Diabetic related eye disease is a group of eye conditions that can affect people with diabetes.
- Diabetic retinopathy affects blood vessels in the retina, the light-sensitive tissue that lines the back of the eye. It is the leading cause of vision impairment and blindness among working-age adults and the most common cause of vision loss among diabetics.
- Diabetes-related macular edema (DME). DME is a complication of diabetic retinopathy that causes swelling in the macula of the retina.
Cataract and glaucoma are also examples of diabetic eye disease:
- Cataract is a clouding of the eye’s lens. Adults with diabetes are 2-5 times more likely than those without diabetes to develop cataract. Cataract also tends to develop at an earlier age in people with diabetes.
- Glaucoma is a group of diseases that affect the optic nerve of the eye, which is a bundle of nerve fibers that connects the eye to the brain. Some types of glaucoma are associated with increased intraocular pressure. Diabetes nearly doubles the risk of glaucoma in adults.
Diabetic eye disease, in its various forms, has the potential to cause severe vision loss and blindness.
Diabetes causes chronically high blood sugar levels, which causes damage to the tiny blood vessels in the retina, resulting in diabetic retinopathy. The retina detects light and converts it into signals that are sent to the brain via the optic nerve. Diabetic retinopathy can cause blood vessels in the retina to leak fluid or bleed, causing vision to blur. In its most advanced stage, new abnormal blood vessels proliferate (grow in number) on the surface of the retina, causing scarring and cell loss.
Diabetic retinopathy may progress through four stages:
- Mild nonproliferative retinopathy. At this early stage of the disease, small areas of balloon-like swelling in the retina’s tiny blood vessels, known as microaneurysms, occur. These microaneurysms may cause fluid to leak into the retina.
- Moderate nonproliferative retinopathy. Blood vessels that nourish the retina may swell and distort as the disease progresses. They may also be unable to transport blood. Both conditions cause distinct changes in the appearance of the retina and may play a role in DME.
- Severe nonproliferative retinopathy. Many more blood vessels are blocked, depriving areas of the retina of blood supply. These areas secrete growth factors, which instruct the retina to form new blood vessels.
- Proliferative diabetic retinopathy (PDR). At this stage, growth factors secreted by the retina stimulate the formation of new blood vessels that grow along the inside surface of the retina and into the vitreous gel, the fluid that fills the eye. Because the new blood vessels are fragile, they are more likely to leak and bleed. Scar tissue can contract and cause retinal detachment, which is the pulling away of the retina from the underlying tissue, similar to how wallpaper peels away from a wall. Permanent vision loss can result from retinal detachment.
Diabetic Macular Edema (DME)
DME is the accumulation of fluid (edema) in the macula, a region of the retina. The macula is essential for reading, recognizing faces, and driving because it provides sharp, straight-ahead vision. DME is the most common cause of vision loss in diabetic retinopathy patients. It affects roughly half of all diabetic retinopathy patients. DME can occur at any stage of the disease, though it is more likely as diabetic retinopathy worsens.
Diabetics of all types (type 1, type 2, and gestational) are at risk for diabetic retinopathy. The longer a person has diabetes, the greater the risk. Between 40 and 45 percent of diabetics in the United States have diabetic retinopathy, though only about half are aware of it. Women who develop or have diabetes during pregnancy are more likely to experience the onset or worsening of diabetic retinopathy.
In the early stages of diabetic retinopathy, there are usually no symptoms. The disease frequently progresses unnoticed until it impairs vision. Bleeding from abnormal retinal blood vessels can cause “floating” spots to appear. These blemishes can sometimes disappear on their own. However, if bleeding is not treated promptly, it frequently recurs, increasing the risk of permanent vision loss. When DME occurs, it can result in blurred vision.
Diabetic retinopathy and DME are detected during a comprehensive dilated eye exam, which includes the following components:
- Visual acuity testing. This eye chart test measures a person’s ability to see at various distances.
- Tonometry. This test measures pressure inside the eye.
- Pupil dilation. Drops placed on the eye’s surface dilate (widen) the pupil, allowing physician to examine the retina and optic nerve.
Optical coherence tomography is a type of imaging technique (OCT). This technique is similar to ultrasound, but instead of sound waves, it uses light waves to capture images of tissues inside the body. OCT images tissues that can be penetrated by light, such as the eye, in great detail.
A comprehensive dilated eye exam allows the doctor to check the retina for:
- Changes to blood vessels
- Leaking blood vessels or warning signs of leaky blood vessels, such as fatty deposits
- Swelling of the macula (DME)
- Changes in the lens
- Damage to nerve tissue
A fluorescein angiogram may be used to look for damaged or leaky blood vessels if DME or severe diabetic retinopathy is suspected. A fluorescent dye is injected into the bloodstream, usually through an arm vein, for this test. As the dye enters the eye, photographs of the retinal blood vessels are taken.
