20/20 correction
20/20 correction is a correction you normally get from a licensed optician, which corrects your eyesight up to a degree of visual acuity that an emmetropic (or "normal-seeing") person achieves on a Snellen Chart. "20" refers to the distance (in ft) to the standardized Snellen Chart. So if you have 20/20 vision, you can see normally. More specifically, 20/20 vision is defined as being able to differentiate details that make up 1 arc minute of your viewing angle, which equals around 0.016° of your 360° visual perception. If you can see 20/15 or even better, this means that your are overcorrected.
It is very difficult to perform Active Focus at this strength of glasses, as there is not enough of a blur horizon to produce stimulus - see Distance vision.