Figure 10 Infrared oculogram derived from a patient with multiple sclerosis with bilateral internuclear ophthalmoparesis

In this case a rightward (upward tracing) 20 deg saccade results in interocular disconjugacy (note separation of the two tracings). Observe that the right eye (OD in blue) achieves the 20 deg target rapidly, whereas the left eye (OS in red) lags behind. The ratio of the eyes when the abducting right eye achieves the target to the position of the adducting eye at that time is referred to as the first pass amplitude (FPA). Ultimately both eyes achieve the fixation target, the final amplitude (FA). During the trajectory of the saccade, the divergence of the two eyes can result in loss of stereoscopy, diplopia (transiently), difficulty reading, visual blur, and risk of fall while turning, or motor vehicle accident with head turning while driving.