Ocular Rotation Research Articles

Transition from self tilt to object tilt during maintained lateral tilt in parabolic flight

19 young healthy subjects were subjected to parabolic rollercoaster flight. A horizontal luminous line was seen by the subjects in a headfixed goggle device. During the hypergravic phases of parabolic flight the luminous line seemed to rotate into and during the hypogravic phase against the direction of static head tilt. Ocular counter rotation and activity of the neck position receptors cannot explain these subjective rotations. We conclude that information from the otolith system, converging with visual information within the brain, dislocated the headfixed visual target line. While the retinal image of the luminous line remains unchanged, loading and unloading the otoliths in parabolic flight changes the sensation of self tilt into object tilt, hereby subjectively rotating visual targets such as the luminous line.

Passive limitation of adduction after Cüppers's 'Fadenoperation' on medial recti.

In 40 eyes of 20 esotropic subjects in which a 'Fadenoperation' was performed on the medial recti we measured the resistance to ocular rotation in adduction before and after the operation. The difference between the two sets of force measurements demonstrates that the Fadenoperation on medial recti produces a mechanical restriction to adduction which can explain the effect of the surgical procedure on the strabismic deviation.

Chapter 18 Representations of ocular rotations in the cerebellar flocculus of the rabbit

The climbing fibres (CFs) of the rabbit flocculus that respond in a speed- and direction-selective manner to retinal image slip produced by eye rotations can be divided into three classes on the basis of the orientation of the rotation axis associated with their greatest modulation (the preferred axis). The similarity of the orientations of these axes to those of the eye rotation axes of the extraocular muscles suggests that a simple geometrical correspondence may exist between the eye rotation associated with the preferred axis of a given class of CFs and the eye rotation produced by activation of the Purkinje cells upon which that class of CFs synapse. To pursue this possibility, the axes of the eye rotations evoked by electrical microstimulation of the alert rabbit's flocculus were determined simultaneously for both eyes in three dimensions using two orthogonal search coils on each eye. A limited number of slow eye movement response patterns were found, and of these, two predominated. The most common response was a counterclockwise (CCW) rotation of the ipsilateral (left) eye around an axis close to the horizontal plane and at about 140 degrees posterior to the nose. The other predominant response was abduction of the ipsilateral eye. These two response patterns, together with the smaller conjugate components for the contralateral eye, are consonant with the orientations of the preferred CF axes. In addition, a clear CCW rotation of the contralateral (right) eye about its 135 degrees axis was also evoked from some stimulation sites. This response, which occurred either alone or as a component of an upward rotation about the nasal-occipital (roll) axis, is at variance with the orientations of the preferred CF axis. However, the latencies of the CCW contralateral 135 degrees component (80-140 ms) were greater than those of the CW contralateral 45 degrees component, the CCW ipsilateral 135 degrees component and the ipsilateral abduction component (8-48 ms). These latency differences may distinguish stimulation of Purkinje cells from stimulation of other neurones.

Overacting oblique muscles in exotropia: a mechanical explanation.

Patients with exotropia often show apparent overaction of the inferior and superior oblique muscles. Are the oblique muscles contracted, are they truly overacting overacting, or does the eye flip up or down in adduction from the leash effect of a contracted lateral rectus muscle? Theoretically, if the mechanical limits of ocular rotations were circular or elliptical, rather than square or rectangular, we would expect a patient with exotropia to develop a vertical deviation in extreme gaze into the oblique quadrants, for the abducting eye would reach the mechanical limit, while the adducting eye would still be free to move up or down, giving the appearance of both inferior and superior oblique overaction. The circular or elliptical limits of ocular rotations were documented with tracings from slow-motion video recordings. Also, reduction of pseudo-overation of the obliques in both eyes following unilateral surgery for exotropia was observed in three patients. The strabismus surgeon should be aware of this possible mechanism for pseudo-overaction of the obliques and should avoid muscle surgery in this clinical setting.

眼筋と頚筋との静的協調性に関する研究

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.

The effect of prismatic spectacle and contact lens corrections on ocular rotation

The effect of prismatic spectacle and contact lens corrections on ocular rotation

Investigation of Limited Ocular Rotations: Current Status

(1987). Investigation of Limited Ocular Rotations: Current Status. American Orthoptic Journal: Vol. 37, No. 1, pp. 2-12.

