Correlation of saccade amplitude during refusion with the fusional convergence amplitude in patients with intermittent exotropia.

Abstract

In patients with intermittent exotropia (IXT), to investigate the correlation between fusional convergence amplitude and saccade during refusion, as well as the differences in saccade caused by suppression.

We measured the fusional convergence amplitude using a synoptophore. Suppression was assessed in 15 patients with IXT (mean age 18.1 ± 11.0 yrs, range 8-54 yrs) having diplopia during exotropia. We performed the cover-uncover test and recorded the saccade during the shift from exotropia to binocular fixation using an eye-tracking system. We analyzed the correlation between the fusional convergence amplitude on the one hand and the saccade peak velocity (PV), the saccade amplitude, and the saccade amplitude of the fusion on the other. We also investigated the difference of those saccade variables between patients with and without suppression.

In 15 patients with IXT, the median fusional convergence amplitude was 14 (range 0-60) °, and suppression was confirmed in 11 patients. When the cover was removed from the dominant eye, the fusional convergence amplitude showed a positive correlation with the saccade PV and the amplitude in non-dominant eye (r = 0.570, p = 0.042 and r = 0.669, p = 0.012, respectively). The mean saccade PV, the mean saccade amplitude and the mean saccade amplitude of the fusion were not significantly different with the presence or the absence of the suppression.

The fusional convergence amplitude was correlated with saccade in patients with IXT. The saccade during refusion can thus be used to quantitatively evaluate sensory and/or motor fusion.