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BRIEF REPORT
Assessment of Verticality Perception by a Rod-and-Frame Test: Preliminary Observations on the Use of a Computer Monitor and Video Eye Glasses Jeff Bagust, PhD ABSTRACT. Bagust J. Assessment of verticality perception by a rod-and-frame test: preliminary observations on the use of a computer monitor and video eye glasses. Arch Phys Med Rehabil 2005;86:1062-4. A computer-based version of the rod-and-frame test for verticality perception has been developed. The task tested verticality perception of subjects by using the computer mouse to rotate a bright rod to a vertical orientation within a square frame that was tilted through a range of angles from 30° counterclockwise to 30° clockwise. In 16 healthy subjects, errors from the true vertical were generated in the direction of the frame tilt. The errors reached statistical significance (P⬍.05) when the frame was rotated by 10° in either direction. In a second study, the images were presented to the subjects who wore a pair of video eyeglasses. The pattern of errors generated by rotation of the frame were similar but were of larger amplitude than those produced in the first experiment and reached statistical significance with frame angles of 10° and 20° in both directions. These preliminary investigations suggest that the computer-based rod-and-frame test may provide a more convenient alternative to the mechanical rod-andframe test for verticality perception. Key Words: Computers; Rehabilitation; Vertical dimension. © 2005 by American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation NJURY TO THE HEAD or neck is frequently associated with sensations of an altered perception of the body’s oriIentation in space. These associations include light-headedness, dizziness, and vertigo. The ability to maintain a stable vertical posture requires the integration of sensory inputs from the visual system, the vestibular system, and neck proprioceptors to allow the brain to construct a spatial model of the orientation of the head in space. Patients with brain damage as a result of stroke frequently show greater errors in judging both vertical and horizontal orientation, when compared with controls with no known central nervous system damage.1,2 These perceptual deficits may be an important factor in rehabilitation of locomotor skills in such patients. The rod-and-frame test, originally developed by Whitkin et al,3 provides a quantitative measure of errors in the perception of verticality. It measures a subject’s ability to align to vertical
From the Anglo-European College of Chiropractic, Bournemouth, UK. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit on the author(s) or on any organization with which the author(s) is/are associated. Reprint requests to Jeff Bagust, PhD, Anglo-European College of Chiropractic, 13-15 Parkwood Rd, Bournemouth, BH5 2DF, UK, e-mail:
[email protected]. 0003-9993/05/8605-9239$30.00/0 doi:10.1016/j.apmr.2004.05.022
Arch Phys Med Rehabil Vol 86, May 2005
a luminescent rod within a luminescent frame. To remove visual cues to verticality, the test is conducted in the dark. When the outer frame is tilted, errors in the alignment of the rod are forced, and these errors can be measured as deviation from true vertical. It has recently been reported that subjects with uncomplicated neck pain showed significantly greater errors in the perception of verticality as measured by the rod-and-frame test than asymptomatic subjects.4 Those researchers suggested that this test might be a useful tool in assessing neck problems and the effects of therapy. Until recently, all published reports have used mechanical rod-and-frame systems that require specialized facilities and would not be easy to use in a field setting.3-12 In 2003, Reger et al13 published an account of a 3-dimensional rod-and-frame test that featured a large-screen, semi-immersive display system designed to measure the effects of frame tilt on vertical perception in older adults (64 – 86y). This instrument produced results that compared well with those reported on mechanical systems but which, using current technology, still require a specialist facility. The present report describes a computerbased version of the rod-and-frame test that is portable, is easy to use, and will run on a standard office computer. It is therefore suitable for investigations in settings, such as practitioners’ consulting rooms, where limited specialist facilities are available. This preliminary study compares results obtained on the computer-based version of the rod-and-frame test with those reported in studies that used mechanical systems. It also compares the effects of presenting the images in 2 different ways: on a conventional computer monitor and using video eyeglasses. METHODS The rod-and-frame program was written using Visual Basic 5.0a software on a personal computer running Windows 98. The edges of the monitor screen were masked with black tape to reduce visual cues. The subject was presented with a square white frame on a plain black background (fig 1A). Within the frame, a single white line could be rotated around its center in clockwise or counterclockwise directions using the mouse buttons. The rod could be moved in steps of 0.5° up to 30° from the vertical in either direction. A preprogrammed sequence of 28 presentations was made with the frame tilted in either a clockwise (positive) or counterclockwise (negative) direction from the vertical and the rod positioned initially at an angle of 30° clockwise. The subject’s task was to rotate the rod to what he/she perceived as vertical relative to gravity. When satisfied with the position of the rod, the subject pressed the space bar on the keyboard, clearing the screen for 1 second before the next rod and frame were displayed. Four replicates of 7 different frame angles were presented in a random order: –30°, –20°, and –10° (counterclockwise); 0° (vertical); and 10°, 20°, and 30° (clockwise). Positioning errors
COMPUTER-BASED ROD-AND-FRAME TEST, Bagust
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Fig 1. (A) Rod-and-frame computer program on a computer monitor display. This system was used in complete darkness. (B) Subject wearing the Olympus Eye-Trek FMD 200 video eyeglasses. (C) Plot of the mean rod angles ⴞ SEM (nⴝ16) measured at different frame angles with subjects viewing the display on the computer monitor screen and through the video glasses. The significance of the differences from the means obtained with the frame set to 0° was determined using repeated-measures analysis of variance and the Dunnett multiple comparison test (*P