THE EFFECT OF PRISMATIC SPECTACLE AND CONTACT LENS CORRECTIONS ON OCULAR ROTATION

The effect of prismatic spectacle corrections on ocular rotation for different object distances is determined and evaluated. The same principles are applied for a correction fitted on the eye, that is, a contact lens correction. The latter must be considered as a thick lens system. The effects of different types of prismatic contact lenses on ocular rotation are considered. Assuming the contact lens to remain stationary and the eye behind the lens to rotate, it is shown that the theoretical effect on ocular rotation of prismatic contact lenses is practically equal to their prismatic effect in air. The effect for high-powered contact lenses is discussed.

The effect of prismatic spectacle and contact lens corrections on ocular rotation

Abstracts— The effect of prismatic spectacle corrections on ocular rotation for different object distances is determined and evaluated. The same principles are applied for a correction fitted on the eye, that is, a contact lens correction. The latter must be considered as a thick lens system. The effects of different types of prismatic contact lenses on ocular rotation are considered. Assuming the contact lens to remain stationary and the eye behind the lens to rotate, it is shown that the theoretical effect on ocular rotation of prismatic contact lenses is practically equal to their prismatic effect in air. The effect for high-powered contact lenses is discussed.

An evaluation of signs in ocular myasthenia gravis and correlation with acetylcholine receptor antibodies.

Fifteen patients with ocular myasthenia gravis were examined in detail for 21 different signs, and tested for acetylcholine receptor antibodies. The major signs of ocular myasthenia gravis included ptosis, disorders of ocular rotations, weakness of eyelid closure, "pseudosupranuclear" signs and the lid twitch sign. Acetylcholine receptor antibodies were found in eight of the 15 patients. One hundred and four normal, non-myasthenic patients were also examined for the lid twitch response, and the relationship between the lid twitch of ocular myasthenia gravis and that found in normal subjects is discussed.

Ocular rotation as a tool for superior oblique tendon exposure.

In several clinical studies involving superior oblique surgery it was noticed that the posterior insertion of the superior oblique tendon can be moved outside from the undersurface of the superior rectus muscle. This was achieved by rotating the eye in a maximum nasal and downwards direction while avoiding intorsion or retraction of the globe. Traction was applied on the superior temporal quadrant of the globe.

Saccadic anomalies: Vergence induces large departures from ball-and-socket behavior

The configuration of muscular forces, which maintains a given orientation of the eye, varies with vergence state. As a consequence, changes in vergence produce both static and dynamic violations of simple ball-and-socket behavior: during strong convergence, the entire eye is displaced temporally within its orbit at steady state by as much as 200 μm; and the axis of ocular rotation for small horizontal saccades is consistently displaced forward within the globe by an average of about 1 mm. These phenomena occur regardless of whether vergence is maintained by accommodation or by binocular disparity. Hence, systematic errors of as much as a full degree can arise in measurement of vergence movement, unless monitoring methods are used which are insensitive to translational motion. The observed displacement on the axis of rotation for saccades may be involved in subjective shrinkage of visual targets during convergence (“experimental micropsia”).

Ocular rotation and corneal reflexes (author's transl)

The location of the corneal reflex (Purkinje's first image) produced by an electronic flash was studied at various degrees of ocular rotation both in adduction and abduction. A statistical analysis of the results showed a good correlation between the decentration of the corneal reflex and the degrees of ocular rotation. The results thus obtained give an experimental basis to the clinical use of the so-called Hirschberg test for measuring the strabismus angle.

Restrictions in the Diagnoses and Management of Strabismus Problems

Restrictions have been found to be a common cause of incomitant strabismus and limitation of ocular rotations. Different types of restrictions have been described and the technique of forced duction testing reviewed. Causes of restriction include endocrine eye disease, orbital floor and medical wall fracture, Brown's syndrome, tight lateral rectus syndrome, congenital tight muscles, scarring, muscle contracture, and orbital celluitis or tumors. The importance of recognizing restrictions in the management of these problems has been emphasized.

Relation between perceived depth and perceived motion in uniform flow fields.

Three experiments are reported that examined the nature of the perceptual linkage between perceived depth and perceived motion in bidirectional uniform velocity fields. In such displays there is systematic misperception of both the speeds and directions of motion of visual objects. It was found that the speed and the direction of perceived motion were related to objective velocity by the addition of a uniform velocity component across the visual field. It is proposed that this uniform component may be the result of compensation for incorrectly registered ocular rotation and that such an account may also apply to classical center-surround induced motion effects.

State reversals of optically induced tilt and torsional eye movements

Alternations of the state of apparent self-motion during observation of a large visual display rotating about the line of sight are associated with alternations in the magnitude of induced tilt and torsional eye rotation. In one experiment, shifts in visually induced tilt during these state alternations are found to be in the opposite direction to corresponding shifts in induced ocular torsion. In a second experiment, the reversals of self-motion perception are shown to be an intravisual phenomenon, independent of competing inputs provided by the vestibular system. These results emphasize the importance of distinguishing between visual and vestibular processes in tilt perception and ocular rotation during human orientation to gravitational vertical.

