Horizontal Eye Rotations Research Articles

Scanning Laser Ophthalmoscopy Demonstrates Pediatric Optic Disc and Peripapillary Strain During Horizontal Eye Rotation

Purpose: We employed automated analysis of scanning laser ophthalmoscopy (SLO) to determine if mechanical strains imposed on disc, and retinal and choroidal vessels during horizontal duction in children differ from those of adults. Methods: Thirty-one children aged 11.3 ± 2.7 (standard deviation) years underwent SLO in central gaze, and 35° ab- and adduction. Automated registration with deep learning-based optical flow analysis quantified vessel deformations as horizontal, vertical, shear, and equivalent strains. Choroidal vessel displacements in lightly pigmented fundi, and central disc vessel displacements, were also observed. Results: As in adults, strain in vessels during horizontal duction was greatest at the disc and decreased with distance from it. Strain in the pediatric disc was similar to published values in young adults, 1 but in the peripapillary region was greater and propagated significantly more peripherally to at least three disc radii from it. During adduction in children, the nasal disc was compressed and disc vessels distorted, but the temporal half experienced tensile strain, while peripapillary tissues were compressed. The pattern was similar but strains were less in abduction (p < .001). Choroidal vessels were visualized in 24 of the 62 eyes and shifted directionally opposite overlying retinal vessels. Conclusions: Horizontal duction deforms the normal pediatric optic disc, central retinal vessels, peripapillary retina, and choroid, shearing the inner retina over the choroid. These mechanical effects occur at the sites of remodeling of the disc, sclera, and choroid associated with typical adult features that later emerge later, including optic cup enlargement, temporal disc tilting, and peripapillary atrophy.

Scanning Laser Ophthalmoscopy Demonstrates Disc and Peripapillary Strain During Horizontal Eye Rotation in Adults

We used automated image analysis of scanning laser ophthalmoscopy (SLO) to investigate mechanical strains imposed on disc, and retinal and choroidal vessels during horizontal duction in adults. Deep learning analysis of optical images. The peripapillary region was imaged by SLO in central gaze, and 35° abduction and adduction, in younger and older healthy adults. Automated image registration was followed by deep learning-based optical flow analysis to track determine local tissue deformations quantified as horizontal, vertical, and shear strain maps relative to central gaze. Choroidal vessel displacements were observed when fundus pigment was light. Strains in the retina and disc could be quantified in 22 younger (mean ± SEM, 26 ± 5 years) and 19 older (64 ± 10 years) healthy volunteers. Strains were predominantly horizontal and greater for adduction than for abduction. During adduction, maximum horizontal strain was tensile in the nasal hemi-disc, and declined progressively with distance from it. Strain in the temporal hemi-retina during adduction was minimal, except for compressive strain on the disc of older subjects. In abduction, horizontal strains were less and largely confined to the disc, greater in older subjects, and generally tensile. Vertical and shear strains were small. Nasal to the disc, choroidal vessels shifted nasally relative to overlying peripapillary retinal vessels. Strain analysis during horizontal duction suggests that the optic nerve displaces the optic canal, choroid, and peripapillary sclera relative to the overlying disc and retina. This peripapillary shearing of the optic nerve relative to the choroid and sclera may be a driver of disc tilting and peripapillary atrophy.

Material properties and effect of preconditioning of human sclera, optic nerve, and optic nerve sheath

