Dermatochalasis stands for excess skin and tissue on the eyelids. Most commonly, dermatochalasis is due to age and the effect of gravity. Although dermatochalasis is typically considered cosmetic surgery, some patients have a substantial amount of excess skin and prolapsed fat that blocks their vision. This would then be considered a functional problem. Lower eyelid dermatochalasis is, however, always considered a cosmetic problem.
Ptosis is a drooping of the eyelid.
There are two extremely thin muscle that are primarily responsible for holding the eyelids up. Age-related changes cause these muscles to become lax. There are also medical conditions which can cause drooping or ptosis. Previous eye surgery or trauma can also lead to ptosis. Eyelid lesions involve a large variety of conditions ranging from styes to malignant cancer.