You dont need to worry about it for most civillian certifications. Still, do as others suggest and check.

For military, it is a bit different. The regulations for the USAF in regard to vision have changed alot in the last few years. When I was considering the military to further my education I would not have been able to fly what I wanted or most others, probably only troop transport in non hostile situations, but now with as much as vision technology has been changing (long wear contacts, lasik, etc) the USAF are starting to adjust as proven documentation comes in that they would not be putting a pilot, other lives, and lots of $$$ at risk by putting someone without 20/20 uncorrected vision in a cocpit.

The bottom line, check into it.