Diabetic retinopathy is a damage to the retina (the light-sensitive inner lining of the back of the eye) associated with the systemic disease diabetes mellitus.   Diabetic retinopathy is the leading cause of blindness among adult Americans.  

What causes diabetic retinopathy?

Diabetes mellitus (also simply called diabetes) is characterized by an altered metabolism of carbohydrates and lipids, resulting in a chronic elevation in blood sugar (hyperglycemia).  Hyperglycemia can lead to long-term changes in the circulatory and nervous systems in the body.  The hyperglycemia experienced by diabetics is related to an inability to produce sufficient insulin, a resistance to the effects of insulin, or both. 

The diagnosis of diabetes is made based on a person's fasting plasma glucose (FPG) levels, (commonly referred to as the fasting blood sugar).  An FPG level of 126 mg/dL or higher indicates the presence of diabetes mellitus.

Diabetic retinopathy is a complication of diabetes in which the tiny blood vessels in the retina are damaged by the disease.  Damage to the retinal blood vessels can cause a number of problems.  In some cases, the damaged blood vessels leak fluid and lipids under the macula, the most sensitive part of the retina that allows us to see details.  The fluid causes the macula to swell, blurring vision.  In other cases, the retinal blood vessels can become blocked, causing portions of the retina to cease functioning because of lack of oxygen and nutrients.

In its advanced stage, diabetic retinopathy is characterized by the growth of fragile blood vessels along the retina and into the clear, gel-like vitreous that fills the inside of the eye.  These tiny blood vessels can break open and bleed, causing vision to be obscured and permanent damage to the retina.

How common is diabetic retinopathy?

Over 18 million Americans - approximately 6.3 percent of the population - have diabetes.  All people with diabetes - those with Type 1 diabetes (previously called juvenile onset diabetes) and those with Type 2 diabetes (previously called adult onset diabetes) - are at risk of developing diabetic retinopathy. 

According to the National Eye Institute, nearly half of all people with diabetes will develop some degree of diabetic retinopathy in their lifetime.  The longer a person has diabetes, the more likely they are to have diabetic retinopathy.  After having diabetes for 15 years, about 80% of Type 1 diabetics will have some degree of retinopathy.   

Risk factors for diabetes (and therefore diabetic retinopathy) include:

• Obesity (more than 20% heavier than your ideal body weight)

• A family history of diabetes

• Hypertension (blood pressure of 140/90 or higher)

• Having a high density lipoprotein (HDL or "good cholesterol") reading of 35 mg/dL or lower

• Elevated triglyceride levels (250 mg/dL or higher)

• Having been diagnosed with gestational diabetes during a pregnancy or having given birth to a baby weighing 9 pounds or more

• Being a member of a high risk ethnic group (Type 2 diabetes is more common among Native Americans, African Americans, and Hispanic Americans)

What are the symptoms of diabetic retinopathy?

Diabetic retinopathy often has no early warning signs.  There is no pain, and vision may remain unaffected until the disease becomes severe. 

If leaking blood vessels cause swelling of the macula (called macular edema) central vision will become blurred, making it hard to see clearly when driving or reading.  Vision may get better or worse during the day, depending on the degree of edema.

If leaking blood vessels cause bleeding in the eye, symptoms will vary based on how much blood is involved.  With relatively limited bleeding, the visual disturbance may appear as spots floating in your visual field.  These spots may go away after a few hours. 

If bleeding is more severe, vision may suddenly become severely clouded.  This can occur overnight during sleep.  It may take months for the blood to clear from the eye, or it may not clear at all.

What is the treatment for diabetic retinopathy?

There are two treatments for diabetic retinopathy - laser surgery and vitrectomy.  These surgical treatments are typically used only when diabetic retinopathy is in an advanced stage.

Laser surgery can be used to seal leaking blood vessels in the retina or to shrink fragile new blood vessels.  Laser surgery is typically performed on an outpatient visit or in the doctor's office.  You will be able to go home the same day.

Laser surgery usually cannot restore vision that has already been lost.  Therefore, early detection of diabetic retinopathy is the best way to prevent serious vision loss from the disease.

If a significant amount of blood has leaked into the vitreous, a vitrectomy may be required to restore vision.  In this procedure, the surgeon makes a tiny incision in the sclera and gently suctions out the bloody vitreous, replacing it with a sterile clear fluid.  After the surgery, you may be able to go home the same day or you may be asked to stay in the hospital overnight.    

Can diabetic retinopathy be prevented?

It's estimated that 50% of people with Type 2 diabetes are unaware of their condition.  In some cases, detection of their diabetes takes place during a routine eye exam. 

During a routine eye exam, your eye doctor will examine your retina and look for early signs of diabetes.  These signs include:

1.      Small hemorrhages from leaking blood vessels

2.      Macular edema

3.      Areas of pale retina (called cotton wool spots) where blood supply has been obstructed

4.      Yellowish, waxy-appearing deposits in the retina caused by localized retinal edema.

If your eye doctor (Optometrist or Ophthalmologist) detects signs of early diabetic retinopathy, they may refer you to an internist and/or an ophthalmologist who is a retinal specialist for additional testing and/or treatment.

Most cases of Type 2 diabetes can be managed through proper diet and exercise.  Daily exercise and a high fiber diet with restricted amounts of carbohydrates, cholesterol, and saturated fat can improve overall health and help lower blood glucose levels.  In cases where diet and exercise cannot sufficiently reduce blood glucose levels, oral medicines or injections of insulin may be added to the treatment plan.

If you have been diagnosed with diabetes, you should have an annual dilated eye exam to monitor the health of your retina.  (Depending on your individual needs, your eye doctor may recommend more frequent exams.)  Annual eye exams are also recommended if you are not a diabetic but have one or more of the risk factors for diabetes listed above.  

Ed. note:  For more information about diabetes, visit the National Diabetes Information Clearinghouse (NDIC) website at http://diabetes.niddk.nih.gov/index.htm.