Diabetic Retinopathy

What is diabetic retinopathy?

If you have diabetes mellitus, your body does not use and store sugar properly. High blood-sugar levels can damage blood vessels in the retina. The damage to retinal vessels is referred to as diabetic retinopathy.

What are the types of diabetic retinopathy?

There are two types, nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR).

RNPD, more commonly known as background retinopathy, is an early stage of diabetic retinopathy. In this stage, tiny blood vessels in the retina leak blood or fluid and the leaking fluid causes the retina to swell or form deposits called exudates. Many people with diabetes have mild NPDR, which usually does not affect their vision. When vision is affected, it is the result of macular edema or macular ischemia.

• Macular edema is swelling or thickening of the macula, a small area in the center of the retina that allows us to see fine details clearly. The swelling is caused by fluid leaking from retinal blood vessels. It is the most common cause of vision loss in diabetics. Vision loss may be mild or severe, but even in the worst cases, peripheral vision continues to function.
• Macular ischemia occurs when small blood vessels (or capillaries) close. Vision blurs because the macula no longer receives sufficient blood supply to work properly.

PDR is abnormal new vessels (neovascularization) growing on the surface of the retina or optic nerve. The main cause of PDR is widespread closure of blood vessels in the retina, which prevents adequate blood flow. The retina responds by growing new blood vessels, attempting to supply blood to areas where the original vessels closed. Unfortunately, the new blood vessels do not supply the retina with normal blood flow. They are often accompanied by scar tissue that may cause wrinkling or detachment of the retina.

PDR can cause more severe vision loss than NPDR because it can affect the central and peripheral vision.

PDR causes vision loss in the following ways:

• Vitreous hemorrhage: The fragile new vessels can bleed into the vitreous, which is the clear, jelly-like substance that fills the center of the eye. If the vitreous hemorrhage is small, a person might see only a few new dark floaters. A very large hemorrhage could block out all vision. It can take days, months, or even years for the blood in the vitreous to dissipate, depending on the amount. If the eye does not clear adequately within a reasonable time, vitrectomy surgery may be recommended.
• Traction retinal detachment: Scar tissue associated with abnormal new blood vessels (neovascularization) can shrink, resulting in wrinkling and pulling of the retina from its normal position. Wrinkling of the macula can cause visual distortion, and more severe vision loss can occur if the macula or large areas of the retina are detached.
• Neovascular glaucoma: Extensive closure of the retinal vessels can cause new, abnormal blood vessels to grow on the iris (colored part of the eye), blocking the normal flow of fluid out of the eye. As a result, pressure in the eye will build up and cause damage to the optic nerve.

How is diabetic retinopathy diagnosed?

A medical eye examination is the only way to find any changes in your eyes. An ophthalmologist can often diagnose and treat serious retinopathy before you are aware of any vision changes. The ophthalmologist will dilate your pupil and examine the inside of your eye with an ophthalmoscope.

If your ophthalmologist finds retinopathy, color photographs of the retina or a special test called fluorescein angiography will be ordered to further evaluate your eye condition.

How is diabetic retinopathy treated?

The best treatment is to prevent development of retinopathy as much as possible. Strict control of your blood sugar will significantly reduce the long-term risk of vision loss. If high blood pressure or kidney problems are present, they need to be treated also.

• Laser surgery: Laser surgery is often used to treat macular edema, PDR, and neovascular glaucoma. For macular edema, the laser is focused on the damaged retina near the macula, to decrease the fluid leakage. The main goal is to prevent further vision loss. Although it is uncommon for people who have blurred vision from macular edema, some may experience partial improvement. For PDR, the laser is focused on all parts of the retina, except the macula. This treatment is called panretinal photocoagulation. Panretinal photocoagulation causes abnormal new vessels to shrink and often prevents them from growing in the future. It also decreases chances that vitreous bleeding or retinal distortion will occur.
• Vitrectomy: In advanced PDR, a vitrectomy may be recommended. During this procedure, which is performed in the operating room, the blood-filled vitreous is replaced with a clear solution. Vitrectomy often prevents further bleeding by removing the abnormal vessels causing the bleeding. If the retina is detached, it can be repaired during the surgery. Surgery usually should be done early because macular distortion or traction retinal detachment will cause permanent visual loss. The longer the macula is distorted or out of place, the more serious the vision loss.