Diabetes is a condition in which the body cannot process sugar or other carbohydrates. We need a hormone called insulin, which is produced in the pancreas, to process carbohydrates and regulate our blood sugar levels. Diabetes occurs when there is a lack of insulin in the body.
There are two main types of diabetes:
Type 1 commonly occurs before the age of 30 and is due to the pancreas producing little or no insulin at all. People with diabetes need regular insulin injections.
Type 2 is more common over the age of 40 and is due either to a lack of insulin or to the body not using insulin efficiently. Some people with type 2 diabetes can control their diabetes just by changing their diet and cutting out or cutting down on certain foods. Others may also need tablets to help stabilise their blood sugar levels. Sometimes insulin injections will still be required in Type 2 diabetes.
Diabetes affects the blood vessels throughout the body and when it affects the small blood vessels in the retina of the eye it is known as Diabetic Retinopathy.
There are different stages of diabetic retinopathy, and we allocate a grade depending on the severity.
Non-proliferative Diabetic Retinopathy
At this stage the walls of the small blood vessels bulge slightly to give microaneurysms. These look like small red dots on the retina. The blood vessels may also leak fluid, exudates or blood and a grade is allocated depending on the quantity of these we see.
There may also be venous beading and dilatation. This is where the larger blood vessels appear thicker and irregular, or IRMA which are abnormalities in the blood vessels themselves. These are more severe and so are allocated a higher grade. People with these signs are more likely to go on to develop proliferative diabetic retinopathy.
Proliferative Diabetic Retinopathy
As diabetic retinopathy progresses, new blood vessels start to grow at the retina of the eye. This occurs because the damaged blood vessels cannot supply enough oxygen to the cells of the retina. New blood vessels are grown to improve the oxygen supply (neovascularisation). Unfortunately, these new blood vessels are much weaker than our normal blood vessels. They grow on the surface of the retina and they bleed very easily causing haemorrhages within the vitreous gel. This can have a sudden and very dramatic effect on your vision, causing blurring or blank patches. This can also lead to scar tissue which can pull on the retina and cause a retinal detachment.
The new blood vessels themselves do not usually affect vision, but the complications they cause can have a very sudden and very serious effect. Without treatment, proliferative diabetic retinopathy can lead to a total loss of vision.
The macular area of the retina is the part of the eye responsible for detailed, central vision. If this area is affected by diabetic retinopathy it can affect your vision. Blood vessels can leak and bleed to cause macular oedema (swelling) which distorts or blurs your vision. If you are diabetic and notice a reduction in your vision, it is important to have a prompt assessment to check this area of the retina.
Diabetic Retinopathy Screening
Diabetic retinopathy does not usually affect your vision until it is quite advanced. Research has shown that early detection of diabetic retinopathy and early treatment is much more effective than waiting until the vision has been affected. As such, Diabetic Retinopathy Screening is carried out throughout the UK. This helps to identify early problems before they start to impact on the vision, meaning that any necessary treatment can be carried out earlier and more effectively.
Diabetic retinopathy screening involves taking detailed photographs of the retina of the eye and monitoring it for any changes. This is not the same as your normal eye examination so if you are diabetic, it is important to make diabetic retinopathy screening appointments on an annual basis.
If treatment is needed, it will usually be in the form of laser treatment. This aims to destroy the areas of the retina that have been damaged, reducing the oxygen demand. As the retina does not then need as much oxygen, the new blood vessels will stop growing. This helps to protect the undamaged areas of the retina that remain, and so helps to preserve your vision. Laser treatment cannot usually restore vision that has already been lost so it is essential that any necessary treatment is carried out before the sight is affected.
Who is at risk of developing diabetic retinopathy?
The main things that increase the likelihood of developing diabetic retinopathy are:
- The length of time you have had diabetes. The longer you have been diabetic the more likely you are to develop any complications including diabetic retinopathy.
- Poor control of blood sugars. If your blood sugar is high or very variable you are much more likely to develop diabetic retinopathy.
- Poor control of blood pressure. High or variable blood pressure increases your risk of developing diabetic retinopathy almost as much as high or variable blood sugars.
- Pregnancy. The hormonal changes in pregnancy can cause very quick changes to your eyes and you can develop diabetic retinopathy very quickly. If you are diabetic and thinking of having a baby, be sure to discuss this with your GP. Diabetic retinopathy screening is carried out more often during pregnancy and is often carried out in the hospital system – your GP will ensure you are given the correct care.
Reducing the risk
You can help to prevent the development of diabetic retinopathy by:
- Keeping your blood sugar well under control.
- Keeping your blood pressure well under control.
- Attending your diabetic appointments with your GP or diabetic nurse to monitor your diabetes.
- Stopping smoking.
- Attending regular eye examinations, including your diabetic retinopathy screening appointments.
Other eye problems
Diabetes can also affect the eyes in other ways:
- Cataract: People with diabetes will often develop cataracts earlier than those who are not diabetic.
- Temporary blurring: If your diabetes is not very well controlled you may experience some blurring of your vision that comes and goes. Sometimes this is the first symptom of diabetes. If your Optometrist finds a large change in your spectacle prescription at an eye examination, and you know your blood sugar is not well controlled at the moment, they may suggest waiting until your diabetes has stabilised before changing your glasses.
- Cranial nerve palsies: A 'palsy' can occur in the nerves that control the eye muscles. If this happens, the nerve does not control the eye muscles properly, which means that the eyes no longer work together as a pair. This leads to a sudden onset of double vision – sometimes just when looking in a particular direction. Often this will resolve itself over a period of a few months, but it needs prompt investigation to rule out anything more serious as palsies can be caused by many different things.