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- Causes of blindness
Diabetic retinopathy is the sixth most common cause of blindness globally, affecting 1.8 million people. It is caused by damage to the small blood vessels in the retina at the back of the eye as a result of 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. There are 180 people with diabetes worldwide.
Types of diabetes
- Type one 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 two 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
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.
When it comes to diagnosing type two diabetes, common symptoms include:
- Excessive urination
- Constant thirst and/or hunger
- Weight loss
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.
To help prevent type two 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)
- 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.
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.
Sightsavers is currently conducting a pilot survey in Chennai, India to assess the various screening models used and to calculate the most efficient and effective method going forward.