If you have diabetes mellitus, your body does not use and store sugar properly. High blood sugar levels causes damage to the small blood vessels in the retina. The damage to retinal vessels is called diabetic retinopathy.
Types of Diabetic Retinopathy:
There are two types of diabetic retinopathy: Nonproliferative Diabetic Retinopathy and Proliferative Diabetic Retinopathy.
Nonproliferative Diabetic Retinopathy (NPDR) is commonly referred to as background retinopathy. It is an early stage of diabetic retinopathy, where tiny blood vessels within the retina become damaged leading to mild leakage of blood or fluid into the retina. Examination of the retina reveals areas of bleeding and swelling of the retina.
Many people with diabetes have mild NPDR, which usually does not affect their vision. The macula is the central vision area of the retina responsible for our detailed vision. When the macular vessels are damaged, macular edema (swelling of the retina), macular ischemia (decreased blood supply to the retina), or both can occur. This can result in decreased vision. Macular Edema is swelling or thickening of the macula, caused by fluid leaking from retinal blood vessels. It is the most common cause of vision loss in diabetics. Vision loss may be mild to severe, but peripheral vision continues to function. Macular ischemia occurs when small blood vessels (capillaries) close. Vision blurs because the macula no longer receives sufficient blood supply to work properly.
Proliferative Diabetic Retinopathy (PDR) develops when the blood supply to the peripheral retina is significantly damaged, thereby preventing proper blood flow. In response to the lack of oxygen (ischemia) the retinal vessels release factors that promote new blood vessel growth in an attempt to resupply blood and oxygen to the damaged retina. These new vessels (neovascularization), are abnormal, growing on the surface of the retina or optic nerve. Unfortunately, the new abnormal blood vessels do not supply the retina with normal blood flow. The new vessels eventually rupture and bleed, filling the eye with blood. They often develop scar tissue that can cause wrinkling or detachment of the retina.
PDR can cause more severe vision loss than NPDR because it can affect both central and peripheral vision.
PDR causes vision loss in the following ways:
The fragile new vessels caused by PDR may bleed into the vitreous. If the vitreous hemorrhage is small, a person might see only a few new, dark floaters. A very large hemorrhage might block out all vision.
It may take several days to a number of years to reabsorb the blood, depending on the amount of blood present. If the eye does not clear the vitreous blood adequately within a reasonable amount of time, vitrectomy surgery may be recommended by the doctor.
Vitreous hemorrhage alone does not cause permanent vision loss. When the blood clears, vision may return to its former level if the macula is undamaged.
Traction retinal detachment:
When PDR is present, scar tissue associated with neovascularization can shrink, thereby wrinkling and pulling the retina from its normal position. Macular wrinkling can cause visual distortion. More severe vision loss can occur if the macula or large areas of the retina are detached.
Occasionally, extensive retinal vessel closure will cause new, abnormal blood vessels to grow on the iris (the colored part of the eye) and in the drainage channels in the front of the eye. This can block the normal flow of fluid out of the eye. Pressure in the eye builds up, resulting in neovascular glaucoma, a severe eye disease that damages the optic nerve.
Diagnosis of Diabetic Retinopathy:
A dilated eye examination is the best way to detect changes inside your eye. Dr. Comaratta can diagnose and treat serious retinopathy before you are even aware of any issues with your vision. Dr. Comaratta will dilate your pupil and look inside of the eye with special equipment and lenses. If Dr. Comaratta finds diabetic retinopathy, he may order one or more tests to determine the extent of the disease:
Optical Coherence Tomography (OCT): OCT can determine the extent of swelling in the macula.
Fluorescein Angiography (FA): With fluorescein angiography, a dye is injected into your arm and high resolution digital photos are taken to evaluate the blood supply to the retina, detect abnormal blood vessel growth or swelling in the macula.
Treatment of Diabetic Retinopathy:
The best treatment for diabetic retinopathy is to prevent the development of retinopathy as much as possible. Strict control and monitoring of blood sugar, blood pressure and cholesterol levels with your primary care doctor will significantly reduce the long-term risk of vision loss. All patients with diabetes should see their primary care doctor regularly. Additionally, smoking is never a good idea for health reasons, but can be catastrophic in diabetes.
