Differential impact of partial cortical blindness on gaze strategies when sitting and walking – An immersive virtual reality study

AbstractThe present experiments aimed to characterize the visual performance of subjects with long-standing, unilateral cortical blindness when walking in a naturalistic, virtual environment. Under static, seated testing conditions, cortically blind subjects are known to exhibit compensatory eye movement strategies. However, they still complain of significant impairment in visual detection during navigation. To assess whether this is due to a change in compensatory eye movement strategy between sitting and walking, we measured eye and head movements in subjects asked to detect peripherally-presented, moving basketballs. When seated, cortically blind subjects detected ∼80% of balls, while controls detected almost all balls. Seated blind subjects did not make larger head movements than controls, but they consistently biased their fixation distribution towards their blind hemifield. When walking, head movements were similar in the two groups, but the fixation bias decreased to the point that fixation distribution in cortically blind subjects became similar to that in controls – with one major exception: at the time of basketball appearance, walking controls looked primarily at the far ground, in upper quadrants of the virtual field of view; cortically blind subjects looked significantly more at the near ground, in lower quadrants of the virtual field. Cortically blind subjects detected only 58% of the balls when walking while controls detected ∼90%. Thus, the adaptive gaze strategies adopted by cortically blind individuals as a compensation for their visual loss are strongest and most effective when seated and stationary. Walking significantly alters these gaze strategies in a way that seems to favor walking performance, but impairs peripheral target detection. It is possible that this impairment underlies the experienced difficulty of those with cortical blindness when navigating in real life

m- and e-Health applications in diagnosis and rehabilitation of balance disorders - Εφαρμογές m- και e-health για τη διάγνωση και αποκατάσταση διαταραχών ισορροπίας

