I was at a Christmas party with a bunch of government workers. True story. They were talking about sick days and excuses department heads got from employees calling in sick.
One department head says a woman who worked with him often called in sick and recently called in sick again early one morning. She told him she wouldn't be in and so he felt a need to ask her what her problem was. After a minute she said, I just have to admit that it is a bad case of anal glaucoma. This drew a blank and so he asked her what that was as it sounded pretty serious. "Well, what it means is, my ass just can't see getting out of bed and coming to work today."