PMMA Retinal Tack with Barb-shaped Scale bars for Retinal Prosthesis

Abstract

Purpose: : A PMMA (Poly-(methyl methacrylate)) retinal tack with barb-shaped scale bars is developed for retinal prosthesis. The proposed PMMA retinal tack has barb-shaped scale bars, which is intended to measure the penetration depth of an inserted 3D electrode in epiretinal implant of the electrode device.

Methods: : Previous retinal tack made with titanium or silicon is not suitable for measuring the depth using OCT, because of their non-transparency. In this research, PMMA is used, due to its transparency. The proposed retinal tack is fabricated using LiGA (Lithographie, Galvanoformung, Abformung) process, which can easily make micro-scaled structures with single x-ray lithography. After fabrication, the PMMA retina tack is implanted with epireitnal electrode onto the retinal surface of the rabbit eye. Using OCT, the number of the scale bars were checked, and then the penetration depth was postulated. In order to investigate the biocompatibility and durability, the implanted PMMA retinal tack is harvested after 4 weeks.

Results: : The size of the fabricated device is 0.55 mm × 1.7 mm, and the length of scale bars is 50 µm. The scale bars of the retinal tack could be discenable on OCT image. Through histological examination, no inflammatory infiltrates in retina, choroid, nor sclera is revealed. Scanning electron microscope (SEM) images show no chemical reaction trace nor mechanical fracture of the implanted device.

Conclusions: : The PMMA retinal tack is developed to measure the penetration depth of an inserted 3D electrode. The penetration depth data can be used to understand the relationship between penetration depth of the inserted 3D electrode and the threshold stimulation current.

Keywords: retina • retinal development • retinal degenerations: hereditary