I am sorry to hear that your left eyelid seems to be drooping, and that it is bothering you. Ptosis (the medical term for drooping of the eyelid) can be caused by many different things. Some of them serious, some of them benign. I don't have any of your medical information, nor am I able to examine you to give me more information to help tell you what I think may be going on, but what I can do is give you some general information about ptosis, and recommend what kind of physician I think you should see. One of the most common reasons that people come to a physician due to ptosis is actually dermatochalasis. Dermatochalasis is a problem where there is excess eyelid skin (typically the upper eyelid), such that it folds over itself when the lid is opened, and can impair the visual fields. This is typically a problem seen in older generations, and is relatively easily fixed surgically with a blepharoplasty
(a "lid lift" done by a facial plastics surgeon
). Otherwise ptosis can be thought of in many different general catergories such as: neurogenic (such as a nerve palsy, or Horner's syndrome), myogenic (meaning the muscles to open the lid are weak as in myasthenia gravis), mechanical (like a tumor or mass that is preventing it from opening completely), etc... There are numerous different reasons (including idiopathic...meaning we don't know what causes it) for ptosis, but a history and physical exam by an ophthalmologist
or facial plastics surgeon will help determine what is going on in your case. I wish you all the best.