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Diabetic Retinopathy

Diabetic retinopathy is a common complication of diabetes. It occurs when high blood sugar levels damage the cells at the back of the eye, known as the retina. If it is not treated, it can lead to blindness.

Therefore, it is important for people with diabetes to keep their blood sugar levels under control. Everyone with diabetes who is 12 years old or over should have their eyes examined once a year for signs of damage (see below).

How diabetes can damage the retina

The retina is the light-sensitive layer of cells at the back of the eye. It converts light into electrical signals.

The signals are sent to the brain through the optic nerve and the brain interprets them to produce the images that you see.

To work effectively, the retina needs a constant supply of blood, which it receives through a network of tiny blood vessels.

Over time, a continuously high blood sugar level can cause the blood vessels to become blocked or to leak. This damages the retina and stops it from working.

Read more about the causes of diabetic retinopathy.

Symptoms of diabetic retinopathy

During the initial stages, retinopathy does not cause any noticeable symptoms. You may not realise that your retina is damaged until the later stages, when your vision becomes affected.

Possible symptoms of late-stage retinopathy include:

• shapes floating in your field of vision (floaters)  
• blurred vision 
• reduced night vision
• sudden blindness

If you have diabetes and start to notice problems with your vision, contact your GP or diabetes care team immediately.

Read more about the symptoms of diabetic retinopathy.

Screening for diabetic retinopathy

As retinopathy can cause blindness, it is very important that it is identified and treated as early as possible.

The National Screening Programme for Diabetic Retinopathy aims to reduce the risk of vision loss in people with diabetes. This is done by identifying retinopathy at an early stage and, if necessary, ensuring that appropriate treatment is given.

Everyone with diabetes who is 12 years of age or over is invited for screening once a year.

Read more about how diabetic retinopathy is diagnosed.

Treating diabetic retinopathy

Treatment for retinopathy will depend on the stage the condition has reached.

For example, if retinopathy is identified in its early stages, it may be possible to treat it by controlling your diabetes more effectively.

If you have more advanced retinopathy, you may need to have laser surgery to prevent further damage to your eyes.

Read more about treating diabetic retinopathy.

Preventing diabetic retinopathy

To reduce your risk of developing retinopathy, it is important to control your blood sugar level and keep your blood pressure as close to normal as possible.

Read more about preventing diabetic retinopathy.

Other steps that you can take to help prevent retinopathy include:

• attending your annual screening appointment
• informing your GP if you notice any changes to your vision (do not wait until your next screening appointment)
• taking your medication as prescribed
• losing weight (if you're overweight) and eating a healthy, balanced diet
• exercising regularly 
• giving up smoking (if you smoke)

Symptoms

Diabetic retinopathy does not usually cause any noticeable symptoms until it has reached an advanced stage.

If retinopathy is not identified and treated, it can lead to sudden blindness.

This is why it is very important that you attend regular screening appointments if you have diabetes.

Other symptoms of advanced retinopathy can include:

• shapes floating in your field of vision (floaters)
• blurred vision
• reduced night vision
• sudden vision loss

When to seek medical advice

If you have diabetes, you are 20 times more likely to develop vision problems than the rest of the population. It is vital that you take any problems with your eyes seriously.

Contact your GP or diabetes care team immediately if you experience any of the symptoms above, or if you have any other problems with your eyesight.

Stages of diabetic retinopathy

The signs and symptoms of diabetic retinopathy become more serious as the condition progresses through the following stages:

• Stage one: background retinopathy – tiny bulges (microaneurysms) appear in the blood vessels of your eye, which can leak blood.
• Stage two: pre-proliferative retinopathy – new blood vessels will have formed in the retina, which may bleed.
• Stage three: maculopathy – vision will be blurred and the macula (the most sensitive part of the retina) will be damaged.
• Stage four: proliferative retinopathy – many new blood vessels and scar tissue will have formed in your retina, causing loss of vision. You may also have some degree of retinal detachment. This is where the retina pulls away from the blood vessels that supply it with oxygen and nutrients.

Read more about how diabetic retinopathy progresses.

Causes

Diabetic retinopathy is caused by high blood sugar levels damaging the network of tiny blood vessels that supply blood to the retina.

