Diabetic Retinopathy

Diabetes can affect sight

If you have diabetes mellitus, your body does not use and store sugar properly. High blood sugar levels can damage blood vessels in the retina, the nerve layer at the back of the eye that senses light and helps to send images to the brain.  The damage to retinal vessels is referred to as diabetic retinopathy.

Types of diabetic retinopathy

There are two types of diabetic retinopathy: nonproliferative diabetic retinopathy (NPDR) and proliferative diabetic retinopathy (PDR). NPDR, commonly known as background retinopathy, is an early stage of diabetic retinopathy. In this stage, tiny blood vessels within the retina leak blood or fluid. The leaking fluid causes the retina to swell or to form deposits called exudates.

Many people with diabetes have mild NPDR, which usually does not affect their vision. When vision is affected it is the result of macular edema (pronounced eh-DEEM-uh), macular ischemia (pronounced ih-SKEE-me-uh), or both.

  • Macular edema is swelling or thickening of the macula, a small area in the center of the reina that allows us to see fine details clearly.  The swelling is caused by fluid leaking from retinal blood vessels. It is the most common cause of visual loss in diabetes. Vision loss may be mild to severe, but even in the worst cases, peripheral vision continues to function.
  • Macular ischemia occurs when small blood vessels (capillaries) close. Vision blurs because the macula no longer receives sufficient blood supply to work properly.

PDR is present when abnormal new vessels (neovascularization) begin growing on the surface of the retina or optic nerve. The main cause of PDR is widespread closure of retinal blood vessels, preventing adequate blood flow. The retina responds by growing new blood vessels in an attempt to supply blood to the area where the original vessels closed.

Unfortunately, the new abnormal blood vessels do no resupply the retina with normal blood flow. The new vessels are often accompanied by scar tissue that may cause wrinkling or detachment of the retina.

PDR may cause more severe vision loss than NPDR because it can affect both central and peripheral vision.

Proliferative diabetic retinopathy causes visual loss in the following ways:

Vitreous hemorrhage.  The fragile new vessels may bleed into the vitreous, a clear, gel-like substance that fills the center of the eye. If the vitreous hemorrhage is small, a person might see only a few new, dark floaters. A very large hemorrhage might block out all vision.

It may take days, months or even years to reabsorb the blood, depending on the amount of blood present. If the eye does not clear the vitreous blood adequately within a reasonable time, vitrectomy surgery may be recommended.

Vitreous hemorrhage alone does not cause permanent vision loss. When the blood clears, vision may return to its former level unless the macula damaged.

How is diabetic retinopathy diagnosed?

A medical eye examination is the best way to detect changes inside your eye.

An ophthalmologist (Eye M.D.) can often diagnose and treat serious retinopathy before you are aware of any vision problems. The ophthalmologist dilates (enlarges) your pupil and looks inside of the eye with special equipment and lenses.

If your ophthalmologist finds diabetic retinopathy, he or she may order color photographs of the retina or a special test called optical coherence tomography (OCT) that creates a detailed, three-demsional view of your retina.

How is diabetic retinopathy treated?

The best treatment is to prevent the development of retinopathy as much as possible. Strict control of your blood sugar will significantly reduce the long-term risk of vision loss from diabetic retinopathy. If high blood pressure and kidney problems are present, they need to be treated.

Medical treatment. Injections of medication in the eye can stop the growth of new blood vessels and subsequent bleeding. Medication is necessary for the eye to build new blood vessels and the use of medication causes regression of these fragile and abnormal blood vessels.  Medication injections are also commonly used to reduce the swelling associated with diabetic macular edema.

Vision loss is largely preventable

If you have diabetes, it is important to know that today, with improved methods of diagnosis and treatment, a smaller percentage of people who develop retinopathy have serious vision problems. Early detection of diabetic retinopathy is the best protection against loss of vision.

You can significantly lower your risk of vision loss by maintaining strict control of your blood sugar and blood pressure, and by visiting your ophthalmologist regularly.

When to schedule an examination

People with Type 1 diabetes should schedule an examination within five years of being diagnosed and then yearly. People with Type 2 diabetes should have an exam at the time of diabetes diagnosis and then once a year.

Pregnant women with diabetes should schedule an appointment in the first trimester because retinopathy can progress quickly during pregnancy.

If you need to be examined for eyeglasses, it is important that your blood sugar be consistently under control for several days when you see your ophthalmologist. Eyeglasses that work well when your blood sugar is out of control will not work well when blood sugar is stable.

Rapid changes in blood sugar can cause fluctuating vision in both eyes, even if retinopathy is not present.

You should have your eyes checked promptly if you have visual changes that:

  • Affect either one or both eyes;
  • Last more than a few days;
  • Are not associated with change in blood sugar.

When you are first diagnosed with diabetes, you should have your eyes checked:

  • Within five years of the diagnosis if you are 29 years old or younger;
  • Within a few months of diagnosis if you are 30 years old or older.

Source: American Academy of Ophthalmology