Objective:

To highlight the clinical utility of optokinetic nystagmus (OKN) through five illustrative video cases.

Background:

Bedside evaluation of OKN allows for rapid assessment of smooth pursuit (slow phase) and saccades (fast phase). Specific abnormalities of OKN have localizing value and may also suggest specific neurologic disorders.

Design/Methods:

We provide five video cases where OKN was helpful in localization and/or diagnosis. Video cases are provided from https://novel.utah.edu/Gold/.

Results:

(1) OKN can be used to make an early diagnosis of progressive supranuclear palsy before there is ophthalmoparesis. Vertical OKN can demonstrate absent or attenuated saccades, particularly when compared to a normal response to horizontal OKN. (2) A subtle sign of internuclear opthalmoparesis, when there is no obvious limitation of adduction, can be demonstrated with horizontal OKN by noting a slow (lagging) adducting saccade. (3) In patients with dorsal midbrain (Parinaud) syndrome, upgaze is often limited or absent, and the characteristic finding of convergence-retraction nystagmus (CRN) can be easily appreciated when an optokinetic stimulus is moved downward (e.g., downward slow phase followed by CRN instead of an upward fast phase). (4) Patients with a homonymous hemianopsia due to an occipital lesion will have normal OKN; whereas, patients with a homonymous hemianopsia due to a parietal lesion will have absent OKN when the stimulus is directed toward the side of the lesion. (5) In patients who claim to have binocular or monocular blindness, the presence of OKN (when monocular, with the good eye covered) is highly suggestive of functional vision loss. Observing OKN does not prove that the patient’s visual function is normal, but does rule out blindness. 

Conclusions:

Assessing optokinetic nystagmus with a flag, tape, drum, or the examiner’s fingertips is a portable, inexpensive, and rapid bedside examination to localize and diagnose a variety of neurologic and neuro-ophthalmic disorders.