The effects of monocular viewing on hand-eye coordination during sequential grasping and placing movements

Eight weeks of exercise intervention improves visuomotor and functional capacity, performance, and physiological profile in a patient with choroidal melanoma

The aim of this case study was to investigate the effects of an 8-wk combined exercise intervention, consisting of visual-coordinative and high-intensity interval training (HIIT), on the physical and visuomotor-functional capacity, performance, and physiological profile of a moderately active 29-yr-old man diagnosed with choroidal melanoma of the left eye. Data were collected on three occasions: at the initial diagnosis (T0), after hospitalization and radiotherapy treatment (T1), and following the recovery through the exercise intervention (T2), spanning a total of 17 wk. The primary outcome variables consisted of visuomotor and functional tests (VFTs), cardiorespiratory fitness (CRF), and microvascular circulation measured via flicker light-induced dilation (FiD). For visuomotor tests in general, a significant decline was observed between baseline T0 and T1 (by 6%-22%), followed by significant improvements at T2 (by 11%-36%), surpassing the initially observed T0 values. The cardiopulmonary exercise testing (CPET)-derived parameters exhibited a similar pattern, declining from T0 to T1 [by 8%-12% for peak V̇o2, peak power output (PO), and CPET duration, respectively], with a subsequent recovery observed in response to 8 wk of exercise training (T2), resulting in increases of 11%-25% for V̇o2, peak PO, and CPET duration. Interestingly, the dilation of both arteries and veins in response to the FiD stimulus exhibited a twofold increase compared with baseline levels. Our results suggest that the 8-wk exercise intervention improved patients' VFT and CRF profiles and exceeded baseline values. Additional investigation, particularly through randomized controlled trials, is needed to comprehensively explain changes in FiD.NEW & NOTEWORTHY Results presented here suggest that combined visual-coordinative and HIIT training improves the visual-functional capacity, performance, and physiological profile of choroidal melanoma patients during treatment recovery. This case study lays the groundwork for further research concerning exercise therapy in this unique patient population. In addition, further investigation is required to fully comprehend the combined effects of exercise and radiation therapy on vasculature and oxygenation in patients with choroidal melanoma.

Targeted reaching with monocular depth information and haptic feedback: Comparing between monocular patients and normally sighted observers

Monocular blindness impairs visual depth perception, yet patients seldom report difficulties in targeted actions like reaching, walking, or driving. We hypothesized that by utilizing monocular depth information and calibrating actions with haptic feedback, monocular patients can perceive egocentric distance and perform targeted actions. We compared targeted reaching in monocular patients, monocular-viewing, and binocular-viewing normal controls. Sixty observers reached either a far or a near target, calibrating reaches to the near target with accurate or false feedback while leaving reaches to the far target uncalibrated. Reaching accuracy and precision were analyzed. Results indicated no difference in reaching accuracy between monocular patients and normal controls; all groups initially underestimated distances before until calibration. Monocular patients responded to calibration sensitively, achieving accuracy in calibrated reaches and generalizing this effect to uncalibrated distances. Thus, with monocular depth information and haptic feedback, monocular patients could perceive distance and accomplish targeted reaching.

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'.

Electroencephalography Study of Frontal Lobe Evoked by Dynamic Random-Dot Stereogram

Purpose

The purpose of this study was to investigate the cortical electrical activity and electroencephalography (EEG) features of the frontal lobe evoked by dynamic random dot stereogram (DRDS) and to probe the functional connectivity (FC) between the frontal lobe and occipital lobe when processing 3D perception based on the binocular disparity.

Methods

The EEG experiment involved 14 healthy adults with normal stereopsis (<60″) and normal corrected visual acuity (20/20). The Neuroscan system and 32-channel EEG cap were used to record EEG signals based on the DRDS stimuli. The maximum energies of 3 frequency bands (theta-/alpha- /beta-wave) from 13 interesting channels (FP1, FP2, F7, F3, FZ, F4, F8, FC3, FCZ, FC4, O1, OZ, and O2) located in the frontal and occipital lobes were calculated and analyzed. The FC between any two electrodes from the frontal and occipital lobes was calculated based on the Phase lag index (PLI).

