Perceptual Development: Visual Acuity

Visual acuity (VA) is a measure of spatial resolution of the visual system, which is determined at least in part by the ability of the eye to focus incoming rays of light directly onto the retina at the back of the eye. For mature, cooperative, verbal individuals, VA is typically measured by having the subject identify letters on an eye chart that is at a precise distance from the individual. The stimuli are black letters on a white background, yielding the highest possible contrast. In a clinical setting, VA is generally defined as a fraction with the denominator specifying the distance at which the subject sees what most individuals see at 20 feet. Normal VA of 20/20 can be achieved for most individuals naturally or ...