Diabetic macular oedema

Diabetic macular oedema (DMO) is the most common cause of sight loss in people with diabetes.

Oedema means fluid retention. When leaky vessels cause fluid to build up in the macula, at the centre of the retina, it is known as diabetic macular oedema. It is a complication of diabetic retinopathy and results in a condition very similar to wet AMD .

Being diagnosed with diabetic macular oedema can be distressing and worrying but, with the right information and support, people can cope very well.

The condition is painless, and although macular oedema affects central vision, peripheral vision is not affected. However, other forms of diabetic retinopathy may affect your wider vision.

How diabetes affects your eyes

People with diabetes are at risk of damage to their eyesight. To work properly, the eye needs a constant supply of blood. When control of blood sugar and insulin levels in the body is poor, the blood vessels of the eye become damaged. The blood vessels of the retina are particularly prone to leaking and a condition known as diabetic retinopathy can develop.

People with diabetes should reduce their risk of vision loss by attending their annual diabetic eye screening appointment.

What is the macula?

The macula is the central bit of the retina (the tissue at the back of the eye which senses light). The macula is about 5mm across. It is responsible for our central vision, our colour vision and the fine detail of what we see.

The macula has a very high concentration of photoreceptor cells that send signals to the brain which interprets them as images. The rest of the retina processes our peripheral, or side vision. Damage to the macula can mean losing the ability to read, watch TV or recognise faces.

Symptoms

In the early stages of diabetes a person may not notice any effect on their vision. Damage to the retina occurs over many years.

It may affect the entire retina but when the damage causes only small bulges in the blood vessels of the retina, the eyesight remains good.

However, when the blood vessels in or close to the macula become damaged, or there is sudden bleeding or fluid leaking into the macula, then sight can worsen dramatically.

  • Dark spots like a smudge on glasses or gaps may appear in your vision, especially first thing in the morning.
  • Objects in front of you might change shape, size or colour or seem to move or disappear.
  • Colours can fade.
  • You may find bright light or glare difficult.
  • You may experience difficulty reading.
  • Straight lines such as door frames and lamp posts may appear distorted or bent.

If you notice a sudden change in your vision, contact your optometrist or hospital eye specialist urgently.

Risk factors

The longer you have diabetes, the greater your chance of developing sight loss through DMO. About 90% of people with type 1 diabetes will have some degree of retinopathy after 10 years.

For people with type 2 diabetes the chance of developing some degree of retinopathy after 10 years varies between 67–80% (or two in three to four in five), depending on whether they need to take insulin.

More than a third of all diabetic patients will develop a level of severity of macular oedema which, without changes to the person’s lifestyle and better control of blood sugar, will require treatment.

If your blood sugar level is high, you increase the risk of developing retinopathy. Small changes in your levels can significantly affect your risk of developing retinopathy and if you have high blood pressure as well, you have a higher risk of developing advanced retinopathy. Overall, 7 per cent (around one in 14) of all people with diabetes develop DMO, which will result in a noticeable loss of vision.

Diagnosis

If DMO is suspected, you will be referred to the eye hospital for tests. Your hospital specialist (ophthalmologist) may use:

  • Eye drops to dilate the pupils to allow them to clearly see the back of the eye. The drops may make your vision blurred and sensitive to light for a short time so consider taking someone with you.
  • Scans using optical coherence tomography (OCT) to produce a cross-sectional image of the retina.
  • Fluorescein dye angiography. A dye is injected into a vein in the arm. It travels to the eye, highlighting the blood vessels in the retina so they can be photographed. The dye will temporarily change the colour of your urine.

If you have any vision problems in between your appointments seek immediate advice from your diabetes care team or GP. Do not wait until your next hospital appointment.

Treating DMO

DMO can be treated if caught early. Drugs are injected into the eye to stop fluid leaking from the blood vessels. Following diagnosis, people will usually have a number of injection treatments in the first few months. Subsequent check-ups will then be required to assess when more injections are needed.

The injections are not as bad as they might sound. The eye is anaesthetised and the needle goes into the corner of the eye so the patient does not see it. These are called intravitreal injections. The treatment cannot restore sight if there is already significant damage to the macula.

There are two drugs in use for treating DMO: Lucentis® (ranibizumab) and Eylea® (aflibercept). They act on the blood vessels in the retina to reduce fluid leakage that leads to oedema in the eye.

The frequency and number of injections depends on how a patient responds to the drug. Ask your eye doctor about your treatment programme. Do not miss a treatment session – any sight loss cannot be recovered.

A third drug, Avastin® (bevacizumab), may be used. However, its routine use is to treat cancer and it is not licensed in the UK for treatment in the eye. Some people who have had cataract surgery or who have a particular form of DMO may be offered an intravitreal injection of a steroid drug called Iluvien® (fluocinolone acetonide) or Ozurdex® (dexamethasone). They are slow-release drugs implanted in the eye.

Laser treatment

Some people may be offered laser treatment when the DMO does not involve the centre of the macula. This treatment aims to stabilise vision and does not generally improve sight. It usually involves one or more visits to an outpatient laser clinic for treatment by an ophthalmologist.

Before the procedure, local anaesthetic will be administered to 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. Laser treatment is not usually painful, but you may feel a sharp pricking sensation.

Protecting your eyes

Diabetes is a lifelong condition, so maintaining a healthy lifestyle and monitoring your blood sugar, blood pressure and cholesterol levels is crucial to avoid damage to your eyes.

The following can help to protect your eyesight.

  • Monitor your blood sugar levels regularly, aiming to keep within limits recommended by your doctor or nurse.
  • Maintain a healthy weight and blood pressure.
  • Eat plenty of fruit and green vegetables.
  • Drink only a modest amount of alcohol.
  • Take regular exercise.
  • Do not smoke.

It is essential that you attend your diabetes clinic appointments. Your diabetes care team will maintain and monitor your diabetes care plan. Make sure that your eyes are screened at least once a year to spot any problems early.

If you wear glasses or contact lenses continue to visit your optician regularly and tell the optometrist that you are diabetic.

Managing daily living

Loss of central vision through DMO can be very frustrating and can greatly affect everyday life. You can make your remaining vision more comfortable by wearing lenses that block UV and blue light and that reduce glare, and by wearing a hat with a brim or visor to shade eyes from direct sunlight.

Even if you are having treatment for DMO, it is important to know what to do if you reach a stage where you begin to struggle with daily tasks.

For more information, please see our Practical guides.

Visual hallucinations

Some people with DMO experience visual hallucinations called Charles Bonnet syndrome. These images might be of people, animals, landscapes or patterns.

People who haven’t heard of Charles Bonnet syndrome often worry they are developing a mental health problem. However, it is actually a normal response of the brain to sight loss. As fewer messages reach the brain, the cells that normally process vision can create images of things that are not there.

They may occur once or twice, or continue for several years and can be distressing. For further information about visual hallucinations, see call the Advice and Information Service on 0300 3030 111.