Looking at your photo, there appear to be a couple of differences between the two sides. First of all, the left brow is elevated compared to the right. Often this is simply a physiologic/normal difference, but it can suggest the presence of an underlying issue such as a droopy or ptotic left upper lid. In this case you use the brow to elevate the lid to a more normal position. There is a slight retraction of the left upper lid that may be related to the brow, or might be associated with other issues such as thyroid abnormalities. It is also possible that the left eye is more prominent, either congenitally or due to an orbital process. Certainly there are other possibilities as well.
I suggest you see an oculofacial plastic surgeon to further identify the underlying process and how best to treat it. Try the ASOPRS website to find a physician.