Fast Eye Movements and Slow Eye Movements in Congenital Neurosensorial Deaf Subjects as Assessed by 2D video-Oculography™

Abstract

Aims:  There is evidence that the deprivation of a sensory system at early developmental stage may lead to a functional change of the remaining one(s). Even if this process has been widely studied, results are still controversial. In particular, the auditory system might affect the oculomotor control, since saccades or fast eye movements (FEMs) and slow eye movements (SEMs) are modulated by the cochleo-vestibular input. It follows that hearing impairment would affect the SEM and saccadic pattern. Therefore, in this study FEMs and SEMs have been evaluated in congenital deaf subjects in order to state whether early auditory deprivation has influence on the oculomotor function. Study Design: Case-control study. Place and Duration of Study: Sample: Department of Ophthalmology, University of Turin, duration of the study: 6 months. Methodology:  20 congenital deaf subjects (12 males, 8 females: age range 7-15 years) and 21 age-matched normal hearing subjects (11 males, 10 females: age range 10-16 years) were recruited. Both groups, who had normal visual acuity, underwent SEM and FEM examination by means of 2D video-oculography. SEM left/right cycle gain and velocity and horizontal/vertical FEM latency, velocity and precision were analysed. Results were then compared in the two samples. Results:  No substantial differences in SEM and FEM efficiency were found between deaf and normal hearing subjects. Conclusion: Auditory deprivation does not seem to lead neither to a compensatory enhancement nor to a worsening of the oculomotor function, in contrast to the improvement of peripheral spatial visual attention as reported in literature. We suggest fine ocular movements program, even though strictly influenced by cochleo-vestibular modulation, does not look to be linked to the auditory processing.