Multiple Microphotodiode Array (MPDA) Implantation in the Minipig Model

Abstract

Abstract: : Purpose: The implantation of single subretinal MPDA´s was successfully demonstrated in the past. Crucial for retinal prosthesis development is the practicable size of a subretinal implant. Larger useable contact areas are desirable however conflict with surgical requirements. Therefore the possibility of the implantation of multiple MPDA´s was evaluated. Methods: 4 Yucatan micropigs received multiple MPDA´s in a single ppV. After complete vitrectomy balanced salt solution (BSS) was injected into the subretinal space with a teflon canula. Viscoelastic substance followed. Up to 3 MPDA´s were implanted via a single retinotomy. All chips were placed in the regio macularis of the minipig. Viscoelastic substance was removed and the retina reattached. The routine postoperative follow up consisted of ophthalmology, fundus photography, fluorescein angiography (FLA) and optical coherence tomography (OCT). Results: Multiple implantation of subretinal MPDA´s could be demonstrated successfully. The postoperative course is not different from single implantations. However the implantation procedure and the positioning of the implants is more complex. All implants remained stable in the follow up period up to 6 month. Fluorescein leakage did not appear and vessels remained stable. The OCT findings did not differ from those of single implants. Conclusion: Subretinal implantation of MPDA´s is limited by surgical factors. It remains unclear how many of the chips can be implanted until the total permanently from the RPE separated retinal area exceeds a critical threshold and retinal complications appear. The findings rise the hope that at least larger or multiple areas could be used for prosthetic supply.

Keywords: 554 retina • 316 animal model