Diabetic retinopathy is damage to blood vessels that supply the retina, the light sensitive outer layer of the eye that senses light and converts images into electrical impulses that are sent to the brain. The retina forms a thin, delicate, membranous layer that lines the back of the eye.
Diabetic retinopathy is a common complication of long-term diabetes and a leading cause of blindness in adults. There are two kinds of diabetic retinopathy:
Non-proliferative diabetic retinopathy is the early stage of this condition and is less severe. Blood vessels in the eye start to leak fluid or protein deposits into the retina, which compromises the amount of oxygen the retina receives. In this early stage there often are no changes in vision or symptoms, however, when fluid collects in the center of the eye, a condition known as macular edema, it leads to blurred and diminished vision.
- Proliferative retinopathy is the second, or more advanced stage of the disease, and more severe. New, abnormal blood vessels start to grow in the retina, toward the center of the eye. These new vessels are fragile and often bleed into the center of the eye, which may cause vision loss and retinal scarring. These abnormal blood vessels may also produce scars large enough to cause the retina to detach.
Approximately 65,000 new cases of proliferative diabetic retinopathy and an additional 75,000 cases of macular edema are diagnosed each year in the United States. Diabetic retinopathy is more prevalent in persons with type 1 diabetes than in those with type 2, 40% compared to 20% respectively. The disease is also related to the duration of diabetes; after 20 years of living with diabetes, more than 90% of persons with type 1 diabetes will experience some degree of diabetic retinopathy as will 60% of those with type 2 diabetes.
Men and women are equally affected by diabetic retinopathy. Although the disease is most commonly diagnosed in persons ages 20 to 65, and is the most common cause of legal blindness in this age group, it is naturally more prevalent among older adults since it is linked to the duration of diabetes. The disease strikes persons of all races, however, because more African Americans have diabetes than other groups, they also have proportionally more instances of diabetic retinopathy.
Causes and symptoms
Diabetic retinopathy is caused by longstanding diabetes, both by type 1 and type 2 diabetes. Contributing or predisposing factors include:
- duration of disease—having diabetes for more than 10 years
- poor control of diabetes
- high blood pressure
- high cholesterol
- kidney disease
- surgery, hospitalization or other traumatic event during which control of blood glucose suffers
Because many persons with non-proliferative diabetic retinopathy have no symptoms, most cases are diagnosed during routine examinations of the eye of persons with diabetes. A small number of patients have poor night vision or blurred vision at the time of diagnosis and even fewer are diagnosed when they experience sudden or dramatic loss of vision.
The diagnosis of diabetic retinopathy is made based on a direct physical examination of the eye performed using an ophthalmoscope, a lighted instrument used to view the inside of the eye. In patients with nonproliferative diabetic retinopathy, an examination may reveal retinal bleeding, exudates from the retina that look like cotton wool spots or retinal microaneurysms, which are very tiny dilations of retinal capillaries.
In proliferative retinopathy, examination of the eye reveals all of the signs seen in non-proliferative disease as well as new and abnormal blood vessels in the retina and other parts of the eye.
Additional diagnostic tests may be performed by an ophthalmologist such as optical coherence tomography, a photographic test performed in the office that permits measurement of the thickness of the macula. Optical coherence tomography also may be used to evaluate the results of treatment of diabetic macular edema. Slit-lamp biomicroscopy is another test that is used to assess the extent of damage to the blood vessels supplying the retina. A fluorescein angiogram, a test in which dye in injected into a vein (usually in the arm) while a camera with a blue filter takes pictures of the retina as the dye travels through the blood vessels supplying it, enables ophthalmologists to see microaneuryms and to identify sources of macular edema.
QUESTIONS TO ASK YOUR DOCTOR
- How can I prevent further damage to my eyes and vision?
- How can I better control my blood sugar levels?
- Which type of treatment will help to prevent or postpone damage to the retina?
- Will lowering my blood pressure help to reduce the risk of future retinal and vision problems?
To establish the diagnosis, the physician also may order blood tests such as fasting blood sugar, to confirm that the patient has diabetes, and hemoglobin A1c, a blood marker that indicates long-term control of blood sugar and the risk of developing microvascular disease.
Treatment for diabetic retinopathy is not likely to reverse existing damage; instead it aims to prevent further damage. Preventing additional damage to the retina and further vision problems generally entails some form of surgical treatment. Laser surgery, known as laser photocoagulation, may be used to eliminate abnormal blood vessels and to stem leakage from blood vessels.
When there is bleeding into the eye, scarring or retinal detachment , a procedure known as vitrectomy may be performed. There also are drugs that may be injected into the eye, which in concert with laser photocoagulation treatment may help to stop or slow the growth of new blood vessels to the retina and other parts of the eye.
It is vitally important that patients with diabetic retinopathy make every effort to reduce and control blood sugar, blood pressure and cholesterol levels. Close adherence to prescribed medication and a diabetic eating plan program designed by a diabetes educator, nutritionist , registered dietician or other health professional can help people with diabetes to effectively manage their disease.
Macular edema —Swelling of the retina in the area of the macula, the highly sensitive part of the retina responsible for detailed central vision.
Microaneurysm —Small bulges or protrusions in the retinal blood vessels.
Retinal detachment —Separation of the retina from its attachments to the back of the eyeball.
Vitrectomy —Surgical removal of the transparent gel that fills the eye.
The outlook for people with non-proliferative diabetic retinopathy is usually quite good; proliferative diabetic retinopathy carries a more guarded prognosis. For both conditions, prognosis also is influenced by the presence of any coexisting illnesses and how well patients adhere to treatment, which includes taking action to control diabetes.
Diabetic retinopathy can recur, even with treatment, and may progress, leading to serious complications including:
- vitreous hemorrhage—vision-distorting accumulation of blood within the vitreous humor of the eye
- blindness from macular edema—swelling in the area of the macula, the highly sensitive part of the retina responsible for detailed central vision
- glaucoma—elevated pressure in the eye
- cataracts—clouding of the lens of the eye
- retinal detachment
- vascular occlusion—blockage of a blood vessel
The progression of diabetic retinopathy may be slowed down by ongoing, successful efforts to control blood sugar, blood cholesterol levels and blood pressure and by getting moderate, habitual exercise . Stopping smoking also helps to prevent or delay the progression of diabetic retinopathy. All people with diabetes should receive regular eye examinations and prompt laser surgery to minimize damage to the retina. Maintaining stringent control of blood sugar is especially important for preventing the development of diabetic retinopathy among persons with type 1 diabetes.
Myron, Yanoff. Ophthalmology 2nd ed. Adam H. Rogers, Chapter 113—Hypertensive Retinopathy New York: Mosby, 2004.
Fong, D.S., L. Aiello, TW Gardner, et al. “Retinopathy in diabetes.” Diabetes Care (27 2004): s84–7
“Standards of Medical Care in Diabetes.” Diabetes Care (30 2007): s4–41S
American Academy of Ophthalmology, P.O. Box 7424, San Francisco, CA, 94120-7424, (415) 561-8500, (415) 561-8533.
Barbara Wexler MPH