The evaluation of an ophthalmological patient is accomplished by a variety of subjective and objective procedures that are performed to obtain a profile that delineates the patient's visual capability. This profile is then appraised to determine whether or not a pathological state exists. It would be desirable in cases of suspected macular disease to obtain a precise estimation of the functional capability of the cone receptor elements since it is probable that the earliest sign of disease will be a disturbance of the normal cellular metabolism. Currently, it is difficult to detect occult aberrations in macular performance. Experience indicates that observation by ophthalmoscopy provides no consistent information about macular capability. The measurement of visual acuity and the detection of central scotomas, although clinically adequate, will not elicit minor aberrations in the physiological mechanism and will not evaluate the performance reserve of the macula. We feel that there is a need