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. Author manuscript; available in PMC: 2026 Jan 5.
Published before final editing as: Ear Hear. 2024 Jul 5:10.1097/AUD.0000000000001547. doi: 10.1097/AUD.0000000000001547

Goggle Versus Remote Camera Video Head Impulse Test Device Comparison

Kristen L Janky 1, Jessie N Patterson 1, Casey Vandervelde 1,2
PMCID: PMC11700229  NIHMSID: NIHMS2001012  PMID: 38965656

Abstract

Purpose:

This study compared remote- vs goggle video head impulse testing (vHIT) outcomes to validate remote-camera vHIT, which is gaining popularity in difficult to test populations.

Methods:

Seventeen controls and 10 individuals with vestibular dysfunction participated. Each participant completed remote-camera and goggle vHIT. The main outcome parameters were canal gain, frequency of corrective saccades, and a normal vs abnormal rating.

Results:

Horizontal and vertical canal vHIT gain was significantly lower in the vestibular compared to the control group; remote-camera gains were significantly lower compared to goggle gain for the vestibular group only. The devices categorized control versus vestibular canals identically except for 1 vertical canal. In the vestibular group, there was not a significant difference in the percentage of compensatory saccades between devices.

Discussion/ Conclusion:

These data provide validation that results obtained with a remote-camera device are similar to those obtained using a standard goggle device.

Keywords: Video head impulse test, vestibular

Introduction:

The video head impulse test (vHIT) is a fast, and efficient means for objectively assessing individual semicircular canal function (MacDougall et al., 2009). VHIT is traditionally completed while patients wear a pair of tightly fitted goggles. The goggles measure eye and head velocity in response to high acceleration, high velocity head impulses by means of an infrared camera and a gyroscope, respectively. The two main outcome measures are gain (a comparison of eye velocity to head velocity) and compensatory saccades (a reset saccade that is generated when the eyes have lost the visual target) (Faranesh et al., 2023; Janky et al., 2018; MacDougall et al., 2009). Vestibular dysfunction is diagnosed by the presence of low gain (typically < 0.8) and the presence of repeatable compensatory saccades (typically present in > 50 – 80% of head impulses) in the horizontal canals, suggesting that fixation on the target was disrupted during the head impulse (Faranesh et al., 2023; Janky et al., 2018; MacDougall et al., 2009; McGarvie et al., 2015).

The use of vHIT is gaining popularity in difficult to test populations such as infants, young children, and individuals with Down syndrome (Dhondt et al., 2019; Leyssens et al., 2021; Martens et al., 2023; Wiener-Vacher & Wiener, 2017). However, remote-camera vHIT is needed to test these populations as they are unable to wear traditional goggles. While remote-camera vHIT is reliable in a young adult cohort (Murnane et al., 2014), there are some distinct differences among vHIT devices which utilize goggles versus a remote camera. First, the gain algorithm is different. Depending on the manufacturer, goggle vHIT devices calculate gain by area under the curve of de-saccaded waveforms or instantaneous gain, where gain is calculated at a set timepoint (i.e., 40, 60 or 80 ms); whereas the remote-camera device calculates gain at the point of minimum error between the eye and head velocity curves. This occurs at different time regions depending on whether there is a saccade present. If there is no saccade present, gain is calculated between ~ 40 and 80 ms. If there is a saccade present, the time region is reduced to eliminate the saccade. Second, there are differences in the number of accepted impulses by which the system calculates gain. The goggle vHIT devices recommends collecting 20 impulses per canal; however, the remote camera device recommends collecting 5 impulses per canal. Third, there are differences in the setup for vertical canal testing with the goggle device requiring a 45° head turn, maintaining visual fixation using a head-centered visual target while the remote-camera device requires a 45° head turn with gaze 20° off center. Lastly, there is the obvious difference in overall acquisition of eye and head velocity data being collected in either the goggles or remotely (~90 cm) in front of the patient/participant.

Few studies have investigated the effects of various vHIT acquisition factors. Previous investigations have noted differences in vHIT gain among vHIT devices / gain algorithms / changes in gaze direction for vertical canal acquisition; however, despite these differences the overall classification of abnormal vs normal in patients with vestibular dysfunction remained similar (Janky et al., 2017; Patterson et al., 2020). It is unknown how the algorithm used to calculate gain using the remote-camera option compares, particularly because calibration is not required for vHIT acquisition using the remote camera. While the number of recommended head impulses varies among devices, Wenzel at al. (2019) reports that as few as 2 artifact-free head impulses are sufficient for accurate interpretation in difficult to test populations, such as children (Wenzel et al., 2019), suggesting that the number of valid impulses acquired will likely not affect validity and reliability of the data.

