Changes In Eye Position Research Articles

Effects of orbital decompression on duction, cyclotorsion and diplopia

BackgroundOrbital decompression is commonly performed to correct proptosis in patients with Graves’ orbitopathy (GO). In literature, the incidence of new-onset constant diplopia after orbital decompression varies. Few studies have evaluated...

Effect of the prism and Maddox rod test as the surgical target for type III acute acquired comitant esotropia.

This study aims to explore more accurate and efficient examination methods to provide precise target surgical measurements for patients with type III acute acquired comitant esotropia (AACE). The study conducted a retrospective analysis of 108 patients diagnosed with AACE who received surgical treatment at the Department of Ophthalmology, the First Affiliated Hospital of Fujian Medical University, from January 2018 to September 2023. All patients underwent examinations of the deviation angle, including the Hirschberg test, prism and Maddox rod test (PMT), and prism and alternate cover test (PACT). For the PACT, the minimum value (PACTmin) and maximum value (PACTmax) were obtained based on differences in examination methods, as well as the deviation angle range (PACT range), which represents the difference between PACTmax and PACTmin. Postoperatively, these patients were followed up for at least 6 months to assess changes in eye position and whether diplopia symptoms recurred. In both near and distant examinations, the results of PACTmax were significantly greater than those of PACTmin (p < 0.001), while the deviation angles obtained from PACTmax and PMT showed no significant statistical difference [p = 0.689 (33 cm), p = 0.436 (5 m)]. There was a strong linear correlation between PACTmin and PMT at both near (R = 0.8887) and distant (R = 0.8950) distances, but each PACTmin corresponded to multiple PMT values. There was no significant difference between the results of PACT range at near and distant distances (p = 0.531). The deviation angles obtained by PMT and PACTmin significantly decreased postoperatively compared to preoperative values, and diplopia disappeared in all patients, with alternative cover test showing no movement or presenting as an esophoria state. The PMT can provide precise target surgical measurements for type III AACE, making it a fast, effective, and cost-efficient examination method. It is worthy of being promoted and applied in clinical practice.

Project Awakesure: Intelligent Drowsiness Detection Using Eye Tracking

Being sleepy or drowsy is referred to as being drowsy. A person who is sleepy may feel exhausted or lethargic and struggle to stay awake. People who are sleepy tend to be less attentive and may even nod off, though they can still be awakened. An increasing number of vocations nowadays call for sustained focus. In order for drivers to respond quickly to unexpected incidents, they must maintain a watchful eye on the road. Many road incidents are directly caused by tired drivers. In order to drastically lower the frequency of fatigue-related auto accidents, it is crucial to develop technologies that can identify and alert a driver to a poor psychophysical state. However, there are many challenges in developing systems that can quickly and accurately recognize a driver's signs of fatigue. Using vision-based technology is one technological option for implementing driver fatigue monitoring systems. The available driver drowsiness detection systems are described in this article. Here, we are assessing the driver's level of sleepiness utilizing his visual system. The automated system for preventing accidents and monitoring sleepy drivers developed for this study is based on detecting variations in the length of eye blinks. Our recommended technique makes use of the eyes' postulated horizontal symmetry property to identify visual changes in eye positions. Our novel approach precisely positions a standard webcam in front of the driver's seat to identify eye blinks. It will identify the eyeballs based on a specific EAR (Eye Aspect Ratio).

Diffusion tensor imaging of horizontal extraocular muscles in patients with concomitant and paralytic esotropia.

