Ptosis, also known as blepharoptosis, is the falling or drooping of the upper eyelid(s). The condition develops due to defective muscles, known as the levator muscles, involved in lifting the eyelids. It often develops congenitally (present at birth), but can also occur due to aging or an injury.

Ptosis can occur on its own or may be associated with another condition; for example, children with blepharophimosis syndrome will also have ptosis.