Due to the difficulty (and impossibility, in some instances) in completing vHIT using both a goggle- and remote-camera device in difficult to test populations, a comparison in a diverse cohort is needed. Thus, the purpose of this investigation was to compare vHIT outcomes among a goggle- and remote-camera vHIT device in individuals with normal and abnormal vestibular function. These data are important in the interpretation and validation of vHIT data acquired in difficult to test populations. Like previous work, it is hypothesized that vHIT outcomes may vary among devices, but that the overall interpretation and classification (i.e., normal vs abnormal) will be similar.

Methods:

Participants:

Seventeen control participants with normal vestibular function (mean age: 26.9, range: 6 – 47; 6 males), and 10 individuals with vestibular dysfunction (mean age: 41.2, range: 16 – 72; 7 males) participated. Individuals in the control group denied history of vestibular impairment or neurologic disorder. All control participants had normal otoscopy, normal 226 Hz tympanometry (Titan, Interacoustics, Middlefart, DK), and passed a hearing screening at 25 dB HL except for 1 control participant with bilateral, congenital, moderate to moderately severe (“cookie bite”) sensorineural hearing loss and 1 control participant with Down syndrome with normal hearing in the left ear and reverse slope sensorineural hearing loss in the right ear. All participants provided informed consent for testing approved through the Institutional Review Board at Boys Town National Research Hospital (IRB 22–09–XP).

Video Head Impulse Test (vHIT):

vHIT was measured using a goggle device (ICS Otometrics Impulse; Natus, Taastrup, DK; monocular eye recording, right eye only, area under the curve gain; software version 4.10; 250 frames/second) and a remote-camera device (Synapsis, Italy; binocular eye recording, minimum error gain; software version 1.20.0; 100 frames/second). Of note, the remote-camera device is not FDA approved. For testing using both devices, the examiner stood behind the participant and performed head impulses in the plane of each semicircular canal (horizontal, posterior, and superior). For each head impulse, the head was displaced 10 to 20° at a peak head velocity between 120 – 300°/s and peak head acceleration between 1000°/s2 and 2500°/s2.

Using the goggle device, standard calibration was completed, per manufacturer recommendation. Participants were seated one meter from a visual target at eye level and were instructed to keep their eyes on the target during testing. The infrared camera measured eye velocity while the gyroscope measured head velocity. Data collection was stopped when a minimum of 10 or maximum of 20 head impulses were collected for each canal. For vertical canal vHIT, the participant’s head was turned approximately 45 degrees while visual fixation was maintained on a center target and head impulses were delivered in the plane of each canal (head turned right for left anterior/right posterior; head turned left for right anterior/left posterior).

Using the remote-camera device, calibration is neither required nor can it be completed per manufacturer recommendation. Participants were seated 90 cm from the vHIT camera. A visual target was placed 60 cm beyond the vHIT camera (~1.5 m from the participant). Data collection was stopped when a maximum of 5 head impulses were collected for each canal. For vertical canal vHIT, the participant’s head was turned approximately 45 degrees while visual fixation was maintained on a target 20° to the right and left of center and head impulses were delivered in the plane of each canal (head turned right for left anterior/right posterior; head turned left for right anterior/left posterior).

The main outcome parameters were gain and frequency of compensatory saccades. Waveforms with compensatory saccades present were re-analyzed, which included adjusting the saccade baseline amplitude and/or start position using the reanalysis function in the software to turn all compensatory saccades red (and thus both de-saccaded from gain calculation and included in the frequency count). All data were inspected for outliers and artifacts (See Mantokoudis et al., 2015; figure 3). Impulses identified as either outliers or artifacts (i.e., high gain, pseudo-saccade, trace oscillations, etc) were deleted. For each participant, the examiner remained consistent between devices.

Figure 3:

Figure 3:

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Depiction of gain changes with data cleaning. vHIT waveforms A) prior to data cleaning, which show early covert saccades that were not identified by the software, thus area under the saccade was included in the gain calculation (gain = 0.67), and B) post data cleaning, which show de-saccaded waveforms, thus area under the saccades were not included in the gain calculation (gain = 0.46).

