Dynamic Visual Acuity during Passive Head Thrusts in Canal Planes

Schubert, Michael C.; Migliaccio, Americo A.; Santina, Charles C. Della

doi:10.1007/s10162-006-0047-6

Cited by 81 publications

(95 citation statements)

References 25 publications

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“…In DVA testing, the subject's visual acuity was measured while sitting 6.5 feet from a monitor that displayed a directional (up, down, left, right) "E" optotype only when head velocity was within 120-180°/s (31)(32)(33). To achieve these velocities in passive head thrust DVA testing, quick head rotations were manually imposed in the excitatory direction of each of the 6 semicircular canals by an examiner standing behind the subject, much like in qHIT described above.…”

Section: Vestibular Testingmentioning

confidence: 99%

The Effects of Cochlear Implantation on Vestibular Function

Melvin¹,

Migliaccio²,

Carey³

et al. 2008

Otolaryngol.--head neck surg.

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Objective-Determine the risk posed by cochlear implantation (CI) to the labyrinth.Study Design-Prospective cohort study. Setting-Academic tertiary referral center.Patients-Thirty-six ears belonging to 35 adult CI candidates (mean: 46, range: 23-69 years old). Intervention-Cochlear implantation.Main Outcome Measures-Vestibular function was assessed using the quantitative 3D head impulse test (qHIT), clinical head impulse test (cHIT), post-headshake nystagmus (HSN), caloric electronystagmography (ENG), vestibular-evoked myogenic potentials (VEMP), dynamic visual acuity (DVA), and Dizziness Handicap Inventory (DHI).Results-All 36 ears were tested using qHIT before CI, and 28 ears were tested 4-8 weeks after CI. Quantitative HIT showed 1/28 of ears suffered reduced function. Clinical HIT was 44% sensitive and 94% specific for identification of severe-to-profound vestibular hypofunction confirmed by qHIT. HSN was unchanged in 11/11 subjects. New hyporeflexia was found in 1/16 of ENG-tested ears. VEMP showed either a disappearance of response or an increase in threshold by >10dB in 5/16 ears. Passive DVA showed no change in 16/16 ears. DHI scores worsened in 3/28 and improved in 4/28 subjects.Conclusions-Although small, the observed rate of labyrinthine injury was comparable to that for other risks of CI. Thus, it is important to educate CI candidates about possible risk to balance function, particularly when CI of an "only balancing ear" is contemplated. Clinical HIT is useful for detecting severe high-frequency vestibular hypofunction and should be part of the pre-CI physical examination.

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Section: Vestibular Testingmentioning

confidence: 99%

The Effects of Cochlear Implantation on Vestibular Function

Melvin¹,

Migliaccio²,

Carey³

et al. 2008

Otolaryngol.--head neck surg.

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“…Head impulse trials including eye blinks, other artifacts, and atypical velocity profiles were excluded from the analysis. aVOR gains were determined by measuring head and eye velocity 20 ms prior to peak head velocity (in order to eliminate quick phases) per trial and then averaging across trials (Schubert et al 2006). …”

Section: Discussionmentioning

confidence: 99%

“…The orientation of the optotype was randomly generated for each trial. Participants were required to identify the orientation of the optotype within three presentations, for a potential of 165 trials (11×5×3; Schubert et al 2006). The optotype size decreased with increasing level of visual acuity-in steps equivalent to a logarithm of the minimal angle of resolution (LogMAR) of 0.1 (Ferris et al 1982).…”

Section: Dynamic Visual Acuity Testmentioning

confidence: 99%

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The Under-compensatory Roll aVOR Does Not Affect Dynamic Visual Acuity

Schubert

Migliaccio

et al. 2012

JARO

Self Cite

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Rotations of the head evoke compensatory reflexive eye rotations in the orbit to stabilize images onto the fovea. In normal humans, the angular vestibulo-ocular reflex (aVOR) gain (eye/head velocity) changes depending on the head rotation plane. For pitch and yaw head rotations, the gain is near unity, but during roll head rotations, the aVOR gain is ∼0.7. The purpose of this study was to determine whether this physiological discrepancy affects dynamic visual acuity (DVA)-a functional measure of the aVOR that requires subjects to identify letters of varying acuities during head rotation. We used the scleral search coil technique to measure eye and head velocity during passive DVA testing in yaw, roll, and pitch head impulses in healthy controls and patients with unilateral vestibular hypofunction (UVH). For control subjects, the mean aVOR gain during roll impulses was significantly lower than the mean aVOR gain during yaw and pitch impulses; however, there was no difference in DVA between yaw, roll, or pitch. For subjects with UVH, only aVOR gain during head rotations toward the affected side (yaw) were asymmetric (ipsilesional, 0.32±0.17, vs. contralesional, 0.95±0.05), with no asymmetry during roll or pitch. Similarly, there was a large asymmetry for DVA only during yaw head rotations, with no asymmetry in roll or pitch. Interestingly, DVA during roll toward the affected ear was better than DVA during yaw toward the affected ear-even though the ipsilesional roll aVOR gain was 60 % lower. During roll, the axis of eye rotation remains nearly perpendicular to the fovea, resulting in minimal displacement between the fovea and fixation target image projected onto the back of the eye. For subjects with UVH, the DVA score during passive horizontal impulses is a better indicator of poor gaze stability than during passive roll or pitch.

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“…This is explained because they lie in planes approximately 45 degrees to the sagittal plane of the head. Vertical head impulses were delivered by the clinician in the following manner: The patient was seated so that their body faced the target on the wall but with their head turned to be positioned about 35 degrees to the left for testing in the right anterior-left posterior (RALP) plane or 35 degrees to the right for testing the left anterior-right posterior (LARP) plane [4].…”

Section: Verticals Vhitmentioning

confidence: 99%

Video Head Impulse Test (vHIT): Main Concepts

Felipe¹

2016

JOENTR

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Video Head Impulse Test (vHIT): Main ConceptsSubmit Manuscript | http://medcraveonline.com producing an eye movement in the opposite direction to head movement, thus preserving the image on the center of the visual field. It involves a 3-neuron arc that consists of the vestibular ganglion, vestibular nuclei, and oculomotor nuclei. With a latency period of only 8 to 12 milliseconds (ms), the VOR is considered the fastest reflex in humans.Supported on this mechanism the VOR can be evaluated using an equipment for recording the movement of the eyes and find quantitatively responses about this reflex, based on the gain between eye velocity/head velocity. The normal value is equal one for healthy subjects.

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Dynamic Visual Acuity during Passive Head Thrusts in Canal Planes

Cited by 81 publications

References 25 publications

The Effects of Cochlear Implantation on Vestibular Function

The Effects of Cochlear Implantation on Vestibular Function

The Under-compensatory Roll aVOR Does Not Affect Dynamic Visual Acuity

Video Head Impulse Test (vHIT): Main Concepts

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