Visual acuity is a measure of how well a person can focus on an object. To test visual acuity, the person may read letters or symbols on a chart from the top down, line by line, covering first one eye and then the other.
A visual acuity score is a ratio comparing the person's performance to that of people who have "normal" vision.
For example, a person who can read what people with normal vision can read at 20 ft (6 m) has 20/20 (6/6) distance vision. The larger the second number, the worse the vision.
If vision is 20/40 (6/12), the person can read at 20 ft (6 m) what people with normal vision can read at 40 ft (12 m).
If vision is 20/60 (6/18), the person can read at 20 ft (6 m) what people with normal vision can read at 60 ft (18 m).
Medical Review:Kathleen Romito MD - Family Medicine & Adam Husney MD - Family Medicine & Christopher J. Rudnisky MD, MPH, FRCSC - Ophthalmology
PeaceHealth endeavors to provide comprehensive health care information, however some topics in this database describe services and procedures not offered by our providers or within our facilities because they do not comply with, nor are they condoned by, the ethics policies of our organization.