Investigation of Camera-Free Eye-Tracking Glasses Compared to a Video-Based System.

Technological advances in eye-tracking have resulted in lightweight, portable solutions that are capable of capturing eye movements beyond laboratory settings. Eye-tracking devices have typically relied on heavier, video-based systems to detect pupil and corneal reflections. Advances in mobile eye-tracking technology could facilitate research and its application in ecological settings; more traditional laboratory research methods are able to be modified and transferred to real-world scenarios. One recent technology, the AdHawk MindLink, introduced a novel camera-free system embedded in typical eyeglass frames. This paper evaluates the AdHawk MindLink by comparing the eye-tracking recordings with a research "gold standard", the EyeLink II. By concurrently capturing data from both eyes, we compare the capability of each eye tracker to quantify metrics from fixation, saccade, and smooth pursuit tasks-typical elements in eye movement research-across a sample of 13 adults. The MindLink system was capable of capturing fixation stability within a radius of less than 0.5∘, estimating horizontal saccade amplitudes with an accuracy of 0.04∘± 2.3∘, vertical saccade amplitudes with an accuracy of 0.32∘± 2.3∘, and smooth pursuit speeds with an accuracy of 0.5 to 3∘s, depending on the pursuit speed. While the performance of the MindLink system in measuring fixation stability, saccade amplitude, and smooth pursuit eye movements were slightly inferior to the video-based system, MindLink provides sufficient gaze-tracking capabilities for dynamic settings and experiments.

EEG reveals deficits in sensory gating and cognitive processing in asymptomatic adults with a history of concussion.

OBJECTIVE: Individuals with a concussion history tend to perform worse on dual-tasks compared controls but the underlying neural mechanisms contributing to these deficits are not understood. This study used event-related potentials (ERPs) to investigate sensory gating and cognitive processing in athletes with and without a history of concussion while they performed a challenging dual-task. METHODS: We recorded sensory (P50, N100) and cognitive (P300) ERPs in 30 athletes (18 no previous concussion; 12 history of concussion) while they simultaneously performed an auditory oddball task and a working memory task that progressively increased in difficulty. RESULTS: The concussion group had reduced auditory performance as workload increased compared to the no-concussion group. Sensory gating and cognitive processing were reduced in the concussion group indicating problems with filtering relevant from irrelevant information and appropriately allocating resources. Sensory gating (N100) was positively correlated with cognitive processing (P300) at the hardest workload in the no-concussion group but negatively correlated in the concussion group. CONCLUSION: Concussions result in long-term problems in behavioral performance, which may be due to poorer sensory gating that impacts cognitive processing. SIGNIFICANCE: Problems effectively gating sensory information may influence the availability or allocation of attention at the cognitive stage in those with a concussion.

Evaluating visuomotor coordination in children with amblyopia.

Past research has reported deficits on reaching and grasping tasks in adults with amblyopia and degraded stereoacuity, but less is known about visuomotor deficits in children-specifically, for complex tasks that require movement sequencing. This study therefore compared the visuomotor performance in 21 children with abnormal binocular vision (patient group) due to amblyopia and/or strabismus to that of 236 children with normal binocular vision development (control group) ages 5-14 years. Visual acuity, stereoacuity, and hand-movement kinematics on a bead-threading task were assessed. The patient group showed significantly longer durations than the control group on grasp, thread, and total movement durations. Both groups of participants were then split into immature (ages 5-9 years) and mature (ages 10-14 years) groups based on the maturation age for these parameters in control children. Grasp duration was longer in both mature and immature patient groups; thread and total movement durations were longer in the mature patient group only. Grasp duration was the most disrupted kinematic parameter in children with disrupted binocular vision due to amblyopia and/or strabismus, regardless of age. The level of stereoacuity loss rather than the depth of visual acuity loss was associated with the severity of visuomotor deficits.

Effects of blocked vs. interleaved administration mode on saccade preparatory set revealed using pupillometry.

