Diabetes and Your Eyes

Diabetic retinopathy is a complication that can affect anyone who has diabetes, whether they are treated with insulin, tablets or diet only. Retinopathy generally has no obvious symptoms until it is well advanced. This is why annual eye examinations are so important for everyone with diabetes. Early detection is the key to successful treatment.

Diabetic retinopathy affects the blood vessels supplying the retina - the 'seeing part' of the eye. Blood vessels can become blocked, leaky or grow haphazardly. This affects the way visual images are received by the retina and, if left untreated, can damage vision.

Diabetic retinopathy is the most common cause of blindness among people aged between 16 and 64 in Britain. It is rarely found in people who have had insulin dependent diabetes for less than five years, but it becomes more common with time. Nearly one in five people with non-insulin dependent diabetes have a significant degree of retinopathy when they are diagnosed. This is because their diabetes may have been present for months or even years before it is diagnosed and blood glucose levels may have been higher than normal for some time.

In this leaflet we explain the different types of retinopathy. An explanation of the medical terms (in italics) can be found in the Glossary at the back of the leaflet.

Blurred vision is common when you are diagnosed with diabetes or just after diagnosis. This is usually caused by the high level of glucose in the blood at this time. Your blood glucose levels may take some weeks to stabilise but once they are under control, your vision will return to normal. If this does not happen, see your doctor.

Your best protection against retinopathy is an eye examination when your diabetes is diagnosed and once a year after that, as part of your annual diabetes review. This is done with your pupils dilated (widened) using special eye drops. This examination ensures that changes in your retina are picked up early and gives you the best chance of successful treatment.

Children with diabetes should start having eye examinations ten years after diagnosis, or from the age of 12 onwards. whichever is sooner.

Don't wait until you notice a change in your vision. Retinopathy frequently has no symptoms until it is well advanced, and by this time treatment is more difficult.

A proper eye examination involves more than reading letters off a wall chart. People with diabetes need to have both retinas examined. This examination is called fundoscopy. It can be done by a diabetologist, an optometrist (ophthalmic optician), an ophthalmologist, or a GP with a special interest in and knowledge of diabetes.

In this examination, the person checking your eyes uses an ophthalmoscope to view the retina and will first dilate your pupils using special eye drops. This allows a clear view of the retina. They may also use a slit-lamp microscope together with a small hand-held retinas imaging lens. A photo of your retina may be taken using a fundus camera. This will show any changes that need to be monitored or treated, and is a useful permanent record for your diabetes team.

The drops used to dilate your pupils during an eye examination can sting at first. You may find it difficult to see clearly for up to several hours after the examination. Your eyes will also be sensitive to bright light for a while afterwards, so wearing sunglasses may help.

If changes in either of your retinas are found, you will be referred to an ophthalmologist. Treatment is most successful when any changes are found early.

Remember - people with diabetes can have free eye examinations at their optician.

The earliest visible changes to the retina are known as background retinopathy. Some of the smallest blood vessels (called capillaries) in the retina become blocked. When this happens, others dilate to compensate, and allow more blood to flow through them.

Dilated capillaries are usually leaky. They allow fluids, called exudates, to get through them into the retina. When many capillaries are blocked, the supply of nutrients like oxygen to the retina is reduced. The capillaries then become fragile and tend to bleed.

Neither these small bleeds, called haemorrhages, nor the leakage will affect vision unless it occurs at the macula - the 'centre of vision' and the part of the eye we use for close, detailed vision.

However, background retinopathy may progress to the more serious forms of retinopathy described below. It needs to be carefully monitored by your GP diabetologist or ophthalmologist.

As more and more capillaries become blocked, larger blood vessels are also damaged and blocked. This means that large areas of the retina will not be getting a proper blood supply. This actually stimulates the growth of new blood vessels to replace the blocked ones. Unfortunately, these do not grow into the areas where they are needed, but proliferate (spread) throughout the retina, and even forward into the vitreous of the eye.

By themselves, these vessels rarely cause obvious symptoms for the person. It is the complications they cause that affect eyesight. These are haemorrhages and scar tissue. Scar tissue is not transparent and may interfere with vision. It tends to contract and, by pulling on the retina, it may cause distortion of vision and later, retinal detachment.

Proliferative retinopathy can occur in all forms of diabetes, but is most common and progresses most rapidly in people with insulin dependent diabetes. The proliferating new blood vessels do not by themselves cause visual symptoms. This is why annual eye examinations are so important.

This is the name given to changes occurring at and around the macula, the sensitive central part of the retina used for detailed vision. Some of the small blood vessels in the retina become blocked and the surrounding ones dilate to compensate for this. The dilated vessels are generally leaky and fluid builds up at the macula, causing swelling. This is called macular oedema. Macular oedema needs to be treated with laser treatment.

Maculopathy can cause blindness and is more common in people with non-insulin dependent diabetes. People with maculopathy usually have some loss of vision and everything may appear blurred, as if looking through a layer of fluid not quite as clear as water.

