Eye Movements Recorded During Convergence and Divergence*

The purpose of the present experiments was to record horizontal binocular eye movements during normal amounts of convergence and divergence by a method having satisfactory sensitivity and accuracy. This is a method of direct photography, based upon collimated beams of light reflected from plane mirrors mounted on tightly fitting contact lenses. The records show that the eyes exhibit relatively rapid and accurate motions of vergence when fixating alternately a near and a far test object. There is no evidence for a systematic discrepancy between the extent of vergence and the geometrical location of the test object. It is concluded that when fusion is maintained, the images of a fixation object are brought to corresponding areas of the retina to an accuracy of about two minutes of arc. This finding is consistent with the reported sizes of Panum’s area and the region of optimal visual resolution.