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Curthoys IS, McGarvie LA, MacDougall HG, Burgess AM, Halmagyi GM, Rey-Martinez J, Dlugaiczyk J. A review of the geometrical basis and the principles underlying the use and interpretation of the video head impulse test (vHIT) in clinical vestibular testing. Front Neurol 2023; 14:1147253. [PMID: 37114229 PMCID: PMC10126377 DOI: 10.3389/fneur.2023.1147253] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 03/20/2023] [Indexed: 04/29/2023] Open
Abstract
This paper is concerned mainly with the assumptions underpinning the actual testing procedure, measurement, and interpretation of the video head impulse test-vHIT. Other papers have reported in detail the artifacts which can interfere with obtaining accurate eye movement results, but here we focus not on artifacts, but on the basic questions about the assumptions and geometrical considerations by which vHIT works. These matters are crucial in understanding and appropriately interpreting the results obtained, especially as vHIT is now being applied to central disorders. The interpretation of the eye velocity responses relies on thorough knowledge of the factors which can affect the response-for example the orientation of the goggles on the head, the head pitch, and the contribution of vertical canals to the horizontal canal response. We highlight some of these issues and point to future developments and improvements. The paper assumes knowledge of how vHIT testing is conducted.
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Affiliation(s)
- Ian S. Curthoys
- Vestibular Research Laboratory, School of Psychology, Faculty of Science, University of Sydney, Sydney, NSW, Australia
- *Correspondence: Ian S. Curthoys
| | - Leigh A. McGarvie
- Neurology Department, Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Camperdown, NSW, Australia
| | - Hamish G. MacDougall
- Institute of Academic Surgery, Royal Prince Alfred Hospital, Camperdown, NSW, Australia
| | - Ann M. Burgess
- Vestibular Research Laboratory, School of Psychology, Faculty of Science, University of Sydney, Sydney, NSW, Australia
| | - Gabor M. Halmagyi
- Neurology Department, Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Camperdown, NSW, Australia
| | - Jorge Rey-Martinez
- Neurotology Unit, Department of Otorhinolaryngology Head and Neck Surgery, Donostia University Hospital, Donostia-San Sebastian, Spain
- Biodonostia Health Research Institute, Otorhinolaryngology Area, Osakidetza Basque Health Service, Donostia-San Sebastian, Spain
| | - Julia Dlugaiczyk
- Department of Otorhinolaryngology, Head and Neck Surgery and Interdisciplinary Center of Vertigo, Balance and Ocular Motor Disorders, University Hospital Zurich (USZ), University of Zurich (UZH), Zurich, Switzerland
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Abstract
Recording and quantifying eye movement is the basis of audiologic balance testing. The ability to record and quantify eye movement is a key part of the electronystagmography (ENG) test battery. With computerization, eye movements can be more accurately detected and analysed--testing the limits of the standard recording technique. In response to this, manufacturers are introducing alternative recording protocols. Specifically, infra-red video technology allows an accurate and sophisticated recording and analysis of eye motion in response to balance-related stimuli. The purpose of this technical note is to discuss the limitations of the EOG recording method and discuss the advantages that video-oculography offers.
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Affiliation(s)
- A M Eckert
- Department of Audiology and Speech Pathology, JFK Medical Center, Edison, NJ 08818, USA
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Moore ST, Haslwanter T, Curthoys IS, Smith ST. A geometric basis for measurement of three-dimensional eye position using image processing. Vision Res 1996; 36:445-59. [PMID: 8746234 DOI: 10.1016/0042-6989(95)00130-1] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Polar cross correlation is commonly used for determination of ocular torsion from video images, but breaks down at eccentric positions if the spherical geometry of the eye is not considered. We have extended this method to allow three-dimensional eye position measurement over a range of +/- 20 deg by determining the correct projection of the eye onto the image plane of the camera. We also determine the orientation of the camera with respect to the eye, allowing eye position to be represented in appropriate head-fixed coordinates. These algorithms have been validated using both in vitro and in vivo measures of eye position.
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Affiliation(s)
- S T Moore
- Department of Electrical Engineering, University of Sydney, NSW, Australia
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Haslwanter T, Moore ST. A theoretical analysis of three-dimensional eye position measurement using polar cross-correlation. IEEE Trans Biomed Eng 1995; 42:1053-61. [PMID: 7498908 DOI: 10.1109/10.469371] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Polar cross-correlation is a commonly used technique for determination of torsional eye position from video images. At eccentric eye positions, the projection of the sampling window onto the image plane of the camera is translated and deformed due to the spherical shape of the eyeball. In this paper, we extend the polar cross-correlation technique by developing the formulas required to determine the correct location and shape of the sampling window at all eye positions. These formulas also allow the representation of three-dimensional eye position in Fick-angles, which are commonly used in oculomotor research. A numerical simulation shows the size of the errors in ocular torsion if the spherical geometry of the eye is not considered. Other effects which can affect the accuracy of video-based eye position measurements are also discussed.
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Affiliation(s)
- T Haslwanter
- Department of Psychology, University of Sydney, NSW, Australia
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