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James D Weiland, Yi Zhang, Juan Carlos Martinez, Bruce Ash, Katie Markley, Helmut Eckhardt, Mark S Humayun; Evaluation of Implantation Feasibility of a Flexible, Tack-Free, Epiretinal Prosthesis in Yucatan Minipig. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4186. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
We tested a model of an epiretinal prosthesis with an intraocular polymeric buckle for tack-free fixation of the electrodes in close proximity to the retina. We assessed a surgical technique for epiretinal implantation and fixation and evaluated the long-term stability over 4 months in two Yucatan minipigs.
The inactive implants comprised of a flex circuit with 60 stimulating electrodes, a dummy silicon chip (with area equivalent to a 250 channel chip), two coils for power and data, and 6 off-chip capacitors were used to validate the chronic implantation. This device was implanted into one eye in each of 2 minipigs. A scleral pocket at the posterior pole of the eye was created to affix the external part of the implant first, and a pars plana approach was used to insert the electrode array and its buckle structure. Implants were planned for 4 months and ocular examinations with fundus photography and ultrasonography were performed at baseline and postoperative at regular intervals to identify the long-term retinal response and record any signs of inflammation, infection, or toxicity from the implant.
One linear pars plana incision of approximately 7.5mm was required to deliver the implant into the eye and another incision of 3mm (180° from the first one) was used to guide and affix the polymeric buckle on the pars plana. The size of incisions induced some bleeding, while the eye condition remained stable. Once in the eye, the implant was pressed gently against the retina by adjusting the polymeric buckle on either side. The buckle was sutured to the sclera on both sides of the eye. The surgery was completed in less than 4 hours. Post-operative follow-up revealed erosion of the conjunctiva over the areas where the internal buckle exited the eye, and concomitant movement of the array away from the retina. The eyes showed no signs of infection. An inferior nasal retinal detachment (caused during surgery) was observed in one eye. One minipig developed a cataract within two months, due to the forceps accidently contacting the lens during the implantation.
The surgical procedure for an epiretinal prosthesis with tack-free fixation appears feasible. An improved mechanical design of the scleral fixation method is needed for long-term stability.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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