Diabetic retinopathy is an eye disease that damages the blood vessels in the retina. The retina is a light-sensitive group of nerves at the back of the eye that interprets visual images and sends them to the brain. Diabetic retinopathy is the leading cause of new cases of blindness among working-age Americans, according to the American Diabetes Association.
Diabetic retinopathy begins as nonproliferative retinopathy. In this stage,high glucose (blood sugar) levels weaken the blood vessels in the retina. Initially, these vessels may develop balloon-like pouches called microaneurysms and leak fluid, causing swelling in the retina. At this stage, few patients experience symptoms.
Over time with poorly controlled glucose, the disorder can progress to a stage known as proliferative retinopathy. This occurs when the retina does not receive enough blood, and new, abnormal blood vessels grow on its surface. These weak vessels cannot carry the blood the starved retina needs. They frequently hemorrhage (bleed), resulting in retinal scarring, retinal death and detachment, conditions that can cause partial or total loss of vision.
The longer a person has diabetes, the higher the risk of developing diabetic retinopathy. After 20 years, it will affect up to 90 percent of patients with type 1 diabetes and up to 60 percent of those with type 2 diabetes, according to the U.S. Centers for Disease Control and Prevention. Scientists have recently learned that diabetic retinopathy can even affect people with prediabetes.
Diabetic retinopathy is most treatable when diagnosed early. Possible treatments include laser therapy (photocoagulation) and a surgical procedure called vitrectomy.
People with retinopathy often do not experience symptoms until it has progressed to the proliferative stage. For this reason, it is crucial that patients with diabetes schedule regular eye exams so that an ophthalmologist can detect, diagnose and treat the disorder before it affects vision. Even with treatment, retinopathy may continue to worsen. However, individuals can reduce their risk of diabetic retinopathy through measures such as control of glucose and cholesterol, and scientists are working on innovations including drug treatments.
About diabetic retinopathy
Diabetic retinopathy is a condition in which progressive damage to the blood vessels in the back of the eye leads to vision impairment or blindness. It causes legal blindness (20/200 or worse vision) in 12,000 to 24,000 Americans each year, according to the Centers for Disease Control and Prevention (CDC).
Scientists have recently found that diabetic retinopathy, as well as heart disease and the nerve disorder diabetic neuropathy, can develop in people with prediabetes. Follow-up research from the Diabetes Prevention Program (DPP) found that nearly 8 percent of prediabetic participants developed diabetic retinopathy during the three-year DPP.
Diabetic retinopathy affects the retina, the light-sensitive structure at the back of the eye that transmits visual images to the brain. In normal vision, light enters the cornea (the clear front part of the eye) before passing through the pupil and lens and finally focusing on the retina. The retina acts like the film in a camera and records the image. Nerve cells in the retina then translate visual images into electrical impulses, which are sent on to the brain to be interpreted.
In diabetic retinopathy, high glucose (blood sugar) levels and other factors weaken the walls of the retinal capillaries (tiny blood vessels). The weak blood vessel walls allow blood to seep out of the vessel and into the eye. During the healing process, deposits called hard exudates cause a hardening that is visible to a physician. Exudates are fluids that pass through a vessel wall into adjoining tissues. They consist of cells, proteins and solid materials.
The hardening causes narrowing of the capillaries that provide nutrient-rich blood to the retina. The blockage prevents the nutrients from getting to the retina. As the retina becomes starved for oxygen and nutrients, the eye responds by stimulating the growth of abnormal new blood vessels. These vessels are weak and prone to leaking additional blood and fluid.
Diabetic retinopathy occurs in two major stages, which cause vision loss in different ways:
Nonproliferative retinopathy or background retinopathy. Retinal blood vessels begin to deteriorate, becoming blocked or developing balloon-like deformities in the vessel walls called microaneurysms. The vessels may leak fluids, fats and proteins that collect in the central part of the retina (macula), causing it to swell. This condition is known as macular edema. Patients with nonproliferative retinopathy may experience blurred vision that impairs the visual sharpness needed for reading and detail work. Nonproliferative retinopathy can damage central vision, but peripheral (side) vision often continues to function.
Proliferative retinopathy. Abnormal new blood vessels grow over the retinal surface. These vessels are fragile and tend to hemorrhage frequently, obscuring vision. This can affect both central and peripheral vision. Girls with type 1 diabetes have a higher risk of developing proliferative retinopathy than boys. Proliferative retinopathy can cause the following problems:
Vitreous hemorrhage. Occurs when vessels grow toward and bleed into the clear, gel-like substance at the center of the eye called the vitreous. The severity of the hemorrhage and its location in the vitreous determines the degree of vision impairment. The blood released in a vitreous hemorrhage usually clears over time, and vision is sometimes restored to its pre-hemorrhage level. If this does not occur, the surgical removal of all or part of the vitreous (vitrectomy) may be necessary.
