Migliaccio Americo A, Della Santina Charles C, Carey John P, Minor Lloyd B, Zee David S
Department of Otolaryngology-Head and Neck Surgery, Johns Hopkins University, MA 21205, USA.
Vision Res. 2006 Aug;46(16):2475-86. doi: 10.1016/j.visres.2006.02.008. Epub 2006 Mar 20.
We examined how the gain of the torsional vestibulo-ocular reflex (VOR) (defined as the instantaneous eye velocity divided by inverted head velocity) in normal humans is affected by eye position, target distance, and the plane of head rotation. In six normal subjects we measured three-dimensional (3D) eye and head rotation axes using scleral search coils, and 6D head position using a magnetic angular and linear position measurement device, during low-amplitude (approximately 20 degrees ), high-velocity (approximately 200 degrees/s), high-acceleration (approximately 4000 degrees /s2) rapid head rotations or 'impulses.' Head impulses were imposed manually and delivered in five planes: yaw (horizontal canal plane), pitch, roll, left anterior-right posterior canal plane (LARP), and right anterior-left posterior canal plane (RALP). Subjects were instructed to fix on one of six targets at eye level. Targets were either straight-ahead, 20 degrees left or 20 degrees right from midline, at distance 15 or 124 cm from the subject. Two subjects also looked at more eccentric targets, 30 degrees left or 30 degrees right from midline. We found that the vertical and horizontal VOR gains increased with the proximity of the target to the subject. Previous studies suggest that the torsional VOR gain should decrease with target proximity. We found, however, that the torsional VOR gain did not change for all planes of head rotation and for both target distances. We also found a dynamic misalignment of the vertical positions of the eyes during the torsional VOR, which was greatest during near viewing with symmetric convergence. This dynamic vertical skew during the torsional VOR arises, in part, because when the eyes are converged, the optical axes are not parallel to the naso-occipital axes around which the eyes are rotating. In five of six subjects, the average skew ranged 0.9 degrees -2.9 degrees and was reduced to <0.4 degrees by a 'torsional' quick-phase (around the naso-occipital axis) occurring <110 ms after the onset of the impulse. We propose that the torsional quick-phase mechanism during the torsional VOR could serve at least three functions: (1) resetting the retinal meridians closer to their usual orientation in the head, (2) correcting for the 'skew' deviation created by misalignment between the axes around which the eyes are rotating and the line of sight, and (3) taking the eyes back toward Listing's plane.
我们研究了正常人类中扭转性前庭眼反射（VOR）的增益（定义为瞬时眼速度除以反向头部速度）如何受眼位、目标距离和头部旋转平面的影响。在六名正常受试者中，我们在低幅度（约20度）、高速度（约200度/秒）、高加速度（约4000度/秒²）的快速头部旋转或“冲动”过程中，使用巩膜搜索线圈测量三维（3D）眼和头部旋转轴，使用磁性角度和线性位置测量装置测量6D头部位置。头部冲动由手动施加，并在五个平面中进行：偏航（水平半规管平面）、俯仰、横滚、左前 - 右后半规管平面（LARP）和右前 - 左后半规管平面（RALP）。受试者被指示注视眼水平高度的六个目标之一。目标要么是正前方、从中线向左或向右20度，距离受试者15或124厘米。两名受试者还注视了更偏心的目标，从中线向左或向右30度。我们发现垂直和水平VOR增益随着目标靠近受试者而增加。先前的研究表明，扭转性VOR增益应随着目标靠近而降低。然而，我们发现，对于所有头部旋转平面和两个目标距离，扭转性VOR增益均未改变。我们还发现在扭转性VOR期间眼睛垂直位置存在动态错位，在近视力且对称会聚时最大。扭转性VOR期间的这种动态垂直偏斜部分是由于当眼睛会聚时，光轴不平行于眼睛围绕其旋转的鼻枕轴。在六名受试者中的五名中，平均偏斜范围为0.9度 - 2.9度，并且在冲动开始后<110毫秒出现的“扭转性”快相（围绕鼻枕轴）将其减小至<0.4度。我们提出，扭转性VOR期间的扭转性快相机制至少可以发挥三种功能：（1）将视网膜子午线重置为更接近其在头部的通常方向，（2）校正由眼睛旋转轴与视线之间的未对准所产生的“偏斜”偏差，以及（3）使眼睛回到利斯廷平面。
