Retinal dystrophies and age-related macular degeneration related to photoreceptor degeneration can cause blindness. In blind patients, although the electrical activation of the residual retinal circuit can provide useful artificial visual perception, the resolutions of current retinal prostheses have been limited either by large electrodes or small numbers of pixels. Here, we report the evaluation, in three awake non-human primates, of a previously reported near-infrared-light-sensitive photovoltaic subretinal prosthesis. We show that multi-pixel stimulation of the prosthesis within radiation-safety limits enabled eye tracking in the animals, that they responded to the stimulations in the direction of the implant with repeated saccades, and that the implant-induced responses were present two years after device implantation. Our findings pave the way for the clinical evaluation of a 378-electrode prosthesis in patients affected by dry atrophic age-related macular degeneration.

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During diseases such as age-related macular degeneration, glaucoma, or retinal degeneration, visualizing and counting retinal cells would be of interest to diagnose early stages and to determine the short-term progression rate of these conditions. This is of major interest to optimize neuroprotective/regenerative therapies in these slowly progressive diseases. Such cellular imaging is already feasible in the eye of laboratory animals. In the near future, it is likely that visualization of individual neuronal cells in humans will become a routine clinical procedure, thanks to continuous technological improvements in optical imaging technologies. In mice, commercially available confocal scanning laser ophthalmoscope (cSLO) allows imaging of axons, capillaries, as well as dye-labelled cells (such as gfp-expressing cells). In humans, commercially available optical coherence tomography (OCT) allows routine imaging of retinal layering, but not of individual cells. Several research groups (including ours) are working in the highly competitive area of retinal cellular-imaging in humans. Different systems of adaptive optics, SLO, and OCT (in spectral domain a-mode or en face mode) and second harmonic generation imaging are under evaluation. These techniques have demonstrated cellular-level imaging capabilities of photoreceptors, of the nerve fibre layer and of capillaries. The main challenges that these systems face are biological (determination of the origin of the signal), medical (the clinical pertinence of the information) and technical (optimization of hardware, development of user interface).

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