Transchoroidal implantation of subretinal devices in rabbit : overview of experimental experiences

Abstract

Abstract: : Purpose: Electronic devices for the restoration of vision in degenerative retinal diseases are developed by different groups and first human trials have been realized. A surgical technique for implantation of subretinal devices is required, including explantability and reimplantabilitys of complex devices with intra– and extraocular parts. Experimental experiences with a transchoroidal access to the subretinal space without vitrectomy and retinotomy are presented here. Methods: Subretinal implantation was performed for acute (n=31) or chronic (up to 15 months) experiments (n=37) in 68 rabbit eyes through a transscleral, transchoroidal incision. Surgical outcomes including intra– and post–operative complications were reviewed. Histology was performed in 51 eyes. Results: Transchoroidal implantation of different implants was achieved without vitrectomy, retinotomy or synthetic vitreous substitution in 63 eyes (93%). In 33 eyes (49%) a small retinal break occurred at the entry site (33 eyes) or at the posterior pole (4 eyes) related to the particular design of the implant. In 4 eyes, implantation was not successful due to further retinal detachment, but it could be performed by using additional custom–made guiding foil in all other 29 eyes. Uncontrollable choroidal bleeding occurred in 1 eye. Explantations or reimplantations of devices were made following the same implantation route in 6 eyes. In acute experiments, histology showed well preserved retinal structures in the area of the implantation channel. In chronic experiments, the retina on top of the implant showed signs of atrophy after approximately 4 weeks, but neither retinal detachment stemming from iatrogenic retinal breaks nor severe inflammation or proliferative reactions were observed. Conclusions: While the absence of retinal detachment in the eyes with an iatrogenic retinal break at the entry site is possibly due to the special nature of the rabbit eye, particular caution should be taken to minimize such a complication in humans. Nevertheless, this novel surgical technique adds new aspects on the transchoroidal implantation or exchange of subretinal devices, thus opening new ways concerning the design and implantation of retinal implants either as electronic devices or drug delivery systems.

Keywords: retina • vitreoretinal surgery • vitreous