To assess metrics of diffusion tensor imagining (DTI) in evaluating microstructural abnormalities of horizontal extraocular muscles (EOM) in esotropia. Six adult concomitant esotropia patients, 5 unilateral abducent paralysis patients and 2 healthy volunteers were enrolled. Conventional magnetic resonance imaging (MRI) and DTI were performed on all subjects using 3T MR scanner. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) of medial and lateral rectus muscles were measured and compared between patients group and control group. Medial rectus MD and RD within the adducted eye of concomitant patients was significantly greater than that in unilateral abducent paralysis patients (0.259×10-2 mm2/s vs 0.207×10-2 mm2/s, P=0.014; 0.182×10-2 mm2/s vs 0.152×10-2 mm2/s, P=0.017). Both strabismus patients showed a significantly decreased MD and AD than that obtained in normal controls for lateral rectus muscles (P<0.05). Medial rectus MD of the adducted eye in concomitant strabismus patients was significantly decreased than that in healthy controls (0.259×10-2 mm2/s vs 0.266×10-2 mm2/s, P=0.010). Lateral rectus AD of the adducted eye in concomitant strabismus patients was significantly decreased as compared with that in healthy controls (0.515×10-2 mm2/s vs 0.593×10-2 mm2/s, P=0.013). No statistically significant differences were present between the adducted and fixating eyes in concomitant strabismus patients. DTI represents a feasible technique to assess tissue characteristics of EOM. The effects of eye position changes on DTI parameters are subtle. Decreased MD and RD could be evidence for remodeling of the medial rectus muscle contracture. Lower medial and lateral recuts MD of concomitant esotropia patients indicates a thinner fibrous structure of the EOM. Lower MD and AD should be general character of esotropia.

Ocular-following responses in school-age children.

Ocular following eye movements have provided insights into how the visual system of humans and monkeys processes motion. Recently, it has been shown that they also reliably reveal stereoanomalies, and, thus, might have clinical applications. Their translation from research to clinical setting has however been hindered by their small size, which makes them difficult to record, and by a lack of data about their properties in sizable populations. Notably, they have so far only been recorded in adults. We recorded ocular following responses (OFRs)-defined as the change in eye position in the 80-160 ms time window following the motion onset of a large textured stimulus-in 14 school-age children (6 to 13 years old, 9 males and 5 females), under recording conditions that closely mimic a clinical setting. The OFRs were acquired non-invasively by a custom developed high-resolution video-oculography system, described in this study. With the developed system we were able to non-invasively detect OFRs in all children in short recording sessions. Across subjects, we observed a large variability in the magnitude of the movements (by a factor of 4); OFR magnitude was however not correlated with age. A power analysis indicates that even considerably smaller movements could be detected. We conclude that the ocular following system is well developed by age six, and OFRs can be recorded non-invasively in young children in a clinical setting.

Behavior of the saccadic system: Metrics of timing and accuracy.

The behavior of saccades in response to a peripheral target is discussed. The saccade latency comprises sensory and motor processing delays of about 80ms, leaving on average more than 100ms for central processing. Many factors influence the latter. Yet, programming express saccades requires little to no central processing time. Typical saccades are hypometric by about 10%, which seems to be a deliberate strategy. A correction saccade requires only about 50ms of central processing. There is no strict dead zone for saccades, as they can be elicited by target jumps as small as 0.05deg. There seems to be no strict refractoriness in the system either, because saccade metrics can be continuously modified during the preparation interval by new target information. This suggests semi-independent processes for the "when" and "where" of saccades, which is incorporated into a neurophysiologically-inspired model. Saccades are not kept in retinotopic coordinates but are goal-directed by incorporating intervening changes in eye position. Although the updating mechanism is unclear, there is strong evidence that it involves the use of efference copy information (the outflow theory). Although the spatial percept of a target may be erroneous around saccades, the motor system seems to be more accurate. The chapter closes with a discussion on the potential function of microsaccades and slow drifts, when fixating a target.

A low-cost, high-performance video-based binocular eye tracker for psychophysical research.

We describe a high-performance, pupil-based binocular eye tracker that approaches the performance of a well-established commercial system, but at a fraction of the cost. The eye tracker is built from standard hardware components, and its software (written in Visual C++) can be easily implemented. Because of its fast and simple linear calibration scheme, the eye tracker performs best in the central 10 degrees of the visual field. The eye tracker possesses a number of useful features: (1) automated calibration simultaneously in both eyes while subjects fixate four fixation points sequentially on a computer screen, (2) automated realtime continuous analysis of measurement noise, (3) automated blink detection, (4) and realtime analysis of pupil centration artifacts. This last feature is critical because it is known that pupil diameter changes can be erroneously registered by pupil-based trackers as a change in eye position. We evaluated the performance of our system against that of a wellestablished commercial system using simultaneous measurements in 10 participants. We propose our low-cost eye tracker as a promising resource for studies of binocular eye movements.

