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Nicole Wagner, Jordan Greco, David Culp, Justin Prater, Brian Gilger; A Pilot Study to Evaluate Surgical Implantation of a Protein-Based Artificial Retina in a Rodent. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3942.
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© ARVO (1962-2015); The Authors (2016-present)
Bacteriorhodopsin-based retinal implants offer an approach to restore vision for patients blinded by retinal degeneration. The retinal implant, via an ion-mediated mechanism, stimulates degenerated retinal tissue. Following ex vivo preclinical studies, surgical methods were established to evaluate the tolerability of the device when implanted into Sprague Dawley (SD) rats.
A6-week, 18-rat study was conducted to evaluate the tolerability of the implant and the surgical procedures in SD rats. Three groups of 6 animals were used, including one group receiving BR-coated implant, one group receiving an un-coated control implant, and one group receiving a sham procedure. Subretinal implantation was achieved via a small incision through the conjunctiva and the posterior sclera. Optical coherence tomography (OCT), fluorescein angiography (FA), and fundus imaging were used to confirm placement of the implant and to assess potential inflammation.Electroretinography (ERG) and visually evoked potential measurements were taken at baseline and weeks 1, 4, and 6 to monitor the health and function of the retina. Central sections of each globe was H&E stained and examined to determine tolerability of the implant compared to the control procedures.
The OCT and fundus images show that the implants were delivered to the subretinal space, showing no significant differences in the general health between the sham and BR-coated implant groups. Despite some retinal deformation from the procedure, there was little observation of an inflammatory response throughout the study. Recorded ERG b-wave amplitudes across all groups and in both eyes were reduced at Week 1 compared to baseline measurements. By Week 2, and for the remainder of the study, b-wave amplitudes in operated eyes remained reduced compared to control eyes, though recovery to near-baseline amplitudes was noted throughout all groups by Week 6. Histology showed some focal retinal degeneration at the site of the implant, which is not unexpected given the subretinal placement of the implant.
A method of subretinal implantation of a BR-based retinal implant in SD rats was established. The BR-coated implant and substrate control were tolerated with minor fibrosis and inflammation noted, as a result of surgery. Based on the success of this study, an in vivo efficacy trial on Royal College of Surgeon rats has commenced.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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