Υπόβαθρο: Η ισορροπία είναι μια αρχέγονη ανθρώπινη αίσθηση που απαιτεί πολυαισθητηριακή ολοκλήρωση από το αιθουσαίο, το οπτικό και το ιδιοδεκτικό σύστημα και συμμετοχή της παρεγκεφαλίδας και αρκετών άλλων νευρωνικών κυκλωμάτων. Επιπλέον, εμπλέκονται ένας αριθμός αντανακλαστικών, όπως το αιθουσοοφθαλμικό και το αιθουσονωτιαίο αντανακλαστικό, μαζί με πολλές άλλες ανώτερες εγκεφαλικές λειτουργίες. Υπό συγκεκριμένες συνθήκες, μια περιφερική ή κεντρική βλάβη μπορεί να συμβεί στο σύστημα οδηγώντας σε αστάθεια και συμπτωματολογία ιλίγγου. Από τη 1940, όταν οι Cooksey και Cawthorne ξεκίνησαν να διερευνούν την αποκατάσταση μετά από τέτοιες βλάβες, πολλά πράγματα έχουν αλλάξει στο πεδίο της αποκατάστασης ισορροπίας και κατά τις τελευταίες δεκαετίες οι νέες τεχνολογίες έχουν ενσωματωθεί σε αυτή την προσπάθεια. Σήμερα, ένας μεγάλος αριθμός από εφαρμογές mHealth, eHealth και εικονικής πραγματικότητας έχον αναπτυχθεί με σκοπό να συνεισφέρουν στη διάγνωση ή/και αποκατάσταση ασθενών με αιθουσαίες διαταραχές. Μεθοδολογία: Η ηλεκτρονική βάση δεδομένων MEDLINE διερευνήθηκε για σχετικές εργασίες από την 1η Ιανουαρίου 2015 έως την 15η Απριλίου 2021. Οι συμπεριληφθείσες στην ανασκόπηση εργασίες καθορίστηκαν βάσει συγκεκριμένων κριτηρίων ένταξης και αποκλεισμού. Αποτελέσματα: Ένας συνολικός αριθμός από 187 εργασίες προέκυψε μετά την αρχική στρατηγική αναζήτησης, από τις οποίες 43 κρίθηκαν επιλέξιμες και συμπεριλήφθηκαν σε αυτή την ανασκόπηση. Χωρίστηκαν σε 5 μείζονες κατηγορίες και συζητήθηκαν περαιτέρω. Συζήτηση: Οι κονσόλες παιχνιδιών, όπως το Nintendo Wii, το Nintendo Wii Fit και το Sony PlayStation 2 EyeToy, και οι εφαρμογές Internet έχουν χρησιμοποιηθεί τα τελευταία χρόνια για να συνδράμουν στη διάγνωση και αποκατάσταση ασθενών με διαταραχές ισορροπίας. Καθώς αναδύονται νέες τεχνολογίες και τα smartphones γίνονται βασικό μέρος της καθημερινότητας μας, η αιθουσαία διάγνωση και αποκατάσταση θα βασίζονται όλο και περισσότερο σε εφαρμογές για γυαλιά εικονικής πραγματικότητας, για smartphones και για εξελιγμένες πλατφόρμες.Background: Balance is a primary human sense which requires multisensory integration from the vestibular, the visual and the proprioceptive systems and involvement of the cerebellum and several other neural circuits. Additionally, a number of reflexes, such as the vestibuloocular and the vestibulospinal reflexes, along with many other higher cerebral functions are engaged. Under certain circumstances, a peripheral or central lesion can occur to the system leading to instability and vertigo symptomatology. Since the 1940s, when Cooksey and Cawthorne began to investigate rehabilitation following such lesions, many things have changed in the field of balance rehabilitation and during the last decades modern technologies have been incorporated in this effort. Nowadays, a great amount of mHealth, eHealth and Virtual Reality applications have been developed aiming to contribute in diagnosis or/and rehabilitation of patients with vestibular disorders. Methods: The electronic database MEDLINE was searched for relevant studies from January 1, 2015 up to April 15, 2021. The papers included in this review were determined according to certain inclusion and exclusion criteria. Results: A total number of 187 studies occurred after the initial search strategy, out of which 43 were considered eligible and included in this review. They were subdivided into 5 major categories and further discussed. Discussion: Gaming consoles, such as the Nintendo Wii, Nintendo Wii Fit and Sony PlayStation 2 EyeToy and Internet-based applications have been implemented during the last years to assist in the diagnosis and rehabilitation of patients with balance disorders. As novel technologies emerge and smartphones become an essential part of our everyday lives, vestibular diagnosis and rehabilitation will rely more and more on head-mounted display, mobile phone and sophisticated platform applications

Collision avoidance in persons with homonymous visual field defects under virtual reality conditions

AbstractThe aim of the present study was to examine the effect of homonymous visual field defects (HVFDs) on collision avoidance of dynamic obstacles at an intersection under virtual reality (VR) conditions. Overall performance was quantitatively assessed as the number of collisions at a virtual intersection at two difficulty levels. HVFDs were assessed by binocular semi-automated kinetic perimetry within the 90° visual field, stimulus III4e and the area of sparing within the affected hemifield (A-SPAR in deg2) was calculated. The effect of A-SPAR, age, gender, side of brain lesion, time since brain lesion and presence of macular sparing on the number of collisions, as well as performance over time were investigated. Thirty patients (10 female, 20 male, age range: 19–71years) with HVFDs due to unilateral vascular brain lesions and 30 group-age-matched subjects with normal visual fields were examined. The mean number of collisions was higher for patients and in the more difficult level they experienced more collisions with vehicles approaching from the blind side than the seeing side. Lower A-SPAR and increasing age were associated with decreasing performance. However, in agreement with previous studies, wide variability in performance among patients with identical visual field defects was observed and performance of some patients was similar to that of normal subjects. Both patients and healthy subjects displayed equal improvement of performance over time in the more difficult level. In conclusion, our results suggest that visual-field related parameters per se are inadequate in predicting successful collision avoidance. Individualized approaches which also consider compensatory strategies by means of eye and head movements should be introduced