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OBJECTIVE Transcranial magnetic stimulation (TMS)-evoked phosphenes are oculocentric; their perceived location depends upon eye position. We investigated the accuracy and precision of TMS-evoked phosphene oculocentric mapping. METHODS We evoked central phosphenes by stimulating early visual cortical areas with TMS, systematically examining the effect of eye position by asking participants to report the location of the evoked phosphene. We tested whether any systematic differences in the precision or accuracy of responses occurred as a function of eye position. RESULTS Perceived phosphene locations map veridically to eye position, although there are considerable individual differences in the reliability of this mapping. CONCLUSIONS Our results emphasize the need to carefully control eye movements when carrying out phosphene localization studies and suggest that individual differences in the reliability of the reported position of individual phosphenes must be considered.

Microsaccades are linked with extraretinal mechanisms that significantly alter spatial perception before the onset of eye movements. We sought to investigate whether microsaccadic activity is modulated by the speed of radial optic flow stimuli. Experiments were performed in the dark on 19 subjects who stood in front of a screen covering 135 × 107° of the visual field. Subjects were instructed to fixate on a central fixation point while optic flow stimuli were presented in full field, in the foveal, and in the peripheral visual field at different dot speeds (8, 11, 14, 17, and 20°/s). Fixation in the dark was used as a control stimulus. For almost all tested speeds, the stimulation of the peripheral retina evoked the highest microsaccade rate. We also found combined effects of optic flow speed and the stimulated retinal region (foveal, peripheral, and full field) for microsaccade latency. These results show that optic flow speed modulates microsaccadic activity when presented in specific retinal portions, suggesting that eye movement generation is strictly dependent on the stimulated retinal regions.

The aim of this study was to investigate perceptual eye position (PEP) and to evaluate the effect of dichoptic visual perceptual training in postoperative intermittent exotropia [X(T)]. We enrolled 30 non-strabismus children (control group) and 54 postoperative X(T) children [divided into training group (33 patients) and non-training group (21 patients)]. All subjects received measurements of PEP, and the postoperative X(T) children were measured both in the third postoperative day and the third postoperative month. All patients in training group received 3-month dichoptic visual perceptual training based on a unique virtual reality platform. The results showed that the postoperative X(T) children with normal eye position still had an abnormal PEP. After a period of visual perceptual training, the PEP pixels in postoperative children dramatically decreased. The results revealed that PEP could evaluate fixation disparity and binocular visual function perceptively and precisely, and the dichoptic visual perceptive training may rebuild binocular visual function.

Haptic exploration produces mental object representations that can be memorized for subsequent object-directed behaviour. Storage of haptically-acquired object images (HOIs), engages, besides canonical somatosensory areas, the early visual cortex (EVC). Clear evidence for a causal contribution of EVC to HOI representation is still lacking. The use of visual information by the grasping system undergoes necessarily a frame of reference shift by integrating eye-position. We hypothesize that if the motor system uses HOIs stored in a retinotopic coding in the visual cortex, then its use is likely to depend at least in part on eye position. We measured the kinematics of 4 fingers in the right hand of 15 healthy participants during the task of grasping different unseen objects behind an opaque panel, that had been previously explored haptically. The participants never saw the object and operated exclusively based on haptic information. The position of the object was fixed, in front of the participant, but the subject’s gaze varied from trial to trial between 3 possible positions, towards the unseen object or away from it, on either side. Results showed that the middle and little fingers’ kinematics during reaching for the unseen object changed significantly according to gaze position. In a control experiment we showed that intransitive hand movements were not modulated by gaze direction. Manipulating eye-position produces small but significant configuration errors, (behavioural errors due to shifts in frame of reference) possibly related to an eye-centered frame of reference, despite the absence of visual information, indicating sharing of resources between the haptic and the visual/oculomotor system to delayed haptic grasping.

Purpose Ocular proton therapy is an effective therapeutic option for patients affected with uveal melanomas. An optical eye-tracking system (ETS) aiming at noninvasive motion monitoring was developed and tested in a clinical scenario. Materials and methods The ETS estimates eye position and orientation at 25 frames per second using the three-dimensional position of pupil and cornea curvature centers identified, in the treatment room, through stereoscopic optical imaging and infrared eye illumination. Its capabilities for automatic detection of eye motion were retrospectively evaluated on 60 treatment fractions. Then, the ETS performance was benchmarked against the clinical standard based on visual control and manual beam interruption. Results Eye-tracking system detected eye position successfully in 97% of all available frames. Eye-tracking system-based eye monitoring during therapy guarantees quicker response to involuntary eye motions than manual beam interruptions and avoids unnecessary beam interruptions. Conclusions Eye-tracking system shows promise for on-line monitoring of eye motion. Its introduction in the clinical workflow will guarantee a swifter treatment course for the patient and the clinical personnel.

Objective: We present a physiologically motivated eye movement analysis framework for model-based separation, detection, and classification (MBSDC) of eye movements. By estimating kinematic and neural controller signals for saccades, smooth pursuit, and fixational eye movements in a mechanistic model of the oculomotor system we are able to separate and analyze these eye movements independently. Methods: We extended an established oculomotor model for horizontal eye movements by neural controller signals and by a blink artifact model. To estimate kinematic (position, velocity, acceleration, forces) and neural controller signals from eye position data, we employ Kalman smoothing and sparse input estimation techniques. The estimated signals are used for detecting saccade start and end points, and for classifying the recording into saccades, smooth pursuit, fixations, post-saccadic oscillations, and blinks. Results: On simulated data, the reconstruction error of the velocity profiles is about half the error value obtained by the commonly employed approach of filtering and numerical differentiation. In experiments with smooth pursuit data from human subjects, we observe an accurate signal separation. In addition, in neural recordings from non-human primates, the estimated neural controller signals match the real recordings strikingly well. Significance: The MBSDC framework enables the analysis of multi-type eye movement recordings and provides a physiologically motivated approach to study motor commands and might aid the discovery of new digital biomarkers. Conclusion: The proposed framework provides a model-based approach for a wide variety of eye movement analysis tasks.