Eye movements have been used extensively to assess information processing and cognitive function. However, significant variability in saccade performance has been observed, which could arise from methodological variations across different studies. For example, prosaccades and antisaccades have been studied using either a blocked or interleaved design, which has a significant influence on error rates and latency. This is problematic as it makes it difficult to compare saccade performance across studies and may limit the ability to use saccades as a behavioural assay to assess neurocognitive function. Thus, the current study examined how administration mode influences saccade related preparatory activity by employing pupil size as a non-invasive proxy for neural activity related to saccade planning and execution. Saccade performance and pupil dynamics were examined in eleven participants as they completed pro- and antisaccades in blocked and interleaved paradigms. Results showed that administration mode significantly modulated saccade performance and preparatory activity. Reaction times were longer for both pro- and antisaccades in the interleaved condition, compared to the blocked condition (p < 0.05). Prosaccade pupil dilations were larger in the interleaved condition (p < 0.05), while antisaccade pupil dilations did not significantly differ between administration modes. Additionally, ROC analysis provided preliminary evidence that pupil size can effectively predict saccade directional errors prior to saccade onset. We propose that task-evoked pupil dilations reflect an increase in preparatory activity for prosaccades and the corresponding cognitive demands associated with interleaved administration mode. Overall, the results highlight the importance that administration mode plays in the design of neurocognitive tasks.

Stereopsis contributes to the predictive control of grip forces during prehension.

Binocular viewing is associated with a superior prehensile performance, which is particularly evident in the latter part of the reach as the hand approaches and makes contact with the target object. However, the visuomotor mechanisms through which binocular vision serves prehension are not fully understood. This study assessed the role of stereopsis in the predictive control of grasping by measuring grip force. Twenty participants performed a precision reach-to-grasp task in four viewing conditions: binocular, monocular, and with reduced stereoacuity (200 arc sec, > 400 arc sec). Monocular, compared to binocular viewing, was associated with a fourfold increase in grasp errors, a 56% increase in grasp duration, 22% decrease in grip force at 50 ms following grasp initiation, and the time of peak force occurred 40% later after grasp initiation (all p < 0.05). Grasp performance was also disrupted when viewing with reduced stereoacuity. Notably, grip force at the time of object lift-off was comparable between all viewing conditions. These results demonstrate that binocular stereopsis contributes to the efficient programming of grip forces. Specifically, stereopsis may provide important sensory information that enables the central nervous system to engage in predictive control of grasping.

Concurrent maturation of visuomotor skills and motion perception in typically-developing children and adolescents.

Perceptual and visuomotor skills undergo considerable development from early childhood into adolescence; however, the concurrent maturation of these skills has not yet been examined. This study assessed visuomotor function and motion perception in a cross-section of 226 typically-developing children between 4 and 16 years of age. Participants were tested on three tasks hypothesized to engage the dorsal visual stream: threading a bead on a needle, marking dots using a pen, and discriminating form defined by motion contrast. Mature performance was reached between 8 and 12 years, with youngest maturation for kinematic measures for a reach-to-grasp task, and oldest maturation for a precision tapping task. Performance on the motion perception task shared no association with motor skills after controlling for age.

The role of somatosensory input in target localization during binocular and monocular viewing while performing a high precision reaching and placement task.

Binocular vision provides the most accurate and precise depth information; however, many people have impairments in binocular visual function. It is possible that other sensory inputs could be used to obtain reliable depth information when binocular vision is not available. However, it is currently unknown whether depth information from another modality improves target localization in depth during action execution. Therefore, the goal of this study was to assess whether somatosensory input improves target localization during the performance of a precision placement task. Visually normal young adults (n = 15) performed a bead threading task during binocular and monocular viewing in two experimental conditions where needle location was specified by 1) vision only, or 2) vision and somatosensory input, which was provided by the non-dominant limb. Performance on the task was assessed using spatial and temporal kinematic measures. In accordance with the hypothesis, results showed that the interval spent placing the bead on the needle was significantly shorter during monocular viewing when somatosensory input was available in comparison to a vision only condition. In contrast, results showed no evidence to support that somatosensory input about the needle location affects trajectory control. These findings demonstrate that the central nervous system relies predominately on visual input during reach execution, however, somatosensory input can be used to facilitate the performance of the precision placement task.

Visuomotor Behaviour in Amblyopia: Deficits and Compensatory Adaptations.

