visual acuity

sharpness of vision: the degree to which a person is able to distinguish and resolve fine detail. Visual acuity depends on how well objects are illuminated and upon such factors as practice and motivation, but the essential requirements are a healthy retina and the ability of the eye to focus incoming light to form a sharp image on the retina. Acuity of distant vision is often expressed as a Snellen score ( see Snellen chart ); acuity of near vision as a Jaeger score (see Jaeger test types ).