When MJ was only 15 months old, we chose to have plastic surgery done on his left eyelid. It had a severe droop, and was blocking his vision. We decided to fix it right away, so as to not strain his vision in that eye as he was growing. You may have noticed it in his pictures. It is still not perfect, but his vision is! And that was all that mattered to us!
As he gets older, if it bothers him, we will let him decide whether to have any more work done on it. But so far, he doesn't even know it's different.
He still visits the plastic surgeon once a year, to check to make sure the correction is not changing, and that his lid is not blocking his vision at all. They take a photo at each visit, and I told him we needed to practice. This is what I got (cell phone pic).