The purpose of this paper is to investigate the surgical feasibility of implantation and long-term structural outcome of retina implant devices with an anterior IOL receiver, a connecting microcable and posterior segment epiretinal microcontacts. Implantation of epiretinal retina (EPI-RET) implants was performed as a one-step surgical procedure including phacoemulsification and pars plana vitrectomy in two adult rabbits. Implants were mechanically stabilized in an anterior position by the lens capsule and in the posterior segment by microtacks with a soft contact collar. Follow-up (6 and 9 months) included regular clinical examination, anterior and posterior segment photography and finally pathohistological evaluation. Implantation was uneventful in case 1 and complicated by vitreous space haemorrhage in case 2. At the end of follow-up, the retina was partially detached in animal 1 and subtotally detached in animal 2. Common features of tissue reaction in both cases were the formation of cyclitic membranes extending around and posterior to the anterior IOL receiver. In addition to that severe proliferations developed around microcables, microcontacts and microtacks forming a tissue capsule around posterior segment foreign materials. Retinal areas in contact to implant devices presented a severe structural damage and disorganization. Results of this preliminary trial suggest that the application of epiretinal prostheses with large diameter IOL receivers may be a critical issue and can give rise to an unfavourable outcome. Further systematic investigation ought to be performed involving a larger number of animals, modified implants and perhaps other species.

Presently there are several lines of new intraocular implants under development (retina stimulators, drug delivery systems and others) that necessitate novel anchoring techniques for the posterior eye segment. It was the aim of this study to test intrasclerally inserted titanium tacks for this purpose in rabbit eyes under long‐term observation. Insertion of titanium tacks was performed through vitreous cavity and retina into the sclera in six rabbits after vitreous removal by mechanical and enzyme assisted (plasmin) vitrectomy. Follow‐up (between 2 weeks and 6 months, median: 4.5 months) and outcome were analyzed using fundus imaging, echography, electroretinography, light microscopy (standard, immunhistochemistry), and scanning electron microscopy. Intraoperative handling of tacks (Heimann design) revealed as a critical manouver due to relatively high mechanical force necessary for insertion. Position of tacks was stable without any signs of extrusion, tilting or dislocation in all eyes during the whole follow‐up period. Tack surface in contact with ocular tissue was embedded by a thin capsule of fibroglial avascular tissue extending from choroid and retina. Scanning electron microscopy of explanted tacks did not present any sign of surface degradation. The retina around inserted tacks presented a regional fibroglial transformation and thickening limited to the surround of insertion (radial diameter < 750 μm). No significant signs of proliferative disease or retinal degeneration were detected outside this area by funduscopy, histology, or in electroretinography. In one case the retina detached due to intraoperative complications not related to the insertion. Results of this study demonstrate that intrascleral tacks provide principially a permanent, stable, and biocompatible option for posterior segment anchoring necessary for the mechanical stabilization of intraocular implants. It is desired to design mimimalized structures in order to limit the surgical trauma of tack insertion.

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