i am also a wannabe but will try shed some light on the questions you have.
eyesight- as far as i know, eyesight correctable to 20/20 is fine, that i hope means myopia is ok.
they don't have a preference for what degree/ subject the candidate studied in the past. but in order for you to get hired, and hopfully be good at the job, you will have to digest alot of technical information about numerous aircraft systems (amongst other subjects...) It would be difficult if you are not interested in it. As for the level of maths required, the ability to do quick addition/subtraction/ multiplication/ division should be adequate for most operations (i think).
check out the archive- it contains topics discussed in the past- should cover most of your worries.
http://www.pprune.org/archive/index.php/f-99.html