Diabetic retinopathy

Diabetic retinopathy is a complication of diabetes. High blood sugar levels damage the back of the eye (the retina). If it isn't diagnosed and treated, it can cause blindness.

It usually takes several years, though, for diabetic retinopathy to reach a stage where it could threaten your sight. To lower the risk of that happening, people with diabetes should:

• keep their blood sugar levels, blood pressure and cholesterol under control
• go to their diabetic eye screening appointments, because annual screening for people with diabetes aged 12 and over helps pick up and treat any problems early on

The retina is the light-sensitive layer of cells at the back of your eye. It turns light into electrical signals and sends them to the brain, and the brain turns those signals into the images you see.

The retina needs a constant supply of blood, and it gets this through a network of tiny blood vessels. If your blood sugar level stays high over a long time, it can damage these vessels. This is how diabetic retinopathy develops, and it happens in three main stages:

• tiny bulges form in the blood vessels, which may bleed slightly but don't usually affect your vision (this is called background retinopathy)
• the blood vessels go through more severe and widespread changes, including more significant bleeding into the eye (this is called pre-proliferative retinopathy)
• scar tissue and new blood vessels develop on the retina, and these new vessels are weak and bleed easily (this is called proliferative retinopathy, and it can cause some loss of vision)

But if a problem with your eyes is picked up early, lifestyle changes and/or treatment can stop it getting worse.

Anyone with type 1 diabetes or type 2 diabetes can develop diabetic retinopathy.

Your risk is higher if you:

• have had diabetes for a long time
• have a persistently high blood sugar (blood glucose) level
• have high blood pressure
• have high cholesterol
• are pregnant
• are of Asian or Afro-Caribbean background

If you keep your blood sugar, blood pressure and cholesterol levels under control, you can reduce your chances of developing diabetic retinopathy.

You won't usually notice diabetic retinopathy in the early stages. It doesn't tend to cause any obvious symptoms until it's more advanced.

Early signs can still be picked up, though, because photographs of the eyes are taken during diabetic eye screening.

Contact your optometrist immediately if you have:

• gradually worsening vision
• sudden vision loss
• shapes floating in your field of vision (floaters)
• blurred or patchy vision
• eye pain or redness

These symptoms don't necessarily mean you have diabetic retinopathy, but it's important to get them checked. Don't wait until your next screening appointment.

Eye screening is offered once a year to everyone with diabetes who is 12 years old or over. This is because:

• diabetic retinopathy doesn't tend to cause any symptoms in the early stages
• the condition can cause permanent blindness if it isn't diagnosed and treated promptly
• screening can find problems in your eyes before they start to affect your vision
• if problems are caught early, treatment can help prevent or reduce vision loss

The screening test involves examining the back of the eyes and taking photographs. Depending on your result, you may be advised to come back for another appointment a year later, to attend more regular appointments, or to discuss treatment options with a specialist.

You can reduce your risk of developing diabetic retinopathy, or help prevent it getting worse, by:

• controlling your blood sugar, blood pressure and cholesterol levels
• taking your diabetes medicine as prescribed
• attending all your screening appointments
• getting medical advice quickly if you notice any changes to your vision
• maintaining a healthy weight, eating a healthy, balanced diet, exercising regularly and stopping smoking

You only need treatment for diabetic retinopathy if screening finds significant problems that put your vision at risk.

If the condition hasn't reached that stage, the advice above on managing your diabetes is what's recommended.

The main treatments for more advanced diabetic retinopathy are:

• laser treatment
• injections of medication into your eyes
• an operation to remove blood or scar tissue from your eyes

Diabetic retinopathy doesn't appear all at once. It develops in stages over time.

If a doctor finds diabetic retinopathy after an eye check for people with diabetes, changes to your lifestyle and/or treatment can lower the chances of the problem getting worse.

The main stages are described below. You won't necessarily go through all of them.

Background retinopathy means tiny bulges (microaneurysms) have appeared in the blood vessels at the back of your eyes (the retina), and these may leak small amounts of blood. This is very common in people with diabetes.

At this stage:

• your sight isn't affected, although you're at a higher risk of developing vision problems in the future
• you don't need treatment, but you'll need to take care to prevent the problem getting worse (read more about preventing diabetic retinopathy)
• if both of your eyes are affected, the chance of it moving on to the stages below within three years is over 25%

With pre-proliferative retinopathy, more severe and widespread changes are seen in the retina, including bleeding into the retina.

