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Intraocular Foreign Body (IOFB)

CRITICAL — Trauma

Symptoms

eye pain and decreased vision

may be asymptomatic if the entry wound is small (e.g., metal-on-metal hammering)

history of grinding, hammering, or high-velocity projectiles striking the eye

Clinical Findings

Strict MRI contraindication

  • do NOT perform mri if a ferrous (iron/steel) iofb is possible
  • the magnetic field can rotate or eject metal, causing catastrophic hemorrhage or nerve transection

Clinical signs

  • peaked pupil or iris transillumination defect (tid) pointing to entry site
  • seidel-positive corneal/scleral perforation wound
  • focal lens opacity along the entry tract or visible iofb in the vitreous/ac
  • asymmetrically low iop compared to the fellow eye

Chronic toxicity (retained IOFB)

  • siderosis bulbi (iron): iris heterochromia (rust color), mydriasis, and pigmentary retinopathy
  • chalcosis bulbi (copper): "sunflower" cataract and peripheral k-f-like rings
  • organic matter (wood): extremely high risk for fulminant b. cereus endophthalmitis

Etiology

Mechanism

  • high-velocity projectiles from metal-on-metal hammering, grinding, or firearms
  • explosions or agricultural machinery accidents

Material reactivity

  • high: iron, steel, copper (>85%), and vegetable/organic matter
  • mild: nickel, aluminum, and zinc
  • inert: gold, silver, glass, plastic, and stone

Red Flags

any history of high-velocity injury necessitates a ct scan of the orbits

wooden/organic foreign bodies are often occult on ct; suspect if mechanism fits

organic iofbs require immediate removal to prevent rapidly blinding endophthalmitis

retained iron iofbs cause irreversible retinal b-wave attenuation on erg

Investigations

Imaging (mandatory)

  • non-contrast ct orbits (1-mm thin cuts) is the gold standard for localization
  • ubm or b-scan (performed gently) if the view is obscured and globe is stable

Clinical exam

  • search the angle and iris for hidden fbs; check for iris tids and lens integrity
  • dilated indirect ophthalmoscopy (if globe is sufficiently stable)
  • serial erg for suspected retained iron to monitor for siderosis

Treatment

Medical

  • iv antibiotics: vancomycin 1 g and ceftazidime 1 g every 12 hours
  • update tetanus prophylaxis status

Surgical

  • urgent pars plana vitrectomy for iofb removal (ideally within 24 hours)
  • primary closure of the entry wound
  • intravitreal antibiotics are often administered at the time of surgery

Clinical Pearl

Every eye injury from metal-on-metal work needs a CT orbit before MRI — a ferrous IOFB pulled by MRI has blinded patients who said "just a little piece went in my eye."

Differential Diagnosis

  • corneal or conjunctival foreign body without penetration
  • ruptured globe without a retained foreign body
  • post-traumatic endophthalmitis
  • traumatic cataract

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