A 50-year-old man with right-sided Bell palsy complains of foreign body sensation in the right eye. Fluorescein staining shows punctate erosions concentrated in the inferior third of the cornea. The reason the superior cornea is relatively spared is:

• A Superior cornea receives greater tear film turnover
• B Superior cornea is covered by the ptotic upper lid
• C Bell phenomenon rotates the globe upward during attempted blink ✓
• D Inferior cornea has lower density of sensory innervation

Explanation

In exposure keratopathy of facial nerve palsy, the protective Bell phenomenon elevates the globe during attempted closure, so the exposed inferior strip of cornea between the lids bears the desiccating insult while the superior cornea remains protected under the upper lid. This inferior distribution of staining distinguishes exposure keratopathy from superior limbic keratoconjunctivitis, where the superior cornea and conjunctiva are affected.

Reference: Parsons' Diseases of the Eye, 23rd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.