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S.R. Montezuma, J. Loewenstein, C. Scholz, J.F. Rizzo; BIOCOMPATIBILITY OF SUBRETINAL MATERIALS IN YUCATAN PIGS . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4169.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:To assess the biocompatibility of materials for possible use with a subretinal prosthesis. Methods:A single strip (0.5 x 5 mm; 10 µm thick) of either plain polyimide, or polyimide coated with: amorphous aluminum oxide; amorphous carbon; parylene; poly(vinyl pyrrolidone); or poly(ethylene glycol) were implanted in the subretinal space of Yucatan miniature pigs (n = 22). For each animal, pars plana vitrectomy and a local retinal detachment (created by subretinal injection of balanced salt solution) was performed. The implants were placed through the retinotomy, using an insertor. Electroretinograms (ERGs) were done pre– and post–operatively. Fundus photography was performed at monthly intervals. The animals were sacrificed at 3 months, and histopathological slides of the retina were prepared. The histological results were assessed for evidence of: inflammation; hemorrhage; outer nuclear layer or inner nuclear layer cell loss or disorganization; glial cell hypertrophy; fibrous encapsulation and retinal pigment epithelium abnormalities (i.e. disruption, proliferation, fibrous metaplasia or migration). Results:The local retinal detachments resolved rapidly, and the strips remained in a stable subretinal position in all but 2 eyes, both of which were implanted with amorphous aluminum oxide strips. Across all animals the mean ERG amplitude (b–wave) was reduced at one week (non–statistically significant) and then remained stable or showed recovery to or above baseline. Histologic examination revealed disorganization of the outer nuclear layer with some loss of the photoreceptors cells and pigment migration in all specimens. Fibrous membranes (< 10 µm thickness) covering part or all of the implant were found in eyes implanted with all materials except amorphous carbon, upon which there were scattered, ectopic pigment epithelial cells but no contiguous fibrous band. However, retinas with amorphous carbon implant were more disorganized. Conclusions:Following subretinal implantation of non–electrically active strips, all slides showed some abnormalities but no gross inflammatory reaction, fibrous proliferation, or retinal pigment epithelial proliferation was evident. Generally, the inner retina was well–preserved, and the retina away from the implant was normal in all samples. Only amorphous carbon–coated polyimide strips were free of a fibrous coating post–implantation.
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