More research is needed to understand the precise causes of retinopathy. But we do know that the chances of developing it can be greatly reduced if 'normal' blood glucose control is maintained. The 'normal' blood glucose level is between 4 and 8 mmol/l, but your ideal range will be determined by you and your health care professional.

The Diabetes Control & Complications Trial (DCCT), which studied a large group of Americans with insulin dependent diabetes, showed that the risk of developing retinopathy could be reduced by approximately 60% if diabetes is well controlled. Other complications such as kidney disease (nephropathy) and nerve damage (neuropathy) can also be reduced if diabetes is well controlled.

Research shows that any improvement in blood glucose control helps reduce the risk of complications such as retinopathy. If you already have proliferative retinopathy or maculopathy, good control can slow down the worsening of the condition but cannot reverse it.

Retinopathy is treated by laser. In laser treatment, tiny beams of laser light are used to seal leaky blood vessels and prevent them from developing. Laser treatment also destroys abnormal new blood vessels in the retina.

Local anaesthetic eye drops are given. The laser beam is then directed onto the abnormal parts of the retina through a contact lens. This enlarges the view for the person treating you.

Laser treatment is carried out by an ophthalmologist, nearly always as an outpatient treatment, allowing you to go home afterwards. A session of treatment can vary in length from person to person. Ask your ophthalmologist how long this treatment will last and whether you will be expected to come back for more treatment.

Laser treatment is not painful for most people, although a few will experience some pain. Many people say that the first laser sessions are not painful but treatment can become painful if many sessions are needed.

If you feel a lot of pain during the treatment, your ophthalmologist can help you in a number of ways. Only a very few people need to have a general anaesthetic.

If retinopathy is found early, laser treatment is usually very successful and vision can be maintained. It also helps to prevent complications such as haemorrhages, scar tissue and retinal detachment. But laser treatment is not a miracle cure. It can only stop further damage to the retina. It will not restore vision that has already been lost. Laser treatment can maintain and occasionally improve vision in 80% of people with proliferative retinopathy. For those with maculopathy, laser treatment can prevent the condition getting worse. or at least delay it, for 60% of people. Laser treatment has revolutionised the treatment of retinopathy and, together with effective screening, is helping to prevent blindness.

Haemorrhages are bleeds from the tiny blood vessels in the retina which can occur in people with retinopathy. They can be treated effectively by laser treatment but will recur if left untreated. Unfortunately, 'bleeds' can occur whether you are resting in bed or active.

Haemorrhages do not generally affect eyesight in the early stages of retinopathy. But a person's eyesight can be affected later on when new vessels have developed and bleeds are larger. Like so many aspects of retinopathy, each person's experience of a bleed is different. Some people describe seeing black 'floaters' or shapes like spiders. Others say it is like looking through dirty curtains, with blots and patches across their vision.

A bleed is not painful but it is obviously upsetting and frightening to have your eyesight affected, sometimes quite suddenly, in this way. If you have a bleed, contact the ophthalmologist treating you and ask for a prompt appointment.

A vitrectomy operation is done when a haemorrhage does not clear within several weeks, or when the person has advanced proliferative retinopathy or retinal detachment which has not been helped by laser treatment.

This operation is usually done under general anaesthetic and generally requires a stay in hospital. The outcome depends on a number of factors including how long the retina has been detached and how healthy it is.

Some lasers operate with bright flashes of light during a session. In others, the beam is invisible to the patient. Whichever method is used, most people describe feeling slightly dazzled or say that their vision is affected for a while immediately after treatment. It is a good idea to ask a friend or family member to come home with you after a session, and to allow yourself time to rest quietly. You may also wish to bring some sunglasses to wear afterwards, as your eyes may be more than usually sensitive to bright light for a while.

It would be unrealistic to expect all eye problems to be gone the day after treatment. It usually takes about three to four months until the results of treatment become apparent. Some people develop macular oedema after laser treatment. This may cause a temporary worsening of vision but in most people this improves within a few weeks. Maculopathy symptoms rarely improve after treatment but laser treatment does aim to prevent them getting worse.

People who have had many sessions of laser treatment may notice some loss of quality in their sight. This is because laser treatment burns abnormal vessels in the retina and can also damage healthy parts of the retina. Sometimes the edges of vision, called the 'peripheral visual field' may be reduced. This means that driving would be unsafe, even if your central vision is quite good. People may also have difficulty seeing in low light or at night, distinguishing colours, or see shimmering or flashing lights.

Many people having laser treatment have very little visual impairment, and continue their lives normally, working and driving as before. Others, usually those who have advanced maculopathy or vitreous haemorrhages may need to consider registering as blind or partially sighted. The ophthalmologist and other professionals such as a social worker or rehabilitation officer will be able to help,

The possible short term and long term effects of laser treatment should be discussed with your ophthalmologist, who knows your eyes best.

Having retinopathy does not necessarily mean that you have to give up driving. It is important for you to find out what degree of retinopathy you have. If you have background retinopathy that is being monitored, you will probably still be able to drive.

