gms | German Medical Science

The subretinally implanted multi-electrode array and its external energy supply via a retroauricular plug requires an extraocular surgical procedure connecting the retroauricular access with the transchoroidal implanted chip via anterior orbit. A safe fixation of the implant in intraorbital and facial structures is mandatory for a successful chronic implantation in humans.

Up to now the device has been chronically implanted into 4 eyes of blind retinitis pigmentosa patients. Chip and stimulation electrodes are positioned on a small subretinal polyimide foil powered via a subretinal transchoroidal, retroauricular subdermal line ending in a radio-controlled, battery-driven receiver-box. The device was implanted into the subretinal space next to the foveal rim of two blind retinitis pigmentosa patients (see Sachs et al. 2006). The subretinal polyimide strip leaves the eye bulb between equator and pars plana through the choroid and a scleral flap. The foil carries connection lanes to a silicone cable that was positioned intraorbitally below the upper lid up to the lateral orbit bone and underneath the M. temporalis to the retroauricular access. The foil and silicone cable were stabilized by scleral and orbital rim fixation patches as well as a retroauricular metal clamp with bone screws. Explantation was scheduled after 4 weeks.

The implantation was successfully performed in all patients and the device was well tolerated without severe adverse events during the observation period. During the first few days after surgery swelling of the upper lid and mild tension during eye movements with conjunctival chemosis occurred. Patients did not report any irritation from the retroauricular plug. After one week the situation was stable and chronic stimulation could be successfully performed. According to study plan, implants were removed after 4 weeks. One patient decided to keep the implant. 6 months after implantation the intraorbital and facial device is still stable without any irritation in spite of the chronic foreign body and the retroauricular transdermal access for the silicone cable.

Our findings demonstrate for the first time the feasibility of a new surgical procedure for highly safe and controlled implantation of complex devices with subretinal and extra-ocular parts in blind humans. The access from the sclera via a loop to the lateral orbital rim with a transdermal cable behind the ear proved to be stable for more than 6 months.