Amblyopia is a neurodevelopmental visual disorder arising from decorrelated binocular experience during the critical periods of development. The hallmark of amblyopia is reduced visual acuity and impairment in binocular vision. The consequences of amblyopia on various sensory and perceptual functions have been studied extensively over the past 50 years. Historically, relatively fewer studies examined the impact of amblyopia on visuomotor behaviours; however, research in this area has flourished over the past 10 years. Therefore, the aim of this review paper is to provide a comprehensive review of current knowledge about the effects of amblyopia on eye movements, upper limb reaching and grasping movements, as well as balance and gait. Accumulating evidence indicates that amblyopia is associated with considerable deficits in visuomotor behaviour during amblyopic eye viewing, as well as adaptations in behaviour during binocular and fellow eye viewing in adults and children. Importantly, due to amblyopia heterogeneity, visuomotor development in children and motor skill performance in adults may be significantly influenced by the etiology and clinical features, such as visual acuity and stereoacuity. Studies with larger cohorts of children and adults are needed to disentangle the unique contribution of these clinical characteristics to the development and performance of visuomotor behaviours.

Research Priorities for Optimizing Long-term Community Integration after Brain Injury.

OBJECTIVE: This paper reports on a funded summit, which convened a multidisciplinary group of experts to provide consensus on the research priorities necessary for improving long-term community integration of individuals with traumatic brain injury (TBI) and their caregivers. METHODS: The 2-day summit was directed using the World Café Methodology, to engage stakeholders and collaboratively arrive at a consensus on the problems to be targeted in research. Participants (n=54), drawn from two Canadian provinces, included an interdisciplinary group of researchers, clinicians, representatives from brain injury associations, individuals with TBI, and caregivers. In small groups, participants discussed challenges to long-term community integration and potential initiatives that would address these barriers. Field notes from the discussions were analyzed using qualitative content analysis. RESULTS: The consensus on prioritized research directions included developing interventions to optimize the functioning and participation of individuals with TBI, reducing caregiver burden, and evaluating how emerging technology can facilitate delivery of care. CONCLUSIONS: The World Café Methodology was an effective method for developing research priorities. The breadth of expertise of participants and the collegial environment allowed for the identification of a broad perspective on important future research directions with potential to enhance the long-term community integration of individuals with brain injury.

The effects of task-relevant saccadic eye movements performed during the encoding of a serial sequence on visuospatial memory performance.

Visuospatial working memory (VSWM) is a set of cognitive processes used to encode, maintain and manipulate spatial information. One important feature of VSWM is that it has a limited capacity such that only few items can be actively stored and manipulated simultaneously. Given the limited capacity, it is important to determine the conditions that affect memory performance as this will improve our understanding of the architecture and function of VSWM. Previous studies have shown that VSWM is disrupted when task-irrelevant eye movements are performed during the maintenance phase; however, relatively fewer studies examined the role of eye movements performed during the encoding phase. On one hand, performing eye movements during the encoding phase could result in a stronger memory trace because the memory formation is reinforced by the activation of the motor system. On the other hand, performing eye movements to each target could disrupt the configural processing of the spatial array because the spatial representation has to be updated with each movement to maintain perceptual stability. Therefore, this work was conducted to examine whether task-relevant saccadic eye movements performed during the encoding phase of a visuospatial working memory task affect the recall of serially presented targets. Results from two experiments showed that average recall accuracy was significantly higher when the spatial array (set size ≥ 7) was encoded using a covert strategy-that is, while participants fixated on a central target, in comparison to an overt strategy-that is, while participants moved their eyes to fixate on each target. Furthermore, the improvement in accuracy was evident only for targets presented in the first half of the sequence, suggesting that the primacy effect is modulated by the presence of eye movements. We propose that executing saccades during encoding could interfere with the ability to use a chunking strategy or disrupt active visualization of the configuration. In conclusion, this is the first study to show that task-relevant saccadic eye movements performed during encoding may actually reduce the spatial span of VSWM. These results extend the current knowledge about the role of eye movements in VSWM, and have implications for future studies investigating the VSWM.

Executive function deficits in team sport athletes with a history of concussion revealed by a visual-auditory dual task paradigm.

