Abnormality of vergence latency in children with vertigo

It is well known that vergence movements are important for distance appreciation, depth vision and stereopsis. Moreover, vergence movements are very probably used by the CNS during head and body motion to adjust the gain of the vestibulo-ocular reflex (VOR) according to the viewing distance. A recent clinical study of Anoh-Tanon et al. suggested that vertigo in children with normal vestibular function could be associated with abnormal vergence clinically assessed. The purpose of this study was to test this hypothesis with objective vergence eye movement recordings. We examined the latency of vergence, saccades and combined movements in twelve children with the complaint of vertigo but without vestibular abnormality. Convergence and saccades combined with convergence or with divergence had abnormally long latencies (relative to normal children of matched age). In contrast, divergence and isolated saccades showed only mild latency increase relative to normals. Lengthening of latency could be due to impaired cortical control. Orthoptic vergence training reduced all latencies; however, even the reduced latency of vergence and of combined movements was still abnormal. The improvement after orthoptic vergence training could be due to increased visual attention, although such mechanism cannot eliminate completely the initiation deficit of vergence movements. Objective eye movement recordings are thus useful for a diagnosis and treatment of children with vertigo.