Diabetes mellitus is a chronic disease that inhibits the proper processing of glucose (sugar) in the body. It affects many parts of the body and can be particularly devastating to the visual system if the disease is not held in check. Diabetic retinopathy, retinal detachments and neovascular glaucoma are among the ocular complications of diabetes.
Diabetic retinopathy is a complication of diabetes that is caused by changes in the blood vessels of the eye. The retina is a nerve layer at the back of the eye that senses light and helps to send images to your brain. When blood vessels in the retina are damaged, they may leak fluid or blood, and grow fragile, brush-like branches and scar tissue. This can blur or distort the images that the retina sends to the brain.
Diabetic retinopathy is the leading cause of new blindness among adults in the United States. People with untreated diabetes are said to be 25 times more at risk for blindness than the general population.
The longer a person has diabetes, the more the risk of developing diabetic retinopathy increases. About 80% of the people who have had diabetes for at least 15 years have some blood vessel damage to the retina. People with Type I, or juvenile, diabetes are more likely to develop diabetic retinopathy at a younger age. If you have diabetes, it’s important to know that today, with improved methods of diagnosis and treatment, only a small percentage of people who develop retinopathy have serious vision problems.
Types of diabetic retinopathy
Background retinopathy is an early stage of diabetic retinopathy. In this stage, tiny blood vessels within the retina become damaged and leak blood or fluid. Leaking fluid causes the retina to swell or to form deposits called exudates. While this stage usually doesn’t affect your vision, it can lead to more sight-threatening stages. For this reason, background retinopathy is considered a warning sign.
Sometimes the leaking fluid collects in the macula, the part of the retina that lets us see fine details, like letters or numbers. This problem is called macular edema. Reading and close work may become more difficult because of this condition.
Proliferative diabetic retinopathy describes the changes that occur when new, abnormal blood vessels begin growing on the surface of the retina. The abnormal growth is called neovascularization. These new blood vessels have weaker walls and may break and bleed into the vitreous. The vitreous is the clear, jelly-like substance that fills the center of the eye. Leaking blood can cloud the vitreous and partially block the light passing through the pupil towards the retina, causing blurred and distorted images.
These abnormal blood vessels may grow scar tissue that can pull the retina away from the back of the eye. This is called a retinal detachment. If left untreated, a retinal detachment can cause severe vision loss. Abnormal blood vessels may also grow around the pupil (on the iris) causing glaucoma by increasing pressure within the eye. Proliferative diabetic retinopathy is the most serious form of diabetic retinal disease. It affects up to 20% of diabetics and can cause severe loss of sight, including blindness.
There are usually no symptoms of background retinopathy, although gradual blurring of vision may occur if macular edema is present. You may never notice changes in your vision. Consequently, a comprehensive dilated eye exam is often the only way to find changes inside your eye. When bleeding occurs, your sight may become hazy, spotty or even disappear altogether. While there is no pain, proliferative diabetic retinopathy is a severe form of the disease and requires immediate medical attention. Pregnancy and high blood pressure may aggravate diabetic retinopathy.
Diabetic retinopathy may be present without any symptoms, so early detection of diabetic retinopathy is the best protection against loss of vision. People with diabetes should schedule dilated examinations by an ophthalmologist or optometrist at least annually. More frequent medical eye examinations may be necessary once diabetic retinopathy has been diagnosed. With careful monitoring, an ophthalmologist can begin treatment before sight is affected. Laser and operative surgery are highly effective treatment for diabetic retinopathy.
In addition to regular eye exams, your attitude and attention to medications and diet are essential to controlling diabetic retinopathy. You must maintain blood sugar levels, avoid smoking and watch your blood pressure. Physical activity is typically allowed for people with background retinopathy. Occasionally, people with active proliferative retinopathy are advised to restrict physical activity.
The best protection against diabetic retinopathy is to have regular comprehensive dilated eye exams with your ophthalmologist or optometrist. Serious retinopathy can be present without any symptoms. The disease can improve with treatment. To find diabetic retinopathy, your eye doctor looks at the inside of the eye using an instrument called an ophthalmoscope. The pupils may need to be dilated (enlarged) with eye drops. If your optometrist discovers diabetic retinopathy, you should be referred to a general ophthalmologist or retinal ophthalmologist for further testing.
Your ophthalmologist may order color photographs of the retina or a special test called fluorescein angiography to find out if you need treatment. Fluorescein angiography is a test where dye is injected into your arm and special photos of your eye are taken. As the dye passes through your eyes, the photos will indicate which blood vessels in your eye are leaking.
Before treating your diabetic retinopathy, your ophthalmologist will consider your age, your medical history, your lifestyle, and how much your retina has been damaged. In many cases treatment is not necessary, but you will need to continue having regular eye exams. In other cases, treatment will be recommended to stop the damage of diabetic retinopathy and improve sight whenever possible.
Laser surgery – A laser procedure called photocoagulation is often helpful in treating diabetic retinopathy. A powerful beam of laser light is focused on the damaged retina. Small bursts of the laser’s beam seal leaking retinal vessels to reduce macular edema.
For abnormal blood vessel growth (neovascularization), the laser beam bursts are scattered throughout the side areas of the retina. The small laser scars reduce the abnormal blood vessel growth and help bond the retina to the back of the eye, preventing retinal detachment.
Laser surgery is typically performed as an outpatient procedure in a surgery center. If diabetic retinopathy is detected early, laser surgery slows down vision loss. Even in the more advanced stages of the disease (proliferative retinopathy), it reduces the chances of severe visual impairment.
Cryotherapy – If the vitreous is clouded by blood, laser surgery cannot be used until the blood settles or clears. In some cases of bleeding into the vitreous, cryotherapy, or freezing, of the retina may help shrink the abnormal blood vessels.
Avastin/Lucentis injections – Avastin and its sister medication are called anti-VEGF medications. Their main purpose is to stop the growth of new abnormal blood vessels in the retina. While Avastin and Lucentis are primarily indicated for the wet form of macular degeneration, the medications may also be used to treat proliferative diabetic retinopathy.
Vitrectomy – In advanced proliferative diabetic retinopathy, the ophthalmologist may recommend a vitrectomy. This microsurgical procedure is performed in the operating room. During a vitrectomy, the retinal surgeon removes the blood-filled vitreous and replaces it with a clear solution. About 70% of vitrectomy patients notice an improvement in sight after surgery. Sometimes the ophthalmologist may wait from several months up to a year to see if the blood clears on its own, before proceeding with a vitrectomy.
Retinal detachment repair – If scar tissue detaches the retina from the back of the eye, severe sight loss or blindness can result unless surgery is performed to reattach the retina.
The animation below provides an introduction to diabetic retinopathy.