Investigation into the verification of the Synapsys videonystagmography (VNG) Ulmer calibration system.

OBJECTIVE To assess the accuracy and stability of the Synapsys VNG Ulmer calibration system when the goggles and infrared camera are repositioned, and the accuracy of the equipment's geometric calibration system. DESIGN Prospective data collection involved participants conducting the system's horizontal calibration test. Eye measurements were then recorded for a 60° deviation (looking from 30° right to -30° left) and repeated after the goggles and infrared camera were removed/repositioned. Participants' eye measurements were also recorded after the geometric calibration had been activated. STUDY SAMPLE Twenty-two participants with no history of visual or vestibular pathology were recruited for this study. RESULTS No significant differences were found when the goggles were removed and replaced (p = 0.21); when the infrared camera was repositioned within the goggles (p = 0.50); or when the goggles were removed and the camera repositioned (p = 0.18) after horizontal calibration. A significant difference was found during the assessment of geometric calibration (p < 0.01). CONCLUSIONS Calibration is not affected by removal or repositioning of the goggles and/or infrared camera within the goggles, therefore suggesting recalibration may not be necessary. Caution should be exercised when using the equipment's geometric calibration and should only be used when the patient is unable to conduct the system's horizontal calibration test.