Results

The maximum powers of theta- and alpha-waves in most channels of the frontal and occipital lobes were significantly increased (P < 0.05) when the depth perception was evoked by DRDS above the threshold, compared with that without stereo vision. The changes in the maximum powers of both theta- and alpha-waves were significantly different among the 13 electrodes (P = 0.0004 and 0.0015, respectively). Tukey's multiple comparisons showed that the changes in the maximum powers of theta-wave were significantly different in F8 vs. O1, F8 vs. OZ, and F4 vs. O1 (P = 0.0186, 0.0444, and 0.0412, respectively). Moreover, the changes in the maximum powers of alpha-waves were significantly different in FP1 vs. O1 (P = 0.0182). The FCs of theta-waves between the frontal channels and the occipital channels were significantly enhanced when processing the depth perception, compared with those without stereopsis. There was no significant change in the FCs of the alpha-waves when having 3D perception except for FC between F8 and O1 and FC between F8 and OZ.

Conclusions

The cortical electrical activity in the frontal lobe and the functional connectivity between the frontal lobe and the occipital lobe increase when participating in the processing binocular disparity and obtaining 3D perception. Theta-waves in the frontal lobe may be crucial in the stereo vision.

Virtual reality-based vision therapy versus OBVAT in the treatment of convergence insufficiency, accommodative dysfunction: a pilot randomized controlled trial

Background

Virtual reality is being increasingly applied in vision therapy. However, the differences in effectiveness, optimal treatment cycle, and prognosis between virtual reality-based vision therapy and traditional therapies remain unknown. The purpose of this study was to compare the effectiveness of virtual reality-based vision therapy and office-based vergence/accommodative therapy in young adults with convergence insufficiency or accommodative dysfunction.

Methods

The patients were randomly assigned to either the virtual reality-based vision therapy group or the office-based vergence/accommodative therapy group. The vision therapy lasted 12 weeks (1 h/week) in both groups. Binocular visual functions (vergence and accommodation) were measured and a subjective questionnaire-based assessment was performed at baseline and after 6 and 12 weeks of therapy.

Results

In total, 33 patients with convergence insufficiency and 30 with accommodative dysfunction completed the study. After 12 weeks of treatment for convergence insufficiency, the Convergence Insufficiency Symptom Survey score (F_2,31 = 13.704, P < 0.001), near point of convergence (F_2,31 = 21.774, P < 0.001), positive fusional vergence (F_2,31 = 71.766, P < 0.001), and near horizontal phoria (F_2,31 = 16.482, P < 0.001) improved significantly in both groups. Moreover, the monocular accommodative amplitude (F_2,25 = 22.154, P < 0.001) and monocular accommodative facility (F_2,25 = 86.164, P < 0.001) improved significantly in both groups after 12 weeks of treatment. A statistically significant difference was observed in monocular accommodative facility (F_1,25 = 8.140, P = 0.009) between the two groups, but not in other vergence and accommodative functions (0.098 < P < 0.687).

Conclusion

Virtual reality-based vision therapy significantly improved binocular vision functions and symptoms in patients with convergence insufficiency and accommodative dysfunction, thereby suggesting its effectiveness as a new optional or additional treatment for young adults with these conditions.

Trial registration

This study was registered at the Chinese Clinical Trials Registry on 16/04/2019 (identifier: ChiCTR1900022556).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02393-z.

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.

Development of eye-hand coordination in typically developing children and adolescents assessed using a reach-to-grasp sequencing task

Eye-hand coordination is required to accurately perform daily activities that involve reaching, grasping and manipulating objects. Studies using aiming, grasping or sequencing tasks have shown a stereotypical temporal coupling pattern where the eyes are directed to the object in advance of the hand movement, which may facilitate the planning and execution required for reaching. While the temporal coordination between the ocular and manual systems has been extensively investigated in adults, relatively little is known about the typical development of eye-hand coordination. Therefore, the current study addressed an important knowledge gap by characterizing the profile of eye-hand coupling in typically developing school-age children (n = 57) and in a cohort of adults (n = 30). Eye and hand movements were recorded concurrently during the performance of a bead threading task which consists of four distinct movements: reach to bead, grasp, reach to needle, and thread. Results showed a moderate to high correlation between eye and hand latencies in children and adults, supporting that both movements were planned in parallel. Eye and reach latencies, latency differences, and dwell time during grasping and threading, showed significant age-related differences, suggesting eye-hand coupling becomes more efficient in adolescence. Furthermore, visual acuity, stereoacuity and accommodative facility were also found to be associated with the efficiency of eye-hand coordination in children. Results from this study can serve as reference values when examining eye and hand movement during the performance of fine motor skills in children with neurodevelopmental disorders.

