Adaptive Gaze Strategies for Locomotion with Constricted Visual Field

Abstract

In retinitis pigmentosa (RP), loss of peripheral visual field accounts for most difficulties encountered in visuo-motor coordination during locomotion. The purpose of this study was to accurately assess the impact of peripheral visual field loss on gaze strategies during locomotion, and identify compensatory mechanisms. Nine RP subjects presenting a central visual field limited to 10–25° in diameter, and nine healthy subjects were asked to walk in one of three directions—straight ahead to a visual target, leftward and rightward through a door frame, with or without obstacle on the way. Whole body kinematics were recorded by motion capture, and gaze direction in space was reconstructed using an eye-tracker. Changes in gaze strategies were identified in RP subjects, including extensive exploration prior to walking, frequent fixations of the ground (even knowing no obstacle was present), of door edges, essentially of the proximal one, of obstacle edge/corner, and alternating door edges fixations when approaching the door. This was associated with more frequent, sometimes larger rapid-eye-movements, larger movements, and forward tilting of the head. Despite the visual handicap, the trajectory geometry was identical between groups, with a small decrease in walking speed in RPs. These findings identify the adaptive changes in sensory-motor coordination, in order to ensure visual awareness of the surrounding, detect changes in spatial configuration, collect information for self-motion, update the postural reference frame, and update egocentric distances to environmental objects. They are of crucial importance for the design of optimized rehabilitation procedures.

Visual brain plasticity induced by central and peripheral visual field loss

“…While the rest of visual field allows for an appropriate spatial orientation and navigation, its low spatial resolution impairs drastically object, face recognition and reading (Safran et al 1999 ; Boucart et al 2010 ). Reversely, peripheral visual field loss excludes the use of covert visual attention, constraining the affected individuals to increase their saccade rate to laboriously explore their environment (Authié et al 2017 ). Affected individuals preserve functions related to the high spatial resolution of the residual central vision such as face and small objects recognition but exhibit impaired spatial orientation (Wittich et al 2011 ) and scene perception (Fortenbaugh et al 2007 ), altered postural control (Berencsi et al 2005 ) and increased risk of object collision during locomotion (Turano et al 1999 , 2002 ) due to the limited coverage of the residual visual field.…”

Measuring dynamic levels of self-perceived anxiety and concern during simulated mobility tasks in people with non-neovascular age-related macular degeneration

“…We evaluated which types of mobility situations cause the greatest self-perceived anxiety for people with dry AMD. Our methods were novel and offer an important advantage over methods of assessing mobility directly in the real world or in a built life-like environment, such as the Pedestrian Accessibility and Movement Environment Laboratory at University College London, UK, 18 and the Streetlab artificial street, Paris, France, 19 in that they may be conducted in a safe environment, free from health and safety risks. The test may be presented in different ways, including through virtual/ augmented reality platforms, and on portable electronic devices.…”

Head and Gaze Behavior in Retinitis Pigmentosa

“…It is not clear to what extent results from the present study's highly synthetic tasks with limited field of view are generalizable to real-word conditions, but laboratory-based COMR has been shown to correlate well with ''outdoor COMR'' measured during passive viewing in a naturalistic setting. 24 In the only study to our knowledge that has commented on both eye and head movement in PVFL, Authié et al 7 showed that during locomotion, head position was more variable in RP than in controls, but eye position variability was similar. This result is congruent with our results, showing an increased propensity for head movement in RP.…”

“…6 In the only PVFL study to our knowledge that has considered the relative contributions of eye and head movement, participants with RP used increased horizontal head movement and a similar eye movement during locomotion compared with healthy sighted controls. 7 None of the aforementioned studies have considered age or field of view extent as possible correlates for eye and head behavior in RP. It is known that healthy subjects can adapt to artificial restrictions of the field of view or oculomotor range by increasing the relative contribution of head movement to overall gaze movement, but it remains unclear whether this effect is observed in RP.…”