Effects of convergence and monocular fixation on the horizontal saccades

Abstract

Binocular eye movements in humans are organized in order to place images on corresponding retinal locations so as to fuse then into a single percept. For more than one hundred years, it has been a matter of dispute how the eyes achieved ta finally adjust their velocities relative to each other during abduction and adduction phases of the saccadic movements. This study included şı healthy subjecets under near and far-targetviewing conditions, subjects fixated rightwardsand leftwards through 20°midline during which their eye movements were recorded by conventional electrooculograhy (EOG). Under near viewing condition, the distance between frontal plane of the both eyes and the midline target was 35 cm. The distance was 5.5 meters under far viewing condition. Recording were made under both mono and binocular conditions. Results were statistically analyzed. Angular velocty was found to be 216°,54/sn29,38 during binocular near-viewing condition and 200°, 18/sn±25,45 during binocular far-viewing condition. Adductional angular velocity during binocular near-viewing was 224°,99/sn±28,91, abductional angular velocity was 208°,09/sn±27,49. Angular velocity rates under binocular near target viewing condition were significantly higher than those recorded during far target viewing (p<0,000). Adductional velocities were again found to be significantly higher than abductional velocities (p<0,000). The difference did not change during monocular fixation. It has been concluded that higher angular velocity rates found under near-target viewing condition might be influenced by convergence. Similarly, we concluded that convergence might have had influence on higher adductional velocty rates in view of the literature knowledge.