We investigated whether the proprioceptive eye position signal after the execution of a saccadic eye movement is used to estimate the accuracy of the movement. If so, saccadic adaptation, the mechanism that maintains saccade accuracy, could use this signal in a similar way as it uses visual feedback after the saccade. To manipulate the availability of the proprioceptive eye position signal we utilized the finding that proprioceptive eye position information builds up gradually after a saccade over a time interval comparable to typical saccade latencies. We confined the retention time of gaze at the saccade landing point by asking participants to make fast return saccades to the fixation point that preempt the usability of proprioceptive eye position signals. In five experimental conditions we measured the influence of the visual and proprioceptive feedback, together and separately, on the development of adaptation. We found that the adaptation of the previously shortened saccades in the case of visual feedback being unavailable after the saccade was significantly weaker when the use of proprioceptive eye position information was impaired by fast return saccades. We conclude that adaptation can be driven by proprioceptive eye position feedback. NEW & NOTEWORTHY We show that proprioceptive eye position information is used after a saccade to estimate motor error and adapt saccade control. Previous studies on saccadic adaptation focused on visual feedback about saccade accuracy. A multimodal error signal combining visual and proprioceptive information is likely more robust. Moreover, combining proprioceptive and visual measures of saccade performance can be helpful to keep vision, proprioception, and motor control in alignment and produce a coherent representation of space.

Corneal cross-linking (CXL) is typically performed under topical anesthesia, which may be unsuitable in children and individuals with severe anxiety, poor cooperation, or neurodevelopmental issues. We describe a technique of CXL under general anesthesia that uses sevoflurane and propofol with laryngeal airway or nasal oxygen cannulas, and forceps or microsponges to stabilize the eye position intraoperatively. We also developed a simple and time-saving technique of bilateral simultaneous CXL, whereby the second eye can undergo CXL concurrently with the first in a staggered fashion. Using this technique, we have been able to eliminate up to 25% of surgical time required in standard bilateral procedures. Postoperatively, multimodal analgesia was administered to ensure patient comfort and prevent excessive eye rubbing. In total, 21 eyes of 13 subjects ≤18 years of age were treated. During a median follow-up of 14.5 months (range, 4-43), the only complication observed was sterile corneal infiltrate in 1 eye that resolved with a short course of corticosteroids.

Significance Individuals with left hemianopic field loss (HFL), especially with neglect history, may have greater difficulties than individuals with right HFL in judging the direction of another person's gaze. Purpose Individuals with HFL often show a spatial bias in laboratory-based perceptual tasks. We investigated whether such biases also manifest in a more real-world task, perception of mutual gaze direction, an important, nonverbal communication cue in social interactions. Methods Participants adjusted the eye position of a life-size virtual head on a monitor at a 1-m distance until (1) the eyes appeared to be looking straight at them, or (2) the eyes were perceived to be no longer looking at them (to the right and left). Results Participants with right HFL (n = 8) demonstrated a rightward error in line bisection but made gaze judgments within the range of normally sighted controls (n = 17). Participants with left HFL without neglect history (n = 6) made leftward errors in line bisection and had more variable gaze judgments; three had estimates of gaze direction outside the reference range. Four participants with left HFL and neglect history made estimates of gaze direction that were to the right of the reference range. Conclusions Our results suggest that individuals with left HFL, especially with neglect history, may have greater difficulties than individuals with right HFL in compensating for low-level spatial biases (as manifested in line bisection) when performing the more complex, higher-level task of judging gaze direction.

BACKGROUND AND PURPOSE Both central (eg, brain stem, cerebellum) and peripheral (eg, vestibular, fourth cranial nerve palsy) etiologies can cause a vertical misalignment between the eyes with a resultant vertical diplopia. A vertical binocular misalignment may be due to a skew deviation, which is a nonparalytic vertical ocular misalignment due to roll plane imbalance in the graviceptive pathways. A skew deviation may be 1 component of the ocular tilt reaction. The purposes of this article are (1) to understand the pathophysiology of a skew deviation/ocular tilt reaction and (2) to be familiar with the examination techniques used to diagnose a skew and to differentiate it from mimics such as a fourth cranial nerve palsy. SUMMARY OF KEY POINTS The presence of a skew deviation usually indicates a brain stem or cerebellar localization. Vertical ocular misalignment is easily missed when observing the resting eye position alone. RECOMMENDATIONS FOR CLINICAL PRACTICE Physical therapists treating patients with vestibular pathology from central or peripheral causes should screen for vertical binocular disorders.

Humans make an effort to stabilize the body when a stable eye position is required to improve visibility. Perceiving the position of one visual object relative to another appearing close is relatively difficult compared with perceiving those objects appearing at a distance. Thus, humans must make an effort to stabilize their body to improve visibility when they attempt to perceive the position of one object relative to another appearing close. This process may enhance the response to postural perturbation. The present study tested this hypothesis. A total of 15 healthy participants maintained a position standing over the platform and gazed at a horizontal fixation line in front of them. One of the two warning sound cues was given in each trial; one predicted the forthcoming appearance of a horizontal line 2 mm above or below the horizontal fixation line (indistinct condition), and another predicted the forthcoming appearance of the horizontal line 2 cm above or 2 cm below the horizontal fixation line (distinct condition). After the warning sound cue, the support surface moved in the forward or backward direction. A horizontal line appeared 40 ms after the onset of the support surface motion at the level above or below the horizontal fixation line with the distance from the horizontal fixation line as the warning cue predicted. The participants verbally stated the position of the horizontal line relative to the horizontal fixation line after the offset of the support surface movement. The displacement of the head and sacrum was measured with acceleration sensors. A test of the simple main effect following an analysis of variance revealed that the peak downward displacement of the pelvis in the indistinct condition was significantly earlier than that in the distinct condition. This finding indicated that the effort to stabilize the body for improvement of visibility enhances the response of the pelvis to the forward movement of the support surface. This effect may be used for improvement of the postural response in patients with problems with postural control.

After the rapid spread of strabismus surgery by total tenotomy, which had been proposed by the orthopedist Louis Stromeyer from Gottingen in 1838 and performed by the plastic surgeon Johann Friedrich Dieffenbach on October 26th and by the ophthalmologist Florent Cunier on October 29th, 1839, brilliant researchers studied the physiology of eye movements, resulting in the laws by Franciscus Cornelis Donders on pseudotorsion in tertiary positions of gaze and by Johann Benedict Listing that each eye position can be reached by rotation about an axis perpendicular to the primary and the new position of gaze. John Hunter had first described ocular counterrolling (OCR) with head tilt in 1786. The anatomist Alexander Friedrich von Hueck inferred from anatomical studies, however, that up to 28.6° OCR would be possible onhead-tilt to right or left shoulder in 1838, and estimated his own OCR seen in a mirror at approximately 25°. Donders, Christian Georg Theodor Ruete, Alfred Wilhelm Volkmann, Albrecht von Graefe and Hermann von Helmholtz subsequently denied the existence of OCR for many years and thought that only pseudotorsion existed. Louis Emile Javal had myopia and astigmatism, and he re-established the existence of OCR in 1867 when he noticed that, on head tilt to either shoulder, the axis of astigmatism of his eyes no longer coincided with the axis of astigmatism of his glasses.

