Levator function

Describing the maximum upper eyelid excursion (measured in mm) from down to upgaze, (and examined with gentle pressure on the eyebrow to stop brow elevation), ‘levator function (‘LF’) gives an indication of the efficacy of the levator muscle (levator palpebrae superioris) in raising the upper eyelid. Normal levels lie between ~12 and 20 mm. Levator function is reduced in the following forms of ptosis: congenital (e.g.congenital levator dystrophy), neurological (e.g. third nerve palsy) and myopathic (e.g.myaesthenia gravis). LF can also be reduced following trauma, or adhesions with other eyelid or orbital structures. LF is usually normal, or minimally reduced in age-related ptosis.