gms | German Medical Science

Objective: Suprachoroidal visual prostheses are joining their counterparts in epi- and sub-retinal neuromodulation with an aim to deliver meaningful visual percepts to recipients blinded by degenerative disorders of the retina. Here, we present the combined outcomes of a chronic, suprachoroidal device implantation study, and acute in vivo studies which demonstrate favourable tolerance of the device and advances in the strategic neuromodulation methods respectively.

Methods: A fully-implantable, split system visual prosthesis device (Phoenix99) was implanted in a cohort of Ovis aries (sheep). Daily monitoring and weekly imaging was undertaken over the course of up to three months after which the animals were humanely euthanaised and histological analysis undertaken. In parallel, a series of experiments were conducted in Rattus norvegicus (rat) wherein a retrobulbar electrode delivered electrical stimuli over a range of frequencies and pulse profiles and the effects recorded in the superior colliculus.

Results: Fundus, OCT and infra-red imaging demonstrated excellent stability of the electrode array over the course of the chronic study in all subjects. Histological analysis revealed good tolerance and acceptable responses. Acute studies revealed an array of strategic ‘tools’ that may be utilised in order to convey more meaningful visual percepts through variation of stimulation frequencies and pulse profiles.

Discussion: The combined outcomes of a well-tolerated implant design and stimulation strategies that produce favourable outcomes in the modulation of visual signals provides confidence that the next step of the Phoenix99 suprachoroidal implant should be a first in human test.