Traction retinal detachment. The scar tissue resulting from neovascularization (growth of new blood vessels) sometimes shrinks. This can put tension on the retina and pull it from its normal location. This condition is known as a tractional retinal detachment, and it can cause severe vision loss. A vitrectomy and retinal reattachment procedure are necessary if vision is to be restored.
Neovascular glaucoma. A form of glaucoma that results from the growth of abnormal blood vessels on the iris (the forward colored portion of the eye, surrounding the pupil). These vessels block fluid from leaving the eye, leading to a pressure buildup that can cause glaucoma.
Scientists have found diabetic retinopathy to be a strong predictor of the kidney disease diabetic nephropathy. This is both because of similar cause (hyperglycemia) and the fact that nephropathy exacerbates retinopathy. Both conditions are forms of diabetic angiopathy (diseases of blood vessels). Patients are advised to ask their physician about having periodic microalbuminuria tests to screen for kidney damage.
Patients with diabetes who keep tight control over glucose levels have a lesser risk of developing eye disease. Maintaining healthy blood pressure and cholesterol levels and a healthy body weight may also help to delay or prevent the development of eye disease.
Retinopathy is the term for the vascular disease seen in patients with diabetes. People with diabetes also have an increased risk of other eye disorders, including glaucoma, cataracts and diabetic optic neuropathy.
Patients with diabetes should schedule an eye examination at least once a year with an ophthalmologist (a doctor who specializes in eye disease). An ophthalmologist is the only specialist who can detect, diagnose and treat diabetic retinopathy. Patients with type 1 diabetes should be seen at five years after diagnosis, and at least annually thereafter. Patients with type 2 diabetes should be seen at diagnosis, and at least annually thereafter.
Potential causes of diabetic retinopathy
The longer a period of time a person has diabetes, the higher the risk is for developing diabetic retinopathy. There are factors that may accelerate diabetic eye disease, including:
High blood glucose (hyperglycemia)
High blood pressure (hypertension)
High blood cholesterol levels
Kidney disease (diabetic nephropathy)
Obesity
Family history of diabetic retinopathy
Smoking
Pregnant women also are at increased risk of vision disorders if they have diabetes, except for those women who develop gestational diabetes, which resolves after childbirth. Pregnant women with pre-existing diabetic retinopathy have an increased risk of vision loss.
Signs and symptoms
Diabetic retinopathy often presents few symptoms initially. There is no pain associated with the disease, and vision may not be noticeably affected until the disease is advanced. Prior good vision is not a factor in the development of diabetic retinopathy.
Eventually, patients with diabetic retinopathy may experience blurred vision. This occurs when:
The macula (part of the retina that provides sharp, central vision) swells from fluid leaking from retinal blood vessels. This condition is known as macular edema.
New blood vessels growing on the surface of the retina (neovascularization) can bleed into the eye, which can decrease vision by blocking light entering the eye. The new vessels can also cause retinal detachments..
The macula can develop ischemia (lack of oxygen) from the decreased blood flow and stop functioning.
Other symptoms associated with diabetic retinopathy, especially in the later stages, include:
Blank areas in the field of vision
Glare when in bright light
Dark streaks or red film that blocks vision
Cloudy vision or blurred vision
Difficulty reading or seeing detailed work
Difficulty adjusting from bright light to dim light
However, many cases of diabetic retinopathy manifest no symptoms and can be detected only during an eye exam. For this reason, patients should have their eyes examined by an ophthalmologist at least once a year.
Diagnosis methods
Many cases of diabetic retinopathy do not show symptoms until the disease has progressed, and can be detected only during an eye exam.
The ophthalmologist is likely to review a medical history and perform a physical examination concentrating on the patient’s eyes. Symptoms related to the eyes or vision problems will be of particular interest, as well as a history of the patient’s range of glucose (blood sugar) levels.
The patient’s visual acuity will be tested, and intraocular pressure (fluid pressure in the eye) will be measured. The eyes will be dilated during the exam. Eyedrops are placed in the eyes to enlarge the pupils and allow the physician to examine more of the inside of the eye. An instrument called an ophthalmoscope or funduscope is used to examine the retina.