The retina is the light-sensitive layer of cells at the back of your eye. It converts light into electrical signals that are sent to the brain through the optic nerve. The brain interprets the signals into the images that you see.

The retina, like all parts of the body, requires a constant supply of blood to survive. Blood is supplied to the retina through a network of tiny blood vessels.

Over the course of many years, the blood vessels can be damaged by high blood sugar (glucose) levels that may be present in people with poorly controlled diabetes.

How diabetic retinopathy progresses

During the initial stages of retinopathy, the damage is limited to tiny bulges (microaneurysms) in the blood vessel walls. Although these can leak blood and fluid, they do not usually affect your vision.

Gradually over time, the blood vessels that supply the most sensitive part of the retina, called the macula, can become damaged. The macula enables you to distinguish colours and focus your eyes for tasks such as reading and writing.

Damage to the macula can lead to some loss of vision. You may not be able to see objects clearly at a distance, or see things in fine detail, such as the small print in a document.

When retinopathy reaches its most advanced stage, some of the blood vessels that supply your retina will become blocked. To compensate for this, new blood vessels will start to form in an attempt to restore the supply of blood.

However, as the new blood vessels are unstable and prone to bleeding, they can lead to blurred and patchy vision because the bleeding obscures your sight.

Over time, the bleeding can lead to the formation of scar tissue which can pull your retina out of position. This is known as retinal detachment, and it can result in a darkening of vision, floaters and, if left untreated, blindness.

Risk factors

Several factors increase your risk of developing diabetic retinopathy. These are described below.

Length of time you have had diabetes

The longer you have had diabetes, the greater your chance of developing retinopathy. 

About 90% of people with type 1 diabetes will have some degree of retinopathy after 10 years of having diabetes symptoms.

For people with type 2 diabetes who do not need to take insulin, about 67% will have some degree of retinopathy after 10 years of having diabetes symptoms.

For people with type 2 diabetes who need to take insulin, about 79% will have some degree of retinopathy after 10 years of having diabetes symptoms.

Blood glucose level

If you have diabetes and your blood glucose level is high, you have a higher risk of developing retinopathy.

Blood glucose levels are measured using the HbA1C test. HbA1C is a form of haemoglobin. This is the oxygen-carrying substance that is found in red blood cells and has glucose attached to it.

Small changes in the levels of HbA1C can significantly affect your risk of developing retinopathy. For example, if you have an HbA1C level of 8%, you are 40% more likely to develop retinopathy than someone with an HbA1C level of 7%.

High blood pressure

If you have diabetes and high blood pressure, your risk of developing advanced retinopathy is increased.

Therefore, taking steps to prevent high blood pressure, such as giving up smoking and cutting down the amount of salt in your diet, can help reduce your risk of developing retinopathy.

Read more about preventing high blood pressure.

Diagnosis

It’s important to identify diabetic retinopathy as soon as possible. Screening is an effective way of detecting retinopathy at an early stage.

The National Screening Programme for Diabetic Retinopathy was introduced to reduce the risk of vision loss in people with diabetes.

If retinopathy is detected early enough, it can be effectively treated using laser treatment. Otherwise, by the time the symptoms of retinopathy become noticeable, it can be much more difficult to treat.

Read more about how diabetic retinopathy is treated.

Everyone with diabetes who is 12 years of age or over should have their eyes screened once a year. You should receive a letter inviting you to attend a screening appointment. Contact your GP if you have not received a letter and your appointment is overdue.

Seek immediate medical advice if you have a problem with your vision in between screening appointments, such as sudden vision loss or deterioration in your vision. Do not wait until your next screening appointment.

The screening procedure

Your invitation to attend a screening appointment will provide details about where you need to go. This may be your GP surgery, your local hospital or another nearby clinic.

When you arrive, the procedure will be explained to you. If you have any questions, ask the healthcare professional who is treating you.

You will be given eye drops to enlarge your pupils and photographs of your retina will be taken. There will be a flash of light each time a photograph is taken. Although the light is bright, it should not be uncomfortable.

The eye drops may cause your eyes to sting slightly and after about 15 minutes your vision will be blurred. You may find it difficult to focus on near objects.

Depending on the type of eye drops used, the blurring can last two to six hours. You will be unable to drive home from your appointment.