Diabetic retinopathy can cause irreversible vision loss. Early detection and treatment, on the other hand, can reduce the risk of blindness by 95%. People with diabetes should have a comprehensive dilated eye exam at least once a year because diabetic retinopathy often has no early symptoms. Diabetic retinopathy patients may require more frequent eye exams. Diabetes patients who become pregnant should have a thorough dilated eye exam as soon as possible. Additional prenatal exams may be required.
Controlling diabetes, according to studies like the Diabetes Control and Complications Trial (DCCT), slows the onset and worsening of diabetic retinopathy. Participants in the DCCT study who kept their blood glucose levels as close to normal as possible were significantly less likely to develop diabetic retinopathy, as well as kidney and nerve diseases, than those who did not. Other studies have shown that controlling high blood pressure and cholesterol levels can reduce the risk of vision loss in diabetics.
Diabetic retinopathy treatment is frequently postponed until it progresses to PDR or DME occurs. Comprehensive dilated eye exams are becoming more necessary as diabetic retinopathy worsens. People who have severe nonproliferative diabetic retinopathy are at a high risk of developing PDR and may require a comprehensive dilated eye exam every 2 to 4 months.
DME can be treated with several therapies that may be used alone or in combination.
ANTI-VEGF INJECTION THERAPY
Anti-VEGF drugs are injected into the vitreous gel to inhibit the activity of a protein known as vascular endothelial growth factor (VEGF), which can cause abnormal blood vessels to grow and leak fluid. By inhibiting VEGF, abnormal blood vessel growth can be reversed, and fluid in the retina can be reduced. Avastin (bevacizumab), Lucentis (ranibizumab), and Eylea are examples of anti-VEGF medications (aflibercept). The U.S. Food and Drug Administration (FDA) has approved Lucentis and Eylea for the treatment of DME. Avastin is FDA-approved to treat cancer, but it is also commonly used to treat eye conditions such as DME.
In a clinical trial, the NEI-sponsored Diabetic Retinopathy Clinical Research Network compared Avastin, Lucentis, and Eylea. According to the study, all three drugs are safe and effective for treating the majority of people with DME. Patients who started the trial with 20/40 vision or better saw similar improvements in vision regardless of which of the three drugs they were given. Patients who started the trial with 20/50 vision or worse saw greater improvements with Eylea.
For the first six months of treatment, most people require monthly anti-VEGF injections. Following that, injections are required less frequently: three to four times during the second six months of treatment, four times during the second year of treatment, two times during the third year, one time during the fourth year, and none during the fifth year. As the disease progresses, dilated eye exams may become less necessary.
Avastin, Lucentis, and Eylea differ in price and frequency of injection, so patients should speak with an eye care professional about these concerns.
FOCAL/GRID MACULAR LASER SURGERY
A few to hundreds of small laser burns are made to leaking blood vessels in areas of edema near the center of the macula during focal/grid macular laser surgery. Laser burns for DME reduce swelling in the retina by slowing fluid leakage. The procedure is typically completed in a single session, but some patients may require more than one treatment. Focal/grid laser is used before anti-VEGF injections, on the same day or a few days after an anti-VEGF injection, and only when DME does not improve adequately after six months of anti-VEGF therapy.
Corticosteroids, either injected or implanted into the eye, can be used to treat DME alone or in combination with other drugs or laser surgery. The Ozurdex (dexamethasone) implant is intended for short-term use, whereas the Iluvien (fluocinolone acetonide) implant is intended for long-term use. Both are biodegradable and produce a steady stream of corticosteroids to suppress DME. The use of corticosteroids in the eye raises the risk of cataract and glaucoma. Corticosteroid-using DME patients should be monitored for increased intraocular pressure and glaucoma.
PROLIFERATIVE DIABETIC RETINOPATHY (PDR) TREATMENT
For decades, PDR has been treated with scatter laser surgery, sometimes called panretinal laser surgery or panretinal photocoagulation.
Treatment consists of 1,000 to 2,000 tiny laser burns in areas of the retina other than the macula. The purpose of these laser burns is to cause abnormal blood vessels to shrink. Although treatment can be completed in a single session, two or more sessions may be required at times. While scatter laser surgery can preserve central vision, it can also cause some loss of side (peripheral), color, and night vision. Scatter laser surgery is most effective before new, fragile blood vessels begin to bleed.
Recent research has shown that anti-VEGF treatment is not only effective for treating DME, but also for slowing the progression of diabetic retinopathy, including PDR, so anti-VEGF is increasingly being used as a first-line treatment for PDR.
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