The optic nerve (ON) is a recently recognized tractional load on the eye during larger horizontal eye rotations. In order to understand the mechanical behavior of the eye during adduction, it is necessary to characterize material properties of the sclera, ON, and in particular its sheath. We performed tensile loading of specimens taken from fresh postmortem human eyes to characterize the range of variation in their biomechanical properties and determine the effect of preconditioning. We fitted reduced polynomial hyperelastic models to represent the nonlinear tensile behavior of the anterior, equatorial, posterior, and peripapillary sclera, as well as the ON and its sheath. For comparison, we analyzed tangent moduli in low and high strain regions to represent stiffness. Scleral stiffness generally decreased from anterior to posterior ocular regions. The ON had the lowest tangent modulus, but was surrounded by a much stiffer sheath. The low-strain hyperelastic behaviors of adjacent anatomical regions of the ON, ON sheath, and posterior sclera were similar as appropriate to avoid discontinuities at their boundaries. Regional stiffnesses within individual eyes were moderately correlated, implying that mechanical properties in one region of an eye do not reliably reflect properties of another region of that eye, and that potentially pathological combinations could occur in an eye if regional properties are discrepant. Preconditioning modestly stiffened ocular tissues, except peripapillary sclera that softened. The nonlinear mechanical behavior of posterior ocular tissues permits their stresses to match closely at low strains, although progressively increasing strain causes particularly great stress in the peripapillary region.

A Pilot Study of Horizontal Head and Eye Rotations in Baseball Batting.

The purpose of the study was to measure and compare horizontal head and eye tracking movements as baseball batters "took" pitches and swung at baseball pitches. Two former college baseball players were tested in two conditions. A pitching machine was used to project tennis balls toward the subjects. In the first condition, subjects acted as if they were taking (i.e., not swinging) the pitches. In the second condition, subjects attempted to bat the pitched balls. Head movements were measured with an inertial sensor; eye movements were measured with a video eye tracker. For each condition, the relationship between the horizontal head and eye rotations was similar for the two subjects, as were the overall head-, eye-, and gaze-tracking strategies. In the "take" condition, head movements in the direction of the ball were larger than eye movements for much of the pitch trajectory. Large eye movements occurred only late in the pitch trajectory. Gaze was directed near the ball until approximately 150 milliseconds before the ball arrived at the batter, at which time gaze was directed ahead of the ball to a location near that occupied when the ball crosses the plate. In the "swing" condition, head movements in the direction of the ball were larger than eye movements throughout the pitch trajectory. Gaze was directed near the ball until approximately 50 to 60 milliseconds prior to pitch arrival at the batter. Horizontal head rotations were larger than horizontal eye rotations in both the "take" and "swing" conditions. Gaze was directed ahead of the ball late in the pitch trajectory in the "take" condition, whereas gaze was directed near the ball throughout much of the pitch trajectory in the "swing" condition.

The relationship between dioptric power and magnification in progressive addition lenses.

Non-uniform magnification (distortion) and dioptric blur are two major undesired optical defects affecting vision when looking through progressive addition lenses (PALs) and studying them is potentially very valuable for PAL design. The major purpose of this paper is to analyse the relationship between dioptric power and magnification and, additionally, to evaluate the expected values of distortion and dioptric blur typically present in PALs. This has not been carefully and rigorously analysed to date. We computed the local dioptric and magnification matrices (using a two-ray differential method) for different gaze directions in an archetypical model of a PAL. We used four different maps: scalar magnification and anamorphic distortion, to describe magnification, and mean power and astigmatism, to describe dioptric power. There is a good correlation between scalar magnification and mean power on the one hand, and anamorphic distortion and astigmatism on the other hand. Changes of 1 D in mean power are associated with variations in scalar magnification of around 3%. Also, 3% of anamorphic distortion is associated with increasing astigmatism up to 1 D. The directions of maximal power and maximal magnification are quite similar, though not equal (differences up to ± 1.5°). These directions strongly change from close to isotropic at the intermediate corridor to around 45° of oblique inclination for a few degrees of horizontal eye rotation. In typical PALs the level of distortion, which is unavoidably present when dioptric blurring appears, is small for usable vision zones (below 1 D of astigmatism). The combined analysis of dioptric power and magnification in PALs helps to understand their limitations as a visual aid. On the one hand, the potentials of including distortion magnitude as a target in the metric function being optimised in the PAL design are reduced; on the other hand, it seems worthwhile to explore adding the degradation orientation as an additional target.

