What is diabetic retinopathy?
There are generally two causes of vision loss from diabetic retinopathy – diabetic macular edema and proliferative diabetic retinopathy.
This stage of diabetic retinopathy is called proliferative diabetic retinopathy (PDR). It is referred to as “proliferative” because at this stage of the disease, new, abnormal blood vessels and scar tissue begin to grow on the surface of the retina. The vessels bleed into the middle cavity of the eye, causing vision loss because light cannot reach the retina. In addition, the scar tissue formation can pull on the retina and cause vision loss by detaching the retina from the back of the eye. Occasionally, these blood vessels and scar tissue may grow in the front of the eye, where fluid normally exits. When the fluid cannot escape, pressure can build in the eye, creating a rare type of glaucoma (neovascular glaucoma) that can damage the vision even further and cause the eye to become painful.
The primary cause of diabetic retinopathy is diabetes – a condition in which the levels of glucose (sugar) in your blood are too high. Elevated sugar levels from diabetes can damage the small blood vessels that nourish the retina, and may in some cases block them completely. As a result, the blood supply to the retina from these damaged blood vessels is cut off, and vision is affected.
In response to the lack of blood supply the eye may create growth factors that cause leakage of blood vessels that result in swelling of the retina (diabetic macular edema) or growth of new blood vessels and scar tissue (proliferative diabetic retinopathy). These new blood vessels can bleed into the middle cavity of the eye, and the scar tissue can pull on the retina — sometimes, leading to vision loss if the retina detaches from the back wall of the eye.
Who is at risk for diabetic retinopathy?
Anyone who has diabetes is at risk of developing diabetic retinopathy. There are, however, additional factors that can increase your risk.
One of the most important factors is the duration of your diabetes. The longer you have had it, the greater your risk of developing diabetic retinopathy. Another key factor is how well you have controlled your blood sugar level over time. Another factor that can influence the control of your blood sugar level and the subsequent development of diabetic retinopathy is high blood pressure. It also is possible that cholesterol levels can have an effect on this process, and pregnancy in someone with diabetes can result in changes in the retina as well.
What are the symptoms of diabetic retinopathy?
It is possible to have diabetic retinopathy for a long time without noticing symptoms. Often, diabetic retinopathy will cause changes unnoticeable to a patient until substantial damage already has occurred.
Diabetic retinopathy usually affects both eyes. Symptoms may include blurred or double vision, difficulty reading, or the appearance of spots – known as “floaters” – in your vision. You also may notice a shadow across your field of vision, pain or pressure in your eyes, or difficulty with color perception. Some patients may experience a partial or total loss of vision.
How is diabetic retinopathy treated?
During the first three stages of diabetic retinopathy, no treatment is needed, unless there is macular edema. To prevent progression of diabetic retinopathy, people with diabetes should control their levels of blood sugar, blood pressure, and blood cholesterol.
Proliferative retinopathy is treated with laser surgery. This procedure is called scatter laser treatment. Scatter laser treatment helps to shrink the abnormal blood vessels. The physician places 1,000 to 2,000 laser burns in the areas of the retina away from the macula, causing the abnormal blood vessels to shrink. Because a high number of laser burns are necessary, two or more sessions usually are required to complete treatment. Although you may notice some loss of your side vision, scatter laser treatment can save the rest of your sight. Scatter laser treatment may slightly reduce your color vision and night vision.
Scatter laser treatment works better before the fragile, new blood vessels have started to bleed. That is why it is important to have regular, comprehensive dilated eye exams. Even if bleeding has started, scatter laser treatment may still be possible, depending on the amount of bleeding.
If the bleeding is severe, you may need a surgical procedure called a vitrectomy. During a vitrectomy, blood is removed from the center of your eye.
Macular edema is treated with laser surgery. This procedure is called focal laser treatment. Your doctor places up to several hundred small laser burns in the areas of retinal leakage surrounding the macula. These burns slow the leakage of fluid and reduce the amount of fluid in the retina. A patient may need focal laser surgery more than once to control the leaking fluid. If you have macular edema in both eyes and require laser surgery, generally only one eye will be treated at a time, usually several weeks apart.
Focal laser treatment stabilizes vision. In fact, focal laser treatment reduces the risk of vision loss by 50 percent. In a small number of cases, if vision is lost, it can be improved.