THE EYES!!!!! AHH!!!!!!!!!!! =_=
This is the strangest thing im going to get into. There are a lot of therioies concerning it, and I have a very logical one, but I respect other peoples theories. Im just listing some commonly used ones, not plagurizing anyones work. The eye theory also sometimes relates to why he wears glasses.
The most commonly used theory was he got a piece of glass stuck in his eye. Other theories include a match, being punched by someone, or just being born that way. My theory is a complicated one, so now for a scheduled trip into my childhood.
When I was little, I scratched my left eye with a ring (I dont mean something like a little scratch, it REALLY hurt). I forget most of that, but now my left eye is weaker than my right. This may also be part of the reason I wear glasses. Now I have a miniscule piece of skin near the tear duct of my left eye and it is pulled up a tiny bit more than on the right. It may be humanely possible for someone to scratch both of their eyes SERIOUSLY so that the skin around their eyes pulls up or down and they could end up with the eye problem so they would look kinda like a living version of Weevil. It could also make them L.B.W.G (my mnemonic device for legally blind without glasses).
So that is my theory thank you for taking a trip into my childhood.