Diabetic Macular Oedema: Causes, Symptoms and Treatment Options

What Is Diabetic Macular Oedema?

Diabetic macular oedema (DMO) is a complication of diabetic retinopathy in which fluid leaks into the macula, the central part of the retina responsible for sharp, detailed vision. The resulting swelling can distort or blur vision and, if left untreated, lead to permanent sight loss.

DMO is the most common cause of moderate-to-severe vision loss in people with diabetes. It can develop at any stage of diabetic retinopathy, though the risk rises as the disease progresses. The condition affects both type 1 and type 2 diabetes, and the chance of developing DMO increases the longer a person lives with diabetes and the less well-controlled their blood sugar, blood pressure and cholesterol are.

Causes and Risk Factors

The root cause of DMO is damage to the small blood vessels that supply the retina. When these vessels weaken, fluid and proteins leak into the macular tissue. Several factors increase the risk:

• Poorly controlled blood glucose levels over a long period.
• High blood pressure, which puts extra stress on retinal vessels.
• High cholesterol and/or high triglycerides.
• Kidney disease (nephropathy), which is linked to fluid retention and vascular damage.
• Pregnancy, where hormonal changes can worsen retinal leakage.
• Severe non-proliferative diabetic retinopathy, the stage where vessel damage is already extensive.

Symptoms to Watch For

DMO often develops gradually and may affect one or both eyes. Common symptoms include:

• Blurred or wavy central vision, especially when looking directly at an object.
• Colors appearing faded or washed out.
• Difficulty reading, recognising faces or driving.
• A dark or empty area in the centre of the visual field.
• Sudden vision changes, which require urgent assessment.

Many people notice no symptoms in the early stages, which is why regular diabetic eye screening is essential. Screening can detect DMO before vision is affected.

How DMO Is Diagnosed

A specialist eye doctor (ophthalmologist or optometrist) will carry out several tests:

• Visual acuity test to measure how clearly you can see.
• Dilated eye examination to look for retinal swelling, haemorrhages and exudates.
• Ocular coherence tomography (OCT), which produces detailed cross-sectional images of the retina and measures the thickness of the macula. OCT is the key test for confirming DMO and monitoring treatment response.
• Fluorescein angiography, where a dye is injected into a vein to highlight leaking blood vessels.

Treatment Options

The goal of treatment is to reduce macular swelling, preserve vision and prevent further loss. Current approaches include:

Anti-Vascular Endothelial Growth Factor (Anti-VEGF) Injections

These are the first-line treatment for most people with DMO. Drugs such as aflibercept, ranibizumab and faricimab are injected into the vitreous cavity of the eye after numbing it. They block VEGF, a protein that drives leakage and abnormal vessel growth. Treatment usually starts with monthly injections, then the interval is extended as the eye stabilises.

Corticosteroid Treatments

Steroids can reduce inflammation and swelling when anti-VEGF therapy is insufficient or not tolerated. Options include intravitreal injections of dexamethasone or fluocinolone acetonide, and a slow-release steroid implant (e.g. dexamethasone implant). Steroids carry a risk of raised eye pressure and cataract progression, which needs regular monitoring.

Laser Photocoagulation

Focal or grid laser treatment seals leaking vessels and can help stabilise vision. It is used less often as a first-line treatment now, but remains valuable for specific patterns of leakage.

Managing the Underlying Diabetes

Optimising blood sugar, blood pressure and lipid levels is fundamental. Good systemic control slows retinopathy progression and reduces the risk of recurrent DMO.

Outlook and Long-Term Management

With early detection and consistent treatment, most people with DMO can stabilise their vision and many experience improvement. However, DMO can recur, so ongoing monitoring is necessary even when the eye looks quiet. The key factors shaping long-term outcomes are the severity of retinopathy at diagnosis, how well diabetes is managed, and adherence to follow-up appointments.

Any sudden change in vision, such as new distortion, dark spots or rapid blurring, should be assessed promptly. Timely treatment offers the best chance of keeping sight intact.