I have glasses for when I cannot wear contacts. Due to some technical difficulty, the glasses correct only about 2/3 of my nearsightedness, and give me a slight case of living in a visibly curved universe. I can drive a car in daylight (though really I shouldn't) and work at a computer if the screen is really close.
And the glasses make me stupid. My memory is bad. I overlook simple things. I can't think logically. I lose the thread of every idea that needs more than two steps. If I go completely without contacts or glasses, I'm not safe to cross the street, but I can think, at least.
This morning, I put in my contacts for the first time in a week and realized that I had made a monumentally stupid error at work last week that would take 12 hours of computer time and 4 hours of work time to fix. So I went to the office today and did just that.
I need better glasses.