Vergence deficits in pontine lesions

Abstract

Eye movements were recorded with the search coil system in two patients to determine whether lesions of the pontine nuclei selectively impair vergence to ramp targets (slow vergence) or step targets (fast vergence). Whereas conjugate saccades were not different from healthy control subjects, conjugate smooth pursuit eye movements had a reduced gain in horizontal and vertical directions. Slow convergence and divergence were impaired, whereas fast vergence did not differ from that of control subjects. Pontine nuclei appear to be involved in the slow vergence control.

Vergence in mild traumatic brain injury: A pilot study

“…They may be helped by appropriate therapeutic intervention, namely small steps of disparity stimuli, as well as smooth and continuous disparity ramp stimuli (e.g., vectograph ramp stimuli) per models of the vergence system [22,31]. Furthermore, the present abnormal static findings suggest, and are consistent with, disturbance of slow vergence control [32][33][34] (e.g., ramp stimulus for NPC testing). Thus, both fast and slow vergence control appear to be adversely affected by the brain injury.…”

“…This would have provided important information regarding the precise sites of damage to the brain, especially as related to vision and, more specifically, to vergence control, as mentioned previously. However, since all were mTBI, it would be expected to be relatively comprehensive in nature, thus having multiple sites of injury per the coupcountercoup aspect [23] frequently found in these patients, and not be as more localized damage as suggested by the cerebrovascular accident results in this area [32][33][34]. Third, because of the relatively small sample size, definitive conclusions cannot be made; thus, further related investigations are warranted.…”

Effect of Vergence Adaptation and Positive Fusional Vergence Training on Oculomotor Parameters

“…Vergence burst-tonic cells carry both vergence velocity and vergence position signals that input directly to the oculomotor neurons and are referred to as "near response cells" (Mays et al, 1986). Though the midbrain consists of a majority of neurons that govern vergence, there also exist neurons that discharge during vergence in the pons (Rambold et al, 2004;Rambold et al, 2005), cerebellum (Westheimer & Blair, 1973) and in a few areas of the cerebral cortex such as the frontal eye field (Gamlin & Yoon, 2000), parietal lobe (Hasebe et al, 1999), middle temporal and medial superior temporal visual areas (Takemura et al, 2001) and in the primary visual cortex (V1). Vergence and accommodation are tightly coupled and studies reported difficulty in distinguishing midbrain cells related to accommodation and vergence separately during near-response (Judge & Cumming., 1986).…”

Effect of oculomotor rehabilitation on vergence responsivity in mild traumatic brain injury

“…While the midbrain comprises the majority of neurons [12], evidence for the existence of neurons that also discharge during vergence have been located in the pons [13][14], cerebellum [15], and some areas of the cerebral cortex, such as the frontal eye field [16], parietal lobe [17][18], middle temporal [19] and medial superior temporal visual areas [20], and primary visual cortex [21]. Since the vergence neural pathway is extensive, any injury to the multitude of related brain and contiguous structures may adversely affect the vergence system.…”