In Europe, patients with vision loss due to severe retinal degeneration have had an option to regain some functional vision in the form of the Argus II retinal prosthesis for eight years. The implantable device has yet to be approved in the United States, but the European market has provided US researchers a testing ground.

A Germany-based research team followed 47 patients for 12 months or longer after implantation in the first year of post CE-approval. They were primarily focused on uncovering the nature and rate of adverse events. The study shows that, of 47 adults with the implant, 49% experienced non-serious adverse events (51 in total) and 26% experienced serious adverse events (13 in total, although only nine were related to the device). The most common of the serious adverse effects was conjunctival erosion, but this was only experienced by four patients.

Secondary endpoints of the study included the outcomes of three visual function tests for patients with the implant: square localization, direction of motion and grating visual acuity.

When averaged across the group, patients’ accuracy on the square localization test, but not on the direction-of-motion test, appeared better when the Argus II was on than when it was switched off. For grating visual acuity, more patients at each point in time achieved the 2.9 grating visual acuity cutoff in the implanted eye when the Argus II was on compared with it switched off.