Diabetic retinopathy is a vision-threatening complication of diabetes mellitus that is marked by changes in the blood vessels in the retina, the light-sensitive tissue at the back of the eye. These changes occur over time owing to high blood sugar levels, which cause the walls of the blood vessels that supply blood to the retina to become thicker. Initially, this causes the blood vessels to become more porous, or leaky. Leakage of fluid, blood, and lipid (fat) may accumulate in the center of the retina, or macula, leading to blurred vision (diabetic macular edema). In later stages of diabetic retinopathy, small blood vessels in the retina close, depriving the tissue of food and oxygen (ischemia). This fosters the release of a vasoproliferative substance inside the eye, which causes new, abnormal blood vessels to proliferate (a condition referred to as neovascularization).
Diabetic retinopathy is the leading cause of blindness in Americans age 20 to 65. However, regular eye exams and timely treatment can prevent or retard visual impairment associated with the condition.
In the early stages of diabetic retinopathy, termed nonproliferative retinopathy, the tiny blood vessels in the retina develop outpouchings, called microaneurysms. These bulges, in conjunction with leaking capillaries, may leak blood or fluid anywhere in the retina. If this fluid builds up in the macula, central fine vision becomes altered. If fluid buildup becomes severe, and if both eyes are affected, reading and driving vision may be lost.
Advanced nonproliferative retinopathy may subsequently develop. This stage of the condition is caused by decreased blood flow within the retina and is marked by a number of additional changes. These include venous beading, which causes veins to resemble a string of beads owing to localized areas of dilation and constriction in the vessels. Intraretinal microvascular abnormalities (IRMA) refer to abnormal, spaghetti-shaped blood vessels that run between the normal vessels in the retina; multiple areas of these vessels predict progression to proliferative retinopathy. Another change is the development of cotton wool spots—areas of swollen nerve tissue that appear like white clouds on the retina and are the result of cell death from blocked blood capillaries.
Proliferative retinopathy, the most advanced stage of diabetic retinopathy, is marked by the spontaneous growth of new blood vessels, which are more fragile than the normal retinal blood vessels and are more prone to breaking and bleeding. These vessels are accompanied by fibrous scarring and this fibrovascular tissue grows out of the retina itself and into the vitreous humor (the gellike substance that fills the eyeball). Blindness can occur if these vessels bleed (vitreous hemorrhage) or pull on the retina, causing a retinal detachment. Similar fibrovascular tissue may develop in the front of the eye on the colored iris. This, too, can cause blindness due to neovascular glaucoma.
What Causes Diabetic Retinopathy?
- Retinopathy is strongly related to duration of diabetes. Nearly all individuals with type 1 diabetes—which generally strikes in childhood—develop some degree of retinopathy within 20 years of diabetes diagnosis, as do more than 60 percent of those with type 2 diabetes.
- Poor blood glucose control is a significant and modifiable risk factor for development and progression of diabetic retinopathy.
- High blood pressure, high blood lipids, and pregnancy are other factors associated with development and progression of diabetic retinopathy.
Symptoms of Diabetic Retinopathy
- People with diabetic retinopathy are often asymptomatic until macular edema or a vitreous hemorrhage occurs; when symptoms do occur, they include:
- Blurred central vision (due to macular edema)
- Seeing floating spots or cobwebs (due to a hemorrhage)
- Loss of central or side vision (due to a retinal detachment)
- Blindness (a complication of retinal detachment or substantial compromise of blood flow)
- Difficulty seeing well at night
Prevention of Diabetic Retinopathy
- Tight blood glucose control significantly reduces the risk of developing diabetic retinopathy and may forestall its progression.
- High blood pressure and high blood lipids should be controlled by lifestyle measures or, when necessary, medications.
- Maintaining an appropriate weight, or losing excess weight, reduces the risk of developing diabetes, high blood pressure, and diabetic retinopathy.
- Early detection and treatment will help prevent vision loss.
Diagnosis of Diabetic Retinopathy
- Characteristics of diabetic retinopathy can be detected with an ophthalmoscope during a dilated eye examination. Adults over 30 who have diabetes should have an annual dilated eye beginning at diagnosis. People who are diagnosed with diabetes before age 30 and have had the disease at least five years should also have a yearly eye exam. Once retinopathy develops, more frequent exams may be necessary.
- A test called fluorescein angiography, which involves the injection of dye into blood vessels in the arm followed by a series of photographs of the back of the eye, may be needed to stage the disorder and guide treatment.
- Visual acuity measurements may be performed to evaluate central vision loss.
- Refraction tests may also be performed to determine if changes to corrective vision prescription (e.g., eyeglasses) are necessary.
- Retinal photography or tomography to evaluate the current status of the retina.
- Fluorescein angiography to detect and monitor abnormal blood vessel growth.
How to Treat Diabetic Retinopathy
- For nonproliferative retinopathy that has led to macular edema, laser photocoagulation is used to seal the leaking blood vessels, which decreases tissue swelling, thereby decreasing the likelihood of further vision deterioration.
- For proliferative retinopathy, laser surgery known as panretinal photocoagulation is used to stop the growth of new blood vessels, thereby decreasing the likelihood of vitreous hemorrhage and retinal detachment.
- Vitrectomy is a surgical treatment that can help restore vision by removing a vitreous hemorrhage or repairing retinal detachment.
- Several new treatments are being evaluated to determine if they retard progression of retinopathy or decrease vision loss associated with it. These treatments include oral medications for nonproliferative disease and intraocular injections of anti-inflammatory medications (steroids) for macular edema.
When to Call a Doctor
- Call a doctor if you have recently been diagnosed with type 2 diabetes, or if you have diabetes and have not seen an ophthalmologist within the last year. Also call a physician if you develop symptoms of diabetic retinopathy.
Johns Hopkins Symptoms and Remedies: The Complete Home Medical Reference
Simeon Margolis, M.D., Ph.D., Medical Editor
Prepared by the Editors of The Johns Hopkins Medical Letter: Health After 50
Updated by Remedy Health Media