Continuity mistake: Janet goes back and forth from needing to wear glasses to seeing perfectly fine.
Suggested correction: Janet wasn't real. She was a character in Jack's delirious dream. In Jack's dream, he was saying the things Janet was doing was written by Federman, and sometimes he controlled the scene. Not to mention the fact that some people only need glasses to see certain things and can see without them in other incidents or she was wearing contacts.