Cystoid Macular Edema (CME): Causes, Diagnosis & Etiology-Based Treatment

Fluid Accumulation in the Central Retina

CME = cystic spaces in the macula from fluid leakage (blood-retinal barrier breakdown). Causes central vision blur, distortion, metamorphopsia.

Etiology (The "CME Causes" Mnemonic)

• Cataract surgery (Irvine-Gass, 1–3% modern phaco; higher with complications)
• Macular pathology: AMD (wet), retinal vein occlusion (BRVO/CRVO), diabetic macular edema (DME)
• Eye inflammation: uveitis (intermediate/posterior), scleritis
• Drug-induced: prostaglandin analogs (latanoprost), EGFR inhibitors, taxanes, niacin
• Trauma / post-surgical (vitrectomy, retinal detachment repair)
• Retinal dystrophies: retinitis pigmentosa, X-linked retinoschisis
• Idiopathic (rare)

Symptoms

• Central blur, metamorphopsia (Amsler grid distortion).
• Micropsia (objects smaller), color desaturation.
• Often asymptomatic if unilateral/extrafoveal.

Diagnosis

• OCT (gold standard): Intraretinal cystic spaces (hyporeflective), retinal thickening, disrupted EZ. Central subfield thickness (CST) quantitative.
• Fluorescein angiography: Petaloid "flower" leakage pattern (late).
• OCT-A: Assess capillary non-perfusion, FAZ.

Treatment by Etiology

Cause	First-Line	Second-Line / Adjunct
Post-cataract (Irvine-Gass)	NSAID drops (bromfenac, nepafenac) × 4–12 wks	Topical steroid; sub-Tenon triamcinolone; intravitreal steroid/anti-VEGF if persistent
DME	Anti-VEGF (aflibercept, ranibizumab, faricimab) + optimize glycemia/BP/lipids	Focal laser (if non-center); dexamethasone implant (Ozurdex); fluocinolone (Iluvien)
RVO (BRVO/CRVO)	Anti-VEGF (monthly → treat-and-extend)	Dexamethasone implant; laser (BRVO only, if perfusion)
Uveitic CME	Periocular/intravitreal steroid + systemic immunomodulation	Anti-VEGF (if steroid-resistant); methotrexate, mycophenolate, biologics
Drug-induced	Discontinue offending agent	Topical NSAID/steroid; anti-VEGF if persistent
RP / retinoschisis	Carbonic anhydrase inhibitors (topical dorzolamide / oral acetazolamide)	Anti-VEGF (limited data); low-vision rehab

Monitoring

• OCT q4–8 weeks during active treatment.
• VA, CST trends guide interval extension.
• Chronic CME → photoreceptor loss → permanent acuity limit.

Prognosis

• Post-cat: 90% resolve with topical therapy.
• DME/RVO: Chronic, relapsing; goal = dry macula + functional vision.
• Uveitic: Control inflammation = control CME.

Bottom Line

CME is a final common pathway of barrier breakdown. OCT defines it; etiology directs therapy. Early treatment preserves photoreceptors. Chronic CME = irreversible damage.