Board Thread:General Discussion/@comment-202.4.173.52-20130611031324/@comment-8505655-20130611125434

Rather, I believe the Omnitrix is intended to be his eye, such that he is not blind, but rather sees with it. (My personal theory is that this has something to do with the Omnitrix integrating itself with an alien's technological nature - the same thing happened with Nanomech.)  WHy this would be the case, no idea, but I highly doubt Upgrade would be blind.