OBJECTIVE To compare the performances among three different systems for video head impulse test (vHIT), and to identify an optimal target angle for precisely evaluating the function of vertical semicircular canals in vHIT. METHODS A two-center prospective study was done. Participants were sit 1.2 m away from the wall in a noise-proved room that dedicated for vHIT experiments. During the comparison experiments, similar settings were ensured in both hospitals, with the same distance to wall and angle of staring. For each equipment, the procedures followed the developers' recommendations. The same examiner performed the comparison between two systems in one location. For the eye-position projects, targets were placed on the wall sequentially at the pre-marked lines for different angles. For the comparison projects, 9 and 13 participants were recruited, respectively. Any participant with otologic or vestibular disorders was excluded. A total of 26 healthy participants were recruited in the eye-position experiments, 16 of which were further involved in inter-examiner tests. RESULTS Our evaluations of three different systems showed that a new vHIT system, VertiGoggles® ZT-VNG-I (VG) performed as good as the long-tested Otometrics® ICS impulse (Oto) and EyeSeeCam® (ESC). During the comparison, we validated 25-degree, instead of right ahead at 0 degree, is a better place to set the targets when torsion was applied at vertical semicircular canal planes. CONCLUSION The new VG system is good for clinical practices. Furthermore, we proposed a new protocol to set the targets 25 degrees from right ahead after tilting head 45 degrees to evaluate vertical canals during vHIT.

Purpose: The purpose of the study was to evaluate the visual functions after implantation of Acrysof monofocal intraocular lenses Alcon (SA60AT. MA50BM a SN60WF a SN6AT). Materials and methods: Four works are presented in the overview. The first work deals with the effect of eye length. corneal optic power and anterior chamber depth on the uncorrected near visual acuity (UNVA) after IOL implantation. The second work compares the effect of eye position (horizontal and vertical) on the final UNVA. The third work deals with the influence of the spherical lenses (SA and MA) and yellow aspherical lenses (SN) on UNVA. The later work examines the effect of pupil width on UNVA. Results: The first work showed the dependence of eye axial length (the largest in eyes bellow 22.5 mm. r = 0.36) on UNVA. 77.4 % of eyes with axial length below 22.5 mm had UNVA better than 0.5 and 70.49 % of all evaluated eyes had UNVA better than 0.5. Uncorrected far visual acuity (UDVA) better than 1.0 was in 97.54 % eyes in the whole group. In the second work we found a mean correlation in eyes shorter than 22.5 mm with UNVA in horizontal position (r = 0.39) and in the vertical position (r = 0.49). UNVA improved in these eyes in horizontal position from 0.53 to 0.58 in vertical position of the eye. In all eyes from the group UNVA changed from 0.51 to 0.56. The third work demonstrated the effect of sphericity and chromaticity on UNVA. Better than 0.5 in the group of eyes shorter than 22.5 mm in SA IOL in 67 % and in SN IOL in 60 %. In eyes with mean axial length was UNVA better than 0.5 in SA IOL in 86.5 %. in MA IOL in 81 % and in SN IOL in 75 %. In eyes longer than 23.5 mm was UNVA better than 0.5 in SA IOL in 100 % of eyes, in MA IOL in 60 % and in SN IOL in 33 % of eyes. In the fourth work the effect of pupil size was not demonstrated. Conclusion: The works showed excellent results of UNVA and UDVA after implantation of Acrysof monofocal lenses.

Microsaccades are small eye movements produced during attempted fixation. During locomotion, the eyes scan the environment, the gaze is not always directed to the focus of expansion of the optic flow field. We sought to investigate whether the microsaccadic activity was modulated by eye position during the view of radial optic flow stimuli, and if the presence or lack of a proprioceptive input signal may influence the microsaccade characteristics during self-motion perception. We recorded the oculomotor activity when subjects were either standing or sitting in front of a screen during the view of optic flow stimuli that simulated specific heading directions with different gaze positions. We recorded five trials of each stimulus. Results showed that microsaccade duration, peak velocity, and rate were significantly modulated by optic flow stimuli and trial sequence. We found that the microsaccade rate increased in each condition from trial 1 to trial 5. Microsaccade peak velocity and duration were significantly different across trials. The analysis of the microsaccade directions showed that the different combinations of optic flow and eye position evoked non-uniform directions of microsaccades in standing condition with mean vectors in the upper-left quadrant of the visual field, uncorrelated with optic flow directions and eye positions. In sitting conditions, all stimuli evoked uniform directions of microsaccades. Present results indicate that the proprioceptive signals when the subjects stand up creates a different input that could alter the eye-movement characteristics during heading perceptions.

Tracking the eye of a blind patient can enhance the usability of an artificial vision system. In systems where the sensing element, i.e. the scene camera that captures the visual information, is mounted on the patient's head, the user must use head scanning in order to steer the line of sight of the implant to the region of interest. Integrating an eye tracker in the prosthesis will enable scanning using eye movements. The eye position will set the region of interest within the wide field-of-view of the scene camera. An essential requirement of an eye tracker is the need to calibrate it. Obviously, off-the-shelf calibration methods that require looking at known points in space cannot be used with blind users.Here we tested the feasibility of calibrating the eye-tracker based on pupil position and the location of the percept reported by the implant recipient, using a handheld marker. Pupil positions were extracted using custom image processing in a field-programmable-gate-array built into a glasses-mounted eye tracker. In the calibration process, electrodes were directly stimulated and the subject reported the location of the percept using a handheld marker. Linear regression was used to extract the transfer function from pupil position to gaze direction in the coordinates of the scene camera.In using the eye tracker with the proposed calibration method, patients demonstrated improved precision on a localization task with corresponding reduction of head movements.

