Mate, it's actually pretty surprising how much you can get away with and still be OK. Ninja has put up the detailed requirments for VA1, 2 & 3 elsewhere on here, so have a look at them, but this is the simplest way to explain it!
I assume you wear glasses/contacts from how you discribed your eyesight above? The easiest way to tell is take a look at your last prescription (or the strength/power written on your contact lens packets) As long as you ar less than +/- 6 in both eyes (and the difference between your eyes isn't more than 1.25) then you'll get in as VA3 which means you'll be fine. more than +/- 6 and it's bad news I'm afraid.
I reckon I must be similar to you; if I take my contacts out now I can't read the text on this forum (on my computer screen) and that's like half a meter away!! my prescription is -5 and -5.75 and I got signed off as VA3 with no questions or problems.
There are other aspects to the test (colour perception etc) but these have little to do with being short sighted, etc. so don't worry too much about them.
Hope that helps.
