Two factors affecting saccadic amplitude during vergence: The location of the cyclopean eye and a left - right bias

Abstract

Saccades occurring during vergence have been reported to differ in amplitude depending on whether the saccade drives the eyes leftward or rightward. Furthermore, this difference varies in degree and direction among individuals. We examined two explanations of the variation--that it is the result of the cyclopean eye being nearer to one eye, and that it is the result of a pervasive bias, within an individual, to make larger saccades either leftward or rightward. Examination of the saccades of 14 subjects, recorded during both divergent and convergent movements that required leftward or rightward saccades, shows that neither explanation alone provides an adequate account of the differences observed. However, statistical analysis (ANOVA) indicates that almost 60% of the total variation in the observed saccadic amplitudes is related to the two explanations taken together. We speculate that both influences act on the saccade in a given individual, and that the amplitude manifested depends on the relative magnitudes of the two influences within that individual.

What does the dominant eye dominate? A brief and somewhat contentious review

“…However, as was discussed in Claim 2, the role of an asymmetry in acuity or contrast sensitivity is yet to be determined for the general population. There are studies in which oculomotor asymmetries have been examined during vergence (B. Clark, 1936), during version (Moiseeva, Slavutskaya, & Shul'govskii, 2000), and during eye movements that require both vergence and version (Barbeito, Tam, & Ono, 1986;Pickwell, 1972), but the correlation between these asymmetries and acuity asymmetry was not examined. If different asymmetries do not correlate, asymmetry dominance as a single unified concept becomes questionable.…”