The purpose of this study was to examine executive functions in team sport athletes with and without a history of concussion. Executive functions comprise many cognitive processes including, working memory, attention and multi-tasking. Past research has shown that concussions cause difficulties in vestibular-visual and vestibular-auditory dual-tasking, however, visual-auditory tasks have been examined rarely. Twenty-nine intercollegiate varsity ice hockey athletes (age = 19.13, SD = 1.56; 15 females) performed an experimental dual-task paradigm that required simultaneously processing visual and auditory information. A brief interview, event description and self-report questionnaires were used to assign participants to each group (concussion, no-concussion). Eighteen athletes had a history of concussion and 11 had no concussion history. The two tests involved visuospatial working memory (i.e., Corsi block test) and auditory tone discrimination. Participants completed both tasks individually, then simultaneously. Two outcome variables were measured, Corsi block memory span and auditory tone discrimination accuracy. No differences were shown when each task was performed alone; however, athletes with a history of concussion had a significantly worse performance on the tone discrimination task in the dual-task condition. In conclusion, long-term deficits in executive functions were associated with a prior history of concussion when cognitive resources were stressed. Evaluations of executive functions and divided attention appear to be helpful in discriminating participants with and without a history concussion.

Evaluation of motor capacity and neuromotor control for tapping and sliding movements reveals differences in visuomotor control.

The Fitts' task is a simple and effective method for evaluating motor capacity that can be used to reveal detailed aspects of visuomotor control when hand and eye kinematics are recorded simultaneously. With advances in technology, the classical Fitts' reciprocal tapping task was modified for use with digitizer tablets and computer screens that require sliding rather than tapping hand movements, which may rely on different visuomotor control strategies. Given the ubiquity of digital devices and touchscreens that often require execution of sliding movements, it is important to compare the underlying visuomotor control and eye-hand coordination involved in reciprocal sliding and tapping movements, which was the aim of the current study. Twelve young adults performed both tasks while their hand and eye movements were recorded. Results revealed motor capacity was significantly higher (p < 0.0001, d = 2.67) in the tapping task (19.62 ± 5.89 bits/s) compared to the sliding task (7.87 ± 2.02 bits/s). Examining hand kinematics showed the deceleration interval was significantly longer in the sliding compared to the tapping task at the lowest task difficulty (ID 2.28: 0.160 s ± 0.026 vs 0.129 s ± 0.017; p < 0.01), which was exacerbated as task difficulty increased (ID 6.97: 0.355 s ± 0.059 vs 0.226 s ± 0.020, p < 0.0001), indicating greater reliance on visual feedback during the sliding task. Examining temporal eye-hand coordination pattern showed that hand movement initiation tended to precede eye movement in both tasks. Overall, the results of this study provide a comprehensive examination of eye and hand kinematics demonstrating salient differences in visuomotor control between tapping and sliding movements. The findings also reveal a novel insight into the temporal pattern of eye-hand coordination for reciprocal tapping and sliding movements, which is in contrast to previous studies that examined discrete (rather than reciprocal) target-directed pointing movements where the eyes typically precede the hand by approximately 100 ms. In conclusion, the current study revealed substantial differences between the two tasks, one major finding being the sliding movements were performed slower compared to parabolic tapping hand movements, which may have implications for designing interactive digital devices and assessment of eye-hand coordination.

Investigating the role of flight phase and task difficulty on low-time pilot performance, gaze dynamics and subjective situation awareness during simulated flight.

Gaze behaviour has been used as a proxy for information processing capabilities that underlie complex skill performance in real-world domains such as aviation. These processes are highly influenced by task requirements, expertise and can provide insight into situation awareness (SA). Little research has been done to examine the extent to which gaze behaviour, task performance and SA are impacted by various task manipulations within the confines of early-stage skill development. Accordingly, the current study aimed to understand the impact of task difficulty on landing performance, gaze behaviour and SA across different phases of flight. Twenty-four low-time (<300 hours) pilots completed simulated landing scenarios under visual flight rules conditions. Traditional gaze metrics, entropybased metrics, and blink rate provided meaningful insight about the extent to which information processing is modulated by flight phase and task difficulty. The results also suggested that gaze behavior changes compensated for increased task demands and minimized the impact on task performance. Dynamic gaze analyses were shown to be a robust measure of task difficulty and pilot flight hours. Recommendations for the effective implementation of gaze behaviour metrics and their utility in examining information processing changes are discussed.

Kinematic Assessment of Fine Motor Skills in Children: Comparison of a Kinematic Approach and a Standardized Test.