Test-retest repeatability reveals a temporal kinematic signature for an upper limb precision grasping task in adults

Hand-eye coordination skills, such as reaching and grasping, are fundamentally important for the performance of most daily activities. Upper limb kinematics recorded by motion tracking systems provide detailed insight into the central nervous system control of movement planning and execution. For example, kinematic metrics can reveal deficits in control, and compensatory neuromotor strategies in individuals with neuropathologies. However, the clinical utility of kinematic metrics is currently limited because their psychometric properties, such as test-retest repeatability, have not been well characterized. Therefore, the purpose of this study was to examine the degree of repeatability of spatiotemporal kinematic metrics and determine which, if any, measures form a kinematic signature for a precision grasping task. Healthy adults (n = 40) were tested on two occasions separated by 5-10 days on a bead threading task consisting of reaching and precision grasping. Results showed good test-retest repeatability for reach peak velocity, reach and grasp durations, whereas poor to moderate reliability was observed for measures of spatial precision and maximum grip aperture. In addition, analysis showed that reliable estimates of kinematic metrics can be obtained using 10 trials. Overall, our results indicate that reach peak velocity and temporal metrics form a stable characteristic, or a kinematic signature, of individual performance on a standardized bead threading task. These findings suggest potential utility in applying kinematic metrics for clinical assessment of upper limb reaching tasks.

Motor skills in children affected by strabismus

OBJECTIVES

To compare motor skills in patients with infantile strabismus and age and sex-matched control subjects aged 5-11 years.

METHODS

Motor performances were assessed by the Italian version of Developmental Coordination Disorder Questionnaire 2007 (DCDQ) in children with infantile strabismus and age and sex-matched control subjects. Patients affected by specific neurological, cognitive and behavioural disorders were excluded from the study.

RESULTS

There were 43 patients included in the study, 23 in the strabismus group (14 males, 9 females, mean age 7.5 ± 2.0 years) and 24 in the control group (14 males and 10 females, mean age 7.2 ± 1.7 years. The overall DCDQ score was significantly lower in children with strabismus compared with control subjects (58.7 ± 11.3 vs. 74.2 ± 1.5; P < 0.001). Children with strabismus and no stereopsis showed a lower DCDQ score compared with those with normal stereopsis (50.8 ± 9.5 vs. 67.3 ± 4.8; P < 0.001).

CONCLUSION

Motor skills are reduced in children with strabismus compared with control subjects. Strabismus and lack of binocular vision are factors potentially contributing to developmental coordination disorder.

Psychomotor, Psychosocial and Reading Skills in Children with Amblyopia and the Effect of Different Treatments

Amblyopia influences psychomotor and psychosocial skills, although not all studies are unanimous. Different treatments coexist, but the effect on those variables is not clear. This study aims to probe whether children with amblyopia have impairments in these areas and if different optometric treatments reduce them effectively. 50 children, diagnosed with amblyopia, and 33 without amblyopia participated in this study. Eye-hand coordination, psychosocial skills and reading abilities, were measured before and after three months of different treatments (patch, patch and near vision activities and perceptual learning). Results revealed lower scores in eye-hand coordination and some reading issues in children with amblyopia, without differences in psychosocial skills in regard to the control group. Moreover, optometric treatments improved eye-hand coordination.

Characteristic of Motor Control in Three-Dimensional Circular Tracking Movements during Monocular Vision

Analysis of visually guided tracking movements is an important component of understanding human visuomotor control system. The aim of our study was to investigate the effects of different target speeds and different circular tracking planes, which provide different visual feedback of depth information, on temporal and spatial tracking accuracy. In this study, we analyze motor control characteristic of circular tracking movements during monocular vision in three-dimensional space using a virtual reality system. Three parameters in polar coordinates were analyzed: ΔR, the difference in the distance from the fixed pole; Δθ, the difference in the position angle; and Δω, the difference in the angular velocity. We compare the accuracy of visually guided circular tracking movements during monocular vision in two conditions: (1) movement in the frontal plane relative to the subject that requires less depth information and (2) movement in the sagittal plane relative to the subject that requires more depth information. We also examine differences in motor control at four different target speeds. The results show that depth information affects both spatial and temporal accuracy of circular tracking movement, whereas target speed only affects temporal accuracy of circular tracking movement. This suggests that different strategies of feedforward and feedback controls are performed in the tracking of movements.

