Retina Health Series

Diabetic Retinopathy

One of the most frequent causes of vision impairment in the United States and throughout the rest of the world is diabetic retinopathy. Diabetic retinopathy is a complication of diabetes that causes damage to the blood vessels of the retina—the light-sensitive tissue that lines the back part of the eye, allowing you to see fine detail.

Diabetic retinopathy occurs in more than half of the people who develop diabetes. The longer someone has diabetes, and the less his or her blood sugars are controlled, the more likely the possibility that person will develop diabetic retinopathy.

There are generally 2 causes of vision loss from diabetic retinopathy: diabetic macular edema and proliferative diabetic retinopathy.

Diabetic macular edema is the term used for swelling in the central part of the retina. The macula—or center part—of the retina is used for sharp, straight-ahead vision. It is nourished by blood vessels that are weakened or begin to leak as a result of diabetes. This causes the central part of the retina to become thickened or swollen and can lead to decreased vision.

Diabetes can cause damage to the small blood vessels in the retina, resulting in poor circulation to the retina. Vision may be lost because some of the retina tissue may die as a result of this inadequate blood supply. Unlike skin tissue, which might grow back if it is lost, retina tissue is like brain tissue and does not grow back once it is lost.

Furthermore, poor circulation may lead to the development of growth factors that can cause new blood vessels and scar tissue to grow on the surface of the retina. This stage of diabetic retinopathy is called proliferative diabetic retinopathy (PDR).

It is referred to as “proliferative” because at this stage of the disease, new abnormal blood vessels and scar tissue begin to grow on the surface of the retina. The vessels bleed into the middle cavity of the eye, causing vision loss because light cannot reach the retina. Scar tissue formation can also pull on the retina, detaching it from the back of the eye, resulting in vision loss.

Occasionally, these blood vessels and scar tissue may grow in the front of the eye, where fluid normally exits. When the fluid cannot escape, pressure can build in the eye, creating a rare type of glaucoma (neovascular glaucoma) that can damage vision even further and cause eye pain.

Video: Vision Treatment Breakthrough: People With Diabetic Eye Disease Have a New Option That Could Preserve or Improve Their Vision


Symptoms

It is possible to have diabetic retinopathy for a long time without noticing symptoms until substantial damage has occurred.

Symptoms may include:

  • Blurred or double vision
  • Difficulty reading
  • The appearance of spots—known as “floaters”—in your vision

A person with diabetic retinopathy may also notice a shadow across the field of vision, eye pain or pressure, or difficulty with color perception. Some patients may experience a partial or total loss of vision.

It is important to note that diabetic retinopathy usually affects both eyes.


Causes

The primary cause of diabetic retinopathy is diabetes—a condition in which the levels of glucose (sugar) in the blood are too high. Elevated sugar levels from diabetes can damage the small blood vessels that nourish the retina and may in some cases block them completely. As a result, the blood supply to the retina from these damaged blood vessels is cut off and vision is affected.

In response to the lack of blood supply, the eye may create growth factors that lead to diabetic macular edema, which can lead to decreased vision, or proliferative diabetic retinopathy, which can lead to retinal detachment and vision loss.

Risk factors

Anyone who has diabetes is at risk of developing diabetic retinopathy. There are, however, additional factors that can increase the risk:

  • Disease duration: the longer someone has diabetes, the greater the risk of developing diabetic retinopathy.
  • Poor control of blood sugar levels over time
  • High blood pressure
  • High cholesterol levels
  • Pregnancy in someone with diabetes can also result in changes in the retina

Diagnostic testing

The best way to diagnose diabetic retinopathy is a dilated eye exam. During this exam, the physician places drops in the eyes to make the pupils dilate (open widely) to allow a better view of the inside of the eye, especially the retina tissue.

The physician will look for:

  • Swelling in the retina (diabetic macular edema)
  • Abnormal blood vessels that may predict an increased risk of developing new blood vessels
  • The actual presence of new blood vessels or scar tissue on the surface of the retina (proliferative diabetic retinopathy)

Regular dilated eye exams by an ophthalmologist are important, especially for those who are at a higher risk for diabetic retinopathy or diabetes. If you are over age 50, an exam every 1 to 2 years is a good idea so the physician can look for signs of diabetes or diabetic retinopathy before any vision loss has occurred.

In addition to this exam, there are 3 other diagnostic tools physicians use to detect and manage diabetic retinopathy:

Example of a fundus photograph Source: Retina Image Bank

The physician may take fundus photographs of the back of the eye to facilitate detection of diabetic retinopathy and to document the retinopathy. These photos make it easier for the physician to track the disease on subsequent visits to determine if it is worsening.

To supplement the eye exam, the physician may conduct a retinal photography test called fluorescein angiography. After dilating the pupils, the physician will inject a dye will into the patient's arm which circulates through the eyes. The dye works like a food coloring; however, it does not affect the kidneys and is unlike the dye that is used with MRIs or CAT scans.

Example of fluorescein angiography Source: Retina Image Bank

As the dye circulates, the physician takes pictures of the retina to accurately detect blood vessels that are closed, damaged, or leaking fluid. The pictures are black and white to facilitate the detection of these changes, but the process is not the same as having an x-ray. Prior to examination, ask your physician to discuss the risks and benefits of obtaining these images.

The physician may also suggest an optical coherence tomography (OCT) exam. This test provides cross-sectional images of the retina that show its thickness, helping determine whether fluid has leaked into retinal tissue.

Example of an OCT Source: Retina Image Bank

With proper examinations, the earliest signs of diabetic retinopathy in the retina can be detected before vision loss begins.

If the physician detects signs of diabetic retinopathy, she/he often can determine how frequently follow-up examinations will be required in order to detect changes that would require treatments.


Treatment and prognosis

As a result of major government and industry-sponsored studies, there are many surgical treatments for diabetic retinopathy, including lasers to the retina or miniscule injections of medications into the middle cavity of the eye. These procedures can be done in an office or hospital setting to prevent, treat, or reverse damage from diabetes in the retina.

Research has shown that eye injections often—but not always in combination with laser treatment—result in better vision than laser treatment alone for patients with diabetic macular edema.

The key to these treatments is their ability to block vascular endothelial growth factor (VEGF), a chemical signal in the body that stimulates blood vessel growth. Repeated doses of anti-VEGF medications may be needed to prevent blood vessels from leaking fluid and causing damage to the eye.

Even if not all vision loss from diabetic retinopathy can be prevented or treated at this time, patients usually are able to find ways to live with diminished vision.

If you have been diagnosed with diabetic retinopathy or diabetes and have vision loss, a retina specialist can help you find a support group and suggest access to rehabilitation with a variety of tools to make everyday living with this disease a little bit easier.