Accommodation without pupillary constriction.

In this paper it will be shown that the association of pupillary contraction with even substantial accommodation breaks down under rigorous control of alignment. Conditions exclude other than "accommodative" (blur induced) pupillary responses by eliminating light reflexes due to temporal and spatial luminance differences, colour and polarization differences. The visual solid angles of the targets were also precisely equalized. A subtle procedure is described to obtain accurate alignment along a single line of sight of the stimulated eye. The pupillary system appears to be quite sensitive to alignment errors, but the "accommodative pupillary reflex" is totally absent under rigorous alignment. Pupillometry used an infrared television camera to monitor the non-stimulated eye in total darkness and silence. Occurrence of correct accommodation for every stimulus event was confirmed by observing accommodative vergence. Judging by the size of the accommodative vergence response and, occasionally, the size of Purkinje-Sanson images, the accommodative response was found to be essentially equal to the stimulation.