Diabetic Retinopathy

Diabetic retinopathy, the most common diabetic eye disease, occurs when blood vessels in the retina undergo changes. Sometimes these vessels swell and leak fluid or even close off completely. In other cases, abnormal new blood vessels grow on the surface of the retina.

The retina is a thin layer of light-sensitive tissue that covers the back of the eye. Light rays are focused onto the retina, where they are transmitted to the brain and interpreted as the images you see. The macula is a very small area at the center of the retina. It is the macula that is responsible for your pinpoint vision, allowing you to read, sew or recognize a face. The surrounding part of the retina, called the peripheral retina, is responsible for your side — or peripheral — vision.

Diabetic retinopathy usually affects both eyes. People who have diabetic retinopathy often don’t notice changes in their vision during the early stages of the disease. But as it progresses, diabetic retinopathy usually causes vision loss that cannot be reversed in some cases.

There are two types of diabetic retinopathy:

• Background or Nonproliferative Diabetic Retinopathy (NPDR)

Nonproliferative diabetic retinopathy (NPDR) is the earliest stage of diabetic retinopathy. With this condition, damaged blood vessels in the retina begin to leak extra fluid and small amounts of blood into the eye. Sometimes, deposits of cholesterol or other fats from the blood may leak into the retina.

NPDR can cause changes in the eye, including:

• Microaneurysms: small bulges in blood vessels of the retina that often leak fluid.
• Retinal hemorrhages: tiny blood spots that leak into the retina.
• Hard exudates: They are deposits of cholesterol or other fats from the blood that have leaked into the retina.
• Macular exudates: It is the swelling or thickening of the macula caused by fluid leaking from the retinal blood vessels. The macula does not work properly when it is swollen. Macular edema is the most common cause of vision loss during diabetes.
• Macular ischemia: Small blood vessels (capillaries) close or obstruct. Your vision blurs because the macula does not receive enough blood to work properly.

Many people with diabetes have mild NPDR, which usually does not affect their vision. However, if their vision is affected, it is the result of macular edema and macular ischemia.

• Proliferative Diabetic Retinopathy (PDR)Proliferative diabetic retinopathy (PDR) occurs mainly when many of the blood vessels in the retina obstruct, hindering a sufficient blood flow. In an attempt to supply blood to the area where the original vessels have closed, the retina responds by growing new blood vessels. This is called neovascularization. However, these new blood vessels are abnormal and do not supply the retina with proper blood flow. The new vessels are also often accompanied by scar tissue that may cause the retina to wrinkle or detach.PDR may cause more severe vision loss than NPDR because it can affect both central and peripheral vision. PDR affects vision in the following ways:
  • Vitreous hemorrhage: delicate new blood vessels bleed into the vitreous — the gel in the center of the eye — preventing light rays from reaching the retina. If the vitreous hemorrhage is small, you may see a few new, dark floaters. A very large hemorrhage might block out all vision, allowing you to perceive only light and dark. Vitreous hemorrhage alone does not cause permanent vision loss. When the blood clears, your vision may return to its former level unless the macula has been damaged.
  • Traction retinal detachment: scar tissue from neovascularization shrinks, causing the retina to wrinkle and detach from its normal position. Macular wrinkling can distort your vision. More severe vision loss can occur if the macula or large areas of the retina are detached.
  • Neovascular glaucoma: if a number of retinal vessels are closed, neovascularization can occur in the iris (the colored part of the eye). In this condition, the new blood vessels may block the normal flow of fluid out of the eye. Pressure builds up in the eye, a particularly severe condition that damages the optic nerve.