The Argus-II Retinal Prosthesis Implantation; From the Global to Local Successful Experience

Abstract

Over the past few years, visual prostheses (namely, Argus II retinal implant) and gene therapy have obtained FDA approval in treating blindness resulting from retinitis pigmentosa. Compared to gene therapy; Argus II is less costly with a demonstrated favorable outcome, though the vision is yet artificial. To obtain better results, expectation counseling and preoperative retinal assessment are critical. The global experience with Argus II has enrolled no more than 300 cases so far. The first Argus II retinal prosthesis in Iran was successfully implanted in Shiraz (October 2017). To date, Argus II artificial retina is implanted in four patients in Iran. Beside successful surgery and post-operative care, rehabilitation efforts with validated outcome measures including visual rehabilitation together with neurovisual, visuo-constructive and cognitive rehabilitation/empowerment approaches are expected to boost the functional outcome. A multidisciplinary approach within a cross-functional team would optimize strategies toward better patient outcomes. As such, establishing a collaborative network will foster organized research efforts to better define outcome assessment and rehabilitation strategies. This technology report paper has been an attempt to provide an overview of Argus-II retinal implant global experience as well as the clinical outcome of the so far cases in Iran. Insights from this report were communicated during the first “Brain Engineering and Computational Neuroscience Conference,” 31 January-2 February 2018 in Tehran.

Effect of the electrode array-retina gap distance on visual function in patients with the Argus II retinal prosthesis

“…The Argus II device is programmed at M1 for initial programming prior to turning on the camera in order to find stimulation levels that are suitable for the patient to be set on their Video Processing Unit (VPU) [ 4 , 5 ]. During the first session, the electrodes whose resistances are too high are disabled and the electrodes that are functional and usable are determined.…”

“…A quick scan of the array is done using various stimulation amplitudes to determine which electrodes are able to produce a percept or phosphene. The minimum current that is needed for the patient to see a phosphene 50 % of the time is defined for each electrode [ 1 , 4 ]. The video signal from the camera is mapped to the electrical signal for individual or groups of electrodes, determining which electrodes are being stimulated and at what respective frequency.…”

“…These values are set to the patients VPU to be used in different conditions [ 1 ]. Programming for this study included use of the “Programming Assistant” software that is designed to streamline the programming process to measure general sensitivity [ 1 , 4 ]. Through use of this software, the camera alignment process is simplified and comfort is determined under more real-world stimulation conditions [ 1 ].…”

Effect of the Electrode Array-Retina Gap Distance on Visual Function in Patients with the Argus II Retinal Prosthesis

“…A quick scan of the array is done using various stimulation amplitudes to determine which electrodes are able to produce a percept or phosphene. The minimum current that is needed for the patient to see a phosphene fty percent of the time is de ned for each electrode 1,4 . The video signal from the camera is mapped to the electrical signal for individual or groups of electrodes, determining which electrodes are being stimulated and at what respective frequency.…”

“…These values are set to the patients VPU to be used in different conditions 1 . Programming for this study included use of the "Programming Assistant" software that is designed to streamline the programming process to measure general sensitivity 1,4 . Through use of this software, the camera alignment process is simpli ed and comfort is determined under more real-world stimulation conditions 1 .…”