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H. Ameri, T. Ratanapakorn, S. Ufer, H. Eckhardt, M.S. Humayun, J.D. Weiland; Surgical Challenges of Large Epiretinal Array Implantation . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3198.
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To assess the feasibility of surgical implantation of large epiretinal array through a small sclerotomy and to evaluate the mechanical effect of the array on the retina.
Four large epiretinal arrays, each 10 mm in diameter, were chronically implanted in four dogs. The arrays are made of a flexible polymer (polyimide) and are designed to allow overlapping of different parts. Surgical implantation involved standard pars plana vitrectomy with peeling of posterior hyaloid membrane. The array was then introduced into the vitreous cavity after one of the sclerotomies was extended to about 5 mm. Following insertion, the array regained its original shape spontaneously and was then fixed on the retina with an Alcon/Grieshaber retinal tack. Postoperatively the animals had weekly ocular examination and had color fundus photograph, fluorescein angiogram and Optical Coherence Tomography (OCT) in a monthly basis. The follow up ranged between six weeks to six months.
In all cases it was possible to insert the array into the vitreous cavity through a 5 mm scleral incision. All arrays appeared to conform to the curvature of the retinal surface at the end of surgery, except in one case that there was minimal elevation of part of the array. Follow up examinations with OCT showed partial separation of the arrays from the retinal surface in all cases. Two dogs were implanted for six months with only minor complications, a third dog was sacrificed at three months due to retinal detachment, and a fourth dog was sacrificed at six weeks due to vitreous and lens opacity. OCT showed that in some areas, the arrays were within 10 microns of the retina, whereas in other areas they were up to 600 microns from the retina. In all cases there was minimal to moderate vitreous hemorrhage from sclerotomy wounds at the end of surgery (after removal of the infusion terminal), which was spontaneously resolved within two to three weeks without recurrence. In three cases, the tacks became progressively loose within 3 weeks. Other findings include retinal pigmentation and corresponding leakage on fluorescein angiogram around the tack and some other areas in almost all cases, retinal fold at the edge of the array in three cases, and retinal tear at the edge of the array in one case.
This study demonstrated the challenges of implanting large epiretinal arrays. Long–term biocompatibility issues that need to be addressed relate to pressure on the retina at the edges and maintenance of close proximity between the array and retina.
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