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Chemical Burn

CRITICAL — Trauma

Symptoms

  • Acute severe pain, burning, and tearing.
  • Intense photophobia and blurred vision following a chemical splash.
  • History of exposure to specific agents (e.g., bleach, oven cleaner, ammonia, battery acid, lime, or plaster).

Clinical Findings

Corneal epithelial status

  • Ranges from scattered superficial punctate keratopathy (SPK) to total epithelial sloughing.
  • Focal or diffuse epithelial loss.

Limbal stem cells

  • Limbal ischemia (blanching of perilimbal vessels): The key prognostic sign.
  • Mild burns show no significant blanching; severe burns show extensive ischemia.

Ocular surface & anterior segment

  • Conjunctival epithelial defects, chemosis, hyperemia, and hemorrhages.
  • Mild eyelid edema and anterior chamber (AC) reaction.
  • First- and second-degree periocular skin burns with potential lash loss.

Etiology

Alkali burns (most dangerous)

  • Agents: Ammonia, lye, lime, magnesium hydroxide, and plaster.
  • Mechanism: Saponify lipid membranes, allowing deep and rapid penetration.

Acid burns

  • Agents: Sulfuric, hydrofluoric, and hydrochloric acids.
  • Mechanism: Cause coagulation necrosis, which typically limits deeper penetration.
  • Exception: Hydrofluoric acid behaves like an alkali and penetrates deeply.

Severity classification

  • Assessed by Roper-Hall or Dua classification systems.
  • Based on the degree of limbal stem-cell ischemia and corneal clarity.
  • Stem cell loss leads to chronic surface failure, conjunctivalization, and neovascularization.

Red Flags

  • Alkali burns: Continue to damage the eye long after exposure due to deep penetration.
  • Limbal ischemia: Blanching at presentation predicts a poor visual prognosis.
  • Grade IV burns: Opaque cornea with no view of iris; high risk of perforation and blindness.
  • Priority rule: Immediate irrigation must start before checking pH or performing an exam.

Investigations

Immediate assessment

  • Litmus paper check: Wait 5–10 minutes after irrigation stops before checking pH (normal 7.0–7.4).

Clinical examination

  • Slit lamp exam with fluorescein staining only after irrigation is complete.
  • Eyelid eversion: Crucial to search for retained caustic particulate matter in the fornices.
  • Diagramming: Document all epithelial defects and ulcerations.

Tonometry

  • IOP measurement: Use Tono-Pen, pneumotonometer, or rebound tonometer if the cornea is distorted.
  • Gentle palpation if instruments are unavailable.

Grading

  • Formally document the Roper-Hall or Dua grade to guide management.

Treatment

Acute irrigation protocol

  • Copious irrigation with saline or Ringer lactate; tap water is a valid emergency alternative.
  • Never attempt to neutralize an alkali with an acid (or vice versa) due to thermal injury risk.
  • Use IV tubing connected to the irrigating solution and an eyelid speculum.
  • Sweep fornices with a moistened cotton-tipped applicator to remove necrotic tissue or particles.

Medical management

  • Cycloplegics: Cyclopentolate 1–2% or homatropine 5% for pain and inflammation; avoid phenylephrine.
  • Lubrication: Frequent (q1–2h) preservative-free artificial tears.
  • Antibiotics: Topical fluoroquinolone or trimethoprim/polymyxin B q.i.d.; erythromycin ointment for large defects.
  • Steroids: Prednisolone acetate 1% (up to q1–2h) for the first 7–14 days; must taper early to prevent melting.

Adjunctive systemic therapy

  • Collagenolysis prevention: Doxycycline 100 mg b.i.d. and Vitamin C 1,000 mg daily.
  • Ascorbate 10% topical q1h for alkali burns (caution in renal patients).
  • Acetylcysteine 10–20% (collagenase inhibitor) if healing is poor.

IOP control

  • Use oral acetazolamide (250 mg q.i.d.) or topical beta-blockers.
  • Avoid alpha-agonists (due to vasoconstriction).

Surgical & advanced care

  • Amniotic membrane (e.g., ProKera) or scleral shells for severe burns.
  • Emergency patch graft or tissue adhesive for corneal melting/perforation.
  • Long-term: Limbal stem cell transplantation (LSCT) if surface fails to re-epithelialize.

Clinical Pearl

Alkali burns are an ophthalmic emergency that keeps damaging the eye after exposure. Limbal ischemia (blanching) is the single most important prognostic sign. Always evert the lids to find hidden caustic particles.

Differential Diagnosis

  • Thermal ocular burn
  • Severe bacterial keratitis
  • Radiation keratopathy
  • Neurotrophic keratopathy
  • Toxic keratopathy (preservative-induced)

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