Visual acuity commonly refers to the clarity and sharpness of a person’s vision.  It is dependent on both optical and neural factors: how sharp the focus of the retina in the eye is, how healthy the retina is and how sensitive the interpretive faculty of the brain is. The common term used to describe visual acuity is expressed in terms such as 20/20. A 20/20 visual acuity means that a person can see at 20 feet distance what someone with normal vision can see at 20 feet distance.