Diabetic retinopathy

What is diabetic retinopathy?

Sinaida is being treated for diabetes at Mafinga District Hospital, Tanzania © Suzanne Porter / Sightsavers

Diabetic retinopathy is a complication of the eye cuased by diabetes.

What is diabetes?

Diabetes is a chronic disorder, meaning it is long-lasting or recurrent. It is characterized by a lack of insulin, or inability to use insulin effectively. This results in hyperglycaemia, an excess of glucose in the bloodstream. Over time, diabetes can also damage the heart, blood vessels, kidneys, and nerves, and increases the risk of cataract.

Types of diabetes

• Type 1 is rare and the onset is usually rapid and before the age of 20. It is caused by the pancreas not producing enough insulin, and is controlled by insulin injections. The cause is not known.

• Type 2 accounts for at least 90% of diabetes in the world today, and is often bought about by poor diet, obesity and a lack of exercise, or a genetic predisposition. It develops more slowly, and is caused by inadequate amounts of insulin, or the body being unable to use its supply of insulin effectively.

• Gestational diabetes is a third type, which affects pregnant women. It is thought that the hormones produced during pregnancy reduce a woman's receptivity to insulin, resulting in high blood sugar.

Facts about diabetes

• The World Health Organization estimates that 180 million people worldwide have diabetes
• This is likely to double by 2030
• Up to 50% do not know they have the condition
• Diabetes increases the risk of blindness x 25 times

New blood vessels growing from the optic disc © London School of Hygiene and Tropical Medicine

How diabetes affects the eye

Diabetes can affect retinal blood vessels in two ways: they can become leaky, or they can become blocked. If blood vessels near the central area of the retina leak, sight loss can result.

The small blood vessels in the retina can also become blocked, which can lead to loss of vision. If peripheral blood vessels become blocked this can stimulate the growth of new, abnormal ones ("proliferative retinopathy") which in turn can bleed, or lead to detachment of the retina.

As a general rule, the risk of retinopathy increases the longer the person has had diabetes. However, not all diabetics will develop retinopathy.

Diagnosis and treatment

Ramenathan is an optometrist at Sankara Hospital, India, who spreads awareness about diabetic retinopathy at screening camps © Fabienne Fossez / Sightsavers

When it comes to diagnosing type 2 diabetes, common symptoms include:

• excessive urination
• constant thirst and/or hunger
• weight loss
• fatigue

Some people do not realise they have diabetes, and the first they know about it is when they develop complications with their eyesight.

Diabetic retinopathy often has no symptoms at the early stages and the vision can be quite normal. Symptoms of diabetic retinopathy include gradual or sudden painless loss of vision in one or both eyes.

Prevention

To help prevent type 2 diabetes, people should:

• Achieve and maintain a healthy body weight
• Be physically active - at least 30 minutes of regular, moderate-intensity activity on most days

To help reduce the risk of retinopathy for people who already have diabetes, people should:

• Have good control of blood sugar (using the treatment they have been prescribed, in combination with a low carbohydrate diet)

• Even when patients are screened it can be difficult to detect early stages of diabetic retinopathy © Suzanne Porter / Sightsavers

  Have good control of blood pressure
• Reduce factors that are known to damage blood vessels, such as smoking
• To help reduce the risk of visual loss from diabetic retinopathy, diabetics should have regular eye examinations even if their vision is normal.

Treatment

At the moment the mainstay of treatment for diabetic retinopathy is laser treatment, which can reduce leaking from retinal blood vessels. Laser treatment is also effective at treating proliferative retinopathy, when abnormal blood vessels have formed. This treatment is more effective at preserving sight if the retinopathy is detected and treated early.

In severe proliferative retinopathy, some people need an operation called a vitrectomy to restore vision.