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Cystoid Macular Edema

ROUTINE — Retina

Symptoms

Decreased central vision (often gradual over weeks).

Metamorphopsia (distorted vision) and central blur.

Typical onset 4–10 weeks following cataract surgery.

Clinical Findings

Pathophysiology

  • Fluid accumulation in the outer plexiform (Henle) and inner nuclear layers (INL).
  • Radial geometry of Henle fibers creates a characteristic "petaloid" pattern.

Irvine-Gass syndrome

  • CME occurring specifically after cataract surgery; peak incidence at 6–10 weeks.
  • Risk factors: vitreous loss, posterior capsule rupture, iris trauma, or prolonged surgery.
  • Pre-existing risks: diabetes, uveitis, ERM, or retinitis pigmentosa.

Fluorescein angiography (FA)

  • Early phase: perifoveal dot-leakage from parafoveal capillaries.
  • Late phase: classic "petaloid" or "spoke-wheel" pattern of hyperfluorescence.
  • Optic disc leakage: frequent in Irvine-Gass (distinguishes it from diabetic or vein-occlusion CME).

Optical coherence tomography (OCT)

  • Hypo-reflective cystoid spaces in the INL and OPL.
  • Loss of foveal depression and increased central foveal thickness (350–600 μm).
  • Possible subfoveal neurosensory detachment.

Differential by FA pattern

  • Petaloid leak (True CME): Irvine-Gass, vein occlusion, uveitis, RP.
  • Diffuse leak: Diabetic macular edema.
  • No leak (Pseudo-CME): MacTel 2, tamoxifen, niacin, taxanes, X-linked retinoschisis.

Red-flag mimic

  • CME + new vitreous cells after cataract surgery → suspect chronic postoperative endophthalmitis (P. acnes or Staph epi).

Etiology

Surgical / traumatic

  • Postoperative: cataract (Irvine-Gass), laser photocoagulation, or cryotherapy.
  • Complications: vitreous-to-wound, iris prolapse, or uveal incarceration.

Vascular & inflammatory

  • Retinal vascular disease: diabetes, CRVO, BRVO, or Coats disease.
  • Uveitis: especially pars planitis (intermediate uveitis) and sarcoidosis.
  • Vasculitis: Eales, Behçet, or MS-associated uveitis.

Degenerative & dystrophic

  • Retinitis pigmentosa (RP).
  • Neovascular AMD and epiretinal membrane (ERM).

Drug-induced

  • Topical: prostaglandin analogs (latanoprost), epinephrine, and dipivefrin.
  • Systemic (Pseudo-CME): nicotinic acid (niacin), taxanes (docetaxel), and fingolimod.

Red Flags

Post-cataract vision loss with cystic changes → Irvine-Gass CME; requires NSAID/steroid combo.

CME in a non-operated eye → search for underlying uveitis, diabetes, or vascular occlusion.

Atypical CME unresponsive to anti-inflammatories → rule out drug toxicity or "Pseudo-CME" (no leak on FA).

CME + vitreous cells → rule out smoldering endophthalmitis.

Investigations

Ocular examination

  • Dilated fundus exam with 60/90D lens to evaluate foveal contour.
  • Gonioscopy to rule out retained lens fragments or haptic malposition.
  • Scleral depression to check for pars planitis (vitreous "snowbanks").

Imaging

  • OCT (Primary tool): documents foveal thickness and cystic spaces; used for serial monitoring.
  • IVFA: confirms breakdown of blood-retinal barrier; distinguishes true CME from pseudo-CME.

Systemic & supplemental

  • HbA1c/Fasting glucose if diabetes is suspected.
  • ERG if retinitis pigmentosa is suspected.
  • Targeted serologies (ACE, syphilis, TB) if uveitis/vasculitis is suspected.

Treatment

First-line (Irvine-Gass)

  • Topical NSAID: Ketorolac 0.5%, Bromfenac 0.09%, or Nepafenac 0.3%.
  • Topical Steroid: Prednisolone acetate 1% QID.
  • Duration: 4–6 weeks, then slow taper.

Second-line / refractory

  • Intravitreal: triamcinolone (1–4 mg) or dexamethasone implant (Ozurdex).
  • Anti-VEGF: Bevacizumab for persistent edema.
  • Sub-Tenon triamcinolone injection.

Systemic & surgical adjuncts

  • Acetazolamide: useful specifically for RP-associated CME.
  • Pars plana vitrectomy: for vitreomacular traction or vitreous-to-wound.

Discontinue offending agents

  • Topical: Prostaglandin analogs, epinephrine, dipivefrin.
  • Systemic: Nicotinic acid (niacin).

Clinical Pearl

Post-cataract CME (Irvine-Gass) peaks 4–6 weeks after surgery — an NSAID-steroid combo usually clears it, but suspect vitreous traction or epiretinal membrane if it refuses to resolve.

Differential Diagnosis

  • Diabetic macular edema
  • Neovascular AMD
  • Macular hole
  • Central serous chorioretinopathy
  • Vitreomacular traction
  • Epiretinal membrane

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