1. Accommodation training apparatus comprising: optometer means for imaging radiation onto the plane of the pupil of an eye to form a retinal image and directly measuring the refraction of said eye as a function of said retinal image, said optometer means providing outputs representing said refraction of said eye on a periodic basis and at a rate corresponding to a plurality of measurements each second; audio means responsive to each output of said optometer means for producing biofeedback tone information having a frequency representative of the refraction of an eye being measured to provide an indication of the current state of accommodation during training; and side channel means for selectively placing blur cue information into said optometer means for projection by said optometer means onto the retina of said eye during training to permit accommodation training to selectively occur in the presence of a focusing target.