PURPOSE To investigate visual cortical responses in children with infantile nystagmus syndrome (INS) and the potential contribution of foveation periods. METHODS The medical records of children with INS who had visual evoked potential (VEP) recordings to reversing checkerboards and onset of horizontal gratings were reviewed retrospectively. VEP recordings underwent objective selective averaging for extraction of brief periods having consistent amplitude and timing with the stimulus presentation. VEP amplitude, latency, and signal-to-noise ratios (SNR) were compared to results from published age-matched controls under the same conditions. Relative foveation in INS subjects was determined from the proportion of time a video-oculography recording met eye position and velocity criteria. RESULTS A total of 26 children met inclusion criteria. Selective averaging increased VEP amplitude and SNR in INS by 270%-420% compared to standard averaging (P

The responses of many cortical neurons to visual stimuli are modulated by the position of the eye. This form of gain modulation by eye position does not change the retinotopic selectivity of the responses, but only changes the amplitude of the responses. Particularly in the case of cortical responses, this form of eye position gain modulation has been observed to be multiplicative. Multiplicative gain modulated responses are crucial to encode information that is relevant to high-level visual functions, such as stable spatial awareness, eye movement planning, visual-motor behaviours, and coordinate transformation. Here we first present a hardwired model of different functional forms of gain modulation, including peaked and monotonic modulation by eye position. We use a biologically realistic Gaussian function to model the influence of the position of the eye on the internal activation of visual neurons. Next we show how different functional forms of gain modulation by eye position may develop in a self-organising neural network model of visual neurons. A further contribution of our work is the investigation of the influence of the width of the eye position tuning curve on the development of a variety of forms of eye position gain modulation. Our simulation results show how the width of the eye position tuning curve affects the development of different forms of gain modulation of visual responses by the position of the eye.

Purpose To evaluate the eye position in subjects with intermittent exotropia and normal subjects under general anesthesia (GA) using the strabismus photo analyzer. Methods 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. Results 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 Conclusions 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.

The normal vestibulo-ocular reflex (VOR) generates almost perfectly compensatory smooth eye movements during a 'head-impulse' rotation. An imperfect VOR gain provokes additional compensatory saccades to re-acquire an earth-fixed target. In the present study, we investigated vestibular and visual contributions on saccade production. Eye position and velocity during horizontal and vertical canal-plane head-impulses were recorded in the light and dark from 16 controls, 22 subjects after complete surgical unilateral vestibular deafferentation (UVD), eight subjects with idiopathic bilateral vestibular loss (BVL), and one subject after complete bilateral vestibular deafferentation (BVD). When impulses were delivered in the horizontal-canal plane, in complete darkness compared with light, first saccade frequency mean(SEM) reduced from 96.6(1.3)-62.3(8.9) % in BVL but only 98.3(0.6)-92.0(2.3) % in UVD; saccade amplitudes reduced from 7.0(0.5)-3.6(0.4) ° in BVL but were unchanged 6.2(0.3)-5.5(0.6) ° in UVD. In the dark, saccade latencies were prolonged in lesioned ears, from 168(8.4)-240(24.5) ms in BVL and 177(5.2)-196(5.7) ms in UVD; saccades became less clustered. In BVD, saccades were not completely abolished in the dark, but their amplitudes decreased from 7.3-3.0 ° and latencies became more variable. For unlesioned ears (controls and unlesioned ears of UVD), saccade frequency also reduced in the dark, but their small amplitudes slightly increased, while latency and clustering remained unchanged. First and second saccade frequencies were 75.3(4.5) % and 20.3(4.1) %; without visual fixation they dropped to 32.2(5.0) % and 3.8(1.2) %. The VOR gain was affected by vision only in unlesioned ears of UVD; gains for the horizontal-plane rose slightly, and the vertical-planes reduced slightly. All head-impulse compensatory saccades have a visual contribution, the magnitude of which depends on the symmetry of vestibular-function and saccade latency: BVL is more profoundly affected by vision than UVD, and second saccades more than first saccades. Saccades after UVD are probably triggered by contralateral vestibular function.

Purpose To assess the relationship between eye position and anesthesia depth using the bispectral index (BIS) value, a parameter derived from electroencephalography data. Methods We investigated the relationship between BIS value and eye position in 32 children who underwent surgery for epiblepharon under general anesthesia. BIS values were recorded continuously throughout the procedure (from induction to awakening). Eye positions were video-recorded and analyzed after surgery. The vertical position of each eye was scored according to its height in relation to the medial canthus. An eye position in which the upper eyelid covered one-third of the cornea was defined as a significant ocular elevation. Results The BIS value correlated inversely with the end-tidal concentration of each anesthetic agent, whereas it correlated positively with the eye elevation score (eye position = 0.014 × BIS + 0.699, p = 0.011). The mean eye position score was significantly greater in patients whose BIS values were over 65. Eleven patients (34.4%) had significant ocular elevation; their mean concurrent BIS value was 61.6. Two of these patients had elevation during surgery and 9 had elevation during emergence from anesthesia. Conclusions We found that high BIS values were correlated with low levels of anesthetic concentration and high eye position, suggesting that BIS monitoring may be useful for predicting eye position during anesthesia. Particular attention must be given to eye position during ophthalmic surgery. Anesthesia depth can be maintained by assuring that the BIS value remains below 65.

Encoding hand position by the cerebral cortex is essential not only for the neural representation of the body image but also for different actions based on eye-hand coordination. These include reaching for visual objects as well as complex movement sequences, such as tea-making, tool use, and object construction, among many others. All these functions depend on a continuous refreshing of the hand position representation, relying on both predictive signaling and afferent information. The hand position influence on neural activity in the parietofrontal system, together with eye position signals, are the basic elements of an eye-hand matrix from which all the above functions can emerge and could be regarded as key features of a network with several entry points, command nodes and outflow pathways, as confirmed by the discovery of a direct parietospinal projection for the control of hand action. The integrity of this system is crucial for daily life, as testified by the consequences of cortical lesions, spanning from severe paralysis to complex forms of apraxia. In this review, I will sketch my personal understanding of the scientific and conceptual trajectory of a line of investigation with many unexpected influences on cortical function and disease, from motor behavior to cognition.

