What are findings of the optokinetic reflex suggestive of acquired nystagmus?

Updated: Oct 17, 2018
  • Author: Christopher M Bardorf, MD, MS; Chief Editor: Edsel Ing, MD, MPH, FRCSC  more...
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Answer

Optokinetic nystagmus (OKN) drum: The optokinetic reflex allows us to follow objects in motion when the head remains stationary (eg, observing individual telephone poles on the side of the road as one travels by them in a car). The reflex develops at about age 6 months. The normal eye movements that one observes depend upon the orientation of the drum in front of the patient. If the drum is held in front of the patient with the bars directed vertically and is spun to the left (the patient's right), one would observe a slow pursuit movement of the eyes to the patient's right as a moving bar is followed, then a quick saccade to the patient's left as the patient searches for the next moving bar to fixate on and again follows that bar with a slow pursuit movement to the patient's right.

  • This reflex is abnormal in patients with congenital nystagmus. One may observe a paradoxical reversal of the optokinetic nystagmus response.

  • Patients with horizontal nystagmus with unilateral hemispheric lesions, especially parietal or parietal-occipital lesions, show impaired optokinetic nystagmus when the drum is rotated toward the side of the lesion.

  • The OKN drum may be used as an estimate of visual acuity. The striped drum is equivalent to a vision of counting fingers when held at a distance of 3-5 feet from the patient. The further the drum is from the patient, the better the visual acuity must be to respond normally to the moving drum.

Confrontational visual field testing may reveal gross field defects that may help determine the presence and/or location of an intracranial lesion.

For Romberg testing have the patient stand with eyes closed and feet together. If a defect in the vestibular system is present, the patient tends to fall toward the side of the lesion.


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