The primer on diabetic retinopathy

By Dr Nisar C Abdulla

With World Diabetes Day celebrated throughout the globe on November 14, one simply cannot ignore the escalating number diabetes cases and various other complications this condition causes. Worldwide, there are 387mn people who at the moment suffer from this lifestyle disease and the number is increasing. Statistics reveal that the Middle East and North Africa ((Mena)  region accouts for 9% of the total cases worldwide.

Speaking about the medical complications of diabetics, Dr  Nisar C Abdulla of Aster Medical Centre, C–Ring Road clinic, added: “If diabetes is not treated, it can lead to many other health complications. Diabetes affects many organs, including your heart, blood vessels, nerves, eyes and kidneys. Controlling your blood sugar levels can help in preventing these complications. Although long-term complications of diabetes develop gradually, they can eventually be life-threatening.”

What is diabetic retinopathy?

Diabetic retinopathy is the most common diabetic eye disease and a leading cause of blindness amongst adults. It is caused by changes in the blood vessels of the retina.

In some cases of diabetic retinopathy, blood vessels may swell and leak fluid. In other cases, abnormal new blood vessels grow on the surface of the retina. The retina is a light-sensitive tissue at the back of the eye. If a person is inflicted with diabetic retinopathy, at first he/she may not notice changes to your vision. But over time, diabetic retinopathy can get worse and cause vision loss. Diabetic retinopathy most of the time affects both eyes. There are four stages of diabetic retinopathy. They are as follows:

l Mild Nonproliferative Retinopathy: This is the first stage. At this stage, microaneurysms occur. They are small areas of balloon-like swelling in the retina’s tiny blood vessels.

l Moderate Nonproliferative Retinopathy: As the disease progresses, some blood vessels that nourish the retina are blocked.

l Severe Nonproliferative Retinopathy: In this stage, many more blood vessels are blocked, depriving several areas of the retina with their blood supply. These areas of the retina send signals to the body to grow new blood vessels for nourishment.

l Proliferative Retinopathy: At this advanced stage, the signals sent by the retina for nourishment trigger the growth of new blood vessels. This condition is called proliferative retinopathy. These new blood vessels are abnormal and fragile. They grow along the retina and along the surface of the clear, vitreous gel that fills the inside of the eye. By themselves, these blood vessels do not cause symptoms or vision loss. However, they have thin, fragile walls. If they leak blood, severe vision loss and even blindness can result.

Symptoms

In the early stage of this condition, there are no symptoms and no pain. Blurred vision may occur when the macula — the part of the retina that provides sharp central vision — swells from leaking fluid. This condition is called macular edema. If new blood vessels grow on the surface of the retina, they can bleed into the eye and block vision.

Symptoms when bleeding occurs

At first, you will notice a few specks of blood, or spots, “floating” in your vision. If spots occur, see your ophthalmologist as soon as possible. Immediate treatment is required before more serious bleeding occurs. Hemorrhages tend to happen more than once, often during sleep.

Sometimes, without treatment, the spots clear, and the sight will become better. However, bleeding can reoccur and cause severely blurred vision. Eye needs to be examined by the ophthalmologist 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.

Detection

 Dr Nisar says diabetic retinopathy and macular edema are detected with the help of various eye exams. They are:

l Visual acuity test: This eye chart test helps in measuring how well you see at various distances.

l Dilated eye exam: Drops are placed in your eyes to widen, or dilate, the pupils. This allows the ophthalmologist to see more of the inside of your eyes to check for signs of the disease. Your ophthalmologist uses a special magnifying lens to examine your retina and optic nerve for signs of damage and other eye problems. After the exam, your close-up vision may remain blurred for several hours.

l Tonometry: An instrument measures the pressure inside the eye. Numbing drops may be applied to your eye for this test.

An ophthalmologist will always check for early signs of this disease. They are:

l Leaking blood vessels.

l Retinal swelling (macular edema).

l Pale, fatty deposits on the retina—signs of leaking blood vessels.

l Damaged nerve tissue.

l Any changes to the blood vessels.

Causes and risk factors

Fragile, abnormal blood vessels can develop and leak blood into the centre of the eye, blurring vision. This is proliferative retinopathy and is the fourth and most advanced stage of the disease. Fluid can leak into the centre of the macula, the part of the eye where sharp, straight-ahead vision occurs. The fluid makes the macula swell, blurring vision. This condition is called macular edema. 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.

Risks that cause diabetic retinopathy

People affected with diabetes — both type 1 and type 2 — are at high risk. That is the reason it is mandatory that every person with diabetes should get a comprehensive dilated eye test on annual basis. The longer someone has diabetes, the more likely he or she will get diabetic retinopathy. If you have diabetic retinopathy, your doctor can recommend treatment to help prevent its progression. For a pregnant woman, diabetic retinopathy may be a problem. To protect vision, every pregnant woman with diabetes should have a comprehensive dilated eye exam as soon as possible. Your doctor may recommend other additional exams during your pregnancy.

Prevention and protection

Getting a comprehensive dilated eye exam on yearly basis is necessary and if you have been detected with diabetic retinopathy, you may need an eye examination more often. People with proliferative retinopathy can reduce their risk of blindness by 95% with timely treatment. Better control of blood sugar levels slows the onset and progression of retinopathy. Better control also reduces the need for sight-saving laser surgery. Studies have also 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,” says Dr Nisar.

He also added: “Educating yourself and communicating with your doctors is necessary. The general medical doctor/endocrinologist and an eye care professional can give the tools required to be able to learn more about diabetes and the effect it has on your vision.”

What are the treatments available?

During the first three stages of diabetic retinopathy, no treatment is needed, unless macular edema has been detected. 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 surgery. This procedure is called scatter laser treatment.

“Scatter laser treatment helps to shrink the abnormal blood vessels. The doctor places 1,000 to 2,000 laser burns in the areas of the retina away from the macula, causing the abnormal blood vessels to shrink. Because a high number of laser burns are necessary, two or more sessions usually are required to complete treatment. Although you may notice some loss of your side vision, scatter laser treatment can save the rest of your sight. Scatter laser treatment may slightly reduce your colour vision and night vision,” says Dr  Nisar.

Scatter laser treatment works better before the fragile, new blood vessels have started to bleed. That is why it is important to have regular, comprehensive dilated eye exams. Even if bleeding has started, scatter laser treatment may still be possible, depending on the amount of bleeding. If the bleeding is severe, you may need a surgical procedure called a vitrectomy.

During a vitrectomy, blood is removed from the centre of your eye. Till date, both treatments are very effective in reducing vision loss. People with proliferative retinopathy have less than a 5% chance of becoming blind within five years when they get timely and appropriate treatment. Although both treatments have high success rates, they do not cure diabetic retinopathy.

Dr Nisar C Abdulla recently received Postgraduate Diploma in Diabetes from the University of Leicester, UK.