Change in the eye position under general anesthesia in children with intermittent exotropia

To evaluate the eye position in subjects with intermittent exotropia and normal subjects under general anesthesia (GA) using the strabismus photo analyzer. This retrospective case-control study included 78 subjects with intermittent exotropia and 25 normal control subjects who underwent epiblepharon surgery. Eye position under GA was assessed using the strabismus photo analyzer, based on eye models generated from corneal lights and limbus in pre- and post-anesthesia images. Eye positions under GA in the control and intermittent exotropia groups were compared. Preoperative angle of deviation was also compared with amount of change in eye position under GA in the intermittent exotropia group. Eye position under GA was more divergent in subjects with intermittent exotropia than in controls (P=0.008). The amount of change in eye position under GA was correlated with the preoperative angle of deviation (r2=0.47; P<0.001). In small preoperative exodeviations, the change in eye position was primarily more divergent, whereas in large exodeviations, a convergent tendency-less exotropic compared with the preoperative angle of exodeviation-was observed. In subjects with small preoperative exodeviations, there was a tendency for eye position to become more divergent after GA; in those with large exodeviations, there was less exotropia after GA.

Deep lateral orbital decompression for Graves orbitopathy: a systematic review.

To systematically review the literature on the deep lateral orbital decompression (DLD). The authors searched the MEDLINE, Lilac, Scopus, and EMBASE databases for all articles in English, Spanish, and French that used as keywords the terms orbital decompression and lateral wall. Two articles in German were also included. Data retrieved included the number of patients and orbits operated, types of the approach employed, exophthalmometric and horizontal eye position changes, and complications. The 95% confidence intervals (CI) of the mean Hertel changes induced by the surgery were calculated from series with 15 or more data. Of the 204 publications initially retrieved, 131 were included. Detailed surgical techniques were analyzed from 59 articles representing 4559 procedures of 2705 patients. In 45.8% of the reports, the orbits were decompressed ab-interno. Ab-externo and rim-off techniques were used in 25.4% and 28.8% of the orbits, respectively. Mean and 95% CI intervals of Hertel changes, pooled from 15 articles, indicate that the effect of the surgery is not related to the technique and ranges from 2.5 to 4.5mm. The rate of new onset of diplopia varied from zero to 8.6%. Several complications have been reported including dry eye, oscillopsia, temporal howling, lateral rectus damage, and bleeding. Unilateral amaurosis and subdural hematoma have been described in only one patients each. The low rate of new-onset diplopia is the main benefit of DLD. Prospective studies are needed to compare the rate of complications induced by the 3 main surgical techniquesused.

Eye Position Changes After Cataract Surgery in Patients with Exotropia

Eye Position Changes After Cataract Surgery in Patients with Exotropia

Effects of prolonged roll-tilt on the subjective visual and haptic vertical in healthy human subjects.

While verticality perception is normally accurate when upright, a systematic bias ("post-tilt bias") is seen after prolonged roll-tilt. The source of the bias could either be central (shifting "null" position) or related to changes in torsional eye-position. To study the mechanisms of the post-tilt bias in vision-dependent and vision-independent paradigms and to characterize the impact of optokinetic stimulation. The subjective visual-vertical (SVV) and subjective haptic-vertical (SHV) were measured after static roll-tilt (±90deg ear-down ("adaptation") position; duration = 5 min; n = 9 subjects). To assess the effect of visual stimuli, a control condition (darkness) was compared with an optokinetic stimulus (clockwise/counter-clockwise rotation, 60deg/sec) during adaptation. A significant post-tilt bias was more frequent for the SVV than the SHV (72% vs. 54%, p = 0.007) with shifts pointing towards or away from the adaptation position with similar frequency. Exponential-decay time-constants were comparable for both paradigms and directions of shifts. The optokinetic stimulus had no effect on the bias for either paradigm. Emerging in both vision-dependent and vision-independent paradigms, the results support the hypothesis that the post-tilt bias results from a shift in the internal estimate of direction of gravity, while optokinetic nystagmus seems not to be a major contributor.

Eye tracking-based estimation and compensation of chromatic offsets for multi-wavelength retinal microstimulation with foveal cone precision.