For the individuals with vestibular dysfunction (n = 10), vHIT gain from the goggle device was used as the gold standard. Individuals were considered to have vestibular dysfunction if gain was < 0.8 and compensatory saccades were present in greater than 80% of head impulses (Janky et al., 2018). Using these criteria, 3 participants had left unilateral vestibular dysfunction, 2 participants had right unilateral vestibular dysfunction, and 5 participants had bilateral vestibular dysfunction. For all comparisons, only the affected ear was included (n = 15 ears).

Statistics:

A within-subjects analysis of variance (ANOVA) was completed to determine if there were significant differences between ears (right vs left) and device (goggle vs remote camera) in the control group. Next, a mixed groups ANOVA was completed with group (control vs vestibular) as the between-subjects factor and device (goggle vs remote camera) as the within-subjects factor. Chi Square analyses were completed to determine if ratings (normal vs abnormal) were similar between devices (goggle vs remote camera). All statistical analyses were performed using SPSS 29.0.

Results:

Horizontal Canal

In the control group, there was no significant difference in horizontal canal gain between devices (goggle: 1.0 [.07], remote camera: 1.01 [.06]; F (1, 16) = .273, p = .609); however, there was a significant main effect of ear (F (1, 16) = 9.697, p = .007) with significantly higher right ear gain (1.02) compared to left ear gain (0.99). This is not considered a clinically significant difference; however, for comparison to the vestibular group, right ear canal gain was used for even numbered control participants (n = 8) and left ear canal gain was used for odd numbered control participants (n = 9).

There was a significant device by group interaction (F (1, 30) = 11.751, p < .002). Post hoc analyses using Tukey’s HSD (minimum mean difference = 0.085) demonstrated that horizontal canal vHIT gain for the vestibular group was significantly lower compared to the control group, and that vHIT gains using the remote-camera device (.21 [.24]) were significantly lower compared to the goggle device (.35 [.22]) for the vestibular group only (Figure 1A). Despite the significant difference in overall gain, the devices categorized the control versus vestibular ears identically (X2 = 32, p < .001). For the frequency of compensatory saccades in the vestibular group, there was not a significant difference in the percentage of compensatory saccades between the goggle (99% [2.3]) and the remote-camera (90% [20.7]) devices (t = 1.748, p = .051). Figure 2 depicts participant data with left vestibular dysfunction, highlighting lower gain in the remote-camera device, yet similar saccades and similar overall classification among devices.

Figure 1:

Figure 1:

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Mean canal vHIT gain for the control and vestibular loss groups by device type for the A) horizontal canals, and B) vertical canals.

Figure 2:

Figure 2:

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Representative vHIT waveforms from one participant with left vestibular dysfunction. Top panel highlights the horizontal canal using the goggle device (left), and the remote camera device (right); gains were smaller using the remote vs the goggle device. Bottom panel highlights the vertical canal using the goggle device (left), and the remote camera device (right); of 14 vertical canals demonstrating vestibular dysfunction, this was the only canal showing a difference among devices.

Two factors were speculated to account for the gain differences among devices: 1) differences in calibration requirements, where the goggles use standard calibration, and the remote-camera device does not; and 2) differences in head velocity. To investigate the effect of calibration, a subset of individuals in the vestibular group (n = 7) completed horizontal canal vHIT using the goggle device with both standard and default calibration. It was hypothesized that if calibration differences are driving gain changes, gain would be higher in the standard calibration condition. Only the affected ears of the vestibular group were used for analysis. Of those with vestibular dysfunction, 3 participants had left unilateral vestibular dysfunction and 4 participants had bilateral vestibular dysfunction for a total of 11 ears. There was no significant difference between the calibrated (.18 [.18]) and default calibration (.19 [.14]) conditions (t = −.442, p = .334) using the goggles.

For the effect of head velocity, it was hypothesized that head velocities would be higher for the remote-camera device in the vestibular group, accounting for lower VOR gains. However, contrary to our hypothesis, there was a significant device by group interaction (F (1, 30) = 27.169, p < .001). Post hoc analyses using Tukey’s HSD (minimum mean difference = 3) demonstrated that head velocities were higher using the goggle device, particularly for the vestibular group (goggle: controls (178 [25]), vestibular (214 [39]); remote camera: controls (166 [18]), vestibular (168 [16]). Collectively, these findings suggest that other methodological factors are responsible for the gain differences among devices in the vestibular group outside of calibration and head velocity.

