You gotta have 20-20 vision when you start you pilot career.  Your eyes can get worse with age, but they must remain correctable to 20-20 to keep flying.

With the advent of laser eye correction, most anybody can get 20-20 vision.  But do NOT go to non-military laser eye facility to get your eyes corrected if you want to be a military pilot.  It MUST be done by a military medical facility.  Military facilities use a different procedure than the civil facilities and the civil procedure is not rated for high G environments.  If you ever get a civil laser eye procedure, you'll never fly in the military.  Besides, the military will do it for free.