Development and surgical implantation of a vision prosthesis model into the ovine eye

Purpose: A surgical technique was designed and tested to enable the implantation of an intraocular electrical retinal stimulator. Method: An inoperative perspex and silicone model was constructed to closely resemble the anticipated proper-ties of the proposed visual prosthesis. The animal model chosen for these experiments was the sheep, because the dimensions of its ocular anatomy are approximately 30% larger than the human's, being otherwise grossly similar. The surgical method involved transplanar port-hole lensectomy and vitrectomy, insertion of the model implant through a limbal incision, and fixation of the perspex subunit close to the location of the native crystalline lens, by way of trans-pars plana fixation sutures. Adequate preretinal positioning of the implant's silicone extension was obtained by way of its inherent elastic recoil. Results: The procedure was performed without macroscopic evidence of undue surgical trauma, Conclusion: Although further long-term experiments are required to fully assess the surgical procedure and biocompatibility of the implant, intraoperative assessment and postmortem computed tomographic imaging of the globe has confirmed the successful intraocular positioning and fixation of the implant.