Corneal abrasion involves injury to which corneal layer?

• A. Endothelium
• B. Stroma
• C. Retina
• D. Epithelium

Answer: (D)

The corneal abrasion involves injury to the outermost layer of the cornea—the epithelium. This thin, protective surface is what gets scraped in a typical abrasion, causing pain, tearing, and photophobia. The epithelium can heal quickly because epithelial cells migrate from the edge of the defect and from limbal stem cells to restore the surface. Deeper layers are not typically involved in a superficial abrasion: the endothelium sits on the inner corneal surface and maintains fluid balance but does not regenerate well; damage there leads to corneal swelling rather than surface erosion. The stroma is the thick middle layer and would be implicated in deeper ulcers with scarring. The retina is not part of the cornea.