Over 20 million people in the United States have diabetes mellitus. Eye disease is 25 times more common among people with diabetes when compared to the general population. A person with diabetes is at higher risk for developing eye problems such as cataracts and glaucoma. However, the majority of cases of irreversible vision loss caused by diabetes are due to diabetic retinopathy. Diabetic retinopathy is the number one cause of legal blindness in working-aged adults in the United States today.
Diabetes primarily affects the blood vessels that nourish the retina. Tiny leaks develop in the blood vessels (microaneurysms) in early stages of the disease. Retinal hemorrhages (small spots of blood)may also develop. These changes are indicative of non-proliferative diabetic retinopathy. Leaky blood vessels can cause swelling in the retina (diabetic macular edema) which can lead to severe, permanent loss of central vision.
In more advanced stages, the retinal circulation becomes severe enough to lead to abnormal blood vessel growth in the retina (proliferative diabetic retinopathy). These abnormal vessels leak and can cause the vitreous cavity in the back of the eye to fill up with blood. Abnormal blood vessels can also cause scar tissue formation which may lead to retinal detachment.
Anyone with diabetes has a risk of developing diabetic retinopathy. In most cases, retinopathy will develop gradually over years. The longer that someone has had the disease, the more likely they are to develop retinopathy. The risk increases in those who have poorly controlled blood sugars and blood pressure. Pregnancy can accelerate the development of retinopathy. Smokers also tend to develop worse retinopathy than non-smokers.
In early stages of diabetic retinopathy, most people have no symptoms at all. Diabetic macular edema can cause decreased central vision and distortion. Proliferative retinopathy can cause new floaters and more sudden vision changes.
Diabetic retinopathy can only be properly diagnosed with a dilated eye examination. All patients with diabetes need to have a dilated eye exam at least annually. Some patients with more advanced disease will need to be seen more often.
Microaneurysms, retinal swelling, and abnormal blood vessel growth can all be identified during the dilated exam. Color photographs may be obtained to help monitor subtle changes over time. A fluorescein angiogram may be done to look at the retinal circulation in greater detail. If retinopathy is severe enough, treatment may be recommended.
One of the most common treatments is laser. A laser is an instrument that produces a high-intensity beam of light energy. The laser can gently heat the retina in desired locations while leaving the surrounding tissue untouched. Laser surgery is performed in the office and usually causes minimal discomfort.
Diabetic macular edema is the most common indication for laser treatment. Sealing leaky blood vessels with laser can reduce swelling and prevent further vision loss. Studies have shown that laser decreases the risk of persistent macular edema and significant vision loss by about 50%.
Some patients with diabetic macular edema fail to respond to traditional laser treatment. This is especially true if the swelling affects the very central portion of the retina. Steroids and Anti-VEGF agents can be delivered via injection directly into the eye. The treatments may actually help improve vision in some patients.
Laser treatment is also used to treat proliferative retinopathy. Laser spots placed in the peripheral retina can improve the overall retinal circulation. Laser often causes the abnormal blood vessels to regress and helps prevent severe complications such as recurrent bleeding and retinal detachment.
In patients with advanced disease, a vitrectomy is sometimes recommended. Vitrectomy surgery is done in the hospital on an outpatient basis. This involves removing the vitreous gel from the eye, as well as any scar tissue. The gel is replaced with a saline solution, and occasionally an air or gas bubble is used to help the retina heal properly. A successful vitrectomy may help restore vision in many cases.
The most effective strategy in dealing with diabetic retinopathy is prevention. Tight control of blood sugar levels reduces the risk of vision-threatening retinopathy. Proper control of blood pressure and cholesterol, as well as not smoking, is crucial as well.
New medications to help prevent the development and progression of diabetic retinopathy are currently under investigation.