After the screening procedure, you may also find that everything looks very bright. Therefore, you may want to take a pair of sunglasses with you to wear afterwards.

Side effects

In very rare cases, the eye drops can cause a sudden pressure increase within the eye. This only occurs in people who are already at risk of developing retinopathy.

A pressure increase within your eye will require prompt treatment at an eye unit. The symptoms of a pressure increase are:

• pain or severe discomfort in your eye
• redness of the white of your eye
• constantly blurred vision, sometimes with rainbow halos around lights

If you experience any of these symptoms after screening, go back to the screening centre or your nearest accident and emergency (A&E) department.

Results

After the screening procedure, you will be told when you can expect to receive your results.

You will not receive your results immediately because the photographs will need to be studied by a number of different healthcare professionals, including someone who is trained in identifying and grading retinopathy.

You may need to have a further assessment if:

• the photographs are not clear enough to give an accurate result
• you have retinopathy that could affect your sight and follow-up treatment is required
• you have retinopathy that needs to be checked more than once a year
• other eye conditions are detected, such as glaucoma (a group of eye conditions that affect vision) or cataracts (cloudy patches in the lens of the eye)

If diabetic retinopathy is detected during screening, you will be given information about how far it has progressed. This will determine the type of treatment you receive.

Treatment

Early-stage retinopathy may not need to be treated, but more advanced retinopathy may require laser treatment or injections of medicine into the eye.

While early-stage (background) retinopathy may not need any immediate treatment, you should have your eyes examined every year by an ophthalmologist to monitor the progress of your retinopathy. An ophthalmologist is a specialist in identifying and treating eye conditions.

If stage two (pre-proliferative) retinopathy is detected during screening, you will be referred for a more detailed assessment of your condition.

You may not need any immediate treatment, but you will need to have regular eye examinations (once or twice a year) so the condition can be closely monitored. You may also be given advice about how to control your diabetes more effectively.

Laser treatment may be recommended in more advanced stages of retinopathy if there is a considerable amount of bleeding from the blood vessels in your eye. Alternatively, a new treatment for retinopathy – intravitreal anti-VEGF injections – may be recommended (see below).

If laser treatment is not possible because retinopathy is too advanced, a type of eye surgery called vitreous surgery may be required (see below).

Laser treatment

The type of laser treatment used to treat diabetic retinopathy is called photocoagulation.

A course of photocoagulation usually involves one or more visits to a laser treatment clinic. An ophthalmologist will carry out the procedure, which is usually available on an outpatient basis. This means you will not have to stay in hospital overnight.

Before the procedure, you will be given a local anaesthetic to numb the surface of your eye and eye drops to widen your pupils. A special contact lens will be placed on your eye to hold your eyelids open and allow the laser beam to be focused onto your retina.

Small laser beams will be aimed at the damaged area of your retina. These will seal any blood vessels that are leaking and destroy any abnormal blood vessels that have grown in your retina.

Photocoagulation is not usually a painful procedure but you may feel a sharp pricking sensation when certain areas of your retina are being treated.

If you have had laser treatment in the past, you may experience some discomfort during the treatment. If this is the case, you may wish to ask your doctor for stronger painkilling medication or a mild sedative.

After the procedure 

After laser treatment, your vision may be blurred. However, it should return to normal after a few hours.

Your eyes may also be more sensitive to light, so you may want to wear a pair of sunglasses until your eyes have adjusted.

You will not be able to drive after having laser surgery so ask a friend or relative to drive you home.

Your eyes may ache if you have had previous eye treatment. Over-the-counter painkillers such as paracetamol should help ease the pain.

Sometimes, photocoagulation can damage the outer part of the retina. If this occurs, there is a chance that your night vision and your peripheral vision (side vision) may be affected.

Over 50% of people who have laser treatment for diabetic retinopathy notice some difficulty with their night vision, and 3% have some loss of peripheral vision.

Contact your GP or ophthalmologist if you experience any new problems with your eyes following treatment.

Intravitreal anti-VEGF injections

Intravitreal anti-VEGF injections are often used to treat age-related macular degeneration (ARMD). However, research has shown that they can also improve the vision of people with diabetic retinopathy.

Intravitreal anti-VEGF injections are given by an ophthalmologist on an outpatient basis. A few days before the procedure, you will be given antibiotic eye drops to help prevent infection.

