How is nystagmus (involuntary eye movement) tested?

Testing for Nystagmus

Nystagmus testing requires systematic observation of eye movements under different conditions: first observe for spontaneous nystagmus in primary gaze, then assess for latent nystagmus with monocular occlusion, and finally perform positional testing including the supine roll test for lateral canal involvement and the Dix-Hallpike maneuver for posterior canal involvement. 1

Initial Observation in Primary Position

• Observe the eyes in primary position (straight ahead gaze) for spontaneous nystagmus, which may be horizontal, vertical, and/or torsional and is present constantly 1
• Document the direction, amplitude, and characteristics of any nystagmus observed, as these features help localize the underlying pathology 2, 3
• Note that manifest nystagmus is typically symmetrical and may vary in magnitude, speed, and waveform depending on the direction of gaze 1

Testing with Monocular Occlusion

• Occlude one eye to detect latent nystagmus, which appears only under monocular viewing conditions and is characterized by horizontal jerk oscillations 1
• Latent nystagmus demonstrates a slow nasal drift of the fixating eye followed by saccadic refixation, and is the only form that reverses direction with a change in fixation 1
• Manifest-latent (fusion maldevelopment) nystagmus has an identical waveform to latent nystagmus but is evident under binocular viewing conditions, with amplitude increasing during monocular occlusion 1

Positional Testing: Supine Roll Test

• The supine roll test is the preferred maneuver to diagnose lateral semicircular canal involvement 1, 4
• Position the patient supine with head in neutral position, then quickly rotate the head 90° to one side while observing the eyes for nystagmus 1, 4
• After nystagmus subsides (or if none is elicited), return the head to the straight face-up supine position 1
• Once any additional nystagmus has subsided, quickly turn the head 90° to the opposite side and again observe for nystagmus 1, 4

Interpreting Nystagmus Patterns During Supine Roll Test

• Geotropic type (most common): Horizontal nystagmus beats toward the undermost ear, with more intense nystagmus when rolled to the affected side 1, 4, 5
• Apogeotropic type: Horizontal nystagmus beats toward the uppermost ear, with direction changing when rolled to the opposite side 1, 4, 5
• Both patterns represent direction-changing positional nystagmus, where the direction changes with changes in head position 1, 4

Assessment of Gaze-Evoked Nystagmus

• Test versions (binocular motility) and ductions (monocular motility) by having the patient look in all directions of gaze 1
• Gaze-evoked nystagmus in all directions indicates cerebellar dysfunction, while purely vertical gaze-evoked nystagmus suggests midbrain lesion and purely horizontal suggests pontomedullary lesion 3
• Note any limitations, overactions, or incomitance (changes in the angle of strabismus in different gaze positions) 1

Special Considerations and Caveats

• Perform sensory testing before motor testing, as motor testing can disrupt ocular alignment 1
• In infants and young children, monocular occlusion and oculocephalic rotations (the "doll's-head maneuver" or vestibuloocular reflex) are particularly valuable for revealing clinically normal ductions 1
• Document preferred head posture, as children with manifest-latent nystagmus often present with a head turn and hold the fixating eye in adduction, which is critical for surgical planning 1
• Exercise caution when performing diagnostic maneuvers in patients with cervical stenosis, severe kyphoscoliosis, limited cervical range of motion, Down syndrome, severe rheumatoid arthritis, cervical radiculopathies, Paget's disease, ankylosing spondylitis, low back dysfunction, spinal cord injuries, or morbid obesity 1, 4, 5

Additional Diagnostic Methods

• Video-oculography (VOG) provides detailed analysis and measurement of slow-phase velocity, though visual inspection may be needed in selected cases to confirm nystagmus occurrence 6
• Systematic examination should include assessment of eye position, range of eye movements, smooth pursuit, saccades, gaze-holding function, and optokinetic nystagmus 3, 7