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).
All people with diabetes are at risk of getting diabetic retinopathy, but good control of blood sugar levels, cholesterol and blood pressure minimises this risk.
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 narrow, bleed or leak. This damages the retina and stops it from working.
When the blood vessels in the central area of the retina (the macula) are affected, it's known as diabetic maculopathy.
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. Vision loss will probably be permanent at this late stage, which is why diabetic eye screening is so important.
If you have diabetes and start to notice problems with your vision, contact your GP or diabetes care team immediately.
Screening for diabetic retinopathy
As severe retinopathy can cause sudden blindness, it needs to be identified and treated as soon as possible.
Everyone with diabetes who is 12 years old or over is invited for screening once a year.
The screening test involves examining the back of the eyes and taking photographs of the retina. Screening can detect diabetic retinopathy before you notice any changes to your vision.
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, you can prevent it from getting worse just by controlling your diabetes.
If you have more advanced retinopathy, you may need to have laser surgery or injection therapy to prevent further damage to your eyes.
Preventing diabetic retinopathy
To reduce your risk of developing retinopathy, it's important to control your blood sugar level, blood pressure and cholesterol level. Good control will prevent diabetic complications in almost everyone.
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
giving up smoking
controlling your blood pressure and cholesterol levels
Symptoms of diabetic retinopathy
Diabetic retinopathy doesn't 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's very important to attend regular screening appointmentsif you have diabetes.
Other symptoms of advanced retinopathy can include:
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. Therefore, it's 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 new 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:
People with diabetes may also suffer from changes to the blood vessels in the macula, which is the central area of the retina.
When the blood vessels in the macula are affected, this is known as diabetic maculopathy.
The vessels in the macula can become leaky and the blood pressure can force fluid, fats and protein out of the bloodstream and into the retina. This is known as macular oedema and causes some loss of vision in most cases.
Injection therapy can be given for severe cases of macular oedema (whereas oedema outside of the macula can be treated by laser).
Occasionally, the blood vessels in the macula become so narrowed that the macula is starved of oxygen and nutrition, causing your sight to get worse. This is called ischaemic maculopathy and does not usually respond to any type of treatment.
shapes floating in your field of vision (floaters)
sudden vision loss
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 (when the retina pulls away from the back of the eye).
Causes of diabetic retinopathy
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, which 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 focuses 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 blood supply, 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.
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% (64 mmol/mol), you are 40% more likely to develop retinopathy than someone with an HbA1C level of 7% (53 mmol/mol).
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 on salt in your diet, can help reduce your risk of developing retinopathy.
Diagnosing diabetic retinopathy
In the early stages, diabetic retinopathy does not cause any noticeable symptoms. Therefore, it tends to be diagnosed as a result of a diabetic eye screening test.
You should receive a letter from your local Diabetic Eye Screening Service inviting you to attend a screening appointment.
Everyone with diabetes who is 12 years of age or over should be invited to have their eyes screened once a year.
A trained person will put eyes drops into your eye to enlarge your pupils, and photographs of your retina will be taken.
Within six weeks, both you and your GP should receive a letter letting you know your results.
The screening results may show either:
background retinopathy – also called stage one retinopathy
degrees of referable retinopathy – this means retinopathy that requires referral to an eye specialist for further assessment and/or treatment
Treating diabetic retinopathy
Early-stage retinopathy may not need treatment, but more advanced retinopathy may require laser treatment or injections of medicine into the eye.
Immediate treatment may not be necessary if you have:
stage one (background) retinopathy
stage two (pre-proliferative) retinopathy
maculopathy with no symptoms
However, you should still attend your annual screening check to monitor the progress of your retinopathy. You may also be given advice on how to control your diabetes.
If maculopathy is detected, you may need more frequent specialised testing (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.
When treatment is necessary
Laser treatment should be offered for proliferative (stage three or four) diabetic retinopathy and some cases of maculopathy.
Intravitreal injections may be recommended if you have maculopathy.
Vitreoretinal surgery may be needed if laser treatment is not possible because retinopathy is too advanced.
These three treatments are covered below.