Vertical Canal

Vertical canal vHIT was collected in 16 control participants with normal vestibular function (mean age: 27.7, range: 6 – 47; 5 males). In the control group, there was a significant main effect of device (F (1, 30) = 19.448, p = <.001) with significantly higher vertical canal gains for the remote-camera (.97 [.08]) compared to the goggle (.92 [.11]) device. There was no main effect of ear (F (1, 30) = .254, p = .618) and no significant interaction (F (1, 30) = .004, p = .949). Like above, for comparison to the vestibular group, right ear canal gain was used for even numbered control participants (n = 7) and left ear canal gain was used for odd numbered control participants (n = 9).

Vertical canal vHIT was collected in 6 participants with vestibular dysfunction (mean age: 39.3, range: 29 – 57; 4 males). As described above, vHIT gain from the goggle device was used as the gold standard. Individuals were considered to have vestibular dysfunction if gain was < 0.8 and compensatory saccades were present in greater than 80% of head impulses (Janky et al., 2018). Using these criteria, 2 participants had bilateral vestibular dysfunction and 4 participants had unilateral vestibular dysfunction (2 right, 2 left). For all comparisons, only the affected ear was included (n = 10 ears, n = 14 canals).

There was a significant device by group interaction (F (1, 43) = 9.894, p = .003). Post hoc analyses using Tukey’s HSD (minimum mean difference = 0.079) demonstrated that vertical canal vHIT gain for the vestibular group was significantly lower compared to the control group, and that vHIT gains using the remote-camera device (.27 [.27]) were significantly lower compared to the goggle device (.36 [.13]) for the vestibular group only (Figure 1B). Despite the significant difference in overall gain, the devices categorized the control versus vestibular ears identically except for 1 vertical canal that was rated as abnormal by the goggle device and normal by the remote-camera device (X2 = 20.16, p < .001, Figure 2). For the frequency of compensatory saccades in the vestibular group, there was not a significant difference in the percentage of compensatory saccades between the goggle (65% [45.23]) and the remote-camera (57% [43.26]) devices (t = 1.077, p = .293).

When investigating the effect of head velocity, there was a main effect of device (F (1, 43) = 53.923, p < .001) with higher head velocities using the goggles (controls: 139 [25]; vestibular: 152 [17]) compared to the remote camera (controls: 120 [14], vestibular: 123 [13]). There was no main effect of group (F 1, 43) = 2.488, p = .122) and no interaction (F (1, 43) = 1.949, p = .17). Collectively, vHIT gains were significantly higher in the control group and significantly lower in the vestibular group using the remote camera, which is not explained by head velocity.

Discussion:

The purpose of this investigation was to compare vHIT outcomes among a goggle- and remote-camera vHIT device in individuals with normal and abnormal vestibular function. Remotecamera vHIT is being administered in difficult to test populations such as infants or individuals with Down syndrome who either cannot wear or will not tolerate wearing goggles (Dhondt et al., 2019; Leyssens et al., 2021; Martens et al., 2023; Wiener-Vacher & Wiener, 2017). These data provide validation for data acquired in difficult to test populations.

Regardless of canal, gain was consistently lower using the remote-camera device within the vestibular group. Previous studies have noted device-level differences, which were attributed to differences in the gain algorithm (Janky et al., 2017). For example, position gain was consistently larger than both area under the curve and instantaneous gain. While device differences in the current study are attributed to differences in gain algorithm, both head velocity and calibration were investigated as possible factors. Head velocities were consistently higher for the goggle- compared to the remote-camera device and higher head velocities/accelerations are generally consistent with lower gain (Weber, Aw, Todd, McGarvie, Curthoys, et al., 2008). Additionally, there was no significant difference between the calibrated and default calibration conditions using the goggle device. While this is not a perfect control trial, as it does not account for other methodologic differences, these additional analyses help build a case that head velocity and calibration are not significant factors contributing to the device differences. Thus, these device- and group-level differences in gain are likely attributed to differences in the algorithm used to calculate gain; whereas other acquisition factors (i.e., sampling rate, filtering, etc) may account for the group-level differences in head velocity.