The physician will look for the following symptoms in making a diagnosis:
Blood vessels that leak
Hemorrhage of the retina
Swollen retina
Fatty deposits (exudates) in the retina
Damage to nerve fibers
Changes in blood vessels
Microaneurysms
New blood vessels (neovascularization)
Vitreous hemorrhage
Formation of scar tissue and possible detachment of the retina
Sometimes a physician will use fluorescein angiography to check for leaky blood vessels. In this test, a dye is injected into a vein in the patient’s arm. When the dye travels to the retina, it fills the blood vessels, which appear white when photographed with blue light.
Treatment options
Diabetic retinopathy can often be successfully treated, when caught early. However, damage can be irreversible in many cases. For this reason, it is important that patients with diabetes follow up with an ophthalmologist as prescribed, so as to diagnose and treat any problems early.
Treatments for diabetic retinopathy usually involve a form of laser therapy. Variations include:
Focal laser photocoagulation. A laser beam is used to make tiny burns in and around the macula (central part of the retina providing sharp vision) to seal leaking blood vessels. It is used for a condition called clinically significant macular edema (CSME), in which the leakage from macular blood vessels encroaches on the fovea (center of the macula). CSME can occur in nonproliferative retinopathy or in proliferative retinopathy.
Scatter photocoagulation. Also called pan-retinal photocoagulation (PRP), this consists of using an argon (green wavelength) laser to make thousands of burns in a polka-dot pattern in the retina in patients with proliferative diabetic retinopathy. This can keep new blood vessels from growing. The procedure reduces the risk of blindness from vitreous hemorrhage or retinal detachment by eliminating retina which is used less, and allowing more blood flow to the remaining central retina. It is most effective if proliferative diabetic retinopathy has not advanced too far.
Some patients may benefit from vitrectomy, which is performed when bleeding in the eye is not controlled with laser, or laser cannot be applied because of blood blocking the ophthalmologist’s view of the retina. In this procedure, blood, the vitreous humor and scar tissue are surgically removed from the eye. A tiny laser called an endophotocoagulator can also be used to perform PRP during the surgery.
Some patients report soreness, redness or irritation in the eye after laser procedures. Temporarily blurred vision also is not unusual. PRP may result in a decrease in peripheral and/or night vision.
In severe cases of diabetic retinopathy, the retina may become detached. This can cause blindness. However, the retina can sometimes be reattached to the back of the eye through vitrectomy surgery.
Medication may also become a treatment option. For more information, see Ongoing research.
Prevention methods
Diabetic retinopathy is the leading cause of new blindness in the United States among adults ages 20 to 74, according to the U.S. Centers for Disease Control and Prevention (CDC). Anyone who has diabetes is at risk for developing diabetic retinopathy.
People with diabetes are 25 times more likely to suffer blindness than the rest of the population. They are also 1.3 times more likely to have glaucoma and 1.6 times more likely to have cataracts than those in the general population, according to the CDC.
By far the most important preventative measure on the part of patients is to schedule regular examinations with an eye physician (ophthalmologist). The ophthalmologist is a medical doctor who specializes in eye conditions and is the only physician who can detect, diagnose and treat diabetic retinopathy.
When patients are first diagnosed with diabetes, they should have their eyes checked by an ophthalmologist:
Within five years of the diagnosis if they have type 1 diabetes, or have type 2 diabetes and are 29 years of age or younger.
At the time of the diagnosis if they are 30 or older, and have type 2 diabetes.
Diabetes patients should schedule such an exam at least once every year. A physician may advise more frequent examinations for individuals at higher risk of eye diseases.
Patients should also have their eyes checked if they have visual changes that:
Affect only one eye
Continue more than a few days
Are not associated with changes in glucose (blood sugar)
Studies have also shown that maintaining a normal glucose level can significantly reduce the risk of developing diabetic retinopathy, or slow the progression of the disease once it has appeared. Intensive insulin therapy is among the treatments that may be prescribed by an individual’s physician to achieve this goal.
Other lifestyle modifications that can help slow the progression of diabetic retinopathy include:
Controlling high blood pressure. Lowering blood pressure appears to substantially hinder development of retinopathy.
Exercise. Regular exercise helps to lower blood pressure and moderate glucose levels because the muscles use glucose for energy. Patients are advised to consult their physician before beginning an exercise program.
Losing excess weight. A recent international review of more than 20 research studies on thousands of patients found obesity to be a major risk factor for diabetic retinopathy and other leading causes of blindness: glaucoma, cataracts and macular degeneration.
Quitting smoking. Smoking causes blood vessels to close.
Controlling cholesterol and triglycerides. Recent research involving data from the Diabetes Control and Complications Trial linked abnormal levels of blood fats (lipids) to risk of diabetic retinopathy.