Multi-wavelength ophthalmic imaging and stimulation of photoreceptor cells require consideration of chromatic dispersion of the eye, manifesting in longitudinal and transverse chromatic aberrations. Contemporary image-based techniques to measure and correct transverse chromatic aberration (TCA) and the resulting transverse chromatic offset (TCO) in an adaptive optics retinal imaging system are precise but lack compensation of small but significant shifts in eye position occurring during in vivo testing. Here, we present a method that requires only a single measurement of TCO during controlled movements of the eye to map retinal chromatic image shifts to the image space of a pupil camera. After such calibration, TCO can be compensated by continuously monitoring eye position during experimentation and by interpolating correction vectors from a linear fit to the calibration data. The average change rate of TCO per head shift and the correlation between Kappa and the individual foveal TCA are close to the expectations based on a chromatic eye model. Our solution enables continuous compensation of TCO with high spatial precision and avoids high light intensities required for re-measuring TCO after eye position changes, which is necessary for foveal cone-targeted psychophysical experimentation.

Eye movement analysis using a binocular video-ophthalmoscope.

This paper describes an application of binocular video-ophthalmoscope for binocular eye movement analysis during target fixation. We analyze eye movements during monocular and binocular fixation and the changes in eye position for 73 subjects. We show that the standard deviations of differences between eye shifts for vertical and horizontal movements are higher for binocular fixation with respect to monocular fixation. We also present different examples of eye movement visualization.

No handedness effect on spatial orientation or ocular counter-roll during lateral head tilts.

Although vestibular inputs are bilaterally represented within the cerebral hemispheres, the higher level vestibular functions exhibit hemispheric asymmetries. Previous studies have suggested that such asymmetries are associated with handedness. Here, we studied the impact of handedness (i.e., hemispheric lateralization) on spatial orientation using a subjective visual vertical (SVV) task. We tested 22 right‐handed and 22 left‐handed subjects in upright position, during prolonged lateral head tilts of 20° (~15 min), and after the head returned to upright position. The corresponding changes in torsional eye position were measured simultaneously using video‐oculography. During lateral head tilts, both right‐ and left‐handers had initial SVV biases in the opposite direction of the head tilt (right‐handers: left tilt 3.0 ± 1.3°, right tilt −4.7 ± 1.5°; left‐handers: left tilt 3.4 ± 1.1°, right tilt −4.1 ± 1.0°). The SVV subsequently drifted in the direction of the head tilt, and there was an aftereffect in the same direction when the head was brought back upright. The ocular torsion initially changed in the opposite direction of the head tilt (right‐handers: left tilt 3.8 ± 0.4°, right tilt −3.8 ± 0.4°; left‐handers: left tilt 4.2 ± 0.5°, right tilt −4.5 ± 0.5°), and there were also drift and aftereffect in the same direction as the head tilt. The changes in upright perception and ocular torsion did not differ between right‐ and left‐handers. These findings show no functional laterality, neither in the higher level neural mechanisms that maintain spatial orientation, nor in the lower level mechanisms that generate the ocular torsion response during lateral head tilt.

Treatment of High Astigmatism with WaveLight Allegretto Eye-Q Excimer Laser Platform

Introduction:The WaveLight Allegretto Eye-Q is a flying-spot excimer laser, with a pulse repetition rate of 400Hz, with two galvanometric scanners for positioning laser pulses. The system has an infrared high speed camera operating at 400Hz to track the patient’s eye movements that either compensates for changes in eye position or interrupts the treatment if the eye moves outside a preset predetermined range.Aim:The purpose of this study was to investigate WaveLight Allegretto Eye-Q 400Hz laser delivery platform aimed to correct astigmatism by subjecting the pre and postoperative astigmatic values to vector analysis.Methods:Patients were divided into two groups, depending on the type of astigmatism. Astigmatism was between 2 and 7 diopters (D). A total of 188 eyes (110 patients), 127 eyes (71 patients) with myopic astigmatism and 61 eyes (39 patients) with mixed astigmatism underwent unremarkable LASIK correction on WaveLight Allegretto Eye-Q 400Hz. The preoperative and postoperative sphere, negative cylinder [C] and axis (ø) of manifest refractions were subjected to vector analysis by calculations of the standard J0 (cos [4π(ø-90)/360]xC/2) and J45 (sin[4π(ø-90)/ 360]xC/2).Results:Reporting the key results, we found that J0 significantly reduced after LASIK (p<0.001) but not J45. There was no significant association between individual pairs of pre and postoperative J0 &J45 values.Conclusion:WaveLight Allegretto 400Hz showed excellent results for treating patients with high astigmatism, regardless whether it is mixed or myopic astigmatism. The J45 did not reduce significantly possibly because of the low number of eyes with oblique astigmatism. There was no genuine difference postoperatively between groups treated on WaveLight Allegretto platform according to the vector analyses.