Early detection of diabetic retinopathy is the key to successful treatment. Every patient should have a dilated fundus exam at least once per year. More frequent examination maybe required if diabetic retinopathy is detected.
Vascular endothelial growth factor (VEGF) is the chemical released by the retina in response to a decrease in blood supply. It promotes the abnormal blood vessel growth and stimulates leakage into the retina. Injections of anti-VEGF medication in the eye can stop the growth of new blood vessels and subsequent bleeding. These injections can also reduce swelling in the macula associated with diabetic macular edema. Sometimes, anti-VEGF therapy is performed in conjunction with steroid injections, laser treatment or surgery.
Often, patients experience some anxiety regarding the injection itself. With appropriate topical anesthesia, the injection itself is painless, and most patients are not aware that the injection has even happened. There is occasionally some discomfort after the injection due to the sterilizing solution placed in the eye to prevent infection. The doctor recommends aggressive lubrication with artificial tears or ointment to ease any discomfort following the procedure. Patients are encouraged to return to normal activity as soon as they feel comfortable.
For macular edema, focal laser photocoagulation is used to treat the leaking blood vessels and resolve the swelling in the macula. It is often used in conjunction with anti-VEGF treatment to stop further leakage.
For PDR, panretinal laser photocoagulation is performed to cause regression of the abnormal blood vessels growing on the surface of the retina. The laser is focused on the peripheral retina, away from the center of fine vision. This type of laser treatment causes abnormal new vessels to shrink and often prevents them from growing in the future. It also decreases the chance that vitreous bleeding or retinal detachment will occur.
Sometimes multiple laser treatments are necessary over the course of months or years. Laser treatment does not cure diabetic retinopathy and does not always prevent the further loss of vision.
In advanced diabetic retinopathy cases involving persistent bleeding in the eye (vitreous hemorrhage) or retinal detachment, the doctor may recommend vitrectomy surgery. During this procedure, performed at Bozeman Deaconess Hospital, the blood-filled vitreous is removed and replaced with a clear solution. The doctor may wait for several months to see if the blood clears on its own before performing surgery. Vitrectomy often prevents further bleeding by removing the abnormal vessels that cause the bleeding. If the retina is detached, it can be repaired during the vitrectomy surgery. Surgery should sometimes be done early because macular distortion or traction retinal detachment will cause permanent vision loss. The longer the macula is distorted or out of place, the more serious the vision loss will be.
Vision Loss is Preventable:
If you have diabetes, it is important to know that with the improved methods of diagnosis and treatment available today, a smaller percentage of people who develop retinopathy have serous vision problems. Early detection is the best protection against loss of vision.
You can significantly lower your risk of vision loss by maintaining strict control of your blood sugar, blood pressure, and cholesterol levels in conjunction with your medical doctor. It is essential to have periodic dilated eye examinations to monitor the retina for the development of, or progression of diabetic retinopathy.
When to Schedule an Examination with Dr. Comaratta:
People with Type 1 diabetes should schedule an examination within five years of being diagnosed, and then yearly. People with Type 2 diabetes should have an exam at the time of diagnosis and then at least once a year, sometimes more frequently.
Pregnant women with diabetes should schedule an appointment in the first trimester, as retinopathy can progress quickly during pregnancy.
If you need to be examined for eyeglasses, it is important that your blood sugar be consistently under control for several days when you see your ophthalmologist. Eyeglasses that work well when blood sugar is out of control will not work well when blood sugar is stable. Rapid changes in blood sugar can cause fluctuations in vision in both eyes, even if retinopathy is not present.
You should have your eyes checked promptly if you have visual changes that: affect either one or both eyes, last more than a few days, are not associated with a change in blood sugar.
When you are first diagnosed with diabetes, you should have your eyes checked within five years of the diagnosis if you are 29 years old or younger; or, within a few months of diagnosis if you are 30 years old or older.