A 32-year-old factory worker sustains a chemical splash injury to the right eye. On examination, the cornea appears cloudy with stromal haze, anterior chamber shows fibrin, and intraocular pressure is elevated. A second worker with identical exposure shows a clear cornea with mild conjunctival injection and normal IOP. Which feature best discriminates between an alkali burn and an acid burn in this scenario?

Explanation

## Discriminating Features Between Alkali and Acid Burns **Key Point:** Alkali burns penetrate deeply into corneal stroma and anterior chamber structures due to saponification of lipids in cell membranes, whereas acid burns cause protein coagulation necrosis that limits further penetration. ### Pathophysiology **Alkali Burns:** - Saponify lipids in cell membranes → cell lysis - Penetrate deeply into stroma and anterior chamber - Damage to corneal endothelium → elevated IOP - Cause anterior chamber inflammation with fibrin - Progressive corneal opacification over days **Acid Burns:** - Cause protein coagulation necrosis → eschar formation - Eschar acts as a barrier → limits further penetration - Superficial injury (epithelium and anterior stroma) - Minimal anterior chamber involvement - Cornea may remain relatively clear ### Comparison Table | Feature | Alkali Burn | Acid Burn | |---------|------------|----------| | **Corneal penetration** | Deep (stroma + endothelium) | Superficial (epithelium + anterior stroma) | | **Corneal clarity** | Cloudy/opaque | Often clear or mildly hazy | | **Anterior chamber** | Fibrin, inflammation, hyphema | Minimal involvement | | **IOP elevation** | Common (endothelial damage) | Rare | | **Conjunctival damage** | Severe (symblepharon risk) | Moderate | | **Prognosis** | Guarded to poor | Better | **High-Yield:** The **depth of stromal involvement** is the single best discriminator. Alkali burns show corneal stromal haze and anterior chamber fibrin because they penetrate deeply; acid burns show clear cornea because the eschar limits penetration. **Clinical Pearl:** A cloudy cornea with anterior chamber fibrin in a chemical burn strongly suggests alkali exposure and warrants aggressive management (frequent irrigation, topical steroids, cycloplegics, IOP control). **Warning:** Do not confuse the presence of conjunctival injection or chemosis as discriminators — both alkali and acid burns cause these. The key is the **depth** of corneal involvement.