Also, until relatively recently glasses were uncool and unfashionable. Computer geeks generally pay less attention to such norms and choose function over form, so a geek with marginally poor eyesight would perhaps be more likely to go for glasses than a non-geek, who would survive without for appearance purposes.

I think jobs with computers are, in many ways, more forgiving to those with bad eyesight than other jobs. I have bad vision (just enough so I can't drive) but thanks to Gtk / Compiz, I can arbitrarily change the font size to be as big as I like it, and Orca and other screenreaders would help if I were completely blind. However, if I were a scientist or a taxicab driver or at a factory or throwing darts for a living, I'd be much worse off because I couldn't make those accommodations.