Needs for precise measures of acuity. Equipment to meet these needs.

The equipment described provides precise, reliable measures of acuity from normal to the lowest measurable and meets all recommendations of the NAS-NRC Working Group 39 of the Committee on Vision. Special features of the equipment are as follows: (1) It is a valuable component of a complete clinical eye examination. (2) Because it measures very low acuities, it is excellent for use in low-vision clinics. (3) It meets the demanding requirements of collaborative research studies in which acuity is the primary measure of the effects of therapy. These studies involve tests at repeated intervals under conditions that can be duplicated in a number of examining centers. The adoption of one standard method of measuring acuity for these diverse needs would aid in establishing a sound, generally understood foundation for this basic measure of visual function.