Both, I think. Uncorrected the limits for an initial are higher, but once you're "in" there is a little reluctance to take it off you, and the stated limits (uncorrected) fall a bit as long as you can be corrected to normal levels.
For example the myopia limit (short sight I am told) is a -5 dioptres uncorrected (it used to be -3 before JAR) for an initial class one test. For renewal the uncorrected limit falls to -8 (almost mole vision!) as long as corrected it is within tolerances.