When a visual stimulus is displaced during a saccade the displacement is often not noticed unless it is large compared to the amplitude of the eye movement. Displacement detection is improved, however, if a blank intervenes between saccade target offset and the presentation of the displaced post-saccadic stimulus. This has been interpreted as evidence that precise information about eye position and accurate memory for the position of the pre-saccadic target are available immediately after saccade offset, but are overridden by the presence of the post-saccadic stimulus if it is present when the eyes land. In the current set of experiments we examined in more detail how blanking contributes to the increase in displacement sensitivity. In two experiments we showed that the presentation of a blank interval between saccade offset and the presentation of the displaced stimulus improved people’s ability to detect that the stimulus had been displaced and also their ability to judge the direction that it had been displaced, but only for displacements opposite to the direction of the saccade (backward displacements). A third experiment suggested that this improvement in the detection of backward displacements was due in part to subjects misremembering the saccade target location as being closer to the initial fixation point than it actually was immediately after the saccade but remembering its location more veridically 50 ms later. This has the effect of improving the detection of displacements as well as their direction of displacement, but preferentially for backwards vs. forward displacements.

Optic flow is a crucial signal in maintaining postural stability. We sought to investigate whether the activity of postural muscles and body sway was modulated by eye position during the view of radial optic flow stimuli. We manipulated the spatial distribution of dot speed and the fixation point position to simulate specific heading directions combined with different gaze positions. The experiments were performed using stabilometry and surface electromyography (EMG) on 24 right-handed young, healthy volunteers. Center of pressure (COP) signals were analyzed considering antero-posterior and medio-lateral oscillation, COP speed, COP area, and the prevalent direction of oscillation of body sway. We found a significant main effect of body side in all COP parameters, with the right body side showing greater oscillations. The different combinations of optic flow and eye position evoked a non-uniform direction of oscillations in females. The EMG analysis showed a significant main effect for muscle and body side. The results showed that the eye position modulated body sway without changing the activity of principal leg postural muscles, suggesting that the extraretinal input regarding the eye position is a crucial signal that needs to be integrated with perceptual optic flow processing in order to control body sway.

Fixational eye movements (FEMs), including microsaccades, drift, and tremor, shift our eye position during ocular fixation, producing retinal motion that is thought to help visibility by counteracting neural adaptation to unchanging stimulation. Yet, how each FEM type influences this process is still debated. Recent studies found little to no relationship between microsaccades and visual perception of spatial frequencies (SF). However, these conclusions were based on coarse analyses that make it hard to appreciate the actual effects of microsaccades on target visibility as a function of SF. Thus, how microsaccades contribute to the visibility of stimuli of different SFs remains unclear. Here, we asked how the visibility of targets of various SFs changed over time, in relationship with concurrent microsaccade production. Participants continuously reported on changes in target visibility, allowing us to time-lock ongoing changes in microsaccade parameters to perceptual transitions in visibility. Microsaccades restored/increased the visibility of low SF targets more efficiently than that of high SF targets. Yet, microsaccade rates rose before periods of increased visibility, and dropped before periods of diminished visibility, for all the SFs tested, suggesting that microsaccades boosted target visibility across a wide range of SFs. Our data also indicate that visual stimuli fade/become harder to see less often in the presence of microsaccades. In addition, larger microsaccades restored/increased target visibility more effectively than smaller microsaccades. These combined results support the proposal that microsaccades enhance visibility across a broad variety of SFs.

The cortical representation of visual perception requires the integration of several-signal processing distributed across many cortical areas, but the neural substrates of such perception are largely unknown. The type of firing pattern exhibited by single neurons is an important indicator of dynamic circuitry within or across cortical areas. Neurons in area PEc are involved in the spatial mapping of the visual field; thus, we sought to analyze the firing pattern of activity of PEc optic flow neurons to shed some light on the cortical processing of visual signals. We quantified the firing activity of 152 optic flow neurons using a spline interpolation function, which allowed determining onset, end, and latency of each neuronal response. We found that many PEc neurons showed multiphasic activity, which is strictly related to the position of the eye and to the position of the focus of expansion (FOE) of the flow field. PEc neurons showed a multiphasic activity comprised of excitatory phases interspersed with inhibitory pauses. This phasic pattern seems to be a very efficient way to signal the spatial location of visual stimuli, given that the same neuron sends different firing patterns according to a specific combination of FOE/eye position.

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.

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.

Prism adaptation (PA) after-effects are assessed using tests that measure changes in sensorimotor systems. After-effects on pointing without feedback to a visual target (open loop pointing - OLP) are traditionally described as being larger than those measured by straight ahead pointing (SAP) with eyes closed, and the difference between them is attributed to a shift in visual localisation. However, neither differences between OLP and SAP, nor shifts in perceptual judgement of visual straight ahead (VSA), are consistently reported. Moreover, since very few studies have directly recorded direction of gaze, an effect of PA on the state estimate of gaze direction has not been reliably documented. The current research aimed to isolate the effects of PA on state estimates of eye position. We measured sensorimotor after-effects through common (OLP, SAP, and VSA) measures, and also recorded eye position and additional after-effect measures to interrogate changes to the oculomotor system and how these might relate to other measures of sensorimotor change. To ascertain if PA's effects on estimates of eye position could be attributed to eye muscle potentiation, we compared the effects of PA to sustained gaze deviation without adaptation. PA induced no effect on visual straight-ahead and no change in direction of gaze, when measured while positioning a target, looking straight ahead in the dark, or looking toward the passively positioned and occluded unexposed hand. We also found that after-effects measured by SAP with the eyes open were larger than SAP with the eyes closed and equal to those observed with OLP. The findings challenge the concept that total adaptation after-effect is a direct sum of arm proprioceptive and visual after-effects as conventionally measured, and suggest that the oculomotor system is altered by prism adaptation only in interaction with an arm motor command when vision is available.

Purpose To observe the change in horizontal smooth pursuit in patients with intermittent exotropia before and after strabismus surgery. Methods The smooth pursuit of patients with intermittent exotropia was recorded using a video eye-tracker before and 1 week, and 1, 3, and 6 months after strabismus surgery. Subjects were asked to track a step-ramp target moving at ±6.1°/sec horizontally as accurately as possible under binocular viewing. The differences in gain (eye velocity divided by target velocity) and amplitude of smooth pursuit between right and left eyes before and after surgery were compared. Results A total of 9 patients (mean age, 22.2 ± 13.9 years) were included. Mean preoperative ocular alignment at near was 59.1Δ ± 34.7Δ. The difference in gain between the left and right eyes before surgery was 0.23 ± 0.1; in amplitude, 3.0° ± 3.7°. These values were improved at 1 week after surgery (gain, 0.08 ± 0.06; amplitude, 0.9° ± 0.65°) and continued to improve for 6 months after surgery; however, ocular alignment at near reverted from 5.9Δ ± 10.5Δ to 18.9Δ ± 17.5Δ by 6 months after surgery. Conclusions In this small patient cohort, surgical correction of ocular alignment improved binocular coordination of smooth pursuit in intermittent exotropia. In the long term, the improvement of the binocular coordination of smooth pursuit tended to remain, although the eye position partially reverted to the presurgical state.