At this stage:

• there's a high risk that your vision could eventually be affected
• you'll usually be advised to have eye check-ups more often, every three or six months, so your eyes can be monitored

In proliferative retinopathy, new blood vessels and scar tissue have formed on your retina. This can cause heavy bleeding and lead to retinal detachment, which is when the retina pulls away from the back of the eye.

At this stage:

• there's a very high risk you could lose your vision
• treatment will be offered to stabilise your vision as much as possible, although it won't be possible to restore any vision you've lost

Sometimes the blood vessels in the macula, the central area of the retina, become leaky or blocked. This is called diabetic maculopathy.

If your doctor finds it:

• there's a high risk that your vision could eventually be affected
• you may be advised to have more frequent specialised testing to monitor your eyes
• you may be referred to a hospital specialist to discuss treatments that can help stop the problem getting worse

Diabetic retinopathy usually needs specific treatment only when it reaches an advanced stage and your vision is at risk. Doctors typically offer it if an eye screening finds stage three (proliferative) retinopathy, or if you have symptoms caused by diabetic maculopathy.

At every stage, managing your diabetes matters a great deal.

Read about the stages of diabetic retinopathy for more on what these terms mean.

Keeping your diabetes under control is the most important part of your treatment.

In the early stages of diabetic retinopathy, good control of your diabetes can help stop vision problems from developing. In the more advanced stages, when your vision is affected or at risk, it can help stop the condition getting worse.

Read about what you can do to reduce the risk of diabetic retinopathy progressing

When diabetic retinopathy is threatening or affecting your sight, there are three main treatments:

• laser treatment, which treats the growth of new blood vessels at the back of the eye (the retina) in cases of proliferative diabetic retinopathy, and can also stabilise some cases of maculopathy
• eye injections, which treat severe maculopathy that's threatening your sight
• eye surgery, which removes blood or scar tissue from the eye when laser treatment isn't possible because the retinopathy is too advanced

Laser treatment is used for diabetic retinopathy when it reaches the advanced stages and new blood vessels have formed at the back of the eyes. These new vessels tend to be very weak and often bleed into the eye, and that is why they are treated.

The treatment can help stabilise the changes that diabetes has caused in your eyes and stop your vision getting any worse. It won't usually improve your sight, though.

Laser treatment:

• involves shining a laser into your eyes. You'll be given local anaesthetic drops to numb your eyes, other eye drops are used to widen your pupils, and special contact lenses are used to hold your eyelids open and focus the laser onto your retina
• normally takes around 20 to 40 minutes
• is usually carried out on an outpatient basis, which means you won't need to stay in hospital overnight
• may need more than one visit to a laser treatment clinic
• isn't usually painful, although you may feel a sharp pricking sensation when certain areas of your eye are being treated

After diabetic retinopathy treatment, you may have some side effects for a few hours. These can include:

• blurred vision, so you won't be able to drive until it passes. Ask a friend or relative to drive you home, or take public transport
• increased sensitivity to light, and it might help to wear sunglasses until your eyes have adjusted
• aching or discomfort, which over-the-counter painkillers such as paracetamol should help with

Your doctor should explain the risks of treatment to you before it begins. The possible complications of diabetic retinopathy treatment include:

• reduced night vision or peripheral (side) vision, and some people may have to stop driving because of this
• bleeding into the eye, or objects floating in your vision (floaters)
• being able to "see" the pattern the laser made on the back of your eye for a few months
• a small but permanent blind spot close to the centre of your vision

If your sight gets worse after treatment, get medical advice.

In some cases of diabetic maculopathy, your doctor may give injections of a medicine called anti-VEGF directly into your eyes. The aim is to stop new blood vessels forming at the back of the eyes.

The main medicines used are ranibizumab (Lucentis) and aflibercept (Eylea). They can help stop the problems in your eyes getting worse, and they may also improve your vision.

During treatment:

• the skin around your eyes will be cleaned and covered with a sheet
• small clips will be used to keep your eyes open
• you'll be given local anaesthetic drops to numb your eyes
• a very fine needle is carefully guided into your eyeball and the injection is given

The injections are usually given once a month to begin with. Once your vision starts to stabilise, they'll be stopped or given less frequently.

Steroid injections may sometimes be given instead of anti-VEGF injections, or if the anti-VEGF injections don't help.

