How do you differentiate a corneal ulcer from an epithelial erosion in terms of depth?

• A. Epithelial erosion involves only the surface epithelium and heals quickly; corneal ulcers extend into the stroma.
• B. Epithelial erosion extends into the stroma; corneal ulcers only involve surface epithelium.
• C. They are the same depth.
• D. Epithelium thickness does not relate to depth.

Answer: (A)

Depth of tissue involvement is what separates an epithelial erosion from a corneal ulcer. An epithelial erosion is a shallow defect limited to the corneal surface epithelium; because the stroma isn’t involved, healing is rapid as epithelial cells migrate to cover the surface. A corneal ulcer, on the other hand, means the defect has penetrated into the stroma. Once the stroma is involved, you get stromal edema, inflammatory response, and a real risk of scarring, thinning, or perforation, requiring more intensive treatment and closer monitoring. So the key idea is that surface-only epithelium loss heals quickly, whereas stromal involvement defines a true ulcer.