What is the definition or description of: visual acuity?

Seeing: Visual acuity is simply how well a person sees, there are international standards.For comparison that transcend language and even metric versus english, it is most commonly based on distance of 20 feet or 6 meters. There is also near vision standards.

Sharpness: Visual acuity is the measure of the sharpness of vision. It is the most important measurement of eye function. In the us, the antiquated snellen visual acuity measurement is most often used. This is the "20/20" thing you have no doubt heard of.