## Chemical Injury Severity by Agent Type **Key Point:** Alkali (base) injuries are more severe than acid injuries because alkalis saponify (dissolve) lipids in cell membranes, allowing deeper penetration into ocular tissues. ### Mechanism of Alkali Injury Alkalis such as sodium hydroxide (NaOH) and calcium hydroxide (Ca(OH)~2~) cause: 1. Saponification of membrane lipids 2. Protein denaturation 3. Deep stromal and anterior chamber penetration 4. Continued damage even after initial exposure (progressive injury) ### Mechanism of Acid Injury Acids (HCl, H~2~SO~4~, acetic acid) cause: 1. Protein coagulation (forms a protective barrier) 2. Superficial injury limited by coagulated proteins 3. Rapid pH neutralization at tissue surface 4. Generally less severe than alkali injuries ### Comparative Table | Feature | Alkali Injury | Acid Injury | | --- | --- | --- | | **Depth of penetration** | Deep (stromal, AC) | Superficial (epithelial, limited) | | **Mechanism** | Saponification of lipids | Protein coagulation | | **Prognosis** | Worse | Better | | **Progressive damage** | Yes (hours to days) | No (self-limited) | | **Common agents** | NaOH, Ca(OH)~2~, NH~3~ | HCl, H~2~SO~4~, acetic acid | **Clinical Pearl:** Alkali injuries are ophthalmologic emergencies requiring aggressive irrigation and close follow-up because of the risk of progressive stromal melting, symblepharon, and vision-threatening complications. **High-Yield:** Sodium hydroxide (drain cleaners, oven cleaners) is the most common severe alkali injury encountered in clinical practice. 
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.