The aim of laser treatment is to stabilise the changes caused in your eyes by your diabetes. The treatment does not generally improve your sight, although it might in some cases.
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.
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 proliferative retinopathy (new blood vessels on the retina), or if the doctor thinks you will very soon have proliferative retinopathy, a large number of laser burns will be applied to the outer part of your retina (the part of the retina that allows you to see to the side and in the dark). This treatment is called peripheral scatter laser photocoagulation.
If you have macular changes, gentle laser burns will be applied close to the central part of the retina – the part you use for seeing clearly. You need much less laser treatment than for proliferative retinopathy.
Possible side effects after the laser treatment
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), and some patients may have to stop driving as a result.
Approximately one in four people who have had laser treatment to both eyes for proliferative diabetic retinopathy have to stop driving.
Occasionally, some people have a bleed into the jelly that fills the eye (the vitreous). If you notice a shower of floaters (specks that float across your vision) or your sight gets worse, you should get medical advice.
Complications are very rare for macular treatment. Some people can still "see" a laser grid pattern after treatment. This usually continues for up to two months, and very occasionally for up to six months after treatment.
In a national survey, around 1 in 10 people who had had laser treatment for their macula reported seeing a small, but permanent, blind spot close to the centre of their sight.
Contact your GP or ophthalmologist if you experience any new problems with your eyes after treatment.
Intravitreal anti-VEGF injections are often used to treat age-related macular degeneration. However, research has shown that they can also improve the vision of people with diabetic maculopathy.
VEGF stands for "vascular endothelial growth factor". It is one of the chemicals responsible for the growth of new blood vessels that form in the eye. Anti-VEGF medicines work by blocking this chemical and stopping it from producing the blood vessels. A medicine calledranibizumab (brand name Lucentis) will be injected directly into the eyeball.
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 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.
Three injections are initially given, one month apart, and an ophthalmologist will assess how you respond to these. Most patients need around 7-10 injections in the first year of treatment, but this decreases sharply in the second and third years.
If you don't respond to anti-VEGF injections or you have had maculopathy for a long time, you may be tried on an intravitreal injection of a steroid drug called Iluvien (fluocinolone acetonide).
Possible side effects of intravitreal injections
The main risks of anti-VEGF drugs are infection of the eye or bleeding inside the eye. There is also a very small increased of risk of stroke or heart attack. Read a full list of the possible side effects of ranibizumab.
The main risk with Iluvien is increased pressure inside the eye, which can be treated.
A vitrectomy (also called vitreoretinal surgery) is surgery 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.
The surgeon will remove any scar tissue that is causing damage to the retina or pulling it out of shape, and will use laser inside the eye to prevent further deterioration.
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.
Possible risks of a vitreous surgery are:
developing a cataract
further bleeding into the vitreous gel
fluid build-up in the cornea (outer layer at the front of the eye)
infection inside the eye
There's a small chance that you will need further retinal surgery afterwards. Your surgeon will explain the risks to you.
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.
Managing your diabetes
Managing your diabetes is the most important part of your treatment. It's important to keep your blood sugar levels under control to stop your eyes deteriorating again.
How should I prepare for my appointment?
You can prepare for your appointment at the eye clinic by bringing with you:
your current glasses (spectacles)
a list of any medication you are taking
sunglasses to wear home, as your eyes may be sensitive to bright light after the appointment
Preventing diabetic retinopathy
To prevent diabetic retinopathy, it's very important to attend your appointments.
You'll also need to keep your blood sugar levels, blood pressure and blood fats (cholesterol) under control.
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.
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.
If your blood pressure is found to be high, it will need to be closely monitored until it is brought under control. Your GP will ask to see you for regular blood pressure checks.
You can prevent high blood pressure by:
eating a healthy, balanced diet
exercising regularly – do at least 150 minutes a week of moderate-intensity activity
giving up smoking if you smoke
sticking to the recommended alcohol limits; this is no more than three to four units of alcohol a day for men, and two to three 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 of spirits)
If you have diabetes, it's very important that you attend your annualdiabetic eye screening appointment. The earlier that retinopathy is detected, the greater the chance of effectively treating it and stopping it progressing.