Is plastic surgery to correct the shape of the eyelid and reduce its prominence, which resulted from continuous self-harm and disfigurement, considered a major sin in Islam, knowing that non-surgical alternatives exist?

There is no harm in using creams that straighten the skin or remove wrinkles, nor in undergoing surgery to remove a deformity or defect that causes psychological harm, provided it is not merely for beautification. If the change in the color of the eyelids, the thinness of the left eyelid, and its drooping are considered a defect or deformity, or cause you psychological harm, then it is permissible to perform the operation; otherwise, it is not.