Normal variation of subjective visual vertical and horizontal in human

Chae, Sayong; Noh, Heil; Suh, Byung Do

Abstract

BACKGROUND AND OBJECTIVES: Otolithic system which senses the head position and linear movement according to gravity acceleration force, plays an important role in maintaining the position of eyeball by otolith-ocular reflex. Measurement of subjective visual vertical and horizontal in darkness with the head upright is one of the static function test of the otolithic system and is simple to perform in man. Several papers reported that perceptual visual vertical and horizontal stays within small range in normal person but numbers of test subjects were limited. Furthermore the effect of age and sex are unknown. MATERIAL AND METHODS: One hundred forty normal subjects(male:70, female:70 ; age 5-70) were selected on the basis of medical history and neurologic examination. The subject was seated upright 100 cm from LED bar(1 mm width , 80 cm length)in the dark. The supporting frame of LED bar was motor driven with minimum rotating angle of 0.01 degree in both directions. After several practice, each subject set the LED bar from random position to subjective vertical or horizontal twice in one session with a motor control switch. Five sessions were repeated with a minimum interval of 5 minutes.
RESULTS
The calibrated mean values were 1.06+/-0.45 degree in vertical and 1.00+/-0.52 degree in horizontal and did not demonstrate any difference in plane and direction of adjustment. Age under 10 and over 60 had a significant higher mean value compared with the mean of all subjects but the difference between over 10 and below 60 was not noted. Female had higher mean values than male. Five repeated tests showed high reproducibility. The direction of adjustment did not show any significant difference.
CONCLUSION
These results would be a useful clinical data for evaluating the static otolith-ocular reflex.