A 45-year-old man develops incomplete lid closure after parotid surgery. He now complains of morning grittiness. Fluorescein staining shows punctate epithelial erosions confined to the lower third of the cornea. Why is the lower cornea predominantly involved?

• A Tear film pools dependently in the lower fornix
• B Gravity draws inflammatory cells inferiorly
• C The lower cornea has fewer epithelial cells
• D Bell phenomenon elevates the exposed cornea upward ✓

Explanation

In lagophthalmos from facial nerve palsy, the reflex Bell movement rotates the eye upward during attempted closure, so the unprotected inferior strip of cornea lies between the lids and bears the brunt of exposure. Tear pooling does not protect it because the film breaks up rapidly over the denuded surface.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.