EFFECTS OF NECK MUSCLE PROPRIOCEPTIVE ACTIVATION ON THE DYNAMICS OF MONOCULARLY DRIVEN HORIZONTAL VERGENCE MOVEMENTS

Purpose: The dynamics of accommodative vergence responses were studied to accommodative stimuli combined with the activation of neck muscle proprioception. Methods: Accommodative stimulation was done with a LED bar. The stimuli were presented monocularly in a stepwise and a sinus oidal mode to either the dominant or the non-dominant eye with the oth er eye covered. The neck proprioceptors were activated by vibration on the neck muscles which turn the head horizontally. Eye movements were recorded with an infra-red reflection system in both eyes. Results: V ibration of the neck muscles shortened the time constant of the accomm odative vergence movement in the covered eye to square wave stimulatio n when the non-dominant eye was fixating the targets. The gain factor to sine wave stimulation was higher when the non-dominant eye was fixa ting, Conclusion: Extraretinal signals from neck proprioception influe nced not only the static eye position, but also the dynamics of monocu larly driven accommodative vergence movements, when the non-dominant e ye was the viewing eye.