Is 18 Years Old Too Young for Eyelid Surgery?

Age is not the most important decision for a patient undergoing a blepharoplasty.  The Anatomy is more important.  If your sister's eyelids are giving her trouble, she may benefit from upper blepharoplasty, which will remove the excess skin. Blepharoplasty in a young patient should be conservative and retain the fat around the eye.  This can be done at any age at which it is needed. Because she's young with presumably excellent skin tone, she should respond well. I hope this helps.

She does seem too young to have upper Blepharoplasty. But there are individuals with abnormal early laxity of their skin. in these cases upper Blepharoplasty could be successful. The possibility of a visible scar should be discussed with the plastic surgeon, as this would be more noticeable in a young person.

Upper eyelid surgery in a young patient is seldom indicated unless they have congenital excess skin which is rare. The other indication for a droopy eyelid surgery might be from a condition called ptosis where the upper eyelid hangs close to the pupil where normally in caucasian eyelids it should rest 1-2mm below the iris. Excess skin alone is very uncommon; however, sometimes a very small amount needs to be removed to accomodate correction of ptosis. On the other hand, I would caution against removing too much upper eyelid skin or removing fat to avoid eyelid closure problems which can lead to dry eyes or if too much fat is removed, a hollowed look can result.

Hi Alexa
She may or may not be too young to make this decision. Certainly she should make this decision with the help and support of her parents. She may very well have a functional issue. If the droopiness of the upper eyelid is due to the eyelid margin (where the eyelashes are) resting low on the eye, this condition is referred to as upper eyelid ptosis. If your are referring to the upper eyelid fold, this needs to be more carefully assessed.
I would strongly recommend assessment by an oculoplastic surgeon. This is a board certified ophthalmologist who has completed a fellowship training in eye plastic surgery. The American Society for Ophthalmic Plastic and Reconstructive Surgery maintains a website that can help you locate a well qualified surgeon in your area (www.ASOPRS.org).
As these are very specialized issues, it is best to see a fellowship trained eye plastic surgeon rather than a generalist like a board certified general plastic surgeon or a facial plastic surgeon. And yes, the results of surgery need to last a lifetime.

It really depends what we are talking about. If she really has excess skin that can be improved by removing it, then so be it. But she would need to be examined to determine the proper diagnosis and then the treatment plan would be based on the problem at hand.
Age does not always play a role.
Good luck.