A great analogy for explaining the connection between the visual system and the vestibular system is described in an article by the Vestibular Disorders Association. That analogy consists of a photographer and camera. The vestibular system is the photographer that is responsible for holding the camera, the visual system, steady for producing clear pictures.
So even if you have a good working visual system, if your vestibular system is not functioning properly you may experience issues with focusing, objects bouncing, or double vision; just like an unsteady photographer would end up with blurry photos or double exposures.
The vestibular system sends signals via the nervous system to the eye muscles through an automatic function known as the vestibulo-ocular reflex (VOR). The VOR maintains balance and controls eye positions while the head moves so that the gaze remains stable.
When the head rotates, the eyes rotate at the same speed but in the opposite direction. This allows the gaze to be stabilized during rotation so that the image being looked at remains on the center of the visual field. Same with vertical movement; when the head moves up the eyes move down. The VOR is automatic and continues to work even when the eyes are closed or in total darkness.
The number of impulses transmitted from the vestibular organs, located within each inner ear, vary depending on a person’s head position. When the head is stationary the impulses from the right side are equal to those from the left side. However, for example, when the head turns toward the right the impulses from the right side increase and the impulses from the left side decrease. As you can imagine, when the vestibular organ in one or both ears is impaired, the brain receives conflicting information about movement. This results in what is known as vertigo, the sensation of feeling off balance.
In our next blog post we’ll follow up on some of the visual symptoms that can arise when the VOR is impaired.
Vestibular Disorders Association. (2009). Vision challenges with vestibular disorders. Retrieved from https://vestibular.org/sites/default/files/page_files/Documents/Vision%20Challenges.pdf