Abstract
BackgroundThe SVV tests the ability of a person to perceive the gravitational vertical. A tilt in SVV indicates vestibular imbalance in the roll plane, and thus injuries to the utricle or its connecting nerves. A validated bedside method (et, al., 2009, 72(19):1689–1692, Neurol, Zwergal) is the bucket method, in which the subject estimates the true vertical by attempting to properly align a straight line visible on the bottom of a bucket that is rotated at random by the examiner. In our study, the subjects need to align the plumb line on the Visual Vertical iOS app to the vertical direction.MethodsMeasurements of the SVV were made in 22 healthy subjects (16 females and 6 males). Each subject conducted 10 iterations of bucket test and 10 iterations of iOS app test. The reliability and validity of the iOS app was analyzed by SPSS21.ResultsCronbach’s α for the plumb line method was 0.976, and the iOS app was 0.978. Statistical comparison of SVV values measured by the iOS app and the bucket method showed no significant difference in distribution (Mann Whitney U test U = 0.944).ConclusionThe Visual Vertical iOS app is an effective and accessible substitute to the plumb line for the measurement of the validated bucket test.
Highlights
The Subjective Visual Vertical (SVV) is one such test, which tests the ability of a person to perceive the gravitational vertical
On the exterior base of the bucket, a plumb line originating from the center projected over a 1800 protractor was aligned with the straight diametric line on the interior base of the bucket
The iOS device can be secured on the interior base of the bucket alone and the subject would look at the vertical line on the device
Summary
The SVV tests the ability of a person to perceive the gravitational vertical. A tilt in SVV indicates vestibular imbalance in the roll plane, and injuries to the utricle or its connecting nerves. The subjects need to align the plumb line on the Visual Vertical iOS app to the vertical direction. In conjunction with a complete and thorough history and physical exam, various vestibular tests are often helpful in the diagnosis of peripheral vestibular conditions. The Subjective Visual Vertical (SVV) is one such test, which tests the ability of a person to perceive the gravitational vertical. There are many tests measuring SVV, The original description of the test uses a bucket with a plumb line on the outside for the examiner to determine the degree of tilt. This method, has its limitations due to potential errors in measurement from parallax. This study aims to validate the iOS (Apple, Cupertino, USA) app in comparison to the previously validated bucket test
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