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movement should be equal in amplitude to the distance between the former
object of interest and the new target.
Smooth pursuit
The smooth pursuit system is responsible for following targets within the visual field.
Care should be taken in interpreting smooth pursuit test results in geriatric and
pediatric patients. Tracking is also affected by attention and patient cooperation. Gain,
Phase, and THD should all be taken into consideration when interpreting smooth
pursuit.
• Gain refers to the ratio of the eye velocity (non saccadic) to the target velocity.
• Phase refers to delay between the target and the tracking wave forms
• THD: Total harmonic distortion. It is refer a global measurement to tracking test
in frequency and amplitude. If the peak is around the target frequency, the
tracking was good
Optokinetic (OKN)
For Optokinetic testing, the patient tracks multiple stimuli. Gain and Asymmetry
should all be taken into consideration when interpreting OKN
• Gain refers to the ratio of the eye velocity to the target velocity.
• Asymmetry refers to gain significantly worse in one direction than another
Active head rotation (AHR)
The vestibular autorotation test provides a measure of vestibular function during
active head rotation. As such, it is a test of canal function during natural active
movement, a common situation for patients. This test is performed recording the eyes
and head movement. The gain, phase and THD of the vestibular ocular reflex are
analyzed.
• Gain refers to the ratio of the eye velocity to the head velocity.
• Phase refers to delay between the head and the eyes movement wave forms,
normalized to the period, and multiplied by 360º
• THD: Total harmonic distortion. It is referring a global measurement to tracking
test in frequency and amplitude. Ifthepeakis around the target frequency,
tracking was good
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