Objective: Validation of a bedside test to measure the monocular and binocular subjective visual vertical (SVV).
Methods: Monocular and binocular measurements of the SVV were made in 30 healthy subjects (mean age 46.1 +/- 16.4 years) and 30 patients with acute peripheral or central vestibular lesions (mean age 51.3 +/- 17.1 years). The established method uses a hemispheric dome (adjustment of a bar to the vertical without spatial orientation clues in a motor-driven, hemispheric dome randomly covered with colored dots). It was compared to a simple, self-made bucket method, in which the subject estimates true verticality by attempting to properly align a straight line visible on the bottom of a bucket that is rotated at random by the examiner.
Results: Comparative measurements of the whole group (n = 60) showed no difference in the distribution of monocular or binocular SVV values while using the hemispheric dome or the bucket method. Intertest reliability was 89% for monocular and 90% for binocular SVV measurements. Intratest reliability of the bucket method in 10 repetitions was 92% for binocular and monocular SVV determinations. With the bucket method, the range of absolute deviations of SVV values from true verticality in healthy subjects was 1.1 +/- 0.7 degrees for monocular and 0.9 +/- 0.7 degrees for binocular measurements (mean +/- SD). There was no significant effect of age or gender.
Conclusions: The bucket method is an easily performed and reliable bedside test for determining monocular and binocular subjective visual vertical. The bucket can be modified within 1 hour and costs less than $5.