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.

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.

Evaluation of the Leap Motion Controller during the performance of visually-guided upper limb movements

Kinematic analysis of upper limb reaching provides insight into the central nervous system control of movements. Until recently, kinematic examination of motor control has been limited to studies conducted in traditional research laboratories because motion capture equipment used for data collection is not easily portable and expensive. A recently developed markerless system, the Leap Motion Controller (LMC), is a portable and inexpensive tracking device that allows recording of 3D hand and finger position. The main goal of this study was to assess the concurrent reliability and validity of the LMC as compared to the Optotrak, a criterion-standard motion capture system, for measures of temporal accuracy and peak velocity during the performance of upper limb, visually-guided movements. In experiment 1, 14 participants executed aiming movements to visual targets presented on a computer monitor. Bland-Altman analysis was conducted to assess the validity and limits of agreement for measures of temporal accuracy (movement time, duration of deceleration interval), peak velocity, and spatial accuracy (endpoint accuracy). In addition, a one-sample t-test was used to test the hypothesis that the error difference between measures obtained from Optotrak and LMC is zero. In experiment 2, 15 participants performed a Fitts’ type aiming task in order to assess whether the LMC is capable of assessing a well-known speed-accuracy trade-off relationship. Experiment 3 assessed the temporal coordination pattern during the performance of a sequence consisting of a reaching, grasping, and placement task in 15 participants. Results from the t-test showed that the error difference in temporal measures was significantly different from zero. Based on the results from the 3 experiments, the average temporal error in movement time was 40±44 ms, and the error in peak velocity was 0.024±0.103 m/s. The limits of agreement between the LMC and Optotrak for spatial accuracy measures ranged between 2–5 cm. Although the LMC system is a low-cost, highly portable system, which could facilitate collection of kinematic data outside of the traditional laboratory settings, the temporal and spatial errors may limit the use of the device in some settings.

Three-dimensional binocular eye-hand coordination in normal vision and with simulated visual impairment

Sensorimotor coupling in healthy humans is demonstrated by the higher accuracy of visually tracking intrinsically-rather than extrinsically-generated hand movements in the fronto-parallel plane. It is unknown whether this coupling also facilitates vergence eye movements for tracking objects in depth, or can overcome symmetric or asymmetric binocular visual impairments. Human observers were therefore asked to track with their gaze a target moving horizontally or in depth. The movement of the target was either directly controlled by the observer's hand or followed hand movements executed by the observer in a previous trial. Visual impairments were simulated by blurring stimuli independently in each eye. Accuracy was higher for self-generated movements in all conditions, demonstrating that motor signals are employed by the oculomotor system to improve the accuracy of vergence as well as horizontal eye movements. Asymmetric monocular blur affected horizontal tracking less than symmetric binocular blur, but impaired tracking in depth as much as binocular blur. There was a critical blur level up to which pursuit and vergence eye movements maintained tracking accuracy independent of blur level. Hand-eye coordination may therefore help compensate for functional deficits associated with eye disease and may be employed to augment visual impairment rehabilitation.

Object-Tool-Actor Interaction: Object Information Drives Intended Action

Tool use is typically explored via actor-tool interactions. However, the target-object (that which is being acted on) may influence perceived action possibilities and thereby guide action. Three different tool-target-object pairings were tested (Experiment 1). The hammering action demonstrated the greatest sensitivity and therefore subsequently used to further investigate target-object pairings. The hammer was removed as an option and instructions were provided using pictorial (Experiment 2), written (Experiment 3), and both pictorial and written formats (Experiment 4). The designed tool is chosen when available (Experiment 1) and when removed as a choice (i.e., the hammer), participants perform the same action associated with the designed tool (i.e., hammering) regardless of instruction method (Experiments 2, 3, and 4).