7) Optometrists, as primary eye care practitioners, are in the position to evaluate a patient's refractive status, ocular motor balance, and vestibulo-ocular
reflexes, all of which have a critical role in vestibular system function.
Abbreviations: BPPV = benign paroxysmal positional vertigo, CDP = computerized dynamic posturography, CNS = central nervous system, DSI = dual sensory impairment, MSI = multisensory impairment, mTBI = mild traumatic brain injury, PIVC = parieto-insular vestibular cortex, PTSD = posttraumatic stress disorder, SVV = subjective visual vertical, TBI = traumatic brain injury, VOR = vestibulo-ocular
Function and Spatial Orientation in Parabolic Flight," Mark Shelhamer, Johns Hopkins University School of Medicine, Baltimore
A complete vestibular examination was performed--including oculomotor tests (smooth pursuit, saccades, optokinesis, and gaze-evoked nystagmus), examination of the cranial nerves, vestibulo-ocular
reflex testing (head-shaking test, etc.
This process, known as the vestibulo-ocular
reflex, is affected by the directions sensed by the canals and the pull directions of the eye muscles.
Conjunctival, corneal, gag and carinal reflexes were absent along with the oculo-cephalic and vestibulo-ocular
Functional Classes of Eye Movements Class of Eye Movement Main Function Gaze-Holding Visual Fixation Holds the image of a stationary object on the fovea Vestibulo-ocular
reflex Holds images of the seen world steady on the retina during brief head rotations Optokinetic Holds images of the seen world steady on the retina during sustained and low frequency head rotations Gaze-Shifting Smooth Pursuit Holds the image of a moving target close to the fovea Nystagmus quick phases Resets the eyes during prolonged rotation and directs gaze towards the oncoming visual scene Saccades Directs images of eccentrically located objects of interest onto the fovea Vergence Moves the eyes in opposite directions so that images of a single object are place simultaneously on both foveas
In a recent study of oculomotor function in thirty patients with MSA, (8) excessive square-wave jerks were observed in 21 of the patients, a mild supranuclear gaze palsy in eight patients, a gaze-evoked nystagmus in 12 patients, a positioning down-beat nystagmus in 10 out of 25 patients, mild-moderate saccadic hypometria in 22 patients, impaired smooth pursuit movements in 28 patients, and reduced vestibulo-ocular
reflex (VOR) suppression in 16 out of 24 patients.
After the final gentamicin injection, all patients had vestibular therapy consisting of oculomotor exercises, balance retraining, and gait training to normalize vestibulo-ocular
reflex and improve functional balance and mobility.
According to Thomas Furness, director of the Human Interface Technology Laboratory at the University of Washington, Seattle, the worst-case scenario, caused by overuse of a poorly designed HMD, is permanent brain damage, including LSD-like flashbacks, caused by the so-called corruption of the vestibulo-ocular
In the acute setting following a loss of unilateral vestibular function, one might see evidence of dysfunction involving vestibulo-ocular
, vestibulospinal, and vestibulocerebellar reflexes.
Effects of unilateral loss of vestibular function on the vestibulo-ocular
reflex and postural control.