Concomitant direction and distance aftereffects of sustained convergence: A muscle potentiation explanation for eye-specific adaptation

Fixating a target for 6 min was shown to produce distance aftereffects that varied in direction and magnitude as a linear function of the convergence angle. Eye-specific direction aftereffects also were obtained in a nasal direction under conditions that produce increased perceived dtstance and in a temporal direction under conditions that produce decreased perceived distance. These aftereffects were shown to be sensitive to the range of horizontal versional eye movements that accompany the near or far convergence positions maintained during exposure. The results provide a logical alter­ native to perceptual learning accounts of eye-specific adaptation. Maintaining the eyes in a fixed or restricted range of convergence positions may induce a muscle potentiation aftereffect in the subset of extraocular muscles innervated to achieve and sustain those postures. Muscle potentiation refers to an involun­ tary component of continued innervation in the direction of previous muscular stimulation. Since the increase in muscle tension is involuntary, registra­ tion of eye-position information based on the monitoring of voluntary motor signals should be in error to the degree that the potentiation effect must be overcome. Assuming that the potentiation effect itself is not registered via an inflow from proprio­ ceptive units in the extraocular muscles, it follows that any perceived spatial dimension that requires compensation for or registration of ocular rotation should undergo changes consistent with the felt position of the eyes. Accordingly, changes in per­ ceived distance should occur whenever the eyes have been maintained predominantly in near or far con­ vergence positions. For example, if the medial recti of each eye are potentiated by maintaining the eyes in a near convergence position, then it would be as if each eye was being involuntarily pulled nasally. Therefore, in order to fixate a visual target, the observer would have to overcome the additional innervation due to potentiation by the same amount of voluntary innervation in the opposite direction, i.e., in a temporal direction that would normally result in a smaller convergence angle. This change in

Letter: Absence of Bell phenomenon during a blink.

To the Editor.— A recent article by Jacobs and Bender ( Arch Neurol 33:289, 1976) warrants clarification of Bell phenomenon. Bell implied that an upward rotation of the eyes took place during any brief eye closure. 1 However, Hall 2 questioned the presence of Bell phenomenon during a spontaneous blink because of its short duration. A few attempts to estimate an upward ocular rotation during a blink yielded a figure of a few degrees at most. 3.4 Evaluation of 225 Right-Handed Focal Brain-Damaged Patients No. (%) of Patients With Left Hemisphere Lesions Aphasic Nonaphasic Right Hemisphere Lesions Literate (n = 182) 115 (63) 42 (23) 25 (14) Illiterate (n = 43) 29 (67) 5 (12) 9 (21) 200μV I SEC Electro-oculogram of a blink by a normal individual when eyes are in primary position, with both eyes open (A) and after the left eye is closed (B). (Electroencephalograph with the time constant 0.12 seconds.)

Forced Duction, Active Force Generation, and Saccadic Velocity Tests

The forced duction test reveals information about mechanical limitations to full ocular rotation. When voluntary ocular rotation is limited, and the forced duction test is completely free, paresis of an extraocular muscle is suggested. The active force generation test and saccadic velocity measurements both provide information about the active forces available to move the globe. Active force can be felt with the forceps in the force generation test. These forces can be measured quantitatively with the calibrated Scott forceps. The saccadic velocity test measures the work an extraocular muscle performs (the eye movement) but does not measure active force directly. The force available is inferred by comparing saccadic velocity measurements to normal control values. This test is especially useful in infants and children, in whom the force duction test cannot be done without general anesthesia, and whose cooperation is insufficient to allow force generation measurements to be performed. It is likely that future improvements in instrumentation and further knowledge of basic oculomotor mechanisms will increase the value of these techniques in clinical strabismus.

Perceptual consequences of potentiation in the extraocular muscles: an alternative explanation for adaptation to wedge prisms.

Two initial experiments demonstrated that direction aftereffects of potentiation in the extraocular muscles (induced through sustained versional rotation to the side) generally increase as a function of the magnitude and duration of the inducing ocular rotation and can be built up under conditions of varied as well as constant fixation. The results suggest an alternative to perceptual learning accounts of adaptation to wedge prisms, namely, that adaptive changes in perceived distance and direction are induced through a systematic bias in eye posture rather than exposure to informational discrepancy. The muscle potentiation hypothesis was tested directly against a learning hypothesis in a final adaptation experiment. Differences in the decay functions for observers engaged in five different types of interpolated activity strongly support the muscle potentiation explanation.