Uncontrolled blood sugar levels over the years can increase risk of serious damage to the retina, a complication called diabetic retinopathy. Diabetic retinopathy affects an estimated four out of every ten people with diabetes who are over the age of 40 years. In about, 8% of people, retinopathy progresses to the point where it is vision-threatening.1
What causes diabetic retinopathy?
Diabetic retinopathy is caused by changes to the small blood vessels that supply the retina. Over time high blood glucose levels cause damage to these vessels. In some cases of diabetic retinopathy, blood vessels become damaged and leak blood into the retina, resulting in swelling of the retinal tissue. This specific type of retinopathy is called retinal edema. In other cases, vessels can become blocked (similar to the way a blood clot can block a vessel and cause a stroke or heart attack), cutting off the supply of oxygen and nutrients to the retina. This type of retinopathy is called retinal ischemia. In areas where the retina loses blood supply, it can stop functioning, resulting in a loss of vision. Another problem that occurs with retinal ischemia is one called proliferative retinopathy.2
When the blood supply to the retina is decreased in retinal ischemia, this causes the growth or proliferation of new blood vessels in the retina in an effort to increase blood supply. The proliferation of new vessels occurs on the retinal surface, on the optic nerve, and in other areas of the eye, including the iris. The problem with these new vessels is that they do not re-establish the flow of blood to damaged areas. Instead, they tend to be weak and fragile and will spontaneously bleed into the fluid areas of the eye, causing scaring that further interferes with the normal function of the retina. The vitreous gel that fills the eye and tends to shrink with age can pull on the weak vessels causing them to hemorrhage into the gel and in front of the retina. This blocks light from reaching the retina and causes a blurring of vision and/or darkened areas in the central field of vision.2
If proliferative retinopathy progresses, it can cause further damage to the retina and scaring that can lead to detachment of the retina, a problem in which the rods and cones (the receptors that cover the retina and transform light into electrical signals) are pulled away from the cells beneath them and cease to function. Detachment of the retina can contribute further to the vicious cycle of proliferation of new retinal vessels in other locations, such as the iris.2
What are the symptoms of diabetic retinopathy?
In many instances, as diabetic retinopathy develops, a person may experience blurring of vision or loss of central vision. As proliferative retinopathy develops, hemorrhage of vessels may cause floating lines or webs that interfere with vision and scarring may affect your ability to distinguish between light and dark. In some people, diabetic retinopathy may develop without signs and symptoms. Therefore, it is very important, if you have type 2 diabetes, to get your eyes checked by an ophthalmologist or optometrist experienced in assessing diabetic retinopathy when you are diagnosed and at least every two years after. If there are signs of retinopathy at this initial assessment, you will need to be re-examined more frequently, depending on how rapidly the retinopathy is progressing.3
How can I lower my risk for diabetic retinopathy?
As with many complications of diabetes, you can do a lot to reduce your risk for vision complications, including retinopathy. The most important step you can take is to control your blood glucose. One study found that strict control of blood glucose significantly reduced both the risk of developing diabetic retinopathy and the progression of existing retinopathy.1
Other important steps you can take to lower your risk for retinopathy include controlling your blood pressure, preventing the development of kidney disease, and keeping your cholesterol and other lipids under control.1
What are the tests for determining diabetic retinopathy?
Your ophthalmologist or optometrist have several tests that can be used to determine whether you have diabetic retinopathy and to monitor the progress of the disease. These techniques include:
Dilated and comprehensive eye exam. You initial and follow-up eye exams will involve dilation of the pupils of your eyes using eye drops. With your pupils dilated, your ophthalmologist or optometrist will use a magnifying lens to examine the retina and optic nerve in each eye to look for evidence of damage and other problems. Typically, after a dilated and comprehensive eye exam, your pupils remain dilated for several hours.
Fluorescein dye angiography. TThis technique is typically done by an ophthalmologist and is particularly useful in determining non-proliferative retinopathy. The retina is photographed while a dye flows through the vessels of the retina to highlight leaks or blockages. Dye is typically injected into a vein in your hand.
Ultrasonography. This procedure is typically performed by an ophthalmologist in a clinic or hospital setting. Ultrasound (the use of sound waves to produce a visual image) is used to assess the back of the eye and hemorrhage into the vitreous gel. It can not be used to visualize the retina itself.
Optical coherence tomography (OCT).This procedure is typically performed by an ophthalmologist in a clinic or hospital setting. Similar to computed tomography (CT) scan, OCT is a sophisticated imaging technique that uses x-rays and a computer to build cross-sectional, detailed images of the retina. It is useful in detecting macular edema, scarring on the retinal surface, or retinal detachment.
What are the treatment options for diabetic retinopathy?
There are a variety of treatment options for diabetic retinopathy, beyond preventive measures (blood glucose control and control of high blood pressure). The specific approach to treatment will depend on the nature and severity of the vision problem.
In non-proliferative retinopathy, laser treatment is often the treatment of choice for macular edema. The laser is used to repair points where leakage is occurring and can even be used to reduce swelling. The procedure can be done in an ophthalmologist’s office on an outpatient basis, with eye drops used as anesthesia. Additionally, medications can be injected directly into the vitreous gel to reduce leakage. In cases of severe retinopathy, surgery called vitrectomy can be used to remove and replace the gel of the eye with a clear fluid.
Treatment options for proliferative retinopathy include laser, cryotherapy (therapy that uses targeted freezing of tissue), and vitrectomy. In proliferative disease, the goal of laser therapy is to destroy ischemic areas (areas of vessel blockage) that promote proliferation of new vessels and to destroy abnormal proliferating vessels themselves.