Modeling gaze position-dependent opsoclonus.

Opsoclonus/flutter (O/F) is a rare disorder of the saccadic system. Previously, we modeled O/F that developed in a patient following abuse of anabolic steroids. That model, as in all models of the saccadic system, generates commands to make a change in eye position. Recently, we saw a patient who developed a unique form of opsoclonus following a concussion. The patient had postsaccadic ocular flutter in both directions of gaze, and opsoclonus during fixation and pursuit in the left hemifield. A new model of the saccadic system is needed to account for this gaze-position dependent O/F. We started with our prior model, which contains two key elements, mutual inhibition between inhibitory burst neurons on both sides and a prolonged reactivation time of the omnipause neurons (OPNs). We included new inputs to the OPNs from the nucleus prepositus hypoglossi and the frontal eye fields, which contain position-dependent neurons. This provides a mechanism for delaying OPN reactivation, and creating a gaze-position dependence. A simplified pursuit system was also added, the output of which inhibits the OPNs, providing a mechanism for gaze-dependence during pursuit. The rest of the model continues to generate a command to change eye position.

Ophthalmic findings in linear scleroderma manifesting as facial en coup de sabre.

To evaluate ophthalmic involvement in a long-term series of patients with en coup de sabre (ECS) close to the eye based on the hypothesis that this is not commonly affected, or simply under-reported. An observational study of ophthalmological findings in patients from Copenhagen University Dermatology Clinics. A standard eye examination further included exophthalmometry, axial length and keratometry (IOLMaster), and horizontal eye muscle thickness (B-scan ultrasonography). Thirty-one consecutive patients were included from 2014 to 2015 (25 females, 6 males; median age, 33 years; range, 11-71 years). Twenty-seven patients had undergone ophthalmic evaluation more than once (observation time, 1-31 years; median, 7 years). Most eyes were normal or had currently adapted to eventual adnexal lesions and to insidious changes in eye position and/or motility. However, significant ipsilateral complications had developed related to 8 eyes, where two patients had more than one disorder. The ophthalmic pathologies were: blind eye (n = 2) due to adult age keratopathy/perforation and to Coats-like retinal detachment in childhood; restricted eye motility and diplopia (n = 2); acquired corneal astigmatism (n = 2); and dense cataract with light sense only (n = 1). Two patients had optic neuritis-like presentations, and lacrimal sac pathology occurred in one. The main ophthalmic focus possibly explained the high proportion of significant lesions in this patient series (in 8 of 31). In addition to the established feature of enophthalmos, the oculometric evidence suggested smaller eye and rectus muscle involvement, interpreted as a secondary (late) negative trophic effect of the overlying skin disorder on eye structures.

Dynamics of fixational eye position and microsaccades during spatial cueing: the case of express microsaccades