The goggle device used an area under the curve of de-saccaded waveforms algorithm while the remote camera used the point of minimum error between the eye and head velocity curves, excluding covert saccades. It is suspected that the differences in gain are attributed to the time frame in which gain is calculated in the vestibular group. With area under the curve gain, gain is calculated along the entire time frame of the head impulse; however, the area under the saccade is eliminated, shown in Figures 2 and 3 by the red colored saccades. Alternatively, calculating gain using the point of minimum error between the eye and head velocity curves occurs prior to the corrective saccade and at different time regions depending on whether there is a saccade present. If there is no saccade present, gain is calculated between ~ 40 and 80 ms. If there is a saccade present, the time region is reduced to eliminate the saccade. What is known from investigating instantaneous gain at various time points (i.e., 40, 60 and 80 ms) is that gain increases as the time increases (Janky et al., 2017). Thus, the lower gain values with the remote-camera device in the vestibular group only could reflect the earlier time point in which gain is calculated.

Of note, data cleaning was required to get accurate gain values using the goggle device, particularly with participants who exhibited early covert saccades (Figure 3). In these instances, the software was not accurately de-saccading the data, which led to higher VOR gains using the goggle device as area under the corrective saccade was included in the gain calculation (Figure 3A). Upon data cleaning, which was comprised of reanalyzing and deleting impulses where the software did not accurately identify saccades, VOR gains were lower (Figure 3B). Failure to data clean results in artificially inflated gains as the area under the compensatory saccade is added to the gain calculation.

Despite these device- and group-level differences, the devices categorized the control versus vestibular dysfunction canals identically except for 1 vertical canal that was rated as abnormal by the goggle device and normal by the remote-camera device. This is consistent with others who noted similar categorizations of normal vs abnormal despite differences in gain (Janky et al., 2017). Vertical canal gain decreases as gaze moves away from the canals stimulated; however, categorization between normal and abnormal does not change (Patterson et al., 2020). Thus, the eye gaze position (~0 degrees for remote camera) for vertical canal vHIT may lower the gain but still provide accurate interpretation.

There were no significant differences among groups for corrective saccade frequency. Both systems noted inaccuracies of characterizing saccades. While there was not a significant difference between devices for compensatory saccades, there was more variability (i.e., a larger standard deviation) in the remote-camera device, which is attributed to the lower number of impulses collected.

In the controls, a right canal preponderance was noted, where gains to the right (1.02) were significantly higher than gains to the left (.99). When looking at individual canal gains across devices, this main effect is driven primarily by the goggle device, which yields a larger right vs left canal gain difference compared to the remote-camera device (goggle: right = 1.03, left = 0.98; remote camera: right = 1.02, left = 1.0). This right canal preponderance has been noted by others (Janky et al., 2017; Matiño-Soler et al., 2015; McGarvie et al., 2015; Weber, Aw, Todd, McGarvie, Pratap, et al., 2008) and is attributed to two factors: 1) eye movements are recorded monocularly with the goggle device and binocularly with the remote camera, and 2) the demand placed on each eye and differences in the neural pathway and timing when adducting versus abducting become evident when vHIT is assessed monocularly (McGarvie et al., 2015; Weber, Aw, Todd, McGarvie, Pratap, et al., 2008). This is not considered to be clinically significant as gains are grossly above the threshold for gain values considered to be abnormal (i.e., 0.8).

Limitations:

Limitations to the current study are that data were collected in a small number of participants. Unfortunately, vertical canal vHIT was not completed on all participants (1 control and 4 vestibular). While the relative consistency of findings suggests that these data are representative of overall trends, further comparisons may be needed in a larger cohort with varying degrees of vestibular dysfunction.

Conclusion:

The use of remote-camera vHIT is gaining popularity in populations such as infants and individuals with Down syndrome (Dhondt et al., 2019; Leyssens et al., 2021; Martens et al., 2023; Wiener-Vacher & Wiener, 2017). These data provide validation that results obtained with a remote-camera device are like those obtained using a standard goggle device. While vHIT gains are lower in the vestibular group using the remote-camera device, the classification of normal vs abnormal is identical.

Funding Sources:

Research reported in this publication was supported by the National Institute on Deafness and Other Communication Disorders under award numbers 5T35DC008757-17 and K23DC019950.

Conflict of Interest Statement:

KLJ: Employee of Boys Town National Research Hospital; NIH Grant Recipient; Consultant: Decibel Therapeutics; Balance Function Assessment and Management Textbook, Editor; Ear and Hearing Section Editor; JNP: Employee of Boys Town National Research Hospital; CV: None

Footnotes

All participants provided informed consent for testing approved through the Institutional Review Board at Boys Town National Research Hospital (IRB 22–09–XP).

All authors have approved the final version and are accountable for all aspects of the manuscript.

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