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R. Iezzi, I. Glybina, R. Kannan, Y. Xu, R. Katragadda, G. Abrams; Electroretinographic and Histological Findings Associated With Chronic Subretinal Prostheses in Albino Sprague–Dawley Rats . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3181.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize the functional and histological impact of subretinal parylene retinal prosthetic devices with and without PLGA polymer coating in albino Sprague–Dawley rats.
18 albino Sprague–Dawley rats aged 5 weeks were used in the study: 6 animals received subretinal parylene implants (SRPIs); 6 animals received SRPIs coated with polylactic glycolic acid (PLGA) polymer; and 6 animals were unoperated controls. Surgery was performed on one eye in each animal, under sterile conditions, using isoflurane mask anesthesia. Animals were followed with fundoscopy, full–field electroretinography (ERG), and intraocular pressure (IOP) measurements prior to surgery and weekly after the surgery for 4 weeks. At the age of 9 weeks animals were euthanized and hematoxilin–eosin retinal histology was performed in all eyes. ERG amplitudes and histological cell counts were statistically analyzed using one way ANOVA with concomitant paired t–testing when valid.
During the follow–up period no retinal detachments or optical media opacities developed. Four weeks after subretinal implantation, eyes that received uncoated SRPIs demonstrated an 80% reduction of the ERG b–wave amplitude (pre: 1.24±0.4µV, post: 0.37±0.29µV, p<0.001). Eyes that received PLGA–coated SRPIs showed a 50% reduction of the ERG b–wave amplitude (pre: 1.16±0.38µV, post: 0.607±0.39µV, p=0.016). IOP did not show significant changes during the follow–up period. Quantitative histological analysis showed that the outer nuclear layer (ONL) cell counts in retinal areas overlaying the uncoated SRPIs were reduced by 66.7%, relative to unoperated controls and 63.4% (p<0.001) relative to fellow eye controls (p<0.001). In eyes that received PLGA–coated SRPIs, ONL density was 55.7% (p<0.001) lower relative to unoperated control eyes and 51.3% (p<0.001) lower relative to fellow eye controls.
Subretinal implantation of parylene–based SRPIs was associated with ONL cell loss, directly overlying the implants. PLGA–coated SRPIs were associated with reduced ONL cell loss and lower reductions in ERG amplitude, relative to uncoated SRPI devices. Consistent with our findings using subretinal polyimide implants, SRPIs are associated with ONL cell–loss, greatest in regions that directly overly the implant.
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