what is the normal vision of human eye
Visual acuity A reference value above which visual acuity is considered normal is called 6/6 vision, the USC equivalent of which is 20/20 vision: At 6 meters or 20 feet, a human eye with that performance is able to separate contours that are approximately 1.75 mm apart.[4] Vision of 6/12 corresponds to lower, vision of 6/3 to better performance. Normal individuals have an acuity of 6/4 or better (depending on age and other factors).