Cystoid Macular Edema

What it is

The macula is the small central area of the retina responsible for sharp, detailed vision. Normally it is thin, dry, and precisely layered. When the blood vessels of the retina leak — because of inflammation, vascular disease, or traction — fluid collects between the retinal layers in a characteristic pattern of small round pockets radiating out from the center. That pattern is what gives cystoid macular edema its name. The swelling disrupts the alignment of the photoreceptors, and vision blurs.

What causes it

Cystoid macular edema is a common endpoint for many different problems. The ones we see most often are:

• After cataract surgery — sometimes called Irvine-Gass syndrome. It typically appears four to twelve weeks after an otherwise successful operation, and is more likely if the surgery was complicated or if you have diabetes or a history of uveitis.
• Diabetic macular edema — see diabetic retinopathy.
• Retinal vein occlusion — see retinal vein occlusion.
• Uveitis and other intraocular inflammation — see uveitis.
• Epiretinal membrane or vitreomacular traction pulling on the macula.
• Medications, including certain glaucoma drops in the prostaglandin class and some systemic drugs.
• Retinitis pigmentosa and other inherited retinal conditions.

Identifying the cause matters, because the treatment follows from it.

Symptoms

• Blurred or hazy central vision
• Straight lines appearing wavy or bent
• Colors looking washed out
• Difficulty reading small print even with the correct glasses

Peripheral vision is not affected, and there is no pain.

How we diagnose it

Optical coherence tomography (OCT) is the key test. It is a quick, non-contact scan that produces a cross-section of the macula and shows the fluid pockets directly, along with a measurement of retinal thickness that we track from visit to visit. Fluorescein angiography is sometimes added to show where the leakage is coming from and to look for associated vascular disease.

Treatment

Treatment is chosen for the underlying cause, and often works in steps:

• Eye drops. For edema after cataract surgery, a topical anti-inflammatory drop, usually combined with a steroid drop, resolves the majority of cases over several weeks.
• Injections. When drops are not enough, or when the cause is diabetes, a vein occlusion, or inflammation, we use intravitreal injections of a steroid or an anti-VEGF medication. These are given in the office and are usually repeated on a schedule that is tapered as the macula dries.
• Treating the source. Controlling blood sugar, treating uveitis systemically, or stopping a causative medication where possible.
• Surgery. If traction from a membrane or the vitreous is the driver, vitrectomy to release it may be the definitive answer.

Outlook

Most patients regain much or all of their vision, particularly when the edema is caught early and the cause is inflammation after surgery. Longstanding edema is harder to reverse, because prolonged swelling eventually damages the photoreceptors themselves — which is the argument for treating it promptly and following it closely. Recurrence is possible, so we typically keep scanning the macula for a period after it has dried.