Tech Briefs

Rehabilitation of Visual and Perceptual Dysfunction after Severe Traumatic Brain Injury (TBI)

A new optical device could help those with TBI detect and avoid obstacles on the affected side.

The aim of this work is to conduct preliminary evaluations of new rehabilitation strategies and new functional assessment methods for homonymous hemianopia (HH) and spatial neglect (SN), two disabling visual and cognitive perception conditions that commonly occur as a result of severe traumatic brain injury (TBI) and stroke. Both HH and SN prevent detection of objects on completed the protocol: an 18-year-old male with left HH without SN, who has had HH for two years as a result of an arteriovenous malformation that required surgery.

S1 advanced through the entire six levels of perceptual motor training in 176 minutes of on-task “run time” accumulated over seven 90-minute visits (approximately two visits per week for four weeks). The median on-task run time for each visit was 26 minutes, with the other time dedicated to set-up, rest breaks, and discussion. Data were collected for each task, in addition to a “standard” task run twice at each visit to enable comparisons of within-visit and between-visit performance.

At the beginning of training, touches to targets presented in the prism zone were inaccurate by an amount equal to the displacement of the prism (i.e. about 30° to the right of the real position). As training progressed and S1 learned to use visual feedback to guide his finger to touch the real position of the target in the prism zone, touch accuracy improved until it was as good as the accuracy of touch to targets in the seeing hemifield. When first using visual feedback, reaction times for touching targets in the prism zone increased and then gradually decreased over subsequent visits until reaction times were similar for touches in the prism zone and the seeing hemifield. By visit six, these improvements in touch accuracy and reaction times to targets presented in the prism zone were sustainable (between visits).

Each driving simulator assessment comprised five test drives (each about 10 minutes) on pre-determined routes guided by computer-generated, spoken navigation cues (similar to GPS instructions). While driving, the participant’s primary task is to press the horn button whenever he/she detects a pedestrian figure that appears periodically at small and large eccentricities on the right and left of the roadway. The pedestrian figures move with biological motion toward the road on a collision course, but do not enter the travel lane. The driving is highly engaging as there is other traffic on the roads and the participants have to obey all the normal rules of the road. Main outcome measures are detection rates and reaction times.

S1 demonstrated marked improvements in blind side detection rates and reaction times when driving in the simulator with EP glasses after training, compared to without the EP glasses before training. In particular, detection rates for pedestrians at large eccentricities on the blindside (outside the usual scanning area of S1 but within the visual field expansion range of the EP glasses) improved from 38% to 100% and the median blind side reaction time improved from 5 s to 1 s. These detection rates and reaction times were as good as those on the seeing side (100% and 1 s). Gaze-tracking data was collected that shows detection of blind side pedestrians without scanning, strongly suggesting the prism-expanded vision was utilized.

This work was done by Eli Peli, Alex Bowers, Robert Goldstein, Gang Luo, Kevin Houston, and Jeff Churchill of Schepens Eye Research Institute for the Army Medical Research and Materiel Command. ARL-0146