The Argus II prosthesis facilitates reaching and grasping tasks: a case series

BACKGROUND To evaluate the reach-to-grasp performance of patients fitted with an epiretinal artifical retina device. METHODS This was a hospital-based case series consisting of six patients fitted with the Argus II (Second Sight Medical Products Inc, California, USA) retinal prosthesis. Participants were asked to reach out and pick up a high-contrast cuboid object with the prosthesis in the 'On', 'Off' or 'Scrambled' setting presented in a randomised order. The 'Scrambled' setting consisted of a random, scattered signal presented to the prosthesis. The session was repeated after a 4-6 week period. Hand movements were measured using motion detection cameras. The number of successful object grasps was calculated. RESULTS The number of successful grasps was greater with the prosthesis in the 'On' setting (visit 1: median [interquartile range] percentage success: 'Off' = 0 [0 to 50]%, 'On' = 69 [67 to 95]%, 'Scrambled' = 59 [42 to 95]%; Friedman Chi-squared test statistic 6.5, p = 0.04; visit 2 median [IQR] percentage success: 'Off' = 0 [0 to 25]%, 'On' = 69 [53 to 100]%, 'Scrambled' = 28 [13 to 63]%; Friedman Chi-squared test statistic 8.4, p= 0.02). CONCLUSIONS The use of an electronic retinal prosthesis facilitates reach-and-grasp performance. Further work should explore how performance can be improved with targeted rehabilitation.