Ptosis, or blepharoptosis, is the formal name for a drooping upper eyelid. In the non-Asian population, most cases occur in the elderly as the tendon connecting the eyelid's otherwise healthy main opening muscle (levator muscle) to the eyelid itself either stretches or develops a tear.

Congenital (in-born) ptosis due to poor development of the levator muscle accounts for only a few percent of cases.

In the Asian population, on the other hand, mild ptosis seems to occur at a strikingly higher incidence in younger people.

In most cases, the tendon shows no sign of abnormality during surgery. Instead, it appears the levator muscle is slightly weak, which leaves the eyelid sitting at too low a level.

Ptosis may affect one eye or both and in differing degrees.

Because a hanging lid may expose more skin above the eyelashes, affected patients may mistakenly believe that they have a naturally higher crease on one side if only one eye has ptosis.

However, undergoing eyelid surgery to raise the lower crease is a mistake since the ptosis will persist on the other side and the two eyes will still appear mismatched.

Ptosis repair is a distinct operation that is very different from double eyelid surgery.

The weak muscle may be tightened from either deep inside of the lid from during incisional double eyelid surgery or from within a separate incision placed along the inside (back) surface of the eyelid.

If ptosis is advanced, it may be preferable to first fix the ptosis and then perform double eyelid surgery after full healing.

Failure to recognize the presence of ptosis and, if necessary, treat it before or during double eyelid surgery is one main reason for patient dissatisfaction after cosmetic Asian eye surgery.