Chemical Eye Injury

Exposure of the ocular surface to alkali, acid, solvent or irritant. It is a true ophthalmic emergency: the extent of injury depends on the pH, concentration, volume, contact time and the speed and adequacy of irrigation.

• Common agents: household cleaners (ammonia, sodium hydroxide, bleach), industrial alkalis (lime, cement, plaster), acids (sulphuric, hydrochloric, hydrofluoric, acetic), solvents, pepper spray, fertiliser, airbag residue, and chemical weapons.
• Injury mechanism: alkali saponifies membranes and penetrates deeply to the anterior chamber; acid precipitates proteins at the surface; both cause limbal stem cell damage, ischaemia, and release of inflammatory mediators.
• Grading by the clinical picture, which predicts prognosis:
  • Grade 1: corneal epithelial damage, no ischaemia (good).
  • Grade 2: haze with iris details visible, ischaemia less than one third of limbus (good).
  • Grade 3: total epithelial loss, stromal haze obscuring iris details, ischaemia one third to one half of limbus (guarded).
  • Grade 4: opaque cornea, ischaemia more than half of limbus (poor).

• Severe pain, photophobia, blepharospasm, tearing, blurred vision, redness, foreign body sensation.
• Signs: conjunctival chemosis, haemorrhage and injection, blanching of conjunctiva and limbus (white eye signalling ischaemia), corneal epithelial defect, stromal haze, anterior chamber inflammation, raised intraocular pressure, lens opacity and iris damage in severe cases.
• Skin burns of lids and face may coexist; hydrofluoric acid causes severe deep pain disproportionate to signs.
• Late: symblepharon, limbal stem cell deficiency with conjunctivalisation and vascularisation, corneal melting and perforation, glaucoma, cataract, dry eye, lid deformity.

• Treat first, examine later. History: substance name and nature, time, first aid given, protective eyewear.
• Check pH of the conjunctival fornix with litmus paper before and 5 to 10 minutes after irrigation; continue irrigation until pH is 7.0 to 7.4.
• Slit lamp after irrigation with fluorescein: epithelial defect, depth of haze, limbal ischaemia (in clock hours), anterior chamber reaction, lens, intraocular pressure; examine the fornices for particulate matter (lime, plaster) and double evert lids.
• Photographs and drawing of the extent; check visual acuity after the initial irrigation.

• Immediate copious irrigation at the scene with any clean neutral fluid (tap water if needed) for at least 15 to 30 minutes; in hospital continue with 1 to 2 L (up to 3 to 5 L in severe injury) of normal saline or balanced salt solution using an irrigating lens or giving set at 1 L per hour, after topical anaesthesia (proparacaine 0.5 percent or oxybuprocaine 0.4 percent) and with lid speculum; sweep fornices with a moistened cotton bud; remove particles; irrigate until pH normal and stable for 30 minutes.
• After irrigation:
  • Topical corticosteroid: prednisolone acetate 1 percent every 2 hours while awake for 7 to 10 days, then taper or switch to a less potent agent to avoid corneal melt (steroids reduce inflammation in the first week and are discontinued by about day 10 to 14 if the epithelium has not healed).
  • Cycloplegia: atropine 1 percent twice daily or cyclopentolate 1 percent three times daily.
  • Topical antibiotic: chloramphenicol 0.5 percent or ofloxacin 0.3 percent four times daily until epithelium heals.
  • Preservative free lubricants hourly.
  • Ascorbic acid: oral 500 mg to 1 g four times daily, and topical ascorbate 10 percent every 2 hours (promotes collagen synthesis); topical sodium citrate 10 percent every 2 hours for 10 days.
  • Doxycycline 100 mg orally twice daily (inhibits collagenase, reduces melt) and topical tetracycline in severe cases.
  • Intraocular pressure control: acetazolamide 250 mg four times daily or timolol 0.5 percent twice daily; avoid prostaglandin analogues in the acute phase.
  • Autologous serum 20 percent drops hourly; therapeutic bandage contact lens or symblepharon ring.
• Surgery: amniotic membrane transplantation (preferably within 7 days) for grade 3 and 4 injuries; limbal stem cell transplantation after the eye is quiet (3 to 6 months); tenonplasty or limbal revascularisation for ischaemia; tectonic keratoplasty for perforation; keratoprosthesis for severe bilateral limbal failure.
• Admit severe injuries; review daily until epithelium is healed.