Deficits in fine motor skills have been reported in some children with neurodevelopmental disorders such as amblyopia or strabismus. Therefore, monitoring the development of motor skills and any potential improvement due to therapy is an important clinical goal. The aim of this study was to test the feasibility of performing a kinematic assessment within an optometric setting using inexpensive, portable, off-the-shelf equipment. The study also assessed whether kinematic data could enhance the information provided by a routine motor function screening test (the Movement Assessment Battery for Children, MABC). Using the MABC-2, upper limb dexterity was measured in a cohort of 47 typically developing children (7-15 years old), and the Leap motion capture system was used to record hand kinematics while children performed a bead-threading task. Two children with a history of amblyopia were also tested to explore the utility of a kinematic assessment in a clinical population. For the typically developing children, visual acuity and stereoacuity were within the normal range; however, the average standardized MABC-2 scores were lower than published norms. Comparing MABC-2 and kinematic measures in the two children with amblyopia revealed that both assessments provide convergent results and revealed deficits in fine motor control. In conclusion, kinematic assessment can augment standardized tests of fine motor skills in an optometric setting and may be useful for measuring visuomotor function and monitoring treatment outcomes in children with binocular vision anomalies.

Path Configuration Complexity Affects Spatial Memory Span on the eCorsi Task but Does Not Influence Performance of a Concurrent Auditory Discrimination Task.

Visuospatial working memory is often assessed using the Corsi block-tapping task where set size is used to estimate capacity. It is well established that characteristics of the Corsi task path configuration such as length, crossings, and angles influence recall accuracy suggesting that more complex path configurations increase the load on working memory. However, the interaction between set size and path configuration is not well understood. Here we used a secondary auditory task to probe if set size and path configuration impose a similar type of load on the system. Nineteen participants (age = 25.3 ± 3.9 years) performed a computerized version of the Corsi test either alone (single) or simultaneously with an auditory tone discrimination task (dual). The eCorsi task involved a set of simple (no crosses, shorter lengths, larger angles) or complex (>2 crosses, longer lengths, smaller angles) paths at set sizes of five to eight blocks. Results showed significantly lower recall accuracy for the complex compared to the simple paths (63.32% vs. 86.38%, p < 0.001) at all set sizes, regardless of task condition (single, dual). Auditory performance (accuracy and response time) was significantly lower in the dual compared to single task (85.34% vs. 99.67%, p < 0.001), but performance was not affected by the complexity of the eCorsi path configuration. These findings suggest that set size and path complexity impose a different type of load on the working memory system and may rely on different resources.

The role of binocular vision in the control and development of visually guided upper limb movements.

Vision provides a key sensory input for the performance of fine motor skills, which are fundamentally important to daily life activities, as well as skilled occupational and recreational performance. Binocular visual function is a crucial aspect of vision that requires the ability to combine inputs from both eyes into a unified percept. Summation and fusion are two aspects of binocular processing associated with performance advantages, including more efficient visuomotor control of upper limb movements. This paper uses the multiple processes model of limb control to explore how binocular viewing could facilitate the planning and execution of prehension movements in adults and typically developing children. Insight into the contribution of binocularity to visuomotor control also comes from examining motor performance in individuals with amblyopia, a condition characterized by reduced visual acuity and poor binocular function. Overall, research in this field has advanced our understanding of the role of binocular vision in the development and performance of visuomotor skills, the first step towards developing assessment tools and targeted rehabilitation for children with neurodevelopment disorders at risk of poor visuomotor outcomes. This article is part of a discussion meeting issue 'New approaches to 3D vision'.

The effects of task difficulty on gaze behaviour during landing with visual flight rules in low-time pilots.

Eye movements have been used to examine the cognitive function of pilots and understand how information processing abilities impact performance. Traditional and advanced measures of gaze behaviour effectively reflect changes in cognitive load, situational awareness, and expert-novice differences. However, the extent to which gaze behaviour changes during the early stages of skill development has yet to be addressed. The current study investigated the impact of task difficulty on gaze behaviour in low-time pilots (N=18) while they completed simulated landing scenarios. An increase in task difficulty resulted in longer fixation of the runway, and a reduction in the stationary gaze entropy (gaze dispersion) and gaze transition entropy (sequence complexity). These findings suggest that pilots' gaze became less complex and more focused on fewer areas of interest when task difficulty increased. Additionally, a novel approach to identify and track instances when pilots restrict their attention outside the cockpit (i.e., gaze tunneling) was explored and shown to be sensitive to changes in task difficulty. Altogether, the gaze-related metrics used in the present study provide valuable information for assessing pilots gaze behaviour and help further understand how gaze contributes to better performance in low-time pilots.

