DIRECTION OF THE SIGHTING LINE FOR DIFFERENT ACCOMMODATIVE RESPONSES

Abstract

ABSTRACT

The sighting line is the only reference axis of the eye that can be experimentally assessed simultaneously with respect to the visual system and its orientation in space. It is different from other axes such as visual axis, line of sight, and fixation axis which are defined for reference points which cannot be readily measured. This experiment was designed to determine if the direction of the sighting line is invariant in the presence of accommodative changes. In the apparatus used two objects could be placed along the subject's sighting line providing an approximately 2.00 D difference in accommodative stimulus. The mean change in the direction of the sighting line for six subjects was found to be of the order of 2′ in the horizotal meridian and 1′ in the vertical meridian and the maximum deviation observed was approximately 4½. In this sample taken as a whole, no systematic shift in direction of the sighting line was observed.