Amblyopia and real-world visuomotor tasks

A question of increasing interest to the basic science and clinical management communities during the past decade is whether children and adults with amblyopia and associated binocular visual abnormalities experience difficulties in executing real-world actions, to which vision normally makes an important functional contribution. Here we provide objective evidence that they do, by reviewing quantitative data from a number of studies comparing their performance with that of matched normally sighted subjects on a range of everyday visuomotor tasks. Because in real life, these tasks (grasping objects, walking, driving, reading) are habitually performed with both eyes open, our focus is on their binocular skill deficits, rather than those with their amblyopic eye alone. General findings are that individuals with abnormal binocularity show impairments in critical aspects of motor control--movement speed, accuracy or both--on every one of these activities, the extent of which correlates with their loss of stereoacuity, but not the severity of their amblyopia. Impairments were especially marked when the task was time-limited or novel. Implications are that children and adults with severely reduced or absent binocularity may be accident-prone when required to respond rapidly to unexpected situations and that amblyopia management should focus more attention on evaluating and restoring stereoacuity and stereomotion processing

Gait in Parkinson’s disease: a visuo-cognitive challenge

Vision and cognition have both been related to gait impairment in Parkinson’s disease (PD) through separate strands of research. The cumulative and interactive effect of both (which we term visuo-cognition) has not been previously investigated and little is known about the influence of cognition on vision with respect to gait. Understanding the role of vision, cognition and visuo-cognition in gait in PD is critical for data interpretation and to infer and test underlying mechanisms. The purpose of this comprehensive narrative review was to examine the interdependent and interactive role of cognition and vision in gait in PD and older adults. Evidence from a broad range of research disciplines was reviewed and summarised. A key finding was that attention appears to play a pivotal role in mediating gait, cognition and vision, and should be considered emphatically in future research in this field

Des preuves récentes sur les habiletés visuo- spatiales pour la formation en chirurgie : revue exploratoire

Background: Understanding the relationships between structures is critical for surgical trainees. However, the heterogeneity of the literature on visual-spatial ability (VSA) in surgery makes it challenging for educators to make informed decisions on incorporating VSA into their programs. We conducted a scoping review of the literature on VSA in surgery to provide a map of the literature and identify where gaps still exist for future research. Methods: We searched databases until December 2019 using keywords related to VSA and surgery. The resulting articles were independently screened by two researchers for inclusion in our review. Results: We included 117 articles in the final review. Fifty-nine articles reported significant correlations between VSA tests and surgical performance, and this association is supported by neuroimaging studies. However, it remains unclear whether VSA should be incorporated into trainee selection and whether there is a benefit of three-dimensional (3D) over two-dimensional (2D) training. Conclusions: It appears that VSA correlates with surgical performance in the simulated environment, particularly for novice learners. Based on our findings, we make suggestions for how surgical educators may use VSA to support novice learners. Further research should determine whether VSA remains correlated to surgical performance when trainees move into the operative environment.Contexte :  Il est fondamental pour les chirurgiens en formation de comprendre les liens qui unissent les diverses structures corporelles. Étant donné l’hétérogénéité de la littérature portant sur les habiletés visuo-spatiales (HVS) nécessaires en chirurgie, les éducateurs ont de la difficulté à prendre des décisions éclairées quant à l’enseignement des HVS dans leurs programmes. On a effectué une étude exploratoire de la littérature sur les HVS en chirurgie afin de répertorier la littérature et de cerner des lacunes pouvant faire l’objet de recherches ultérieures. Méthodologie : On a interrogé des bases de données jusqu’à décembre 2019 à l’aide de mots-clés reliés aux HVS et à la chirurgie.  Les articles trouvés ont été évalués de façon indépendante par deux chercheurs pour déterminer leur inclusion à la revue. Résultats :  Au total, 117 articles ont été inclus dans la revue finale. Cinquante-neuf faisaient état d’importantes corrélations entre les tests d’évaluation des HVS et la performance chirurgicale. Cette association est étayée par les résultats d’études en neuro-imagerie.   Il n’est pas clair cependant si les HVS devraient faire partie des critères de sélection des résidents et si une formation sur les techniques de visualisation en trois dimensions (3D) est préférable à une formation sur les techniques de visualisation en deux dimensions (2D). Conclusions : Il semble exister un lien entre les HVS et la performance chirurgicale en contexte de simulation, particulièrement chez les apprenants novices. À la lumière de nos résultats, nous présentons des recommandations sur la façon dont les formateurs en chirurgie pourraient se servir des HVS pour aider les apprenants novices. D’autres travaux de recherche devraient permettre de savoir si les HVS restent reliés à la performance chirurgicale lorsque les stagiaires passent à un environnement opératoire réel

