What is Visual Motion Sensitivity?
Does watching this make you dizzy or perhaps, even nauseous?
Or perhaps you feel this way when are sitting as a passenger in a car?
This is called visual vertigo or visual motion sensitivity, which is defined as dizziness provoked by visual stimulation, including:
Optic flow
This is related to the flow of visual motion as it "streams" past you, such as when you walk through the aisles of a grocery store. This flow of visual motion creates a divergence, such that objects to the left side are projected as moving leftward on the periphery of the eye, and objects on the right are projected as moving rightward on the periphery of the eye. Normally, the two sides of flow fields cancel out so that there is no net sensation of rotation; however, when flow processing is asymmetrical or tilted (i.e. unilateral vestibular dysfunction), movement through such environments may induce vertigo.
General visual motion
Normally, our brains are able to distinguish visual motion related to movement that we make ourselves from motion occurring in the environment. This helps us to remain properly oriented and move about in space in an accurate and efficient manner. With impaired vestibular inputs, dependence on visual inputs may increase and self-motion and environmental motion may become difficult to distinguish. Consequently, visual motion can result in postural sway, such that it takes longer for one with visual motion sensitivity to adapt to visual input and stop swaying (i.e. when the train goes by and it feels like you’re moving with it too).
Computer screens
The reason why computer screens can cause symptoms associated with visual motion sensitivity is due to flicker (a.k.a. refresh rate). Although it is not perceptible to the naked eye, the flicker can be sufficient to create a sensation of visual motion that can be provoking for those with vestibular disorders. Furthermore, the action of scrolling on a screen, whether it be a cellphone, laptop, or computer, can also create visual motion sensitivity.
Visual motion sensitivity is a common symptom experienced with vestibular disorders and concussions and can be due to sensory conflict or mismatch among the visual, vestibular and somatosensory systems. Also, when there is an injury to the cervical spine (i.e. whiplash injury) or vestibular system (i.e. brain injury), there tends to be increased compensatory dependence on our vision during our daily activities.
When we move about our environment, we have internal mechanisms that constantly process all of the sensory inputs and weigh them according to their relevance to the task at hand. For example, if we were walking on sand, the proprioceptive input coming from our feet may not be as reliable, so we will depend more on our visual and vestibular systems; however, when we walk in the dark, we would rely more on our proprioceptive and vestibular systems, since our vision won’t be as dependable.
With a vestibular disorder or following a concussion, visual dependence is so common, as our vestibular and proprioceptive inputs may not be as reliable; thus, we reweigh our senses to depend more on our vision. In theory, this is a wonderful compensatory mechanism so that we don’t immediately lose our balance and have difficulties moving about, however, when you use your eyes more than you have to, processing repetitive and visually-busy patterns can be quite difficult and result in symptoms, such as dizziness and vertigo.
There are several ways to manage visual motion sensitivity and it should be approached from different angles in order to successfully treat it:
Coping Strategies
Reduce visual exposure to environments that provoke symptoms (i.e. patterned walls or floors, rooms with curved walls that may distort vision)
Minimize situations that involve sensory conflict (i.e. using an escalator where you can see your environment move, but you’re not moving)
Take breaks from constant motion exposure (i.e. make frequent stops if you’re on a long car ride to recalibrate your body’s processing of the visual environment from moving to being still)
Use an assistive device if necessary in visually-stimulating environments (i.e. use a cane at the mall, even if you don’t need to use one at home)
Visual and Vestibular Rehabilitation
The purpose of Vestibular Rehabilitation would be to perform exercises to decrease symptoms of motion and visually-provoked dizziness.
Types of exercises include habituation exercises and visual motion sensitivity training, including optokinetic stimulation.
Improve the reliability of the vestibular and proprioceptive systems, so that there is less mismatch in sensory inputs
Practice sensory switching to improve adaptability in a variety of visually-stimulating environments
It is important that these exercises are very specific to the motions and stimuli that provoke symptoms, as treatment involves repetitive exposure to the stimuli until the symptoms lessen. By decreasing dependence on vision and increasing the use of vestibular and proprioceptive cues for balance, symptoms of dizziness will diminish.
For example, to increase tolerance to motion sensitivity experienced when sitting in the car, treatment may involve watching videos of a moving car from the passenger’s perspective. The exercise could be made easier by watching it on a smaller screen while sitting in a chair with back support and progressed by watching it on a larger screen while standing up. Eventually, treatment would progress to sitting in an actual car and tolerating increasing distances and speed. The more specific the exposure is to the provoking stimuli, the more successful treatment will be.
