Two patients present with chemical eye injuries. Patient A has a white, opaque cornea with anterior chamber fibrin, elevated IOP, and symblepharon formation. Patient B has a clear cornea with mild stromal haze, normal IOP, and conjunctival erythema without symblepharon. Which clinical finding best distinguishes the severity and type of chemical burn between these two patients?

Explanation

## Distinguishing Alkali (Severe) from Acid (Mild-Moderate) Burns: Role of Conjunctival Damage **Key Point:** Symblepharon (adhesion between palpebral and bulbar conjunctiva) is pathognomonic for alkali burns and indicates deep, progressive conjunctival scarring. Acid burns rarely cause symblepharon because the eschar limits penetration and conjunctival damage is superficial. ### Pathophysiology of Conjunctival Involvement **Alkali Burns:** 1. Saponification of conjunctival lipids → cell death 2. Progressive necrosis over days → conjunctival scarring 3. Loss of goblet cells → dry eye 4. Adhesion formation between palpebral and bulbar conjunctiva → **symblepharon** 5. Fornix foreshortening and entropion develop **Acid Burns:** - Coagulation necrosis → eschar acts as barrier - Conjunctival damage limited to epithelium and superficial stroma - Minimal goblet cell loss - **Symblepharon does NOT form** - Conjunctiva heals without significant scarring ### Clinical Staging and Discriminators | Aspect | Alkali Burn | Acid Burn | |--------|------------|----------| | **Symblepharon** | Present (pathognomonic) | Absent | | **Conjunctival scarring** | Severe, progressive | Minimal | | **Fornix depth** | Foreshortened | Preserved | | **Goblet cell loss** | Extensive | Minimal | | **Dry eye severity** | Severe | Mild | | **Long-term sequelae** | Entropion, trichiasis, blindness | Good visual prognosis | **High-Yield:** **Symblepharon is the single best clinical discriminator** between alkali and acid burns. Its presence indicates alkali exposure and deep conjunctival damage; its absence suggests acid burn or mild alkali burn. **Clinical Pearl:** A patient with symblepharon requires aggressive long-term management including: - Frequent lubricants and topical steroids - Lysis of adhesions (surgical or chemical) - Amniotic membrane transplantation - Limbal stem cell transplantation (in severe cases) **Mnemonic:** **SCAR** = **S**ymblepharon = **C**onjunctival **A**dhesion in **R**ecurrent alkali burns **Warning:** Do not confuse conjunctival erythema with scarring. Erythema is acute inflammation (non-specific); symblepharon is chronic scarring (alkali-specific).