A standardized test chart used to measure visual acuity. Visual acuity is expressed as a fraction (e.g., 20/20) in which the numerator denotes the testing distance and the denominator indicates the distance at which a person with normal eyesight can read the letters on the chart. For example, if the smallest letters that a person being tested can see are on the 20/40 line, it means a person with normal eyesight can see these same letters at a testing distance of 40 feet. (Ref: Contact Lens Council)