眼筋と頚筋との静的協調性に関する研究

Abstract

In this study of the static coordination of the ocular and the cervical muscles the rotatory angle the head makes with the trunk and the angle of ocular version in the orbit were measured in the right and left directions in 20 healthy persons (40 measurements) who maintained a fixed lateral gaze in a natural, unrestricted condition or with the head turned through a certain angle.1. There was no difference in measured values between the right and the left directions. There was a close positive correlation of measurements between the two angles (r>0.9).2. The fixed lateral gaze was the sum of the ocular version and head rotation in the same direction. As the angle of gaze increased, there appeared three linear relations of differing inclination where the ocular muscle played the leading role when the subject gazed in the lateral direction at an angle of less than 20 degrees, while the cervical muscles took the place of the ocular muscles when the angle of gaze was greater than 70 degrees. These muscles were in coordination when the angle of gaze was between these ranges.3. The maintenance of a rotated head position was achieved by the ocular version in the same direction. As the angle of head rotation increased, there appeared three linear relations of differing inclination where the cervical muscle assumed the leading role when the angle of head rotation was smaller than 10 degrees and the ocular muscle took its place when the angle of head rotation was greater than 60 degrees. These muscles were in coordination when the angle of head rotation was between these ranges.4. Despite the difference in the muscular task (or purpose of movement) there was a shift in the inclination of the three linear relations of ocular and cervical muscle coordination at the critical angles of ocular version, that is, 8 and 22 degrees. These critical angles of ocular version appear to have specific physiological implications in regard to equilibrium.These observation suggest that there is a direct reflex system as a mechanism of static coordination, as distinguished from the known dynamic coordination, and that it is regulated by the ocular muscles.