Despite strong evidence to the contrary in the literature, microsaccades are overwhelmingly described as involuntary eye movements. Here we show in both human subjects and monkeys that individual microsaccades of any direction can easily be triggered: (1) on demand, based on an arbitrary instruction, (2) without any special training, (3) without visual guidance by a stimulus, and (4) in a spatially and temporally accurate manner. Subjects voluntarily generated instructed “memory-guided” microsaccades readily, and similarly to how they made normal visually-guided ones. In two monkeys, we also observed midbrain superior colliculus neurons that exhibit movement-related activity bursts exclusively for memory-guided microsaccades, but not for similarly-sized visually-guided movements. Our results demonstrate behavioral and neural evidence for voluntary control over individual microsaccades, supporting recently discovered functional contributions of individual microsaccade generation to visual performance alterations and covert visual selection, as well as observations that microsaccades optimize eye position during high acuity visually-guided behavior., Microsaccades are small-amplitude, fixational eye movements that are largely thought to be involuntary. Here, the authors demonstrate that monkeys (and humans) can be easily trained to respond to a remembered target location with a volitional microsaccade, and that a population of superior colliculus neurons is selectively associated with them.

Studies are being actively conducted on camera-based driver gaze tracking in a vehicle environment for vehicle interfaces and analyzing forward attention for judging driver inattention. In existing studies on the single-camera-based method, there are frequent situations in which the eye information necessary for gaze tracking cannot be observed well in the camera input image owing to the turning of the driver&rsquo, s head during driving. To solve this problem, existing studies have used multiple-camera-based methods to obtain images to track the driver&rsquo, s gaze. However, this method has the drawback of an excessive computation process and processing time, as it involves detecting the eyes and extracting the features of all images obtained from multiple cameras. This makes it difficult to implement it in an actual vehicle environment. To solve these limitations of existing studies, this study proposes a method that uses a shallow convolutional neural network (CNN) for the images of the driver&rsquo, s face acquired from two cameras to adaptively select camera images more suitable for detecting eye position, faster R-CNN is applied to the selected driver images, and after the driver&rsquo, s eyes are detected, the eye positions of the camera image of the other side are mapped through a geometric transformation matrix. Experiments were conducted using the self-built Dongguk Dual Camera-based Driver Database (DDCD-DB1) including the images of 26 participants acquired from inside a vehicle and the Columbia Gaze Data Set (CAVE-DB) open database. The results confirmed that the performance of the proposed method is superior to those of the existing methods.

To examine the relationship between visual imagery and autobiographical memory, eye position and pupil size were recorded while participants first searched for memories and then reconstructed the retrieved memories (Experiment 1), or only searched for memories (Experiment 2). In Experiment 1, we observed that, although recollective experience was not associated with the number of fixations per minute, memories that took longer to retrieve were linked to increased pupil size. In Experiment 2, we observed that directly retrieved memories were recalled more quickly and were accompanied by smaller pupils than generatively retrieved memories. After correcting for response time, retrieval mode also produced an effect, showing that decreased pupil size is not simply due to directly retrieved memories being recalled more quickly. These findings provide compelling evidence that objective measures, such as pupil size, can be used alongside subjective measures, such as self-reports, to distinguish between directly retrieved and generatively retrieved memories.

Purpose To identify cases of synergistic divergence whose characteristics suggest that this entity is a form of Duane syndrome. Methods The records of all patients with a Duane syndrome diagnosis, including standardized eye position photographs, from the E-Consultation program of Cybersight, Orbis International were analyzed. Results A total of 350 Duane syndrome cases were identified. Of these, 19 (5%) had features consistent with synergistic divergence, or type 4 Duane syndrome. Of the 19, 16 (84%) were male, 15 (79%) had palpebral fissure narrowing, all had anomalous head posture, and 18 (95%) were exotropic. Only 9 (47%) patients were reported to have undergone surgery. Conclusions Synergistic divergence is a rare entity with features similar to those of Duane syndrome. We suggest that this entity be classified as type 4 Duane syndrome, because it has unique findings and an innervation pattern that differs from the other 3 recognized types.

A mathematical model and a possible neural mechanism are proposed to account for how fixational drift motion in the retina confers a benefit for the discrimination of high-acuity targets. We show that by simultaneously estimating object shape and eye motion, neurons in visual cortex can compute a higher quality representation of an object by averaging out non-uniformities in the retinal sampling lattice. The model proposes that this is accomplished by two separate populations of cortical neurons — one providing a representation of object shape and another representing eye position or motion — which are coupled through specific multiplicative connections. Combined with recent experimental findings, our model suggests that the visual system may utilize principles not unlike those used in computational imaging for achieving “super-resolution” via camera motion.

Humans and other animals move their eyes in anticipation to compensate for sensorimotor delays. Such anticipatory eye movements can be driven by the expectation of a future visual object or event. Here we investigate whether such anticipatory responses extend to ocular torsion, the eyes' rotation about the line of sight. We recorded three-dimensional eye position in head-fixed healthy human adults who tracked a rotating dot pattern moving horizontally across a computer screen. This kind of stimulus triggers smooth pursuit with a horizontal and torsional component. In three experiments, we elicited expectation of stimulus rotation by repeatedly showing the same rotation (Experiment 1), or by using different types of higher-level symbolic cues indicating the rotation of the upcoming target (Experiments 2 and 3). Across all experiments, results reveal reliable anticipatory horizontal smooth pursuit. However, anticipatory torsion was only elicited by stimulus repetition, but not by symbolic cues. In summary, torsion can be made in anticipation of an upcoming visual event only when low-level motion signals are accumulated by repetition. Higher-level cognitive mechanisms related to a symbolic cue reliably evoke anticipatory pursuit but did not modulate torsion. These findings indicate that anticipatory torsion and anticipatory pursuit are at least partly decoupled and might be controlled separately.

