An Overview of Diabetic Retinopathy

Proliferative Diabetic Retinopathy
National Eye Institute, National Institutes of Health

Diabetic retinopathy, a complication of diabetes (both type 1 and type 2) that affects the eyes, is the leading cause of blindness among adults in the United States, affecting as many 4.1 million people ages 20 to 74, according to the U.S. Centers for Disease Control and Prevention (CDC). It results from damage to blood vessels in the retina—the light-sensitive layer of tissue at the back of the eye. A major risk factor for this condition is poorly controlled levels of glucose (sugar) in the blood. Diabetic retinopathy affects both eyes, typically progressing through four distinct phases. In the early stages, the condition may produce few, if any, symptoms. As it progresses, symptoms such as floaters and blurred vision may develop which, if caught early, may be treated with careful management of diabetes. More advanced diabetic retinopathy may require laser treatment or surgery. Untreated, diabetic retinopathy can lead to full loss of vision.

Stages and Symptoms

Diabetic retinopathy progresses through four stages each distinguished by the degree and type of damage to the retina.

Stages of Diabetic Retinopathy
Stage Damage Occurring
Mild nonproliferative diabetic retinopathy (NPDR) Small areas of swelling called microaneurysms from which fluid can leak into the retina
Moderate nonproliferative diabetic retinopathy  Changes in blood vessels prevent blood from being delivered to the retina, triggering swelling called diabetic macular edema (DME)
Severe nonproliferative diabetic retinopathy  Increase in blockage depriving the retina of blood needed to grow new vessels; in the areas where this happens proteins called growth factors appear.
Proliferative diabetic retinopathy (PDR) Complete blockage leading to growth of abnormal and fragile blood vessels inside the retina and also the vitreous (the clear jelly-like substance in the center of the eye). Scar tissue can form, which in turn can cause the retina to pull away from the tissue underneath—a condition called retinal detachment that can lead to permanent blindness.

In the early stage of diabetic retinopathy, a person in which the condition is developing won't be aware there's anything wrong with his or her eyes. As it advances, however, symptoms will begin to arise:

  • Floaters (specks, spots, dots, or other shapes that appear to be floating in the field of vision)
  • Blurred vision
  • Focus that goes in and out
  • Impaired color vision
  • Blockage of vision (usually due to a large hemorrhage inside the eye)
  • Difficulty seeing at night
  • Vision loss

Cause

Diabetic retinopathy occurs when blood glucose levels are not controlled adequately. This is because the healthy function of the retina—absorbing light and sending signals through the optic nerve to the brain to be interpreted as what we see—depends on a rich supply of blood vessels. High levels of blood sugar (hyperglycemia) weakens blood vessels, leading to the leakage of fluid into the retina and vitreous and the growth of new, weak blood vessels as described above.

The longer a person has uncontrolled diabetes, the more likely he or she is to develop diabetic retinopathy. Women with diabetes who become pregnant or who develop gestational diabetes are at increased risk, as are people of Hispanic, Native American, or African-American heritage. Smoking also increases the risk of diabetic retinopathy.

Certain complications of diabetes are associated with the development of diabetic retinopathy as well—specifically high blood pressure (hypertension) and high cholesterol.

Diagnosis

The only way to diagnose diabetic retinopathy is with a comprehensive eye examination. According to the National Eye Institute, of the several standard tests done during an eye exam, the ones that will help to home in on a diagnosis of diabetic retinopathy are:

  • Visual acuity, which determines how well a person can see at various distances using an eye chart
  • Tonometry, a measure of pressure inside the eye
  • Retinal exam, in which drops are placed in the eye to cause the pupils to dilate, allowing the doctor a clear view of the retina. He or she will be able to see changes to or leakage from blood vessels; warning signs of leaky blood vessels such as fatty deposits; swelling of the macula; changes in the lens of the eye; and damage to nerve tissue.

Other tests sometimes performed if diabetic retinopathy is suspected or diagnosed include:

  • Optical coherence tomography (OCT), a non-invasive imaging technology used to obtain high-resolution cross-sectional images of the retina 
  • Fluorescein angiogram, in which a fluorescent dye injected into the bloodstream (usually through a vein in the arm) travels through the bloodstream to the vessels in the retina. Pictures can then be taken of the retina and used to zero in on specific problem areas.

Treatment

How diabetic retinopathy is treated depends largely on what stage it has reached. Early on, no treatment may be necessary aside from closely monitoring the health of the eyes and taking steps to improve how well diabetes is being managed. Improving blood sugar control often can slow the progression of damage to the retina.

If diabetic retinopathy reaches an advanced stage, however, any of a number of surgical procedures may be necessary right away. According to the Mayo Clinic, these are:

  • Photocoagulation, also known as focal laser treatment, in which lasers are used to stop or slow leakage from abnormal blood vessels. This treatment, which usually takes place in a doctor's office or eye clinic, isn't likely to return blurry vision to normal but it will help prevent it from worsening.
  • Panretinal photocoagulation, another procedure using lasers that sometimes is called scatter laser treatment. The goal is to shrink abnormal blood vessels. It also can be performed in a doctors' office or eye clinic. It may lead to the loss of some peripheral or night vision.
  • Vitrectomy, in which a tiny incision is made in the eye in order to remove blood from the vitreous as well as scar tissue that may be pulling on the retina. A vitrectomy is done in a surgery center or hospital using local or general anesthesia.
  • Anti-VEGF therapy. This procedure involves the injection of medications called vascular endothelial growth factor (VEGF) inhibitors into the vitreous in the eye to help stop the growth of new blood vessels. VEGF inhibitors work by blocking the effects of growth signals the body sends to generate new blood vessels. Sometimes anti-VEGF therapy is used along with panretinal photocoagulation. While studies of anti-VEGF therapy in the treatment of diabetic retinopathy are promising, this approach is not yet considered standard.

    A Word From Verywell

    As with many complications of diabetes, it's entirely possible to head off diabetic retinopathy and other eye problems associated with the disease before measures such as surgery are needed. The most effective thing you can do is manage your diabetes according to your doctor's instructions. This will mean eating healthfully, with an emphasis on foods that are low in carbs and calories and rich in nutrients; being physically active; if you smoke, kicking the habit; monitoring your blood sugar regularly; and taking insulin or any medications you've been prescribed exactly as your doctor tells you to. You also should be proactive about your eye health: Get regular exams and if you notice any vision changes, see your eye doctor right away.

    Was this page helpful?

    Article Sources