[[Refraction]] is only one part of visual acuity. Various medical conditions can cause physical blockage/dispersion of light in the eye, problems detecting light in the eye, or problems with the visual processing that turns a series of electrochemical signals into a picture in our mind's eye. See an [[optometrist]] if your vision can't be corrected with [[refraction]].
==20/x==Shorthand for 20 over a single digit, or considerably better than 20/20 vision. ==See Also==
* [[Emmetropia]]
* [[Optics_related_math#Visual_acuity]]