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 sinusoidal mode to either the dominant or the non-dominant eye with the other 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

Vibration of the neck muscles shortened the time constant of the accommodative vergence movement in the covered eye to square wave stimulation when the non-dominant eye was fixating the targets. The gain factor to sine wave stimulation was higher when the non-dominant eye was fixating.

CONCLUSION

Extraretinal signals from neck proprioception influenced not only the static eye position, but also the dynamics of monocularly driven accommodative vergence movements, when the non-dominant eye was the viewing eye.