Contributor: Gordon K. Klintworth
Ptosis (blepharoptosis) can be classified according to the age of onset, severity, cause and pathophysiology. It may be congenital [ptosis - congenital] or acquired and usually results from an abnormality of the levator palpebrae superioris or Müller muscle or in the innervation of those muscles. Orbital masses and trauma can also produce ptosis. The differential diagnosis of ptosis includes myopathic ptosis [ptosis - myopathic], blepharoptosis syndrome, Marcus Gunn syndrome, oculomotor nerve palsy, Horner syndrome, myasthenia gravis, chronic progressive ophthalmoplegia [ophthalmoplegia - chronic progressive], aponeurotic ptosis [ptosis - aponeurotic], and mechnical ptosis [ptosis - mechanical] (from cicatricial processes, enophthalmos and masses in the orbit or eyelid). Ptosis may be associated with myasthenia gravis and myotonic dystrophy.  Ptosis can also be due to a congenital sympathetic palsy, synkinetic ptosis, intermittent pseudo-ptosis occurs in the retraction syndrome. A late-onset ptosis occurs in oculopharyngeal muscular dystrophy.  Ptosis can also be due to a congenital sympathetic palsy, synkinetic ptosis [ptosis - synkinetic], intermittent pseudo-ptosis occurs in the retraction syndrome. A late-onset ptosis occurs in oculopharyngeal muscular dystrophy