Diabetic Macular Edema (DME)

What diabetic macular edema is

High blood sugar over years damages the walls of the tiny blood vessels in the retina, the light-sensing layer at the back of the eye. This is diabetic retinopathy. The damaged vessels become leaky, and starved areas of retina release VEGF (vascular endothelial growth factor), a signal protein that makes vessels leak even more.

When the leaked fluid collects in the macula, the retina thickens like a wet sponge. Because the macula handles reading, recognizing faces and seeing fine detail, even a little swelling blurs vision. DME can occur at any stage of diabetic retinopathy, both the earlier non-proliferative stage and the advanced proliferative stage. It becomes more likely the longer someone has had diabetes.

Doctors divide it into two types:

Macular swelling also occurs after cataract surgery, in retinal vein blockages and in uveitis. Those causes are covered under macular edema.

Symptoms

• Blurred or hazy central vision, often worse when reading
• Wavy or bent lines (distorted vision)
• Colors looking washed out
• A gray or dim patch in the center of vision
• Vision that changes during the day

Side vision is usually unaffected. Many people have no symptoms at first, especially when only one eye is involved, because the better eye compensates. That is why regular eye exams matter.

Risk factors

• Long duration of diabetes
• High HbA1c (poor blood sugar control)
• High blood pressure
• High cholesterol and triglycerides
• Diabetic kidney disease
• Pregnancy, which can speed up retinopathy
• Sleep apnea and smoking

Diagnosis

1. Visual acuity test with a letter chart.
2. Dilated eye examination: drops widen the pupil so the ophthalmologist or optometrist can see swelling, leakage deposits (hard exudates) and small bleeds.
3. Optical coherence tomography (OCT): a quick, painless scan using light waves that measures retinal thickness in microns and shows fluid pockets. It is the key test for diagnosing DME and for tracking treatment.
4. Fluorescein angiography: a dye injected into an arm vein shows which vessels leak and whether areas of retina have lost their blood supply.
5. Retinal photographs, often used in diabetes screening programs.

Diabetic macular edema treatment

Anti-VEGF injections

These are first-line treatment for center-involved DME with reduced vision. The medicine is injected into the white of the eye after numbing drops, through a very fine needle. The procedure takes a few minutes and most people feel only pressure. Drugs used include aflibercept, ranibizumab, bevacizumab and faricimab.

Injections are usually given monthly at first, often for 4 to 6 months, then spaced out as the swelling responds. Many people need treatment for several years, with gradually fewer injections. In large trials, a substantial share of patients gained two or more lines on the eye chart.

Risks are low but include eye infection (endophthalmitis), raised eye pressure, bleeding on the eye's surface and, rarely, retinal detachment. Call your eye doctor the same day for increasing pain, redness or worsening vision after an injection.

Steroid treatment

Long-acting steroid implants (dexamethasone or fluocinolone) are placed into the eye when anti-VEGF injections do not work well enough or are unsuitable. They can last months to years. Side effects include cataract and raised eye pressure, so they are often preferred for people who have already had cataract surgery.

Laser treatment

Focal or grid laser seals specific leaking vessels. It is now mostly used for non-center-involved DME, or alongside injections. It aims to stop vision getting worse rather than to improve it.

Watching closely

For center-involved DME with good vision (20/25 or better), research from the DRCR Retina Network found that careful observation, starting injections only if vision drops, gave similar results to treating straight away. Your eye doctor will discuss this option.

Vitrectomy

Surgery to remove the vitreous gel may help when scar tissue pulls on the macula.

Controlling diabetes protects your eyes

Eye treatments do not fix the underlying cause. The following lower the chance of DME developing or returning:

• keeping HbA1c in the target range agreed with your doctor
• controlling blood pressure and cholesterol
• not smoking
• treating kidney disease and sleep apnea

When blood sugar is very high, lower it steadily rather than very quickly, because a sudden large drop can temporarily worsen retinopathy. Your diabetes team can guide this.

Screening

The American Diabetes Association recommends a dilated eye exam or retinal photography:

• within 5 years of diagnosis for type 1 diabetes
• at diagnosis for type 2 diabetes
• then every 1 to 2 years if normal, and more often if retinopathy is present
• before or early in pregnancy for women with pre-existing diabetes

Outlook

Left untreated, center-involved DME causes gradual, often permanent loss of central vision. With modern injections, most people keep or improve their vision, especially when treatment starts before major loss. DME can come back, so ongoing check-ups are needed even after the swelling clears. Total blindness from DME is rare because side vision is preserved.

Frequently asked questions

Can diabetic macular edema be reversed?

Often, yes. Anti-VEGF injections dry the macula in most people, and many gain vision. Results are best when treatment starts early, before the retina has been swollen for a long time. Long-standing swelling can leave permanent damage, so some loss may remain even when the fluid has gone.

How long do you need injections for DME?

Most people need monthly injections for the first several months, then fewer as the swelling settles. Treatment commonly continues for 2 to 3 years or longer, with intervals stretched to 8 to 16 weeks. Some people eventually stop injections and are simply monitored.

Is diabetic macular edema the same as diabetic retinopathy?

No. Diabetic retinopathy is the overall damage to retinal blood vessels from diabetes. Diabetic macular edema is one complication of it, in which leaked fluid swells the macula. You can have retinopathy without DME, and DME can occur at any stage of retinopathy.

Can you go blind from diabetic macular edema?

DME can cause serious loss of central vision, enough to stop reading or driving, but it does not affect side vision, so complete blindness from DME alone is rare. With regular screening and prompt treatment, severe vision loss can usually be prevented.

Does DME affect both eyes?

It can affect one or both eyes, often at different times and to different degrees. Because the better eye hides problems in the other, check each eye separately by covering one at a time, and keep your scheduled eye exams.