What is Diabetes?

Estimates suggest that nearly one person in twenty-five in the UK is affected by diabetes mellitus, a condition which means that, due to a lack of insulin, the body cannot cope normally with sugar and other carbohydrates in the diet.

Diabetes can start in childhood, but more often begins in later life. It can cause complications which affect different parts of the body, the eye being one of them. There are two different types of diabetes mellitus:

  • Type 1 diabetes, which can also be referred to as insulin dependent diabetes mellitus (IDDM). This type of diabetes commonly occurs before the age of 30 and is the result of the body producing little or no insulin. Type 1 is controlled by insulin injections.
  • Type 2 diabetes, which can also be referred to as non-insulin dependent diabetes mellitus (NIDDM). This type of diabetes commonly occurs after the age of 40. In this type of diabetes the body does produce some insulin, although the amount is either not sufficient or the body is not able to make proper use of it.

Type 2 diabetes is generally controlled by diet or tablets, although some people in this group will use insulin injections.

Why Diabetics Have an Annual Eye Examination

If you have diabetes, it does not necessarily mean that your sight will be affected. If your diabetes is well controlled then you are less likely to have problems, and if you do then, they may be less serious.

If your diabetes is poorly controlled or unstable then the risks of complications in relation to your vision are higher, and in some cases can result in the loss of sight.

Most sight loss due to diabetes can be prevented, but it is vital that it is diagnosed early. This can only be detected by a detailed examination of the eye. Therefore, this is why we advocate an annual eye examination, as you may not realise you have any issues with your eyes until the damage is irreparable.

How the eye works

In understanding how diabetes can affect the eye, it is worth looking at how the eye works.

Your eye has a lens and an aperture (opening) at the front known as the pupil, which adjusts to bring objects into focus on the retina at the back of the eye. The retina is made up of a delicate tissue that is sensitive to light, rather like the film in a camera. It also contains a fine network of small blood vessels.

At the centre of the retina is the macula, which is a small area about the size of a pinhead. This is the most highly specialised part of the retina and is vital because it allows you to see fine detail for activities such as reading and writing and also to recognise colours. The other parts of the retina give you side vision (peripheral vision). Filling the space in front of the retina is a clear jelly-like substance called the vitreous gel.

How can Diabetes affect the eye?

Diabetes can affect the eye in a number of ways. The most serious eye condition associated with diabetes involves the retina, and, more specifically, the network of blood vessels lying within it. The name of this condition is diabetic retinopathy.

Diabetic Retinopathy

Background diabetic retinopathy

This condition is very common in people who have had diabetes for a long time. Your vision will be normal with no threat to your sight.

At this stage the blood vessels in the retina are only very mildly affected, they may bulge slightly (micro aneurysm) and may leak blood (haemorrhages) or fluid (exudates). The macula area of the retina mentioned earlier remains unaffected.


With time, if the background diabetic retinopathy becomes more severe, the macula area may become involved. This is called maculopathy. If this happens, your central vision will gradually get worse. You may find it difficult to recognise people’s faces in the distance or to see detail such as small print. The amount of central vision that is lost varies from person to person. However, the vision that allows you to get around at home and outside (peripheral vision) will be preserved.

Maculopathy is the main cause of loss of vision and may occur gradually but progressively. It is rare for someone with maculopathy to lose all their sight.

Proliferative diabetic retinopathy

As the eye condition progresses, it can sometimes cause the blood vessels in the retina to become blocked. If this happens then new blood vessels form in the eye. This is called proliferative diabetic retinopathy, and is nature’s way of trying to repair the damage so that the retina has a new blood supply.

Unfortunately, these new blood vessels are weak. They are also in the wrong place – growing on the surface of the retina and into the vitreous gel. As a result, these blood vessels can bleed very easily and cause scar tissue to form in the eye. The scarring pulls and distorts the retina. When the retina is pulled out of position this is called retinal detachment.

Proliferative retinopathy is rarer than background retinopathy.

The new blood vessels will rarely affect your vision, but their consequences, such as bleeding or retinal detachment may cause your vision to get worse. Visual loss in this case is often sudden and severe.

Your eyesight may become blurred and patchy as the bleeding obscures part of your vision. Without treatment, total loss of vision may happen in proliferative retinopathy.

With treatment, sight-threatening diabetic problems can be prevented if caught early enough. However, laser treatment will not restore vision already lost.

What can I do to reduce the risk of site loss?