The assessment of visual behaviour and depth perception in surgery

Imperial Users onl

Neural mechanisms for reducing uncertainty in 3D depth perception

In order to navigate and interact within their environment, animals must process and interpret sensory information to generate a representation or ‘percept’ of that environment. However, sensory information is invariably noisy, ambiguous, or incomplete due to the constraints of sensory apparatus, and this leads to uncertainty in perceptual interpretation. To overcome these problems, sensory systems have evolved multiple strategies for reducing perceptual uncertainty in the face of uncertain visual input, thus optimizing goal-oriented behaviours. Two available strategies have been observed even in the simplest of neural systems, and are represented in Bayesian formulations of perceptual inference: sensory integration and prior experience. In this thesis, I present a series of studies that examine these processes and the neural mechanisms underlying them in the primate visual system, by studying depth perception in human observers. Chapters 2 & 3 used functional brain imaging to localize cortical areas involved in integrating multiple visual depth cues, which enhance observers’ ability to judge depth. Specifically, we tested which of two possible computational methods the brain uses to combine depth cues. Based on the results we applied disruption techniques to examine whether these select brain regions are critical for depth cue integration. Chapters 4 & 5 addressed the question of how memory systems operating over different time scales interact to resolve perceptual ambiguity when the retinal signal is compatible with more than one 3D interpretation of the world. Finally, we examined the role of higher cortical regions (parietal cortex) in depth perception and the resolution of ambiguous visual input by testing patients with brain lesions

Binocular vision enhances a rapidly evolving affordance priming effect: Behavioural and TMS evidence

Extensive research has suggested that simply viewing an object can automatically prime compatible actions for object manipulation, known as affordances. Here we explored the generation of covert motor plans afforded by real objects with precision (‘pinchable’) or whole-hand/power (‘graspable’) grip significance under different types of vision. In Experiment 1, participants viewed real object primes either monocularly or binocularly and responded to orthogonal auditory stimuli by making precision or power grips. Pinchable primes facilitated congruent precision grip responses relative to incongruent power grips, and vice versa for graspable primes, but only in the binocular vision condition. To examine the temporal evolution of the binocular affordance effect, participants in Experiment 2 always viewed the objects binocularly but made no responses, instead receiving a transcranial magnetic stimulation pulse over their primary motor cortex at three different times (150, 300, 450 ms) after prime onset. Motor evoked potentials (MEPs) recorded from a pinching muscle were selectively increased when subjects were primed with a pinchable object, whereas MEPs from a muscle associated with power grips were increased when viewing graspable stimuli. This interaction was obtained both 300 and 450 ms (but not 150 ms) after the visual onset of the prime, characterising for the first time the rapid development of binocular grip-specific affordances predicted by functional accounts of the affordance effect

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Oštećenja vida uslijed diskinetskih poremećaja pokreta očiju u djece s diskinetskom cerebralnom paralizom

