Levator palpebrae superioris function is assessed clinically before ptosis surgery by measuring the excursion of the upper eyelid margin from extreme downgaze to extreme upgaze while the frontalis is immobilized. In a normal adult, this excursion measures:
- A 5 mm or less
- B 8 to 10 mm
- C 15 mm or more ✓
- D 20 to 25 mm
Correct answer: C. 15 mm or more
Explanation
Levator function is the lid excursion between extreme downgaze and upgaze with the brow fixed. Normal function is 15 mm or more; 8 to 12 mm indicates fair function, 5 to 7 mm poor, and under 5 mm very poor function. This measurement decides surgical choice: good function allows levator resection or aponeurotic repair, while poor function requires a frontalis sling. Option B describes fair function seen in some involutional cases, not the normal value.
Reference: Khurana, Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.