PURPOSE: To describe the long-term results of Anderson procedure, which includes recession of the two extraocular yoke muscles responsible for eccentric eye position and abnormal head posture (AHP) in patients with infantile nystagmus. METHODS: Retrospective data collection of patients who underwent an Anderson procedure at a single medical center by one surgeon from 2008 to 2016. The main outcome measure was the elimination of AHP following surgery. RESULTS: Twenty-seven patients (18 males, 9 females) underwent an Anderson procedure during the study period. The average age at surgery was 8.6 ± 7.7 years and mean follow-up was 3.5 ± 2.4 years (range, 6 months–9 years). Before surgery all patients had AHP (17 left and 10 right head turns) greater than 25° (mean 40.1 ± 6.7°) that decreased significantly following surgery (mean 7.2 ± 7.6°, P

The recent growth in low-cost eye-tracking systems makes it feasible to incorporate real-time measurement and analysis of eye position data into activities such as learning to read. It also enables field studies of reading behavior in the classroom and other learning environments. We present a study of the data quality provided by two remote eye trackers, one being a low-sampling-rate, low-cost system. Then we present two algorithms for mapping fixations derived from the data to the words being read. One is for immediate (or real-time) mapping of fixations to words and the other for deferred (or post hoc) mapping. Following this, an evaluation study is reported. Both studies were carried out in the classroom of a Finnish elementary school with students who were second graders. This study shows very high success rates in automatically mapping fixations to the lines of text being read when the mapping is deferred. The success rates for immediate mapping are comparable with those obtained in earlier studies, although here the data is collected some 10 min after initial calibration of low-sample (30 Hz) remote eye trackers, rather than a laboratory setting using high-sampling-rate trackers. The results provide a solid basis for developing systems for use in classrooms and other learning environments that can provide immediate automatic support with reading, and share data between a group of learners and the teacher of that group. This makes possible new approaches to the learning of reading and comprehension skills.

The present study addresses the effect of the eye position in the cockpit on the flight altitude during the final approach to landing. Three groups of participants with different levels of expertise (novices, trainees, and certified pilots) were given a laptop with a flight simulator and they were asked to maintain a 3.71Ê glide slope while landing. Each participant performed 40 approaches to the runway. During 8 of the approaches, the point of view that the flight simulator used to compute the visual scene was slowly raised or lowered with 4 cm with respect to the cockpit, hence moving the projection of the visible part of the cockpit down or up in the visible scene in a hardly noticeable manner. The increases and decreases in the simulated eye height led to increases and decreases in the altitude of the approach trajectories, for all three groups of participants. On the basis of these results, it is argued that the eye position of pilots during visual approaches is a factor that contributes to the risk of black hole accidents, The participation of Antoine Morice, Cyril Camachon and Gilles Montagne in this research project was supported by a grant from the Délégation Générale pour l'Armement (DGA). The participation of David M. Jacobs was supported by a grant from the Spanish Ministry of Economy and Competitiveness (PSI2013-43742)

In this study, the authors describe the first report of 2 patients of fat prolapse into the nasal cavity by orbital blowout fracture. The patients were a 58-year-old male and an 86-year-old female. The patients could not attain binocular single vision in any eye position because of severe impairment of the extraocular muscle motility. Computed tomographic images of both patients revealed orbital blowout fractures with orbital fat prolapse into the nasal cavity. The fractures were reduced under transconjunctival/transcaruncular and endonasal endoscopic approaches. Six months postoperatively, the patients attained a binocular single vision field, including in the primary eye position.

Introduction Earlier work revealed that vHIT examination is often difficult to perform on very young children. In particular, the calibration of the system can be difficult, as active cooperation of the patient is required. Additionally, the patient must be able to follow the examiner's instructions, which is challenging for very young children. Therefore, the aim of the present study was to develop and validate a new, software-based approach enabling vHIT testing of young children and infants. Methods and materials Six patients (3 boys and 3 girls) aged 5-36 months were included in a prospective, monocentric study between January 2015 and August 2015.The newly developed intuitive software enabled calibration of the eye position signal with the subjects fixating on animated animal graphics which were projected on a screen. Testing ten healthy adults validated this new calibration and measurement method. After calibration, a vHIT goggle (EyeSeeCam ©) was used to perform head impulses in the horizontal plane while the patient was watching a movie sitting on their parent's lap or in a baby chair. At least 15 impulses to each side were obtained and the occurrence of refixation saccades was analyzed. All tests were performed by one of two experienced examiners. Results The new calibration method and modified test setup provided reproducible results for all patients tested. An increased incidence of artifacts was not observed. In 2 patients, more than one test was needed. None of the included children showed catch-up overt or catch-up covert saccades. There was no gain reduction of more than two standard deviations as compared to the normative results published in the literature on vHIT examinations of children. Conclusion The proposed protocol allows vHIT testing in very young children and infants (aged 5 months to 3 years). The study emphasizes that vHIT is an easy and sensitive screening tool to evaluate vestibular function in children and should be used as the gold standard in pediatric vestibular assessment.

People know surprisingly little about their own visual behavior, which can be problematic when learning or executing complex visual tasks such as search of medical images. We investigated whether providing observers with online information about their eye position during search would help them recall their own fixations immediately afterwards. Seventeen observers searched for various objects in "Where's Waldo'' images for 3 s. On two-thirds of trials, observers made target present/absent responses. On the other third (critical trials), they were asked to click twelve locations in the scene where they thought they had just fixated. On half of the trials, a gaze-contingent window showed observers their current eye position as a 7.58 diameter "spotlight.'' The spotlight "illuminated'' everything fixated, while the rest of the display was still visible but dimmer. Performance was quantified as the overlap of circles centered on the actual fixations and centered on the reported fixations. Replicating prior work, this overlap was quite low (26%), far from ceiling (66%) and quite close to chance performance (21%). Performance was only slightly better in the spotlight condition (28%, p = 0.03). Giving observers information about their fixation locations by dimming the periphery improved memory for those fixations modestly, at best.

The neuronal circuitry that supports voluntary changes in eye position in tasks that require attention-driven oculo-motor control is well known. However, less is known about the neuronal basis for eye control during visual fixation. This, together with the fact that visual fixation is one of the most commonly used baseline conditions in resting-state functional magnetic resonance imaging (fMRI) studies, prompted us to conduct a study in which we employed resting-state fMRI and concurrent recordings of eye gaze to investigate the relationship between spontaneous changes in eye position during passive visual fixation and intrinsic brain activity. As a control experiment, we recorded fMRI brain activity related to cued voluntary vertical and horizontal changes in eye position in a block-related task-evoked fMRI experiment. Our results for the voluntarily performed changes in eye position elicited brain activity in the bilateral occipitotemporal cortex, supplementary motor cortex and frontal eye fields. In contrast, we show that slow fluctuations in eye position during passive visual fixation are linked to intrinsic brain activity, foremost in midline cortical brain regions located in the posteromedial parietal cortex and the medial prefrontal cortex, brain regions that act as core cortical hubs in the brain's default mode network. Our results suggest that subconscious and sustained changes in behavior are tied to intrinsic brain activity on a moment-by-moment basis.

