Background: Due to low energy levels in microphotodiode based subretinal visual prostheses external power supply is mandatory. We report on the surgical feasibility and the functional outcome of the extra-ocular part of an approach to connect a subretinal prosthesis to an extra-corporeal connector in the retro-auricular space via a trans-scleral, trans-choroidal cable.
Methods: Seven volunteers with retinitis pigmentosa received an active subretinal implant; energy was supplied by gold wires on a trans-sclerally, trans-choroidally implanted polyimide foil leading to the lateral orbital rim where it was fixated and connected to a silicone cable. The cable was implanted subperiostally beneath the temporal muscle using a trocar to the retro-auricular space where it penetrated the skin for connection to a stimulator. To avoid subretinal movement of the implant three tension relief points have been introduced.
Results: All implantations were performed as planned without complications, no serious adverse events occurred in the post-operative period. Fixation of the implants was stable throughout the entire study duration of 4 weeks; permanent skin penetration proved to be uncomplicated. Motility was minimally restricted in downgaze and ab-/adduction. Explantation was uneventful.
Conclusion: The above described procedure provides a method for stable fixation of a subretinal device with a trans-scleral, trans-choroidal cable connection to an extra-corporeal connector.