Binocular fixation disparities in reading in people with unilateral strabismus: A case study.

Abstract

Recent studies of binocular coordination during reading have discovered that the eyes do not always fixate on the same location. This current study explored the patterns of eye movement of participants with unilateral strabismus during reading. It was found that crossed horizontal disparities were more dominant than uncrossed, and that aligned fixations were least prevalent. The right eye above the left fixations were most prevalent of vertical disparities. The strabismic eye made fewer fixations on words when the higher cognitive load was on the other eye. The healthy eye had to compensate for the intermittent drifts of the strabismic eye. The participants had better control of the strabismic eye when it took on a role of the dominant eye (in crossed fixations). Both vertical and horizontal disparities were distinctly larger than reported in previous research, there were also distinctly fewer aligned horizontal fixations than reported in the majority of previous studies. Horizontal disparities distinctly larger than vertical disparities were observed. Eye coordination in participants with strabismus differed from typical adult readers in terms of magnitudes of fixation disparities due to the drifts of the strabismic eye. Crossed fixations being most advantageous in terms of cognitive processing speed have been observed to be the most prevalent, same as in previous research involving similar experimental setup.