gms | German Medical Science

Purpose: The Argus II System is being studied in an ongoing clinical trial to determine ist safety and probable benefit (clinicaltrials.gov NCT00407602); here, we present 5-year data from the clinical trial.

Methods: All subjects implanted with a Second Sight Argus II System were blind (bare light perception or worse) from retinitis pigmentosa or similar disorders. In the clinical trial, visual function was evaluated by visual function tests such as Square Localization (the ability to locate and touch a high-contrast target), Direction of Motion (the ability to determine the direction of a high-contrast bar), and Grating Visual Acuity (the ability to distinguish the orientation of black and white bars of different widths). Assessments of functional vision included controlled Orientation and Mobility (O&M) tasks and self-report questionnaires. All outcome measures were performed with the System ON and OFF.

Results: Thirty (30) subjects were implanted at 10 centers in the clinical trial. As of October 15, 2015, subjects (excluding three who have been explanted) have been implanted an average of 7.1 ± 0.9 years (range of 6.0 – 8.4) – over 200 subject-years total. The Argus II remains implanted and functioning in 24 subjects. The safety profile remains acceptable: up to 5 years post-implant, there were a total of 24 serious adverse events, which were addressed with standard ophthalmic techniques. There were no lost eyes. At five years post-implant, performance improved with the System ON compared to OFF for 81% of subjects on Square Localization, 50% of subjects on Direction of Motion, and 38% of subjects on Grating Visual Acuity. As a group, performance on the Door and Line O&M tasks was significantly better with the System ON than OFF.

Conclusions: With over 200 cumulative subject-years of clinical trial follow-up on 30 clinical trial subjects, this is the largest and longest-running study of a visual prosthesis to date. The results validate that the Argus II prosthesis improves visual function and functional vision over five years of chronic device use, beyond the time frame reported previously. Current research efforts are directed toward a feasibility study for age-related macular degeneration and the development of a prosthesis for the primary visual cortex.