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Patient Education: Diabetic Retinopathy


What is Diabetic Retinopathy?
 

Diabetic Retinopathy is damage to the small blood vessels in the retina (light-sensitive tissue at the back of the eye).  This damage can cause leakage of blood and/or fluid, abnormal blood vessel formation, and ischemia to the retina.

Initially, you may not notice changes in vision even though you may have the early stages of diabetic retinopathy.  However, as the retinopathy progresses, you may start to notice a decline in vision, usually in both eyes.  With advanced retinopathy, you may have severe vision loss or blindness.

What are the stages of diabetic retinopathy?

Nonproliferative diabetic retinopathy (NPDR) and macular oedema: The earliest retinal changes of diabetic retinopathy are a result of damage to small blood vessels in the retina. 

Proliferative diabetic retinopathy: In the later stages of diabetic retinopathy, signals sent by the retina for nourishment cause new blood vessels to form. However, the walls of these blood vessels are thin and fragile.  If these vessels leak, severe vision loss and potential blindness may occur.

Who is at risk for diabetic retinopathy and what preventative measures can be taken?

Individuals with Type I, Type II, and gestational (during pregnancy) diabetes are all at risk.  As there are no symptoms in the early stages of diabetic retinopathy, individuals with diabetes should have a comprehensive dilated exam once a year.  However, depending on the stage of diabetic retinopathy, your optometrist or ophthalmologist may examine your eyes more often.  If you are pregnant with diabetes, you should have the examination as soon as possible.  Whether or not symptoms are present, early detection and appropriate timely treatment can prevent vision loss.

The Diabetes Control and Complications Trial (DCCT) have shown that tight control of blood sugar levels may slow down the onset and progression of retinopathy.  If blood sugar levels are kept in normal ranges, you are not only at a lower risk for diabetic retinopathy complications but also for developing nerve and kidney complications.  Good blood sugar, blood pressure, lipid control and exercise and diet can significantly decrease the progression of retinopathy and are an important part of managing diabetic retinopathy.

What are the symptoms of diabetic retinopathy?

Diabetic retinopathy often has no early warning signs, which is why it important to have your eye thoroughly checked yearly.  As the diabetic retinopathy advances, you may experience blurred vision, which will make it difficult for you to read and drive.  This is often attributed to the swelling of the macula, which is the part of the retina that provides sharp central vision.  This condition is called macular oedema.

With diabetic retinopathy, new blood vessels may grow on the surface of the retina.  These vessels are fragile and may bleed (hemorrhage) into the eye, which may blur the vision.  You may see spots or speck of blood "floating" in your vision.  If this occurs, consult your ophthalmologist immediately.

Sometimes, the spots may resolve resulting in an improvement in vision.  However, due to the fragile nature of the blood vessels, more bleeding may occur.  This can cause severe blurring of vision.  If left ignored, vision loss and potential blindness may occur.  Again, if any of these symptoms occur, visit your eye care specialist immediately.  The earlier you receive treatment, the more likely you will be able to save your vision.

How are diabetic retinopathy and macular edema detected?

Diabetic retinopathy and macular edema are detected during a comprehensive eye examination which includes:

Visual Acuity Testing: The eye chart measures how well you see at various distances.

Tonometry: This test determines the fluid pressure of your eye.  Elevated eye pressure could be a possible sign of glaucoma, which may be a complication of diabetic retinopathy.

Dilated Eye Exam: During this part of the examination, the ophthalmologist or optometrist uses a special magnifying lens to examine you retina and optic nerve for signs of damage, such as leaking blood vessels, macular edema, fatty deposits, areas of ischemia, new blood vessel formation, and any change in shape to the blood vessels.

If the eye specialist suspects macular oedema or leaking of vessels, additional testing may be performed.  These tests include:

Fluorescein Angiography: In this test, a special dye is injected into your arm.  As the dye passes through the blood vessels in your retina, pictures are taken. This test allows the ophthalmologist to find areas of leaking vessels and determine the best treatment.

OCT: OCT, which stands for Optical Coherence Tomography, is a highly specific diagnostic test that allows the ophthalmologist to examine the cell layers of the retina and optic disc in detail.  This diagnostic test is very useful in the diagnosis of macular oedema.

What are the treatment options for diabetic retinopathy?

No treatment is typically needed during the first three stages of diabetic retinopathy, unless macular oedema is present.  The best way to prevent progression of diabetic retinopathy is to control levels of blood sugar, blood pressure, and cholesterol.

Macular Oedema:

Macular oedema can be treated with an intravitreal injection of triamcinolone.  This is steroid injection which reduces the swelling of the macula.

Macular oedema may also be treated with focal grid laser using the Pascal laser.  Your ophthalmologist will place up to several hundred small laser burns in the areas of retinal leakage surrounding the macula.  These burns slow the leakage of fluid and reduce the amount of fluid in the retina.  Focal laser treatment stabilises vision.  It can reduce the risk of vision loss by 50 percent. This treatment is usually completed in one session, however, further treatment may be needed.

Although both treatments have high success rates, they are not a cure for diabetic retinopathy.

Proliferative Retinopathy:

Laser

Laser treatments shrink the abnormal blood vessels and prevent further bleeding.  Your doctor places laser burns in the peripheral areas of the retina, causing the abnormal vessels to shrink.  Due to the high number of laser burns, several treatment sessions are necessary.  Although you may notice some loss of your side vision, laser treatments can preserve the rest of your sight.  Laser treatment may slightly reduce your color and night vision.

Above: Angiogram picture showing diabetic retinopathy treated with laser.

Vitrectomy

If there is severe bleeding in the retina, a vitrectomy may be performed.  During a vitrectomy, blood is removed from the center of the eye.  A vitrectomy is performed under local anesthesia.  Your doctor makes are tiny incision in your eye and inserts a small instrument which is used to remove the vitreous gel that is clouded with blood.  The vitreous gel is replaced with salt solution.

Anti-VEGF

Avastin (Bevacizumab) is an anti-growth factor drug that is delivered through an intravitreal injection.  This drug is used to reduce macular oedema associated with diabetes and also to reduce new vessel growth.