Lowering stress. Stress hormones are known to cause blood sugar levels to rise or fall. Stress also raises blood pressure.
Pregnant women are at increased risk of developing diabetic retinopathy. Diabetic women who are pregnant or who plan to become pregnant within the next year should see an ophthalmologist. They should be tested for the disorder prior to becoming pregnant, as dilating drops should not be used during pregnancy.
Ongoing research
Scientists are studying the causes of diabetic retinopathy and trying to develop treatments and preventive methods.
An application for an oral medication, ruboxistaurin (Arxxant), was submitted to the U.S. Food and Drug Administration (FDA) in 2006. Clinical trials found that the drug, a protein kinase inhibitor, reduced loss of vision from diabetic retinopathy. If approved, it would be the first oral medication to reduce risk of vision loss in people with diabetes.
Among other treatments being studied:
Corticosteroids, a class of anti-inflammatory immunosuppressives, may offer hope. One recent clinical trial found that an injected corticosteroid may improve vision in people with diabetic retinopathy. Side effects included increased risk of glaucoma and cataracts but were described as manageable. Also, a corticosteroid approved to treat an inflammatory eye condition called uveitis may improve vision in people with macular edema. This drug is released from a tiny device that is surgically placed or injected into the eye. This has been done successfully for a number of years but is used off-label, meaning it is not FDA-approved for this use.
Retinopathy and other diabetic conditions are a focus of gene therapy, the introduction of normal genes to fill in for malfunctioning ones. Genetic engineers are also studying stem cells as a way to prevent diabetic retinopathy.
Recent research suggests that a cholesterol-reducing drug may reduce the need for laser treatment of diabetic retinopathy, in addition to preventing nonfatal heart attacks.
A study at the University of Florida is offering some hope that scientists eventually may be able to block the development of diabetic retinopathy. Researchers used an antibody to block a protein called SDF-1 and prevented mice from developing blindness when they had a condition similar to diabetic retinopathy. SDF-1 signals blood stem cells to rush to certain areas of the body.
New research is also suggesting a promising direction for treating proliferative retinopathy, which occurs when the retina does not receive enough blood and new, abnormal blood vessels grow on its surface.
Researchers are studying the role of vascular endothelial growth factor (VEGF) and its receptors. VEGF is one of the known substances that cause new vessels to grow on the retinal surface. It is secreted by retina that is damaged by diabetes.
Studies have confirmed that VEGF is elevated in the eye fluids of patients with diabetes and proliferative diabetic retinopathy. Hypoxia – a deficiency in the amount of oxygen that reaches tissues, and a major factor in triggering the growth of abnormal blood vessels – spurs the secretion of VEGF.
Treatments such as laser photocoagulation cause changes to blood vessel circulation, which improves oxygen delivery to the retina. This results in reduced secretion of VEGF and other factors, leading to fewer troublesome new blood vessels.
In addition, chemicals are being developed that block the effect of VEGF. Researchers are focusing on other methods of blocking the formation of VEGF in the eyes, while allowing it to continue elsewhere in the body (such as in the heart and legs, where formation of new blood vessels is beneficial).
Japanese researchers recently found that a hormone called erythropoietin may be even more strongly linked than VEGF to advanced diabetic retinopathy. They suggested that treatment blocking erythropoietin could prevent the abnormal growth of blood vessels (neovascularization).
Oxygen therapy may hold potential as a treatment option. Scientists at the National Eye Institute and Johns Hopkins University found in a small pilot study that diabetic individuals with macular edema experienced decreased swelling in the eyes and, in some cases, sharper vision after inhaling supplemental oxygen for three months.
Questions for your doctor
Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about diabetic retinopathy:
Do I have or am I at risk of developing diabetic retinopathy?
How often should I have my eyes examined, and by whom?
What should my eye exam include?
What other tests for diabetic retinopathy might I need to undergo, and what do they involve?
What do my test results show?
Can my vision loss be reversed or compensated for?
Can treatment help me avoid further loss of vision?
What are my treatment options, and which do you recommend?
What is the expected course of my retinopathy? What are my odds of going blind?
What is the definition of legal blindness, and what are my rights if I develop this condition?
If I am risk of losing my eyesight, should I prepare now by starting low-vision therapy, learning Braille or taking other measures?
What sort of glucose control and blood pressure should I aim for to reduce my risk of diabetic retinopathy?
Should I quit smoking or make any other changes to fight diabetic retinopathy?
Does any recent research into diabetic retinopathy have implications for me? Are any drug treatments that may benefit me near approval?