It has been shown that excellent control of diabetes significantly reduces sight threatening complications. It is also important to monitor and treat high blood pressure. Maintaining excellent diabetic control and normal blood pressures are the two main things that you can do to prevent visual loss from diabetes.

Your diabetic clinic, GP or hospital can monitor your blood pressure at your regular check-ups. High blood pressure can usually be helped by lifestyle changes and medication. Your doctor would be able to discuss with you what would be best in your case.

Nerve damage, kidney and cardiovascular disease are more likely in smokers with diabetes. Smoking increases your blood pressure and raises your blood sugar level which makes it harder to control your diabetes.

Not smoking, good sugar, blood pressure and cholesterol control can all reduce the risk of diabetes related sight loss.

The importance of early treatment

Although your vision may be good, changes can be taking place in your retina that need treatment. Because most sight loss due to diabetes is preventable, remember early diagnosis of diabetic retinopathy is vital.

You should have an eye examination every year without fail, should you notice any deterioration in your vision out with this interval, and you should arrange an eye examination immediately.

Where possible photographs of the retina are used to detect abnormalities. If a problem is found you will be referred to a consultant ophthalmologist (eye specialist) at a hospital eye clinic.

Remember, however, that if your vision is getting worse, this does not necessarily mean you have diabetic retinopathy. It may simply be a problem that can be corrected with glasses.

What is the treatment?

Most sight-threatening problems caused by diabetic retinopathy can be managed by laser treatment if it is given early enough. It is important to realise, however, that laser treatment can only preserve the sight you have – not make it better. The laser, a beam of high intensity light, can be focused with extreme precision so that the blood vessels that are leaking fluid into the retina can be sealed.

If new blood vessels are growing, more extensive laser treatment has to be carried out.

How is the treament carried out?

Treatment is normally carried out in an outpatient clinic and you usually do not have to stay in hospital. Eye drops are used to enlarge the pupils so that the eye specialist can look into your eye. The eye is then numbed with drops and a small contact lens is put onto your eye to stop it blinking. During the treatment you will be asked to move your eyes in certain directions but this can easily be done with the contact lens in place.

Is it painful?

The treatment for sealing blood vessels does not usually cause discomfort. However, the treatment to remove new blood vessels can be a bit uncomfortable, so you may need a pain-relieving tablet at the same time as the eye drops.

There is further pain relief available and so remember:

Do not be afraid to tell the eye specialist if the treatment is painful or if you have found a previous session of laser treatment distressing.

Does the laser treament have side effects?

No treatment is possible without some side effects, but the risks of laser treatment are far fewer than the risks of not having laser treatment.

The treatment for sealing blood vessels has few side effects, although the laser is very bright and causes a temporary reduction of sight which may last an hour or two after the treatment. You may also lose a little central vision or notice the after-effects of the laser as small black spots in your vision.

You may also find you night time and colour vision to be affected.

Occasionally your central vision may not be as good as before so that, for example, print is not as easy to see (this is usually temporary, but sometimes does not improve).

Laser treatment to remove new blood vessels is more complicated.

If you do have any concerns about the side effects of laser treatment you should discuss them with your eye specialist.

What if my eye becomes painful?

After lengthy treatment, most people develop a headache and so taking your usual headache remedy should help. However, if the pain is severe, or if your eyesight gets worse, you should contact your eye specialist immediately. If this is not possible, go straight to the hospital Accident and Emergency (A&E) department.

Research is continuing into diabetes-related eye conditions, and treatment is constantly improving.

What if my sight cannot be fully restored?

If your vision is impaired, it is also worth registering as partially sighted or blind through your eye specialist. This opens the door to expert help and financial benefits.

Other ways Diabetes can affect the eyes

Temporary blurring

This may occur as one of the first symptoms of diabetes although it may also occur at any time when your diabetes is not well controlled. It is due to a swelling of the lens of the eye and will clear without treatment soon after the diabetes is brought under control again.

Important points to remember

  • Early diagnosis of diabetic retinopathy is vital. Have an eye examination every year.
  • Do not wait until your vision has deteriorated to have an eye test.
  • Most sight-threatening diabetic problems can be managed by laser treatment if it is given early enough.
  • Do not be afraid to ask questions or express fears about your treatment.
  • Good sugar, blood pressure and cholesterol control reduces the risk of diabetes related sight loss.
  • Attend your diabetic clinic or GP surgery for regular diabetes health checks, including blood pressure and cholesterol monitoring.