Subjects Implanted With the ArgusTM II Retinal Prosthesis Are Able to Improve Performance in a Spatial-Motor Task

Abstract

Purpose: : To determine to what extent subjects implanted with the Argus II retinal prosthesis can improve performance compared with residual native vision in a spatial-motor task.

Methods: : White square stimuli (2.3 inch sides) were displayed in random locations on a 19" LCD touch screen monitor with a black background located 12" in front of the subject. Subjects were instructed to locate and touch the square center with the system on and then off (40 trials each). The coordinates of the square center and of the location touched were recorded. For twelve subjects dark-adapted luminance threshold was measured using the Espion Full Field Stimulus Threshold (FST) test (Diagnosys, Lowell, MA).

Results: : 96% (26/27) of subjects show a significant improvement in accuracy and 93% (25/27) show a significant improvement in repeatability with the system on compared with off (p<0.05, Student’s t-test). A group of five subjects (group A) that had both accuracy and repeatability values <250 pixels (2.9") with the system off (i.e. using only their residual vision) was significantly more accurate and repeatable than the remainder of the cohort (group B)(difference of means analysis; p<0.01). Group A also had a corresponding lower FST threshold (difference of means analysis; p<0.01) compared with group B, and there was a significant correlation between FST threshold and accuracy with system off (R2=0.40; p<0.05). 80% (4/5) of subjects with comparatively good light perception (group A), showed a significant improvement in both accuracy and repeatability with the system on.

Conclusions: : Artificial vision augments information from existing vision in a spatial-motor task in retinal prosthesis implant recipients. We believe this is the first report of a visual prosthesis improving the performance of subjects with a measurable amount of bare light perception in a spatial-motor task. The results presented here are also on the largest cohort of visual prosthesis recipients to date.

Clinical Trial: : www.clinicaltrials.gov NCT00407602

Keywords: clinical (human) or epidemiologic studies: outcomes/complications • low vision • degenerations/dystrophies