Changes of visual localization induced by eye and neck muscle vibration in normal and strabismic subjects

Abstract 

· Background: It has been reported that vibratory activation of eye- and neck-muscle proprioception can induce eye position changes in normal and strabismic subjects. This study investigated the effects of proprioception in the eye and neck muscles on space localization. · Method: Vibration was applied to either the eye or neck muscle in normal subjects, intermittent exotropes, and constant exotropes/esotropes. The subjects pointed at the immediately remembered position of an extinguished visual target with the hand both before and immediately after vibration of the muscles under binocular and monocular viewing conditions. The hand-pointing performance in darkness was recorded by an infrared camera, and the pointing shifts were analyzed qualitatively and quantitatively. · Results: With vibration of the vertically moving muscles of the eye and neck, the direction of the pointing shifts was the same in all groups of the subjects and under all viewing conditions. With vibration of the horizontally moving muscles of the eye and neck, the directions were the same in the normals and in most of the intermittent exotropes. However, in the constant exotropes and esotropes, the directional shifts were dependent on which eye was vibrated, and the directions were more variable, always directed only to one side. · Conclusion: Proprioception in the eye and neck muscles participates in visual space localization, but the effects of proprioceptive activation were differed in normal subjects from those in patients having constant strabismus. The differences may be related to the level of binocular function.