Anti-VEGF injections for diabetic retinopathy can cause some side effects. These include:

• eye irritation or discomfort
• bleeding inside the eye
• floaters or a feeling of having something in your eye
• watery or dry, itchy eyes

There's also a risk that the injections could cause blood clots to form, which could lead to a heart attack or stroke. This risk is small, but your doctor should discuss it with you before you give your consent to treatment.

The main risk with steroid injections is increased pressure inside the eye.

Surgery may be done to remove some of the vitreous humour from your eye. This is the clear, jelly-like substance that fills the space behind the lens.

The operation is called vitreoretinal surgery, and you may need it if:

• a large amount of blood has collected in your eye
• there's extensive scar tissue that's likely to cause, or has already caused, retinal detachment

During the operation, the surgeon makes a small cut in your eye. Then some of the vitreous humour is removed, along with any scar tissue, and a laser is used to stop your vision getting worse.

Vitreoretinal surgery is usually done under local anaesthetic and sedation. So you won't feel any pain, and you won't be aware of the surgery while it's happening.

Most people can go home on the same day as the surgery or the day after.

You may need to wear a patch over your eye for the first few days. Your eye tires quickly at the start, and things like reading or watching television can wear it out.

Your vision will probably be blurred after the operation. It should get better gradually, though it can take several months before your vision fully returns to normal.

Your surgeon will tell you which activities to avoid while you recover.

Vitreoretinal surgery for diabetic retinopathy carries some risks. These include:

• developing a cataract
• further bleeding into the eye
• retinal detachment
• fluid build-up in the cornea (the outer layer at the front of the eye)
• infection in the eye

There's also a small chance that you will need more retinal surgery afterwards. Your surgeon will explain the risks to you.

You can lower your risk of getting diabetic retinopathy, or stop it from getting worse, by keeping your blood sugar, blood pressure and cholesterol levels under control.

Often this comes down to healthy lifestyle choices, though some people will need to take medicine as well.

A few lifestyle changes can improve your general health and lower your risk of developing diabetic retinopathy. These include:

• eating a healthy, balanced diet, and in particular trying to cut down on salt, fat and sugar
• losing weight if you're overweight, and aiming for a BMI of 18.5 to 24.9
• exercising regularly, with at least 150 minutes of moderate-intensity activity a week, such as walking or cycling (doing 10,000 steps a day can be a good way to reach this target)
• stopping smoking if you smoke
• not going over the recommended alcohol limits, since men and women are advised not to regularly drink more than 14 alcohol units a week

Your doctor may also prescribe medicine to help control your blood sugar level (such as insulin or metformin), your blood pressure (such as ACE inhibitors) and/or your cholesterol level (such as statins).

You'll find it easier to keep your blood sugar, blood pressure and cholesterol under control if you know what your levels are and check them regularly.

The lower you can keep them, the lower your chances of developing diabetic retinopathy. Your diabetes care team can tell you what your target levels should be.

If you check your blood sugar at home, the level should be 4 to 10 mmol/l. It can change through the day, so try to test at different times.

The test your doctor does measures your average blood sugar level over the past few weeks. You should know this number, because it's the most important measure of how well your diabetes is controlled.

It's called HbA1c, and for most people with diabetes it should be around 48 mmol/l or 6.5%.

Read about treating type 1 diabetes and treating type 2 diabetes.

You can ask a doctor to check your blood pressure, or you can buy a blood pressure monitor and use it at home. Blood pressure is measured in millimetres of mercury (mmHg), and you get two figures when it's taken.

If you have diabetes, you'll normally be advised to aim for a reading of no more than 140/80mmHg. The aim is less than 130/80mmHg if you have diabetes complications, such as eye damage, which includes diabetic retinopathy.

Read more about high blood pressure

Your cholesterol level can be measured with a simple blood test done at your doctor's chamber. The result is given in millimoles per litre of blood (mmol/l).

If you have diabetes, you'll normally be advised to aim for a total blood cholesterol level of no more than 4 mmol/l.

Even if you think your diabetes is well controlled, you should still go for your yearly diabetic eye screening. It can pick up signs of a problem before you notice anything is wrong.

The earlier diabetic retinopathy is found, the better the chance of treating it effectively and stopping it getting worse.

You should also contact your eye doctor immediately if you develop any problems with your eyes or vision, such as:

• gradually worsening vision
• sudden vision loss
• shapes floating in your field of vision (floaters)
• blurred vision
• eye pain or redness

These symptoms don't necessarily mean you have retinopathy, but it's important to get them checked straight away.