Saccadic reaction times in alternating cover

The aim of this study was to compare saccadic reaction times (SRTs) during the alternating cover with SRTs during monocular viewing.

Seven subjects with intermittent exotropia, eight subjects with esophoria and ten control subjects were participated. The normal-task was to fixate the central fixation point until the peripheral target appeared randomly either 5 degrees to the right or left. In the alternating cover task (AC-task), the cover was switched from the fixating eye to the other eye, central fixation target was simultaneously extinguished and peripheral target was lit. An infrared limbal-tracking system and electro-oculogram were used for measurements of eye movements. The study followed the tenets of the Declaration of Helsinki. We certify that there is no conflict of interest.

In AC-task, the average SRTs of control subjects, subjects with exophoria and subjects with intermittent exotropia were 224.2 ± 46.5 ms, 198.2 ± 45.3 ms and 227.3 ± 69.9 ms, respectively. On the other hand, the average SRTs of control subjects, subjects with exophoria and subjects with intermittent exotropia in normal-task were 200.7 ± 37.8 ms, 178.2 ± 34.6 ms and 185.4 ± 54.1 ms, respectively.

The SRTs of most control subjects, subjects with exophoria and subjects with intermittent exotropia in AC-task were prolonged compared to normal-task.