Latency and Initiation of the Human Vestibuloocular Reflex to Pulsed Galvanic Stimulation

Cathodal galvanic currents activate primary vestibular afferents, whereas anodal currents inhibit them. Pulsed galvanic vestibular stimulation (GVS) was used to determine the latency and initiation of the human vestibuloocular reflex. Three-dimensional galvanic vestibuloocular reflex (g-VOR) was recorded with binocular dual-search coils in response to a bilateral bipolar 100-ms rectangular pulse of current at 0.9 (near-threshold), 2.5, 5.0, 7.5, and 10.0 mA in 11 normal subjects. The g-VOR consisted of three components: conjugate torsional eye rotation away from cathode toward anode; vertical divergence (skew deviation) with hypertropia of the eye on the cathodal and hypotropia of the eye on the anodal sides; and conjugate horizontal eye rotation away from cathode toward anode. The g-VOR was repeatable across all subjects, its magnitude a linear function of the current intensity, its latency about 9.0 ms with GVS of >or=2.5 mA, and was not suppressed by visual fixation. At 10-mA stimulation, the g-VOR [x, y, z] on the cathodal side was [0.77 +/- 0.10, -0.05 +/- 0.05, -0.18 +/- 0.06 degrees ] (mean +/- 95% confidence intervals) and on the anodal side was [0.79 +/- 0.10, 0.16 +/- 0.05, -0.19 +/- 0.06 degrees ], with a vertical divergence of 0.20 degrees . Although the horizontal g-VOR could have arisen from activation of the horizontal semicircular canal afferents, the vertical-torsional g-VOR resembled the vestibuloocular reflex in response to roll-plane head rotation about an Earth-horizontal axis and might be a result of both vertical semicircular canal and otolith afferent activations. Pulsed GVS is a promising technique to investigate latency and initiation of the human vestibuloocular reflex because it does not require a large mechanical apparatus nor does it pose problems of head inertia or slippage.

Effects of unilateral vestibular deafferentation on the linear vestibulo-ocular reflex evoked by impulsive eccentric roll rotation.

The effects of unilateral vestibular deafferentation (UVD) on the linear vestibulo-ocular reflex (LVOR) were studied by measuring three-dimensional eye movements in seven UVD subjects evoked by impulsive eccentric roll rotation while viewing an earth-fixed target at 200, 300, or 600 mm and comparing their responses to 11 normal subjects. The stimulus, a whole-body roll of approximately 1 degrees, with the eye positioned 815 mm eccentric to the rotation axis, produced an inter-aural linear acceleration of approximately 0.5 g and a roll acceleration of approximately 360 degrees /s(2). The responses generated by the LVOR comprise horizontal eye rotations. Horizontal eye velocity at 100 ms from stimulus onset in UVD subjects was significantly lower than in normal subjects for all viewing distances, with no significant difference between ipsilesional and contralesional responses. LVOR acceleration gain, defined as the slope of actual horizontal eye velocity divided by the slope of ideal horizontal eye velocity during a 30-ms period starting 70 ms from stimulus onset, was bilaterally significantly reduced in UVD subjects at all viewing distances. Acceleration gain from all viewing distances was 1.04 +/- 0.28 in normal subjects, and in UVD subjects was 0.49 +/- 0.23 for ipsilesional and 0.63 +/- 0.27 for contralesional acceleration. LVOR enhancement in the first 100 ms by near viewing was still present in UVD subjects. LVOR latency in UVD subjects (approximately 39 ms) was not significantly different from normal subjects (approximately 36 ms). After UVD, LVOR is bilaterally and largely symmetrically reduced, but latency remains unchanged and modulation by viewing distance is still present.

The torsional component of "horizontal" congenital nystagmus.

