many small laser burns in the areas of retinal leakage surrounding the macula. Laser treatment has been shown to reduce the chance that more vision will be lost by about half (50%). In addition, about 30% with decreased vision from macular edema will improve in vision by a substantial amount. Another treatment used in some cases is injection of corticosteroids into the eye. This treatment helps the retina in many eyes, but risks the development of cataracts and glaucoma and is usually not used as the first treatment. It is important to identify and treat patients early in the disease before permanent vision loss and the treatments described above, particularly the anti-VEGF medications, can stabilize or improve vision in the vast majority of patients.