This study proposes a mathematical model to estimate the initial tension forces of the extraocular muscles (EOMs). These forces are responsible for the mechanical equilibrium of the eye suspended in primary position. The passive contributions were obtained using the corresponding Cauchy stress-stretch relationships based on the previous clinical experimental data; whereas the active contributions were obtained using an optimum method with weakening the effect of innervation. The initial tension forces of the EOMs were estimated to be 48.8±14.2mN for the lateral rectus, 89.2±31.6mN for the medial rectus, 50.6±17.6mN for the superior rectus, 46.2±13.4mN for the inferior rectus, 15.6±8.3mN for the superior oblique, and 17.1±12.1mN for the inferior oblique.

The goal of this investigation was to explore the feasibility of characterizing the visual search characteristics of dermatologists evaluating images corresponding to single pigmented skin lesions (PSLs) (close-ups and dermoscopy) as a venue to improve training programs for dermoscopy. Two Board-certified dermatologists and two dermatology residents participated in a phased study. In phase I, they viewed a series of 20 PSL cases ranging from benign nevi to melanoma. The close-up and dermoscopy images of the PSL were evaluated sequentially and rated individually as benign or malignant, while eye position was recorded. Subsequently, the participating subjects completed an online dermoscopy training module that included a pre- and post-test assessing their dermoscopy skills (phase 2). Three months later, the subjects repeated their assessment on the 20 PSLs presented during phase I of the study. Significant differences in viewing time and eye-position parameters were observed as a function of level of expertise. Dermatologists overall have more efficient search than residents generating fewer fixations with shorter dwells. Fixations and dwells associated with decisions changing from benign to malignant or vice versa from photo to dermatoscopic viewing were longer than any other decision, indicating increased visual processing for those decisions. These differences in visual search may have implications for developing tools to teach dermatologists and residents about how to better utilize dermoscopy in clinical practice.

To further evaluate the spontaneous eyeblink rate (SEBR) of healthy adult human subjects according to direction of gaze, especially in the presence of bright light reflective glare. On 32 subjects aged between 18 and 24 years, separate video recordings of 5 min duration were made with different conditions of gaze (horizontal, slightly upwards or slightly downwards) under normal lighting or a distant lighting glare source. The SEBR in primary eye gaze under normal lighting was 11.7 +/− 0.9 eyeblinks/min with a coefficient of variation (COV) of 20.5 %. A non-significant decrease in SEBR was noted with downward gaze, but a slight significant increase with upward gaze in both SEBR (to 13.0 +/− 1.1 eyeblinks/min) and COV (average 26.1 %). In the presence of glare, SEBR in primary eye gaze increased significantly (p

Congenital blepharoptosis is a common pediatric disease. Frontalis muscle flap advancement is an effective surgical technique to treat patients with severe ptosis and poor levator function. However, since eye position changes under general anesthesia, it is necessary to adjust the position of the upper eyelid to achieve a better surgical outcome. A total of 162 children with severe congenital blepharoptosis underwent frontalis muscle flap advancement under general anesthesia. Patients were divided into two groups according to the different positions of eyelid suspension. The eyelid position of 82 children (96 eyes) in group A was adjusted to set at the superior limbus under general anesthesia, while the eyelid level of 80 children (94 eyes) in group B was adjusted according to the level labeled before anesthesia or the orthophoria level predicted using Krimsky’s test. Lid level, ptosis recurrence, cosmetic appearance, and complications were evaluated 12 months after surgery. Excellent functional and cosmetic results were achieved in 61 (63.5 %) children from group A and 85 (90.4 %) from group B. Fewer complications were observed in group B (36.5 vs. 9.6 %). To achieve better surgical results after frontalis flap advancement for severe ptosis, it is necessary to adjust the eyelid level according to eye position changes that occur when the patient is under general anesthesia. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

When the target of a saccadic eye movement is displaced while the eyes move this displacement is often not noticed (saccadic suppression of displacement, SSD). We present a neurobiologically motivated, computational model of SSD and compare its simulation results to experimental data. The model offers a simple explanation of the effects of pre- and post-saccadic stimulus blanking on SSD in terms of peri-saccadic network dynamics. Under normal peri-saccadic conditions pre-and post-saccadic stimulus traces are recurrently integrated with reference to present and future eye position, whereas blanking diminishes the pre-saccadic stimulus trace and thus leads to an uninfluenced integration of the post-saccadic stimulus trace. We show that part of the intersubject variability in SSD can be explained by differences in decision thresholds of this integration process.

Earlier work by one of us examined a historical corpus of portraits and found that artists often paint the subject such that one eye is centred horizontally. If due to psychological mechanisms constraining artistic composition, this eye-centring bias should be detectable also in portraits by non-professionals. However, this finding has been questioned both on theoretical and empirical grounds. Here we tested eye-centring in a larger (N ~ = 4000) and more representative set of selfies spontaneously posted on Instagram from six world cities. In contrast with previous selfie results, the distribution of the most-centred eye position peaked almost exactly at the horizontal centre of the image and was statistically different from predictions based on realistic Monte-Carlo predictions. In addition, we observed a small but statistically reliable pseudoneglect effect as well as a preference for centring the left-eye. An eye-centring tendency appears to exist in self-portraits by non-artists.

We present the Delft Assessment Instrument for Strabismus in Young children (DAISY) a device designed to measure angles of strabismus in young children fast and accurately. DAISY allows for unrestrained head movements by the mean of a triple camera vision system that simultaneously estimates the head rotation and the eye pose. The device combines two different methods to record bilateral eye position: corneal reflections (Purkinje images) and pupillary images. Detailed results are provided on three orthotropic subjects (age 25-27). Three different conditions were tested: 1) gaze ahead, 2) gaze ahead with different head rotations, and 3) fixed head with different eye positions. Systematic errors occurred between subjects that need further study. The system reached sufficient accuracy to be applied for the measurement of angles of strabismus, almost independent from the head pose.