I'm a bit near-sighted and wear glasses for driving but it doesn't affect boxing at all (that I'm aware of).
I'm not visually impaired to any great degree, but my sensei was.
http://2.bp.blogspot.com/-isE-WhXA46k/UnV1MosZ1nI/AAAAAAAAIOk/JQk81dfRjz8/s1600/Kung_Fu-From_Dark_Angel_zps46fbfeba.png