Analysis on the optimal horizontal eye position as well as the
effectiveness of a new system for video head impulse test
Abstract
Objective: To identify an optimal gaze angle for precisely evaluating
the function of vertical semicircular canals in video head impulse test
(vHIT) and draw a comparison on the performances among three different
systems for vHIT. Design: Two-center prospective study. Setting:
Participants were sit 1.2 meters away from the wall in a noise-proved
room that dedicated for vHIT experiments. For the gaze-angle projects,
targets were placed on the wall sequentially at the pre-marked lines for
different angles. During the comparison experiments, similar settings
were ensured in both hospitals, like distance to wall and angle of
staring. Same examiner performed the comparison between two systems in
one location. Participants: 26 healthy participants were recruited in
the gaze-angle experiments, 16 of which were further involved in
inter-examiner tests. For the comparison projects, 9 and 13 participants
were recruited, respectively. Any participant with otologic or
vestibular disorders was excluded. Results: Our research showed that
instead of right ahead at 0 degree, when torsion applied at vertical
semicircular canal planes, 25-degree is a better place to set the
targets. At this angle, a more accurate VOR gain was easier to be
obtained. Besides, our evaluations of three different systems showed
that a new vHIT system, VertiGoggles ZT-VNG-I (VG) performed as good as
the long-tested OtometricsICS impulse (Oto) and EyeSeeCam (ESC).
Conclusion: We proposed a new protocol to set the targets 25 degrees
from right ahead after tilt head 45 degrees to evaluate vertical canals
during vHIT. Furthermore, the new VG system is good for clinical
practices.