If you have one of the more serious forms of retinopathy - maculopathy or proliferative retinopathy - you need to know that these conditions and their treatment may affect your visual field or night vision, and therefore your fitness to drive. Discuss these points with your health care professional, who knows your circumstances best.

You do not need to tell the DVLA if you have retinopathy or are receiving laser treatment in one eye. However, you will be asked whether you have had laser treatment when your licence comes up for renewal. If you have had laser treatment in both eyes you must tell the DVLA. The DVLA is within its rights to ask you to have a visual field test. If you are unsuccessful in this, your licence will be revoked. Information on how to appeal if you are unhappy about a DVLA decision can be obtained from the Care & Information Services at the BDA.

A. It is quite safe for people with diabetes to wear contact lenses as long as they are removed at any hint of discomfort. You should not put your lenses back in until your eyes have been completely comfortable for at least 24 hours. Disposable lenses are suitable for people with diabetes, except the type which are worn for 24 hours and then thrown away. These are not recommended because they do not allow the eye to get as much oxygen as it needs.

There is some evidence that people with diabetes have a 'lower corneal sensitivity'. This means that if your cornea becomes scratched by wearing contact lenses, you may be less likely to feel any symptoms. Ask your health care professional if you are concerned.

Q. Am I more likely to get cataracts if I have diabetes?

A. A cataract is the hardening and cloudiness of the lens of the eye. People with diabetes are more liable to develop cataracts at an earlier age than those without diabetes. Cataracts only need treating if they affect your eyesight to the point where you are unable to do the things you want to do.

A. Cataracts are removed by an operation. This can be done under local or general anaesthetic and it is usually quite safe for people with diabetes to have the operation. It is quite common nowadays to replace the natural lens in the eye with an implant. Sometimes contact lenses or spectacles are used instead.

Occasionally the ophthalmologist may advise this operation because the cataract prevents laser treatment.

Q. I have had several sessions of laser treatment. How many more will I need?

A. Only your ophthalmologist can answer this question because it depends very much on your individual eye condition. Be sure to ask.

A. Your ophthalmologist will tell you when next to come in as s/he knows what type of retinopathy you have and how it may progress. Even after successful laser treatment, regular monitoring is needed as further changes in the eyes may need treatment. Ask your ophthalmologist about this.

Capillaries: tiny, thin-walled vessels found in the various tissues throughout the body, including the retina.

Cornea: the clear membrane at the front of the eye through which light passes.

Exudates: the name given to fluids which have leaked from blood vessels in the retina. These form hard deposits on the retina which are a feature of retinopathy.

Fundoscopy: another name for the examination of the retinas which is recommended for people with diabetes. Also known as ophthalmoscopy.

Fundus camera: a special eye camera available in some health authorities, which provides a photograph of the retina.

Haemorrhages: bleeds from the capillaries in the retina which can occur in people with retinopathy.

Macular oedema: swelling at the macula, or 'centre of vision', caused by leaky blood vessels In the retina. This is associated with a type of retinopathy called maculopathy.

Optometrist: a professional also known as an ophthalmic optician. Ophthalmic opticians are qualified to carry out the full range of eye examinations, including the annual examination of the retinas recommended for people with diabetes. Dispensing opticians supply glasses and contact lenses according to prescriptions but do not carry out eye tests. A high street optician will generally have both an ophthalmic optician and a dispensing optician on hand.

Ophthalmologist: an eye specialist, generally based at a hospital.

Ophthalmoscope: an instrument used during an eye examination, which shines light into the eye, enabling the eye specialist to see the retina and check for any changes to the blood vessels there.

Retinal detachment: scar tissue can develop on some damaged blood vessels. This can contract if left untreated, causing pressure on the retina and eventually detaching the retina from the back of the eye.

Visual field test: a test to find out the full range of what can be seen from the centre to the sides of vision.

Vitrectomy: an operation carried out when laser treatment has been unsuccessful or is not possible, due to haemorrhage or retinal detachment.

Vitreous: the clear jelly filling the centre of the eye.

Vitreous haemorrhage: bleeding of the fragile new blood vessels that have grown into the vitreous Jelly in front of the retina.

We hope you have found this booklet useful. Retinopathy need not threaten your sight. Your annual eye examination and early treatment, if required, is an effective way of protecting your vision.

The British Diabetic Association has a wide range of leaflets and booklets on all aspects of diabetes. including retinopathy. A number of BDA publications are available in large print and on tape. Call our Diabetes Care Service for details. Balance, our bimonthly magazine, is also available on tape and can be obtained by contacting our Membership Services on 0171 323 1531.

The BDA Careline offers help and support on all aspects of diabetes. We provide a confidential service which takes general enquiries from people with diabetes, their carers and from health care professionals. Our trained staff can give you the latest information on topics such as care of your diabetes, blood glucose level, diet, illness, pregnancy, insurance. driving, welfare benefits and employment.

We produce a wide range of leaflets on all aspects of diabetes, including diet, hypoglycaemia. insurance, diabetes tablets, insulin and employment, many of which are available on tape for people with visual impairment.

If you would like further information on any aspect of diabetes telephone or write to our

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