Ptosis
The upper eyelid can itself hang low, a condition known as a ptosis. In the early stages this can make your eyes look sleepy, if the eyelid comes lower then it can cover your pupil and affect your visual field and even your vision. In most cases the cause is simply a stretching of where the levator muscle that lifts your upper lid inserts into the lid. It is important to exclude rare neurological and muscular problems. So long as these are excluded the treatment involves tightening up the levator muscle. There are two broad techniques based essentially on whether an upper lid blepharoplasty is also required.
Anterior Approach Ptosis Repair
Posterior Approach Ptosis Repair