Binocular Viewing Facilitates Size Constancy for Grasping and Manual Estimation.

A prerequisite for efficient prehension is the ability to estimate an object's distance and size. While most studies demonstrate that binocular viewing is associated with a more efficient grasp programming and execution compared to monocular viewing, the factors contributing to this advantage are not fully understood. Here, we examined how binocular vision facilitates grasp scaling using two tasks: prehension and manual size estimation. Participants (n = 30) were asked to either reach and grasp an object or to provide an estimate of an object's size using their thumb and index finger. The objects were cylinders with a diameter of 0.5, 1.0, or 1.5 cm placed at three distances along the midline (40, 42, or 44 cm). Results from a linear regression analysis relating grip aperture to object size revealed that grip scaling during monocular viewing was reduced similarly for both grasping and estimation tasks. Additional analysis revealed that participants adopted a larger safety margin for grasping during monocular compared to binocular viewing, suggesting that monocular depth cues do not provide sufficient information about an object's properties, which consequently leads to a less efficient grasp execution.

Gaze behaviour: A window into distinct cognitive processes revealed by the Tower of London test.

The analysis of gaze behaviour during complex tasks provides a promising non-invasive method to examine how specific eye movement patterns relate to various aspects of cognition and action. Notably, the association between aspects of gaze behaviour and subsequent goal-directed action during high-level visuospatial problem solving remains elusive. Therefore, the current study comprehensively examined gaze behaviour using traditional and entropy-based gaze analyses in healthy adults (N = 27) while they performed the Freiburg version of the Tower of London task. Results demonstrated that both gaze analyses provided crucial temporal and spatial information related to planning, solution elaboration and execution. Specifically, gaze biases toward task-relevant areas (i.e., the work space) and an increase in gaze complexity (i.e., gaze transition entropy) during optimal performance reflected changes in cognitive demands as task difficulty increased. A comparison between optimal and non-optimal performance revealed sub-optimal gaze patterns that occurred in the early stages of planning, which were taken to reflect poor information extraction from the task environment and impaired maintenance of information in visuospatial working memory. Gaze behaviour during movement execution indicated an increased need to extract and process information from the goal space. Consequently, movement execution time increased in order to reverse erroneous movements and re-sequence the problem solution. Taken together, the traditional and entropy-based gaze analyses applied in the present study provide a promising approach to identify eye movement patterns that support neurocognitive performance on tasks relying on visuospatial planning and problem solving.

Temporal Eye-Hand Coordination During Visually Guided Reaching in 7- to 12-Year-Old Children With Strabismus.

Purpose: We recently found slow visually guided reaching in strabismic children, especially in the final approach. Here, we expand on those data by reporting saccade kinematics and temporal eye-hand coordination during visually guided reaching in children treated for strabismus compared with controls. Methods: Thirty children diagnosed with esotropia, a form of strabismus, 7 to 12 years of age and 32 age-similar control children were enrolled. Eye movements and index finger movements were recorded. While viewing binocularly, children reached out and touched a small dot that appeared randomly in one of four locations along the horizontal meridian (±5° or ±10°). Saccade kinematic measures (latency, accuracy and precision, peak velocity, and frequency of corrective and reach-related saccades) and temporal eye-hand coordination measures (saccade-to-reach planning interval, saccade-to-reach peak velocity interval) were compared. Factors associated with impaired performance were also evaluated. Results: During visually guided reaching, strabismic children had longer primary saccade latency (strabismic, 195 ± 29 ms vs. control; 175 ± 23 ms; P = 0.004), a 25% decrease in primary saccade precision (0.15 ± 0.06 vs. 0.12 ± 0.03; P = 0.007), a 45% decrease in the final saccade precision (0.16 ± 0.06 vs. 0.11 ± 0.03; P < 0.001), and more reach-related saccades (16 ± 13% of trials vs. 8 ± 6% of trials; P = 0.001) compared with a control group. No measurable stereoacuity was related to poor saccade kinematics. Conclusions: Strabismus impacts saccade kinematics during visually guided reaching in children, with poor binocularity playing a role in performance. Coupled with previous data showing slow reaching in the final approach, the current saccade data suggest that children treated for strabismus have not yet adapted or formed an efficient compensatory strategy during visually guided reaching.