I was just reading this thread earlier from this future sailor who had the same issue and they said he was allowed to wear contacts and get sent to the eye doctor very early:
http://www.navydep.com/forums/showthread.php?t=2580
But then this thread says you'll basically be blind if you don't bring some glasses:
http://www.navydep.com/forums/showthread.php?t=676
But since I have a month before I ship out, I'm probably going to order some cheap glasses anyway...
I hate my poor eyesight T____T