(a) Photograph of the external portion of the Argus II prosthesis system (Second Sight Medical Products, Inc., Sylmar, CA) including glasses-mounted video camera, radio-frequency (RF) coil, and video processing unit (VPU) with rechargeable battery. (b) Photograph of the implanted portion of Argus II prosthesis system including the 610 electrode array, electronics case, and implant RF coil. (c) Fundus photograph of an Argus II array implanted in the macular region. A retinal tack secures the electrode array to the retina. The surgeon uses the white handle to position the device in the eye. Scale bar: 5 mm, corresponding to 16.7° visual angle. Adapted from Humayun et al [33].