Exams for Patients with Diabetes

Diabetic eye disease is one of the leading causes of blindness in the United States. Unfortunately, in its early stages it may have no symptoms. The most common form of diabetic eye disease is diabetic retinopathy.

The retina is a thin layer of light-sensitive tissue that lines 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 responsible for your central vision, allowing you to see fine details clearly. The surrounding part of the retina, called the peripheral retina, is responsible for your side—or peripheral—vision.

Diabetic retinopathy usually affects both eyes. Diabetic retinopathy progresses in an orderly fashion, from minimal changes to more severe stages if there is no intervention. It is vital to recognize the stages of treatable retinopathy as early as possible in order to have the best visual outcome and avoid irreversible blindness.

Video: Diabetic Retinopathy

This video explains how diabetes can affect the blood vessels within the eye and its symptoms.

Non-Proliferative Diabetic Retinopathy

Excess glucose in the blood causes damage to the blood vessels in the retina. In the early stages this is referred to as non-proliferative diabetic retinopathy (NPDR). Damage to the blood vessels results in the following:

  • Microaneurysms: Small bulges in blood vessels of the retina that often leak fluid.
  • Retinal Hemorrhages: Tiny spots of blood that leak into the retina.
  • Hard Exudates: Deposits of cholesterol or other fats from the blood that have leaked into the retina.
  • Macular Edema: Swelling or thickening of the macula caused by fluid leaking from the retina’s blood vessels. The macula doesn’t function properly when it is swollen.
  • Macular Ischemia: Small blood vessels called capillaries close. The macula can no longer receive enough blood and oxygen to work properly. This results in vision loss and can also lead to proliferative retinopathy, as described below.

All of these forms of NPDR can result in significant vision loss. Macular edema is the most common cause of vision loss in diabetes. Because the retina is composed of delicate nerve tissue, damage may be permanent if it is not diagnosed early and treated appropriately. As the vessels continue to sustain damage, they may close and no longer provide enough oxygen and nutrition to the retina. This results in further complications including proliferative diabetic retinopathy or PDR.

diabetes-1

Proliferative Diabetic Retinopathy (PDR)

Once the capillaries in the retina close, other parts of the eye become ischemic, or deficient in oxygen and nutrients. The body tries to fix this problem by growing new blood vessels on the optic nerve, retina, iris, and filtration angle in the front of the eye. This is referred to as neovascularization.

While this sounds like a good idea, these blood vessels leak, bleed, put traction on the retina, and do not provide adequate blood flow to the retina. This may result in more retinal hemorrhage and edema. It also may result in the following:

  • Vitreous Hemorrhage: Delicate new blood vessels bleed into the vitreous—the gel in the center of the eye—and prevent 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.
  • Traction Retinal Detachment: Scar tissue from neovascularization shrinks, causing the retina to wrinkle and pull 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 enough 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, causing neovascular glaucoma, a particularly severe condition that causes damage to the optic nerve.

diabetes-2

Who is At Risk For Diabetic Retinopathy?

All people with diabetes—Type 1, Type 2 and gestational diabetes—are at risk for diabetic retinopathy. Factors that influence the risk of diabetic retinopathy include:

  • Glucose Control: Keeping your blood glucose under good control can prevent or delay the onset of diabetic retinopathy and slow its progression.
  • Duration of Diabetes: The risk of developing diabetic retinopathy increases over time the longer you have diabetes. After 15 years, about 80 percent of people with Type 1 diabetes will have diabetic retinopathy. After 19 years, about 80 percent of people with Type 2 diabetes will have diabetic retinopathy.
  • Blood Pressure: Effectively controlling blood pressure reduces the risk of retinopathy progression and visual acuity deterioration. High blood pressure, even without diabetes, can damage the blood vessels and cause visual loss.
  • High Cholesterol: High blood lipid levels can lead to greater accumulation of exudates, protein deposits that leak into the retina; this is associated with higher risk of vision loss in diabetics.
  • Pregnancy: If you have gestational diabetes, your risk of developing diabetic retinopathy increases during pregnancy. If you already have diabetic retinopathy, it may progress during pregnancy. However, some studies indicate that there is no increase in long-term progression of the disease.
How Do I Prevent Diabetic Retinopathy?

You can decrease your risk of developing diabetic retinopathy by controlling some of the factors described above. There is extensive research to show that glucose control is the key to prevention.

In addition to controlling your blood sugar, the most important thing you can do is have a comprehensive eye examination at least once a year. At this time there is no technology (i.e., retina photos) that is considered a replacement for a comprehensive eye evaluation.

Diagnosis

Your ophthalmologist diagnoses diabetic retinopathy during a comprehensive dilated eye exam. It is important that your blood sugar is well controlled for a few days prior to your eye exam. When blood glucose is too high (i.e., above about 150) or too low (i.e., below about 70), it interferes with your eye’s ability to focus. This may in turn interfere with the measurements necessary to accurately prescribe new eyeglasses.

The American Academy of Ophthalmology recommends the following diabetic eye-screening schedule for people with diabetes:

  • Type 1 Diabetes (Juvenile Onset): Within five years of being diagnosed and then yearly. In practice it is a good idea to have a complete eye exam as soon as possible after diagnosis and yearly after that.
  • Type 2 Diabetes (Adult Onset): At the time of diabetes diagnosis and then yearly.
  • During Pregnancy: Pregnant women with diabetes should schedule an appointment with their ophthalmologist in the first trimester because retinopathy can progress quickly during pregnancy.
Treatment

Prevention is the key in diabetic retinopathy. Early detection of diabetic eye disease is the best way to maximize treatment efficacy and prevent vision loss. In its early stages, diabetic retinopathy may resolve with glucose control and/or treatment of the retina. Once diabetic retinopathy has reached a certain stage however, treatment may not be able to restore normal vision; it may only slow the progression of vision loss.

  • Laser Surgery
    Laser surgery is the treatment for certain forms and stages of diabetic retinopathy, including macular edema, PDR and neovascular glaucoma. With NPDR, a laser is applied to parts of the macula in order to stop bleeding of abnormal blood vessels and decrease swelling in the macula. In PDR, the laser is applied to all parts of the retina except the macula (called PRP, or panretinal photocoagulation). The goal of this treatment is to cause abnormal new blood vessels (called neovascularization) to shrink and to prevent further neovascularization. It also decreases the chance of vitreous bleeding and retinal detachment. PRP laser has proven to be very effective for preventing severe vision loss from vitreous hemorrhage and traction retinal detachment. Multiple laser treatments over time may be necessary in NPDR and PDR. Again, it is important to remember that laser surgery does not cure diabetic retinopathy and does not always prevent further loss of vision.
  • Vitrectomy Surgery
    Vitrectomy is a surgical procedure performed by a retina specialist in the operating room of a hospital or outpatient surgery center. It is usually performed on an outpatient basis under either a local or general anesthesia. Vitrectomy is done to remove the vitreous gel from the back of the eye, along with any blood and scar tissue that is present. Removing the vitreous allows light rays to focus on the retina again, and removing the abnormal blood vessels often prevents further vitreous hemorrhage. Scar tissue removal helps the retina to heal in its normal location. Laser surgery is often performed during vitrectomy.
  • Medication Injections
    Some types of diabetic retinopathy are treated with either steroid injections or anti-VEGF (vascular endothelial growth factor) injections in the back of the eye. This substance contributes to neovascularization in the eye. The purpose of blocking VEGF is to reduce the growth of new blood vessels in the eye. A retina specialist does these injections in the office. Injections are usually done every four to six weeks.