Microsaccades are systematically modulated by peripheral spatial cues, and these eye movements have been implicated in perceptual and motor performance changes in cueing tasks. However, an additional oculomotor factor that may also influence performance in these tasks, fixational eye position itself, has been largely neglected so far. Using precise eye tracking and real-time retinal-image stabilization, we carefully analyzed fixational eye position dynamics and related them to microsaccade generation during spatial cueing. As expected, during baseline fixation, microsaccades corrected for a foveal motor error away from the preferred retinal locus of fixation (the so-called ocular position "set point" of the oculomotor system). However, we found that this relationship was violated during a short period immediately after cue onset; a subset of cue-directed "express microsaccades" that were highly precise in time and direction, and that were larger than regular microsaccades, occurred. These movements, having <100-ms latencies from cue onset, were triggered when fixational eye position was already at the oculomotor set point when the cue appeared; they were thus error-increasing rather than error-decreasing. Critically, even when no microsaccades occurred, fixational eye position itself was systematically deviated toward the cue, again with ~100-ms latency, suggesting that the oculomotor system establishes a new set point at different postcue times. This new set point later switched to being away from the cue after ~200-300 ms. Because eye position alters the location of retinal images, our results suggest that both eye position and microsaccades can be associated with performance changes in spatial cueing tasks. NEW & NOTEWORTHY Covert spatial cueing tasks are a workhorse for studying cognitive processing in humans and monkeys, but gaze is not perfectly stable during these tasks. We found that minute fixational eye position changes, independent of the more studied microsaccades, are not random in cueing tasks and are thus not "averaged out" in analyses. These changes can additionally dictate microsaccade times. Thus, in addition to microsaccadic influences, retinal image changes associated with fixational eye position are relevant for performance in cueing tasks.

Response of pursuit cells in MST after eye position perturbation by microstimulation of the Superior Colliculus (SC)

Primates use the fovea to maintain high quality central vision of the world. When a target is moving, smooth pursuit eye movements (SEM) keep the fovea of both eyes on target. A large proportion of neurons in area MST discharge during SEM. These smooth pursuit cells (SPC) carry visual and extraretinal signals. We recorded 27 SPC in MST of a macaque monkey during SEM trials interrupted with a saccade that was elicited by electrical microstimulation (MS) in the SC. The MS consisted of a train of pulses (0.1ms, 400Hz, 40ms) at low currents (< 40mA). The tracking behavior was characterized by 1) an evoked saccade that brought the eye outside the target path, 2) a SEM following this abrupt change in eye position and 3) a corrective saccade. We quantified the ratio of activity after the evoked saccade, before the corrective saccade and during the corrective saccade. A majority of neurons (63%) presented ratios between 0.8 and 1.2 after the evoked saccade but ratios less than 0.8 during the corrective saccade. Among this subpopulation, 59% actually had a decrease of their firing rate before the corrective saccade. On average, this drop of activity occurred 54 (±11ms) after the evoked saccade offset or 109 (±9ms) after its onset. Interestingly, in 90% of cases the latency of this drop of activity was sensitive to the delay between the evoked and corrective saccades. Finally, 22% neurons did not present a drop of activity during these intervals while 15% presented a decrease from the evoked saccade offset. This eye position perturbation showed that the activity of a majority of MST smooth pursuit cells was not interrupted by a direct corollary discharge from the saccadic system. However this activity seems inhibited by the occurrence of a corrective saccade even though not always time-locked to it. Meeting abstract presented at VSS 2017

The effect of orbital decompression surgery on interpupillary distance and angle kappa in patients with thyroid-associated orbitopathy.

The purpose was to investigate the effects of orbital decompression surgery on postoperative changes in interpupillary distance (IPD) and angle kappa in patients with thyroid-associated orbitopathy (TAO). In patients with TAO who underwent orbital decompression surgery between January 1, 2014 and February 21, 2016, we measured exopthalmometry, IPD, inner intercanthal distance (IICD) and outer intercanthal distance (OICD) using a computer software program and angle kappa with an ORB scan II. We then analyzed preoperative and 3-month postoperative exophthalmometry, IPD, IICD, OICD and angle kappa to evaluate changes in eye position or rotation of the eyeball following orbital decompression surgery. Fifty-four patients (35 women and 19 men) with a mean age of 34.59 (range, 16-64years) were enrolled in this study. After decompression surgery, the IPD was significantly decreased by 1.76mm (preoperative, 63.14 ± 3.93mm; postoperative, 61.38 ± 3.84mm; P < 0.001), but angle kappa, IICD, and OICD did not vary significantly (P = 0.814, P = 0.635 and P = 0.092, respectively). A significant decrease in IPD was noted after orbital decompression in patients with TAO. However, there was no significant change in angle kappa. Therefore, the mechanism of change in the IPD is not an inward rotation of the eyeball, but rather an actual dorsal shift causing a wedging of the eye position itself within the orbit.