Before the procedure, your eye and the skin around it will be cleaned and the area around your eye will be covered with a drape to keep it sterile (free of infection). A small clip will be used to keep your eye open during the procedure.

You will be given local anaesthetic eye drops to numb your eye so you do not feel any pain during the injection. Medication will be injected into your eye which stops the damaged blood vessels in your eye leaking.

After the procedure

After an intravitreal anti-VEGF injection, the pressure in your eye will be measured. The pressure may increase after the treatment and you may need further treatment if it remains high.

Your vision may be blurred for a few hours after treatment, but it should soon start to improve. You may also be able to see the medication moving around in your eye for a few weeks after the injection.

You should notice an improvement in your vision one month after the injection. However, it is recommended that further injections are given at one-month intervals until there is no further improvement to your vision for three consecutive months.

At this point, treatment should be stopped. Your eyes will need to be checked regularly to assess whether further treatment is required.

The long-term effectiveness of intravitreal anti-VEGF injections is unknown because they have not been used to treat diabetic retinopathy for very long. More research is also needed to determine their effectiveness compared to laser treatment.

Vitrectomy

A vitrectomy is surgery to remove some or all of the vitreous humour. This is the transparent jelly-like substance that fills the space behind the lens of the eye. This type of surgery may be needed if:

• a large amount of blood has collected in the centre of your eye, obscuring your vision
• there is extensive scar tissue that is likely to cause, or has already caused, retinal detachment

During the procedure, the surgeon will make a small incision in your eye before removing the vitreous humour in front of the retina. Any scar tissue will be removed from your retina and tiny clamps may be used to strengthen the position of the retina. The vitreous gel will be replaced with a gas or liquid to help hold the retina in place.

The gas or liquid will gradually be absorbed by your body, which will create new vitreous gel to replace the gel that was removed during surgery.

Vitreous surgery is usually carried out under local anaesthetic and sedation. This means you will not experience any pain or have any awareness of the surgery being performed.

After the procedure

You should be able to go home on the same day or the day after your surgery.

For the first few days, you may need to wear an eye patch at certain times of the day. This is because activities such as reading and watching television can quickly tire your eye. Wearing an eye patch will allow you to gradually make more and more use of your eye.

If gas was used to hold your retina in place, you should not travel by plane until all the gas has been absorbed by your body. Your surgeon will be able to advise you about this.

After vitreous surgery, you are likely to have blurred vision for several weeks. This should improve gradually, although it may take several months for your vision to return to normal.

Prevention

To prevent diabetic retinopathy, it is very important to keep your blood sugar levels under careful control.

You should also keep your blood pressure as close to normal as possible.

Blood sugar levels

In home testing, blood sugar levels are usually measured in millimoles of glucose per litre of blood, or mmol/l. A millimole is a measurement of the concentration of glucose in your blood.

Blood glucose levels vary from person to person and the amount of glucose in your blood will change throughout the day. Therefore, there is no such thing as an "ideal" blood glucose level.

However, a normal blood glucose level is 4–6 mmol/l before meals (preprandial) and less than 10 mmol/l two hours after meals (postprandial). Your diabetes care team will be able to discuss your blood glucose level with you in more detail.

Read more about testing your glucose levels.

High blood pressure

Having high blood pressure can make the blood vessels in your eyes more susceptible to damage and increases your risk of developing advanced diabetic retinopathy.

The most effective way of preventing high blood pressure is to eat a healthy, balanced diet, including plenty of fruit and vegetables (at least five portions a day).

You should also exercise regularly, and do at least 150 minutes a week of moderate-intensity activity.

Giving up smoking, if you smoke, will also help lower your blood pressure because smoking increases blood pressure.

Drinking alcohol can also increase your blood pressure, so stick to the recommended limits. These are no more than 3–4 units of alcohol a day for men and no more than 2–3 units for women.

One unit of alcohol is roughly equivalent to half a pint of normal strength beer, a small glass of wine or a single measure (25ml) of spirits.

Regular screening

If you have diabetes, it is very important that you attend your annual diabetic retinopathy screening appointment. The earlier that retinopathy is detected, the greater the chances of effectively treating it and preventing it from progressing.

Read more about the National Screening Programme for Diabetic Retinopathy.