What is Diabetic Retinopathy?
Diabetic retinopathy is the most common diabetic eye disease and is one of the main causes of blindness in adults. It is caused by changes in the blood vessels of the retina. In some people with diabetic retinopathy, blood vessels may swell and leak fluid. In other people, abnormal new blood vessels grow (indicated by blue arrows in the figure) on the surface of the retina.
What are the Symptoms of Diabetic Retinopathy?
If you have diabetic retinopathy, at first you may not notice any changes to your vision. But over time, diabetic retinopathy can get worse and cause vision loss. Diabetic retinopathy usually affects both eyes but may be asymmetrical. Blood vessels damaged from diabetic retinopathy can cause vision loss in two ways:
Fragile, abnormal blood vessels can develop (this is called proliferative retinopathy) and leak blood into the retina. At first, you may only see a few specks of blood, or spots, “floating” in your vision. If spots occur, see your eye doctor as soon as possible. You may need treatment before more serious bleeding occurs. Hemorrhage (bleeding) tends to happen more than once, often during sleep. Sometimes, without treatment, the spots clear, and you will see better. However, bleeding can recur and cause severely blurred vision. You need to be examined by your eye doctor at the first sign of blurred vision, before more bleeding occurs. If left untreated, proliferative retinopathy can cause severe vision loss and even blindness. Also, the earlier you receive treatment, the more likely treatment will be effective.
This is proliferative retinopathy and if not treated on time can also lead to more serious conditions such as (tractional) retinal detachments whereby these abnormal blood vessels start pulling the retina off. Once the retina gets pulled off it no longer works (ie. you can't see), and in most cases you will need retinal surgery to fix this to avoid permanent vision loss.
Fluid can leak into the center of the macula, the part of the eye where sharp, straight-ahead vision occurs. The fluid makes the macula (See Retinal Anatomy) swell, blurring vision. This condition is called macular oedema. It can occur at any stage of diabetic retinopathy, although it is more likely to occur as the disease progresses. About half of the people with proliferative retinopathy also have macular edema.
How do you Detect Diabetic Retinopathy?
Diabetic retinopathy and macular edema are detected during a comprehensive eye check that includes:
Visual acuity test: this eye chart test measures how well you see at various distances
Tonometry. An instrument measures the pressure inside the eye. Numbing drops may be applied to your eye for this test.
Optical Coherence Tomography (OCT) (Figure): this is a special scan of the retina which displays a cross-sectional view of the retina and can calculate exactly how swollen your retina is.
If your eye care doctor believes you need treatment for macular edema, s/he may suggest a fluorescein angiogram. In this test, a special dye is injected into your arm. Pictures are taken as the dye passes through the blood vessels in your retina. The test allows your eye doctor to identify any leaking blood vessels and recommend treatment.
** It is important to advise your doctor of any allergies you may have before this test
How do you Treat Diabetic Retinopathy?
During the early stages of diabetic retinopathy, no treatment is needed unless you have macular edema. To prevent progression of diabetic retinopathy, people with diabetes should control their levels of blood sugar, blood pressure, and blood cholesterol.
Proliferative retinopathy is treated with laser (Fig.) This procedure is called Pan-Retinal Photocoagulation (PRP). PRP helps to shrink the abnormal blood vessels. Your doctor places about 3,000 to 4,000 laser burns in the areas of the retina away from the macula. Because a high number of laser burns are necessary, two or more sessions per eye are usually required to complete course. PRP may slightly reduce your night-time and side (peripheral) vision. However, it is debatable as to whether this would already be damaged due to the diabetes. As such, most people do not notice such symptoms. Furthermore, the benefits of performing PRP laser far out-weigh the risks as it conserves the rest of your sight.
PRP also works better before the fragile, new blood vessels have started to bleed. That is why it is important to have regular, comprehensive dilated eye check-ups. Even if bleeding has occured, PRP may still be possible, depending on the amount of blood in your eye. If the bleeding is severe, you may need a surgical procedure called a vitrectomy. During a vitrectomy, blood is removed from the center of your eye and laser can be done during surgery. A gas or oil bubble may need to be inserted at the end of surgery and this will blur your vision while it remains in your eye. (See Vitrectomy for more details)
Lastly, if you still have difficulty, magnifying lenses may make reading easier - just let your doctor know and they can assess you or send you to an optometrist or 'Low-Vision Aid' clinic for further evaluation of what tools would suit you best.
How can you Avoid Diabetic Retinopathy?
Often there are no symptoms in the early stages of the disease, nor is there any pain. Don’t wait for symptoms. Be sure to have a comprehensive dilated eye check-up at least once a year.
The Diabetes Control and Complications Trial (DCCT) showed that better control of blood sugar levels slows the onset and progression of retinopathy. The people with diabetes who kept their blood sugar levels as close to normal as possible also had much less kidney and nerve disease. Better control also reduces the need for sight-saving laser.
This level of blood sugar control may not be best for everyone, including some elderly patients, children under age 13, or people with heart disease. Be sure to ask your doctor if such a control program is right for you.
Other studies have shown that controlling elevated blood pressure and cholesterol can reduce the risk of vision loss. Controlling these will help your overall health as well as help protect your vision. Maintaining good control of your blood sugar levels will also means you are more likely to have a heart attack, stroke or other diabetes-related complications.
Diabetes is a long-term condition which can lead to serious health problems. If you have diabetes, you have too much glucose in your blood and if it builds up in your blood it can damage your vessels. This can cause damage to your feet, kidneys, eyes, and other parts of body. The longer you have diabetes and the poorer your sugar control, the more likely it is you will suffer these problems. When it affects the retina, we call this diabetic retinopathy.