Diabetic macular oedema (DMO): symptoms, screening and treatment

Moorfields Eye Hospital describes diabetic eye disease as a leading cause of blindness registration among working-age adults in England and Wales. It arises from changes to the tiny blood vessels of the retina, the light-sensitive layer at the back of the eye. In diabetic macular oedema these vessels leak fluid into the retina. When the fluid reaches the macula, the centre of the retina that provides sharp vision, it builds up and causes swelling.

The NHS places macular oedema in the wider picture of diabetic retinopathy, a complication where high blood glucose damages blood vessels at the back of the eye. It also describes diabetic maculopathy, in which in the early stages there are no symptoms, and in a very small number of people it progresses to affect central vision so that edges of vision may be seen but reading becomes difficult.

Moorfields says that at first you may not notice changes to your vision, and over time central vision can become blurred. The NHS lists later symptoms of diabetic retinopathy as worsening eyesight, blurred vision, floaters (dots and lines) and difficulty seeing in the dark or low light, and says symptoms can affect one or both eyes.

The NHS advises contacting a GP, your diabetes care team or an optician if you have diabetes and eyesight problems such as vision worsening over time, floaters or trouble in low light. These symptoms do not always mean retinopathy but should be checked. Ask for an urgent GP appointment or call NHS 111 if your eyesight suddenly gets worse or you get blurred vision.

Moorfields says all people with type 1 and type 2 diabetes are at risk. You are at greater risk if you have had diabetes for a long time (it quotes about one in three people living with diabetes for 20 years or more developing diabetic macular oedema), have poorly controlled blood sugar, high blood pressure or high cholesterol, smoke, or are pregnant.

The same source notes that large studies show that people with well-controlled blood sugar, blood pressure and cholesterol who do not smoke are less likely to develop it. Reducing risk therefore means not smoking and keeping those three measures under control, with regular reviews with your diabetes nurse, GP or consultant.

The NHS says diabetic eye screening checks for diabetic retinopathy, often before you notice changes. If you have diabetes and are aged 12 or over you will get a letter every 1 or 2 years, usually when diagnosed, then every year, or every 2 years if your last two tests found no changes. Gestational diabetes does not lead to an invitation. Screening is your choice, and it is not the same as a regular optician eye test, which is still important for other conditions.

The appointment lasts around 30 minutes: you read letters on a chart, drops widen your pupils, and photographs are taken of the back of the eyes. Sight may be blurry for a few hours so you should not drive afterwards. Results usually arrive by letter within 3 weeks. The NHS describes three outcomes: no retinopathy (repeat in 1 to 2 years), background retinopathy (screening again in 1 year or earlier), and referable retinopathy, meaning damage that could affect your sight, leading to referral to a specialist for more tests or treatment.

Those referred are assessed in hospital eye services. NICE defines centre-involving macular oedema as swelling involving the central subfield of the macula and says it is always clinically significant, which is the version most likely to threaten reading vision.

NICE guideline NG242 says to offer treatment to people with clinically significant macular oedema, centre-involving or not, after discussing the benefits and side effects of anti-VEGF treatment, macular laser, steroid treatment and observation. Which suits best depends on the type of oedema and vision, and NICE sets out recommendations for each situation.

• NICE says that in August 2024 its technology appraisals recommended ranibizumab, brolucizumab, faricimab and aflibercept as options for visual impairment with central retinal thickness of 400 micrometres or more.

• Anti-VEGF medicines are injected into the eye to reduce leakage; NICE refers to a loading phase before response is assessed.

• The NHS says it is not possible to cure sight loss caused by diabetic retinopathy; treatment aims to stop vision getting worse, and managing diabetes well helps stop it worsening.

NICE advises that decisions about eye treatment and follow-up take into account the stage of retinopathy, HbA1c, kidney function and blood pressure, and that information about the severity of diabetic eye disease is shared with those involved in diabetes care so that it can inform overall management. It also says that before cataract surgery in someone with diabetes, the surgeon should obtain information about their diabetic eye disease status to tailor surgery, medication and follow-up.

Blood pressure management matters where hypertension is present: NICE notes it can reduce progression of non-proliferative retinopathy, but advises against giving blood pressure medicines to people without hypertension solely for that purpose. For people with non-proliferative retinopathy and type 2 diabetes, ophthalmologists should consider fenofibrate, which NICE noted was off-label use in 2024. This is a prescriber decision and not something to start independently.

Treatment often means regular hospital visits. Because pupils are widened for screening and some eye treatments, arrange transport. GOV.UK lists diabetic retinopathy with laser treatment among eye conditions that must be reported to the DVLA, and says driving standards include reading a number plate from 20 metres and having a normal field of vision in at least one eye.

Reduced central sight can affect reading, screens and recognising faces. Ask the eye clinic or your optometrist about low vision assessment and sight loss support, and let your diabetes team know about vision changes since they influence foot care, medicines and self-monitoring.

Screening, hospital eye service treatment including injections and laser, and monitoring are available through the NHS to people with diabetes. NICE technology appraisals determine which anti-VEGF medicines the NHS can fund for this condition.

Private retinal specialists can offer quicker assessment, imaging and a second opinion, and can provide treatments by self-funding or insurance. Share all results with your NHS team so screening and diabetes reviews stay coordinated, and ask providers to explain why a specific injection or laser treatment is recommended against NICE options.