To study the relationship between the major horizontal and minor torsional components of congenital nystagmus to elucidate the diagnostic importance, effects on vision, and pathogenetic implications of the torsional components. We recorded the eye movements of 13 subjects with congenital nystagmus using a three-dimensional magnetic search coil technique over a 15-year period. The subjects fixated on stationary targets straight ahead and along the horizontal and vertical meridians. Six of the 10 subjects with horizontal congenital nystagmus were asymptomatic; the remaining 4 (plus two with a vertical component to their congenital nystagmus) had adult-onset symptoms. An additional subject without symptoms had a vertical congenital nystagmus component plus seesaw nystagmus; one of the symptomatic subjects also had seesaw nystagmus. In all 13 subjects, the horizontal and torsional cycles were phase-locked, and positive horizontal (rightward), vertical (upward, if any), and torsional (clockwise) motion coincided in 10 subjects. That is, rightward horizontal eye rotation coincided with clockwise curvilinear motion (rightward and downward) of the upper pole of each eye. During the horizontal foveation periods, torsional motion was also of low velocity. In 2 of 13 subjects, the torsional waveforms differed from those in the horizontal plane; in others, the direction or the variation with gaze angle differed from that predicted by Listing. In each of the 13 subjects, the torsional components ranged from 8.16% to 94.42% (median, 32.94%) of the peak-to-peak magnitudes of the congenital nystagmus. In most cases, the measured torsion was far greater than that predicted by Listing's law for a worst-case analysis (range, 0.69-11.83%; median, 4.91%). The torsional components of the two subjects with seesaw nystagmus were 60.48% and 264.02%. The manner in which the horizontal and torsional components of "horizontal" congenital nystagmus were phase-locked made clinical detection of the torsional component difficult. Most "horizontal" congenital nystagmus is actually horizontal-torsional congenital nystagmus. Visual acuity during horizontal foveation periods is not significantly diminished by torsional motion. In only one subject did the torsional component of the congenital nystagmus have an amplitude equivalent to Listing torsion; in the other 12 subjects, torsion exceeded our estimate of what Listing's law would predict. The torsional components of the seesaw nystagmus in two subjects also greatly exceeded the torsion predicted by Listing torsion. The most parsimonious explanation for our data is that the cyclic torsion in congenital nystagmus was generated centrally and not a result of Listing torsion, mechanical crosstalk, or normal or abnormal extraocular-muscle (plant) dynamics. Further measurements are needed to confirm this hypothesis.

Torsional dynamics and cross-coupling in the human vestibulo-ocular reflex during active head rotation

Six subjects fixated an imagined space-fixed target in darkness, or a visible target against a structured visual background, while rotating their heads actively in yaw, pitch and roll at four different frequencies, from 0.3 to 2.4 Hz. We used search coils to measure the 3-dimensional rotations of the head and eye, and described the relation between them--the input-output function of the rotational vestibulo-ocular reflex (VOR)--using gain matrices. We found consistent cross-coupling in which torsional head rotation evoked horizontal eye rotation. The reason may be that the eyes are above the axis of torsional head rotation, and therefore may translate horizontally during the head motion, so the VOR rotates them horizontally to compensate. Torsional gain was lower than horizontal or vertical, more variable from subject to subject and decreased at low frequencies. One reason for the low gain may be that torsional head rotation produces little retinal slip near the fovea; hence little compensatory eye motion is needed, and so the VOR reduces its torsional gain to save energy or to approximate Listing's law by keeping ocular torsion near zero. In addition, the human VOR has little experience with purely torsional head rotations and so its adaptive networks may be poorly trained for such stimuli. The drop in torsional gain at low frequencies can be explained based on the leak in the neural integrator that helps convert torsional eye-velocity commands into eye-position commands.

Compensation of the human vertical vestibulo-ocular reflex following occlusion of one vertical semicircular canal is incomplete.