Despite the fact that ocular and cerebral visual abnormalities are shown to be very frequent in cerebral palsy (CP), children with CP are underreferred to rehabilitation services for visual impairments. Visual component is, together with the motor disorder, an integral part of the clinical picture of CP and not an associated symptom. Therefore, an accurate detection of visual disorders and visual function not only lead to a complete clinical diagnosis but also to an appropriate intervention plan. Hence, the need for a study aiming specifically to describe all the aspects of visual involvement in the dyskinetic CP. Research goals were aimed at gaining insights into the nature of visual impairments and functional vision of children with dyskinetic CP, determining the nature of connection between visual functions and functional vision, with an emphasis on searching for dyskinetic eye movement disorder for understanding the difficulties in performing visual activities of two children with dyskinetic CP from the Zagreb’s county register of CP, which is part of national C28 RCP-HR-Register of cerebral palsy of Croatia included in Surveillance Cerebral Palsy Europe (SCPE). The data were collected using standardized and non-standardized tests for visual function assessment. Dyskinetic eye movement disorder was tested comparing the tested results of visual functions. Functional vision was tested through the observation of the children’s behavior and through open structured questions addressed to parents. Cerebral visual impairment was examined by a questionnaire for cerebral visual impairment screening. Qualitative research analysis shows which ocular and cerebral visual impairments are present as well as their relation to visual functioning. Moreover, it shows clinical features of dyskinetic eye movement disorder that haven’t been shown present among tested children. Since this is the second research up to this date, testing an eye movement disorder that specifically occurs in dyskinetic CP, its characteristics are further discussed and defined. In contrary to previous study, in a child where highly inefficient visual functioning was shown, the cause goes wider from the abnormal eye motility. It consists of combination of several motor and sensory problems (lacking binocular visual acuity, contrast sensitivity, fixation, voluntary eye movements and oculomotricity). Due to the small sample and findings that are, on account of heterogeneity of dyskinetic CP hard to compare, future research is needed to expand overall knowledge of functional vision and visual functions needed for planning rehabilitation and education management for children with dyskinetic CP.Unatoč činjenici da su okularne i cerebralne vizualne abnormalnosti česte u cerebralnoj paralizi (CP), djeca s CP nedostatno podliježu uslugama rehabilitacije oštećenja vida. Vizualna komponenta je, zajedno s motoričkim poremećajem, sastavni dio kliničke slike CP, a ne samo pridruženi simptom. Točno otkrivanje vizualnog profila djece s CP dovodi do sveobuhvatne kliničke dijagnoze i do odgovarajućeg plana intervencije. Stoga je potrebna studija čiji je cilj opisati sve aspekte vizualne uključenosti u diskinetskom tipu CP. Ciljevi istraživanja bili su usmjereni na stjecanje uvida u prirodu vidnih funkcjia i funkcionalnog vida djece s diskinetskom CP, utvrđivanje prirode povezanosti vizualnih funkcija i funkcionalnog vida, s naglaskom na otkrivanje diskinetskog poremećaja pokreta očiju, kako bi se poboljšalo razumijevanje poteškoća u izvođenju vizualnih aktivnosti dvoje djece s diskinetskom CP iz zagrebačkog županijskog registra CP-a, koji je dio nacionalnog registra C28 RCP-HR cerebralne paralize Hrvatske uključen u Surveillance Cerebral Palsy Europe (SCPE). Podaci su prikupljeni korištenjem standardiziranih i nestandardiziranih testova za procjenu vidnih funkcija. Diskinetski poremećaj pokreta očiju testiran je uspoređujući testirane rezultate vidnih funkcija. Funkcionalni vid testiran je promatranjem dječjeg ponašanja u vizualnim zadacima i kroz otvorena strukturirana pitanja upućena roditeljima. Cerebralno oštećenje vida ispitano je upitnikom za screening na cerebralno oštećenje vida. Kvalitativna analiza podataka pokazuje koja su okularna i cerebralna oštećenja vida prisutna kao i njihov odnos prema funkcionalnom vidu. Budući da je ovo drugo do sada istraživanje ispitivanja diskinetskog poremećaja pokreta očiju koji je karakterističan za diskinetsku CP, opisana su njegova klinička obilježja. Suprotno već objavljenoj studiji, kod djeteta kod kojeg je prikazano vrlo neučinkovito vizualno funkcioniranje, uzrok je širi od abnormalne pokretljivosti oka. Sastoji se od kombinacije nekoliko motoričkih i senzoričkih problema (nedostatna binokularna oštrina vida, kontrastna osjetljivost, fiksacija, voljni pokreti očiju i okulomotorika). Zbog malog uzorka i nalaza koji su zbog heterogenosti diskinetičke CP teško usporedivi, potrebna su buduća istraživanja kako bi se proširilo sveukupno znanje o diskinetskom poremećaju pokreta očiju, funkcionalnom vidu i vizualnim funkcijama potrebnim za planiranje edukacije i rehabilitacije djece s diskinetskom CP

Gaze-grasp coordination in obstacle avoidance: differences between binocular and monocular viewing

Most adults can skillfully avoid potential obstacles when acting in everyday cluttered scenes. We examined how gaze and hand movements are normally coordinated for obstacle avoidance and whether these are altered when binocular depth information is unavailable. Visual fixations and hand movement kinematics were simultaneously recorded, while 13 right-handed subjects reached-to-precision grasp a cylindrical household object presented alone or with a potential obstacle (wine glass) located to its left (thumb's grasp side), right or just behind it (both closer to the finger's grasp side) using binocular or monocular vision. Gaze and hand movement strategies differed significantly by view and obstacle location. With binocular vision, initial fixations were near the target's centre of mass (COM) around the time of hand movement onset, but usually shifted to end just above the thumb's grasp site at initial object contact, this mainly being made by the thumb, consistent with selecting this digit for guiding the grasp. This strategy was associated with faster binocular hand movements and improved end-point grip precision across all trials than with monocular viewing, during which subjects usually continued to fixate the target closer to its COM despite a similar prevalence of thumb-first contacts. While subjects looked directly at the obstacle at each location on a minority of trials and their overall fixations on the target were somewhat biased towards the grasp side nearest to it, these gaze behaviours were particularly marked on monocular vision-obstacle behind trials which also commonly ended in finger-first contact. Subjects avoided colliding with the wine glass under both views when on the right (finger side) of the workspace by producing slower and straighter reaches, with this and the behind obstacle location also resulting in 'safer' (i.e. narrower) peak grip apertures and longer deceleration times than when the goal object was alone or the obstacle was on its thumb side. But monocular reach paths were more variable and deceleration times were selectively prolonged on finger-side and behind obstacle trials, with this latter condition further resulting in selectively increased grip closure times and corrections. Binocular vision thus provided added advantages for collision avoidance, known to require intact dorsal cortical stream processing mechanisms, particularly when the target of the grasp and potential obstacle to it were fairly closely separated in depth. Different accounts of the altered monocular gaze behaviour converged on the conclusion that additional perceptual and/or attentional resources are likely engaged compared to when continuous binocular depth information is available. Implications for people lacking binocular stereopsis are briefly considered