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.