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Rotatory chair calibration error

See "blunders". See also here for OKN calibration error.

The eyes and the rotatory chair velocity are calibrated independently. Independent things can be mismatched. When there is a mismatch, there can be a peculiar pattern where mid-frequency VOR gain is too high. No human being can produce r-chair gain of 0.9 at 0.02 hz.

Note that the phase is normal. This means that there is a gain error, but timing is normal. If the phase were 0 degree at all frequencies, this could mean that there was instead a light leak.

This is the rotatory chair test done with the calibration array closer to the head than configured in the software.

This causes the eye to move more than it should for a given displacement of the chair. It is puzzling to us that the eye velocity does not exceed chair velocity.

calibration error

This is the rotatory chair test done properly

Now the gain is low-normal, and phase is unchanged.

Correct SHA

Copyright August 3, 2016 , Timothy C. Hain, M.D. All rights reserved. Last saved on August 3, 2016