Introduction

Ptosis is a lowering of the eyelid to below its normal position. The word ‘ptosis’ derives from the Greek ‘πτωσις’, which translates as ‘to fall’. It is an abbreviation of ‘blepharoptosis’—a fallen eyelid—but this longer version is now almost never used. The normal palpebral fissure measures 12–15 mm. The distance between the corneal light reflex and the upper eyelid margin is termed the upper marginal reflex distance. These two measurements are used for objective assessment of ptosis (figure 1). The official definition of ptosis is an upper marginal reflex distance below 2 mm or an asymmetry of more than 2 mm between the eyes. Ptosis has many causes and is a presenting symptom in both emergency and outpatient settings. While most ptosis presents to ophthalmologists, neurologists often see cases in day to day practice. Ptosis may point towards something as dramatic as a leaking aneurysm or something as mundane as a soft …