A 28-year-old male factory worker presents to the emergency department 15 minutes after splashing of a chemical substance into both eyes while working without protective eyewear. He reports severe eye pain, blepharospasm, and blurred vision. On examination, the cornea appears hazy with loss of epithelial lustre, and the conjunctiva is blanched and oedematous. The anterior chamber is clear. Which of the following chemical injuries is most likely responsible for this presentation?

Explanation

## Chemical Injury Classification and Mechanism **Key Point:** Alkali (base) burns cause more severe and penetrating ocular injuries compared to acid burns due to saponification of lipids in cell membranes and deeper tissue penetration. ### Pathophysiology of Alkali vs Acid Burns | Feature | Alkali (Base) | Acid | |---------|---------------|------| | **Penetration** | Deep, progressive (hours–days) | Superficial, self-limited | | **Mechanism** | Saponifies lipids; denatures proteins | Coagulates proteins; forms eschar | | **Corneal opacity** | Hazy, diffuse (loss of lustre) | Opaque white (frosted appearance) | | **Conjunctiva** | Blanched, ischaemic | Hyperaemic initially | | **Anterior chamber** | Often involved; hyphema/iritis | Usually spared early | | **Prognosis** | Guarded; late complications | Better if treated early | | **Examples** | NaOH, KOH, ammonia, lime | HCl, H₂SO₄, acetic acid | **High-Yield:** The **blanched conjunctiva** in this case is pathognomonic for alkali injury. Alkali causes ischaemia by saponifying conjunctival lipids and destroying blood vessels. Acid burns produce a hyperaemic conjunctiva initially because the protein coagulum limits penetration. ### Clinical Presentation Correlation The patient's findings—hazy cornea with loss of epithelial lustre, blanched oedematous conjunctiva, and clear anterior chamber at 15 minutes—are classic for **sodium hydroxide (NaOH)** injury: - NaOH is a strong base commonly used in industrial settings (cleaning agents, drain cleaners). - Immediate blanching of conjunctiva reflects acute ischaemia. - Progressive corneal opacification occurs over hours due to continued penetration. - The anterior chamber may appear clear initially, but iritis and secondary glaucoma develop later. **Clinical Pearl:** Alkali injuries are **time-dependent emergencies**. The degree of tissue damage continues to evolve for 24–48 hours post-injury. Immediate and aggressive irrigation is critical to prevent irreversible blindness. ### Grading of Chemical Injuries (Roper Hall Classification) ```mermaid flowchart TD A[Chemical Eye Injury]:::outcome --> B{Assess corneal clarity<br/>& limbal ischaemia}:::decision B -->|Grade 1: Clear cornea<br/>No limbal ischaemia| C[Good prognosis]:::outcome B -->|Grade 2: Hazy cornea<br/>< 1/3 limbal ischaemia| D[Moderate prognosis]:::outcome B -->|Grade 3: Opaque cornea<br/>1/3-1/2 limbal ischaemia| E[Guarded prognosis]:::outcome B -->|Grade 4: Opaque cornea<br/>> 1/2 limbal ischaemia| F[Poor prognosis]:::urgent ``` **Mnemonic:** **ALKALI = Aggressive, Late complications, Keratitis, Anterior chamber involvement, Lipid saponification, Ischaemia** ### Management Priority 1. **Immediate copious irrigation** (at least 15–20 minutes with normal saline or Ringer's lactate). 2. Remove particulate matter (lime particles, etc.). 3. Topical antibiotics, lubricants, and cycloplegics. 4. Systemic vitamin C (500 mg IV/oral) to reduce scar formation. 5. Referral to corneal specialist for long-term management (conjunctival grafting, amniotic membrane transplant if needed). [cite:Khurana 7e Ch 8]