An optometer is described that provides an electrical signal proportional to the amount of movement of the anterior surface of the crystalline lens. Dynamic recordings of this movement were made on a number of subjects tracking predictable (periodic) and nonpredictable target step movements. Histograms of the reaction times definitely show that the accommodation system can reduce its delay time when presented with a predictable stimulus. Typical accommodative reaction times are compared to those published by other authors in the literature.The change of anterior chamber depth lens curvature, and pupil diameter are related to accommodative target distance by a photographic method and help to provide a clearer understanding of accommodative lens changes.