Macular Edema

What happens in macular edema

The macula is only about 5 mm across but contains most of the cells that give you sharp central vision. Normally, tight barriers in the retinal blood vessels keep fluid out of the retina. When those barriers are damaged by high blood sugar, raised vein pressure, inflammation or abnormal new vessels, fluid and protein leak into the retinal layers. The retina thickens like a sponge. When the fluid collects in small, petal-shaped pockets, it is called cystoid macular edema (CME).

Short-term swelling can resolve completely. Long-standing swelling damages the light-sensing cells and can cause permanent central vision loss.

Causes

Medicine-related swelling is discussed further under drug-induced retinopathy.

Symptoms

• blurred or wavy central vision
• straight lines appearing bent (distorted vision)
• colors looking faded
• objects appearing smaller or larger in one eye
• difficulty reading, sewing, driving or recognizing faces
• side (peripheral) vision usually stays normal

Early macular edema may cause no symptoms, particularly in diabetes. When only one eye is affected, the other can mask the problem until you cover the good eye.

Diagnosis

1. Visual acuity test: a letter chart.
2. Amsler grid: a grid of straight lines that reveals distortion.
3. Dilated eye examination: the retina is examined with drops to widen the pupil.
4. Optical coherence tomography (OCT): a quick, painless scan that shows retinal thickness and fluid pockets in cross section. It is the main test for diagnosis and for tracking treatment.
5. Fluorescein angiography: a dye is injected into an arm vein and photographed as it passes through the retinal vessels, to show where leakage comes from.
6. Tests for underlying causes: blood sugar, HbA1c, blood pressure and, with uveitis, inflammation work-up.

Treatment

Treatment targets both the swelling and its cause.

Anti-VEGF injections

Vascular endothelial growth factor (VEGF) is a protein that makes vessels leak. Anti-VEGF drugs such as aflibercept, ranibizumab, bevacizumab and faricimab are injected into the eye with a very fine needle after numbing drops. They are the first-line treatment for diabetic macular edema, retinal vein occlusion and wet AMD. Injections usually start monthly, then the gap is extended as the swelling settles. Many people need treatment for years.

Corticosteroids

• Steroid implants or injections into the eye (dexamethasone or fluocinolone implants, triamcinolone) last weeks to years. They are useful when injections do not work well, in uveitis, or after cataract surgery. Side effects include raised eye pressure and cataract.
• Steroid and NSAID eye drops are the main treatment for swelling after cataract surgery.

Laser

Focal or grid laser seals specific leaking vessels, mainly in diabetic macular edema that does not involve the very center. It is now used less often than injections.

Other treatments

• Stopping or switching a medicine that causes swelling, with the prescribing doctor
• Surgery (vitrectomy) when scar tissue or the vitreous gel pulls on the macula
• Carbonic anhydrase inhibitor drops or tablets for some inherited causes

Controlling the underlying condition

For diabetes, good control of blood sugar, blood pressure and cholesterol lowers the risk and slows progression. For vein occlusions, controlling blood pressure and other cardiovascular risk factors matters.

Outlook

Swelling after cataract surgery usually clears within a few months with drops. With regular anti-VEGF treatment, many people with diabetic macular edema or vein occlusion keep or gain vision. Delayed treatment or long-standing swelling is more likely to leave permanent blur. Keeping injection appointments is the most important factor in a good result.

Prevention

• Have a dilated eye exam every year if you have diabetes, more often if retinopathy is found.
• Keep blood sugar, blood pressure and cholesterol in target ranges, and do not smoke.
• If you have had cataract surgery and have diabetes or uveitis, use any anti-inflammatory drops exactly as prescribed.
• Use an Amsler grid at home if you are at risk, and report new distortion promptly.

Frequently asked questions

Can macular edema go away on its own?

Sometimes. Mild swelling after cataract surgery and some cases from vein occlusions can resolve without treatment. Swelling that lasts or threatens central vision should be treated, because prolonged edema can damage the retina permanently.

Is macular edema the same as macular degeneration?

No. Macular edema is swelling from fluid in the macula and can have many causes. Macular degeneration is an age-related disease that damages the macula. The wet form of macular degeneration can cause macular edema, which is why both are treated with similar injections.

How long does macular edema last after cataract surgery?

Cystoid macular edema after cataract surgery usually appears 4 to 12 weeks after the operation and often settles within 3 to 6 months with anti-inflammatory eye drops. A few cases last longer and need steroid injections.

Do eye injections for macular edema hurt?

Most people feel pressure rather than pain. The eye is numbed with drops or gel first, and the injection takes seconds. The eye may feel gritty or look red at the injection site for a day or two. Severe pain or worsening vision afterwards should be reported the same day.

Can macular edema cause blindness?

It rarely causes total blindness, because side vision is preserved. Untreated, it can cause permanent loss of central vision needed for reading and driving. Prompt treatment prevents most serious vision loss.