Timothy C. Hain, MD Please see our disclaimer.
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Content last updated: 12/1/1999
Visual stimulation is often a trigger for dizziness. Patients often complain of disturbances related to
This must be considered in the context that persons with dizziness may have
This has to do with how things "stream" past. When one is walking through the aisles of a grocery store, there is a "flow field" of visual motion which can be visualized like water going past the prow of a ship. 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. Ordinarily, the two flow fields cancel out so that there is no net sensation of rotation. When flow processing is asymmetrical or tilted, movement through such enviroments may induce vertigo. Many times persons with this symptom become faint and have to leave the environment. There is often a panic component.
These sorts of symptoms can usually be managed by avoidance, conditioning, and dark glasses.
The brain must separate out visual motion related to self movement from environmental motion in order to remain well oriented in space and to determine whether other sensory inputs such as the ear and legs. Persons who have impaired vestibular inputs may inappropriately depend on visual input, and confuse environmental movement with self motion. Most people who drive have experienced the illusion of movement when they are stopped at an intersection, and another car starts to slowly creep forward. This is an example of environmental motion being confused with self motion.
While these sorts of symptoms are well understood, and are often treated by vestibular rehabilition, it is not entirely clear how effective this treatment is.
Some people with vestibular disorders become unable to work on computer screens. The precise reason for this is not entirely clear, but some have speculated that it relates to flicker (refresh rate -- see the VEDA newsletter, Vol 16, #4, 1999). According the authors of the VEDA newsletter (optometrists), one should use faster refresh rates, dim and small displays (such as laptop displays), and make sure that your vision is otherwise normal.
Some people just can't tolerate light. This is called photosensitivity. It is most commonly seen in migraine sufferers, but sometimes it also is found in people with dizziness, especially after head injuries. The treatment is avoidance, migraine medications, and dark glasses.