The vestibulo-ocular reflex (VOR) was studied in nine human subjects 2-15 months after permanent surgical occlusion of one posterior semicircular canal. The stimuli used were rapid, passive, unpredictable, low-amplitude (10-20 degrees), high-acceleration (3000-4000 degrees/s2) head rotations in pitch and yaw planes. The responses measured were vertical and horizontal eye rotations, and the results were compared with those from 19 normal subjects. After unilateral occlusion of the posterior semicircular canal, the gain of the head-up pitch vertical VOR--the vertical VOR generated by excitation from only one and disfacilitation from two vertical semicircular canals--was reduced to 0.61 +/- 0.06 (normal 0.92 +/- 0.06) at a head velocity of 200 degrees/s. In contrast the gain of the head-down pitch vertical VOR--the VOR still generated by excitation from two, but disfacilitation from only one vertical semicircular canal--was within normal limits: 0.86 +/- 0.11 (normal 0.96 +/- 0.04). The gain of the horizontal VOR in response to yaw head rotations--ipsilesion 0.81 +/- 0.06 (normal 0.88 +/- 0.05) and contralesion 0.80 +/- 0.11 (normal 0.92 +/- 0.11)--was within normal limits in both directions (group means +/- two-tailed 95% confidence intervals given in each case). These results show that occlusion of just one vertical semicircular canal produces a permanent deficit of about 30% in the vertical VOR gain in response to rapid pitch head rotations in the excitatory direction of the occluded canal. This observation indicates that, in response to a stimulus in the higher dynamic range, compensation of the human VOR for the loss of excitatory input from even one vertical semicircular canal is incomplete.

眼か周囲における角膜網膜電位分布の研究 ＥＮＧ記録にみられる仮性眼球運動波形

Pseudo-eye-movement weves, or PEWs, which represent false eye movements on electronystagmograms in the horizontal eye lead during vertical rotation of the eye or in the vertical eye lead during horizontal eye rotation, cause some difficulties in clinical practice. This electronystagmographic study is aimed to find a way to cope with PEWs and to clarify their nature. Twelve electrodes were attached to 12 points of the face, and one electrode was placed on a mastoid process. The electric potential at each point was measured monopolarly or bipolarly by a topography system (NEC San-ei, Japan) during both horizontal and vertical alternating gaze. 1) Eye movements were successfully recorded from all 12 points. The maximum amplitude was seen in a pair of horizontal eye leads during horizontal eye movements and in a pair of vertical eye leads during vertical eye movements. 2) Horizontal and vertical PEWs disappeared or were reduced in amplitude when the electrodes at the inner canthus, nasal and lower margin of the orbit were shifted slightly lower than their conventional points. 3) A PEW is assumed to appear when the potential difference between a pair of conventional horizontal or vertical electrodes is not zero, during vertical and horizontal eye movements, respectively.

An adaptive control model for human head and eye movements while walking

When a person walks the head undergoes horizontal and vertical rotations, and also horizontal and vertical translations. To visually fixate on an object while walking, compensatory horizontal and vertical eye movements must be made. The model for this gaze (head plus eye) control system includes three types of eye movements: smooth pursuit, saccadic, and vestibulo-ocular. The smooth pursuit system uses a target-selective adaptive controller that compensates for the large inherent time delay and produces zero-latency tracking of predictable targets. Target movements were selected to minimize the role of the saccadic control system. Typical tracking is shown while seated with the head restrained, standing with unrestrained head, performing voluntary head rotations, and walking. Each additional degree of freedom produced additional head movements that were compensated by additional eye movements. It is shown that while a human walks the effects of head rotations (yaw) cancel the effects of head translations, thus minimizing the resulting horizontal eye rotations necessary to maintain fixation.

魚の眼球水平運動の回転軸

To clarify the axis of horizontal eye rotation of fish, a 35mm camera filmed the optomotor reaction of the animal from above, and the axis of horizontal eye rotation was estimated mechanically. Moreover, the muscles and the space between the eye and the orbit were studied anatomically. The axis of the horizontal eye rotation is not a single point. The axes measured geometrically seem to lie around an optic center of an eye, and the axis tended to shift a little bit nasalward when the eye rotated nasalward.