Abstract
Abstract: :
Purpose: A theory of ocular kinetmatics is presented based on the video demonstration that there is no so–called compensatory partial static counter–rolling with the eye in any gaze position and that the X–axis (Fick system) is fixed in the orbit. Methods: A video–oculographic (VOG) apparatus was designed to allow free head movement and, at the same time, maintain the retinas (eyes) in the same gaze direction during head tilt. By synchronizing the fixation target, video cameras, and light source with the head movement, any shift of gaze position during head tilt that might result from yaw, pitch, pro– and retro–pulsion of the head was neutralized. A bite–bar was added to study eye movements during fixed head positions. The eyes were tracked in various trajectories that included version, convergence and cyclo–version with the head in various positions. Frame analysis was done by Adobe Photoshop and Premiere. Results: There are intermittent forward–rolling ocular movements around an anterior–posterior axis during head tilt, but when the eyes move independently of the head or the head comes to rest in any position, there is no so–called compensatory static counter–rolling of the eyes on earth or in space. The X–axis (in the Fick coordinate system ) is fixed in the orbit and coincident with the X–axis of the opposite eye when the eyes move independently of the head. The visual line rotates the fixation plane (FP), which is the Y–Z plane. There is no rotation around an anterior–posterior axis (torsion) during convergence. On a microscopic level the retinas are constantly moving. Conclusions: The eyes are oriented to the brain and not to the horizon. The visual line rotates in the X–Y plane to the horizontal secondary positions by rotating around the Z–axis. The visual line rotates to the vertical secondary positions by rotating in the Y–Z plane around the X–axis. Both trajectories are great circles. Oblique eye movements consist of microscopic alternating great and small circles (The fixed physiological equator, which is 90° from the pole of the X–axis, for this purpose is considered a small circle of latitude). To reach a tertiary gaze position the visual line first rotates in the FP. The FP then rotates around the X–axis causing the visual line to rotate in a small circle or, vise versa, the visual line rotates in a small circle followed by rotation in a great circle. The Law of the Fixation Planes: The extraocular muscles, in both version and vergence movements, maintain the fixation planes coplanar in all stable head and gaze directions on earth and in space. They direct the visual lines to the fixation object so that the fusion reflex Is able to maintain stereoacuity.
Keywords: eye movements • eye movements: recording techniques • eye movements: conjugate