It is the impossibility to lift the upper eyelid appropriately. There are cases that are not that extreme, in which the eyelid does not cover the pupil. There are more severe cases in which the eye is completely covered by the eyelid. The reasons for this may be varied. Among them we find Dermatochalasis (excess of baggy skin in the upper eyelid), the stretching of the tendon that links the eyelid with the muscle that lifts it, muscular or neurological diseases, etc.
Acquired ptosis can be cured with eyelid ptosis surgery to tighten the tendon, or with blepharoplasty surgery, in case it is for esthetic reasons. There are different techniques to do it, but in most of the cases, they usually leave no scars. It is an outpatient surgery, performed under local anesthesia, and the after surgery care is quite short.