Speed-accuracy of saccades, vergence and combined eye movements in children with vertigo.
Vergence abnormalities could lead to inappropriate vestibulo-ocular reflex (VOR), causing vertigo and imbalance.... a recent study by Anoh-Tanon et al. ... reported the existence of a population of children with symptoms of vertigo in the absence of vestibular dysfunction but with abnormal vergence findings in orthoptic tests. .... children with vertigo perform saccades as normal subjects of comparable age. In contrast, vergence, particularly convergence, shows abnormalities: poor accuracy, long duration and low speed....... Orthoptic training improves significantly the accuracy of all eye movements; such improvement was significant for all types of eye movements except for divergence (pure and combined). Furthermore, convergence remains abnormal and the lack of acceleration by the saccade persists. These specific convergence deficits could be of both subcortical and cortical origin. Orthoptic training improves the accuracy presumably via visual attentional mechanisms, but cannot completely override deficits related to subcortical deficiencies.