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Diabetes and your Eyes

When darkness descends

RetinaThe Tale of Mr T
Mr T walked into my office late one Friday afternoon. He had suddenly lost his vision during lunch that day. This distressed 30-year-old man explained that he was living alone in Singapore. He had arrived barely one week ago and had minimal social support here. He had left his wife and young son back in India and was working in a computer firm. The only numbers on his handphone were those of his immediate boss and his landlord. He was worried that with his sudden vision loss, he would be unable to cope with living alone.

Mr T had developed diabetes four years ago and was being treated with insulin injections. However, he admitted that his diabetes control was poor. He’d never had any problems with his vision and had never visited an eye doctor. Earlier that day, he started seeing red streaks in his eyes and subsequently his vision gradually became blur and dark. Mr. T had developed proliferative diabetic retinopathy; his sudden vision loss was due to bleeding within his eyes.

The eye works like a camera. Light rays are focused by the lens onto the retina, the “film” of the eye. The retina then sends messages through the nerve into the brain so we can perceive our surroundings. A healthy retina is crucial to good vision, and it is this layer that diabetes affects.

Diabetic retinopathy is caused by changes to the blood vessels at the back of the eyes. In diabetic retinopathy, blood vessels become obstructed, leak and bleed. Often, these changes do not have symptoms and by the time vision is affected, the disease could be advanced.

How does diabetic retinopathy cause vision loss?

The body’s entire circulatory system, from the heart to the smallest blood vessels, is lined by endothelium. An increase in blood sugar causes changes to the endothelial cells and these malfunction. Changes also occur to the shape and coagulation (stickiness) of the red blood cells. The diseased endothelial cells and increased coagulation of the blood are the main causes of vision loss.

How does diabetic retinopathy progress?

Mild to Moderate Diabetic Retinopathy

In the early stages, the walls of the blood vessels weaken and dilate. Smaller blood vessels start to leak proteins and blood. These changes are visible in the eye as yellow spots, bleeding (retina haemorrhage) and dilation of blood vessel walls (micro aneurysms). These protein leakages and retina bleeding can affect the centre of the eye and decrease vision.

An increase in blood sugar also causes the blood to become more sticky. This makes blood flow in a sluggish fashion in the blood vessels. This sticky blood can clog up the vessels, so oxygen and important nutrients can no longer reach that part of the retina. That area of the retina can no longer function and vision is affected.

Severe Diabetic Retinopathy

In later stages, the oxygen-deprived tissues send signal to the body to develop new blood vessels. However, these new blood vessels are thin, weak, tortuous and crumble easily. They break and bleed easily, causing massive haemorrhages in the eyes, blocking out light and vision. This massive bleeding within the eye was the cause of sudden vision loss for Mr T.

Traction Retinal Detachment

Finally, as the bleeding within the eye settles, the scarring tissue causes a tractional pull on the retina and retinal detachment occurs. The retina quickly becomes devitalised and vision loss becomes permanent.

How can diabetic retinopathy be treated?

Management of diabetic retinopathy depends on the stage at presentation. In the early stages, observation and good blood glucose control is sufficient.

As the diabetic retinopathy progress, laser treatments and intra-ocular injection of medication may be useful. In the late stages, management will include surgery.

Diabetes KitHave diabetes? Don’t turn a blind eye!

Diabetes can also cause other eye problems, such as:

Cataracts

Besides affecting the retina, diabetes can also cause changes in the lens. The increased glucose levels within the eye cause the lens to absorb water and swell. This swelling changes the characteristics of the lens proteins and its structure. The lens then loses clarity and transparency; cataracts are thus formed.

Cataracts develop earlier in patients with diabetes and this process is worse when diabetes control is poor. Cataract surgery will have to be performed to improve vision.

Glaucoma

Glaucoma occurs when the pressure in the eye is elevated. This pressure causes damage to the optic nerve and vision is affected.

Open angle glaucoma is the most common form of glaucoma and studies have shown that there is a two-fold increased risk of glaucoma in diabetics.

Neovascular glaucoma is a special type of glaucoma seen in patients with severe diabetic retinopathy. New abnormal blood vessels are seen growing on the iris surfaces. This type of glaucoma is aggressive and often difficult to treat. Treatment options for glaucoma include eye drops, lasers or surgery.

What are some steps to prevent diabetic retinopathy?

Control of blood sugar is crucial in preventing development of diabetic retinopathy. The Diabetes Control and Complications Trial, a major medical study conducted by the United States National Institute of Diabetes and Digestive and Kidney Diseases, has shown that better blood sugar control slows down the progress of the retinal disease. Other steps include:

  1. Have an annual retina screening upon diagnosis of diabetes.
  2. See an eyecare specialist as early as possible when there is a change in vision.
  3. Control other vascular risk factors, such as hypertension, high cholesterol and smoking.
  4. Pregnant women with diabetes should have a retina examination within the first trimester and be followed up closely during the pregnancy.
  5. Get adequate exercise to control blood sugar levels.
  6. Avoid high impact activities such as boxing which may trigger bleeding within the eye.

Diabetes can affect vision in many ways. Some can even lead to blindness. Early detection and intervention can help save the vision of many patients.

What happened to Mr T?

Fortunately for Mr T, his vision improved after surgery and lasers. He was able to continue working at the computer firm and his family also travelled here to help him recover post-surgery. However, he is still at risk of losing his vision and will need continued monitoring by an eye doctor.

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Dr Cheng Jin Fong is an Ophthalmologist at Gleneagles Hospital Singapore. She graduated from the University of Manchester (UK) and completed her ophthalmology training at the Singapore National Eye Centre and National University Hospital. She was awarded the Health Manpower Development Award for a fellowship in Oculoplastics at Royal Brisbane Women and the Royal Children’s Hospital, Australia.
Posted by ezyhealth on Mar 5 2015. Filed under Eye Health. You can follow any responses to this entry through the RSS 2.0. Both comments and pings are currently closed.

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