- Visual fixation typically suppresses nystagmus caused by a peripheral lesion, but it does not usually suppress nystagmus from a central lesion. It may be therefore be helpful to manipulate a patient's visual fixation to determine whether their nystagmus is due to a central or peripheral lesion.
- Frenzel lenses (see attached picture) are large magnifiers that blur vision and inhibit visual fixation. When a patient looks through this type of lens, one would expect peripheral nystagmus to increase, as visual fixation would be inhibited.
- If Frenzel lenses are not available, ask the patient to maintain their visual gaze on a single location to reproduce visual fixation. Then note whether the nystagmus ceases (i.e. peripheral lesion) or continues (i.e. central lesion).
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