Eye Movements During Change of Stationary Points of Fixation in Space

Abstract

If points of fixation are removed to various distances from an observer’s eyes, the change is accompanied not only by a saccade, but by convergence of the eyes (convergence or divergence of the optical axes). Together with accommodation (and other factors), the relative position of the optical axes and the retinal images enables us at moments of fixation to judge the distance and size of objects. In this book there is no need to dwell in detail on questions of binocular vision; the necessary information can be obtained from other sources—the book by S.V. Kravkov (1950), for example. The important issue so far as we are concerned is that the convergence and divergence of the optical axes during a change in points of fixation differ sharply from saccades, particularly in duration. The duration of convergence and divergence of the eyes is approximately ten times that of saccades. Convergence or divergence of the eyes very often is equal in duration to fixation.