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

The retina is the light-sensitive layer of nerve 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 these signals into the images you see.

The retina, like all parts of the body, needs a constant supply of blood, which flows to the retina through a network of tiny blood vessels.

Over 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.

This can damage the blood vessels that supply the most sensitive part of the retina, called the macula, which distinguishes colours and focus your eyes for tasks such as reading and writing.

If fluid leaks into the macula, it can cause swelling (macular oedema), leading 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 small print in a document.

When retinopathy reaches more advanced stages, some of the blood vessels that supply your retina will become blocked. In an attempt to restore the supply of blood, new blood vessels will start to form.

However, they are unstable and prone to bleeding, which can cause blurred and patchy vision.

Over time, this bleeding can lead to scar tissue forming, which can pull your retina out of position. This is known as retinal detachment, and can lead to 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 diabetic 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 diabetic 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 diabetic 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 and 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, you have a higher risk of developing advanced retinopathy.

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

Read more about preventing high blood pressure.

 

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

The NHS Diabetic Eye Screening Programme 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 symptoms 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.

If you have sight problems in between screening appointments, such as sudden vision loss or deterioration in vision, seek immediate medical advice. Do not wait until your next screening appointment.

The screening procedure

Your invitation for a screening appointment will say where you need to go. This may be your GP surgery, your local hospital or another nearby clinic. The screening appointment should last between 30 and 45 minutes.

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, which takes between 15 and 20 minutes, and photographs of your retina will be taken. There will be a flash of light each time a photograph is taken, but the camera will not touch your eye. 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 objects that are close to you.

Depending on the type of eye drops used, the blurring can last between two and six hours. You won’t be able 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 to wear afterwards.

Side effects

In very rare cases, the eye drops can cause a sudden pressure increase within the eye. This only happens 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 receive your results.

You will not get them 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.

The screening results may show either:

• no retinopathy
• background retinopathy
• degrees of referable 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 needed
• 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.

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 isn’t treated, it can cause blindness.

It’s important for people with diabetes to control their blood sugar levels. 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 
• 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 sudden blindness, it needs to be identified and treated as soon as possible.

The NHS Diabetic Eye Screening Programme aims to reduce the risk of vision loss in people with diabetes. This is done by identifying retinopathy at an early stage and ensuring that 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 can be treated by controlling your diabetes more effectively.

If you have more advanced retinopathy, you may need to have laser surgery or injection therapy 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
• controlling your blood pressure and cholesterol levels

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

You should also keep your blood pressure as 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 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 can 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 at least five portions of fruit and vegetables a day.

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

Giving up smoking will also help lower your blood pressure.

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

One unit of alcohol is equivalent to around 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 chance of effectively treating it and preventing it from progressing.

Read more about the NHS Diabetic Eye Screening Programme.

The Map of Medicine is used by doctors throughout the NHS to determine the best treatment options for their patients. NHS Choices offers everyone in England exclusive and free access to this cutting-edge internet resource, which lets you see exactly what your doctor sees.

The information in the Map has been approved by the UK’s leading clinical experts, is based on the best available clinical evidence, and is continually updated. To take advantage of this unique resource go to:

Map of Medicine: diabetic retinopathy

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 to 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
• 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 listed 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 -more severe and widespread changes are seen in the retina, including bleeding into the retina.
• Stage three: proliferative retinopathy – new blood vessels and scar tissue will have formed on your retina, which can cause loss of vision.
• Stage four: advanced diabetic retinopathy – this can cause either bleeding into the eye, resulting in sudden loss of vision (vitreous haemorrhage) or retinal detachment. This is when the retina pulls away from the wall of the eye and a layer of blood vessels.

Read more about the causes of diabetic retinopathy.

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 (who specialises in eye procedures) to monitor the progress of your retinopathy. 

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

Should maculopathy be detected, you may need more frequent screening with a highly specialised scan (called optical coherence tomography). Additional tests may include a fluorescein angiography, which uses a camera and dye to examine blood flow in the back of the eye.

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.

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 needed (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, as well as 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 you do, your doctor may give you stronger painkillers 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, and some people wear sunglasses until their eyes have adjusted.

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

If you have had previous eye treatment, your eyes may ache afterwards. Over-the-counter painkillers, such as paracetamol, should help.

Photocoagulation can sometimes affect your night vision and peripheral vision (side vision).

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

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

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, stopping the damaged blood vessels leaking.

After the procedure

The pressure in your eye will be measured a few hours after an intravitreal anti-VEGF injection. This may increase after you have had treatment, and more treatment may be needed if it remains at a high level.

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

You may notice an improvement in your vision about a month after the injection, but improvement is usually seen with treatment, over many months. However, it is recommended that injections are given at one-month intervals, until there is no further improvement in 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 needed.

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 that is used 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 hold the retina in place.

The gas or liquid will gradually be absorbed by your body, which will create fluid 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, but wearing an eye patch will allow you to gradually make more use of it.

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 can talk to 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.