Surgical Approach for the Implantation of a Ring Electrode into the Sulcus in a Phakic Non-human Primate

To evaluate the feasibility of surgical implantation of electrical components needed for the operation of biomimetic artificial intraocular lenses (IOLs) for presbyopia correction in phakic non-human primates. This included positioning a ring electrode into the posterior chamber sulcus, securing a circuit board-mounted implant under the superior rectus muscle, and placing a battery pack in the orbit. The full implant allows for recording and transmission of electrical signals within the ciliary muscle during accommodation.

The implant consists of a microcontroller, a biopotential amplifier, and a Bluetooth transmitter on a flexible printed circuit board (PCB), a battery, and the ring electrode. After mobilization and placement of traction sutures under three muscles, the PCB was positioned under the superior rectus muscle. The ring-shaped electrode was pushed into the anterior chamber via a clear cornea tunnel incision in the upper temporal quadrant. The electrode was carefully advanced under the iris with two forceps to prevent tilting and damaging the anterior capsule until its final position under the iris above the ciliary muscle.

During the implantation tests, in two eyes the ring electrode broke during the advancement into the posterior chamber underneath the iris. After optimizing the process, the device was successfully implanted in three eyes of three living phakic primates. An inflammatory response was visible during the postoperative follow-up period, but postmortem histopathological analysis revealed no clinically relevant adverse changes.

The primate model demonstrated the feasibility of the surgical implantation of a circular electrode into the posterior chamber. Regarding future developments of biomimetic accommodative IOLs, a concomitant improvement of surgical techniques and the device is crucial to ensure treatment success.