Definition
Diabetic retinopathy is a damage to the blood vessels in the retina caused by complications of diabetes, which can eventually lead to blindness. It is an ocular manifestation of systemic disease which affects up to 80% of all patients who have had diabetes for 10 years or more.
Symptoms
Most often, diabetic retinopathy has no symptoms until the damage to your eyes is severe. Even macular edema , which may cause vision loss more rapidly, may not have any warning signs for some time. In general, however, a person with macular edema is likely to have blurred vision, making it hard to do things like read or drive. In some cases, the vision will get better or worse during the day.
Symptoms of diabetic retinopathy include:
• Blurred vision and slow vision loss over time
• Shadows or missing areas of vision
• Trouble seeing at night
Blurred vision may occur when the macula (the part of the retina that provides sharp central vision) swells from leaking fluid. If new blood vessels grow on the surface of the retina, they can bleed into the eye and block vision. At first, you will see a few specks of blood, or spots, "floating" in your vision. You may need treatment before more serious bleeding occurs. Hemorrhages tend to happen more than once, often during sleep. Sometimes, without treatment, the spots clear, and you will see better. However, bleeding can reoccur and cause severely blurred vision. If left untreated, proliferative retinopathy can cause severe vision loss and even blindness.
Pathogenesis
Diabetic retinopathy is the result of microvascular retinal changes.
Hyperglycemia-induced intramural pericyte death and thickening of the basement membrane lead to incompetence of the vascular walls. These damages change the formation of the blood-retinal barrier and also make the retinal blood vessels become more permeable.
Small blood vessels, such as those in the eye, are especially vulnerable to poor blood sugar (blood glucose) control. An overaccumulation of glucose and/or fructose damages the tiny blood vessels in the retina.
During the initial stage, called non-proliferative diabetic retinopathy, most people do not notice any change in their vision. Non-proliferative diabetic retinopathy shows up as cotton wool spots, or microvascular abnormalities or as superficial retinal hemorrhages. As the disease progresses, severe nonproliferative diabetic retinopathy enters an advanced, or proliferative, stage when blood vessels proliferate.
Diabetic retinopathy has four stages:
• Mild Nonproliferative Retinopathy . At this earliest stage, microaneurysms occur. They are small areas of 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.
Causes and risk farctors
Blood vessels damaged from diabetic retinopathy can cause vision loss in two ways:
• Fragile, abnormal blood vessels can develop and leak blood into the center of the eye, blurring vision. This is proliferative retinopathy and is the fourth and most advanced stage of the disease.
• Fluid can leak into the center of the macula. The fluid makes the macula swell, blurring vision. This condition is called macular edema . It can occur at any stage of diabetic retinopathy, although it is more likely to occur as the disease progresses. About half of the people with proliferative retinopathy also have macular edema.
People with type 1 diabetes and type 2 diabetes are at risk for this condition. That's why everyone with diabetes should get a comprehensive dilated eye exam at least once a year.
Having more severe diabetes for a longer period of time increases the chance of getting retinopathy. Retinopathy is also more likely to occur earlier and be more severe if your diabetes has been poorly controlled. The longer a person has diabetes, the higher the risk of developing some ocular problem. Between 40 to 45% of Americans diagnosed with diabetes have some stage of diabetic retinopathy. After 20-30 years of diabetes, nearly all patients with Type I diabetes and >60% of patients with Type II diabetes have some degree of retinopathy.
During pregnancy, diabetic retinopathy may be a problem for women with diabetes. To protect vision, every pregnant woman with diabetes should have a comprehensive dilated eye exam as soon as possible.
Treatment
As already said many people with early diabetic retinopathy have no symptoms before major bleeding occurs in the eye.This is why everyone with diabetes should have regular eye exams.
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 and stop smoking. However, they should be closely followed by an eye doctor who is trained to treat diabetic retinopathy.
Treatment usually does not reverse damage that has already occurred. However, it can help keep the disease from getting worse.
Once your eye doctor notices new blood vessels growing in your retina (neovascularization) or you develop macular edema, treatment is usually needed.
Several procedures or surgeries are the main treatment for diabetic retinopathy. Laser eye surgery creates small burns in the retina where there are abnormal blood vessels. This process is called photocoagulation . It is used to keep vessels from leaking or to get rid of abnormal, fragile vessels and is used to treat macular edema.
Scatter laser treatment or panretinal photocoagulation treats a large area of your retina. Often two or more sessions are needed.
A surgical procedure called vitrectomy is used when there is bleeding (hemorrhage) into the eye. It may also be used to repair retinal detachment. Drugs that prevent abnormal blood vessels from growing. A vitrectomy is performed when there is a lot of blood in the vitreous. It involves removing the cloudy vitreous and replacing it with a saline solution.
Studies show that people who have a vitrectomy soon after a large hemorrhage are more likely to protect their vision than someone who waits to have the operation.
Early vitrectomy is especially effective in people with insulin-dependent diabetes, who may be at greater risk of blindness from a hemorrhage into the eye.
Then there is another treatment that is an injection of corticosteroids or Anti-VEGF into the eye; Recent studies have found a very good result with multiple doses of intravitreal injections of Anti-VEGF drugs. Intravitreal Anti-VEGF Therapy Blocks Inflammatory Cell Infiltration and Re-Entry into the Circulation in Retinal Angiogenesis.
Another recent study is based on the suppression of GLUT1, new strategy to prevent diabetic complications.
Diagnosis
Diabetic retinopathy is detected during an eye examination 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.
• Fluorescein angiogram If your eye care professional believes you need treatment for macular edema. 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.
Complications
Other problems that may develop are:
• Cataracts
• Glaucoma : increased pressure in the eye that can lead to blindness
• Macular edema if fluid leaks into the area of the retina that provides sharp vision straight in front of you, your vision becomes more blurry
• Retinal detachment : scarring may cause part of the retina to pull away from the back of your eyeball
