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B. Niggemann, G. F. Weinbauer, H. Gerding; The Minimal Invasive Retinal Implant (miRI) Project: Implantation of the Utah Array With Long-Term Follow-Up in a Nonhuman Primate. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2553.
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To evaluate the biocompatibility of an extrasclerally implanted Utah array (100 electrodes) for up to 6 months in the nonhuman primate model.
The surgical concept was suturing of the implant onto the sclera temporal to the fovea to enable penetration of electrodes through sclera, choroidea and retina. With this method, vitrectomy or other treatment in advance of the surgery were not necessary. The Utah implant with 100 electrodes were fixed to remain in the cynomolgus monkey (M. fascicularis) eye for 6 months. Compatibility was checked by ophthalmoscopy, fundus photography, IOP, ERG, and VECP measurements as well as histopathology.
During follow-up only few electrodes were penetrating through sclera and choroid. IOP measurement did not show significant differences between the implanted right and the non-implanted left eye. There were no permanent changes in amplitudes or latencies of the ERG and latencies of the VECP were stable throughout the 6 months period. Formation of a relatively thin fibrous capsule around the implant was observed. Histopathologically, penetration of the sclera could detected by very few electrodes. Penetration was accompanied by signs of scleral degeneration. At the site of electrode penetration the retina presented destruction of inner and outer nuclear layers and degeneration of the pigment epithelium.
In this long-term oberservation an episclerally sutured Utah array did not penetrate the sclera in the intended way. Few electrodes penetrating the sclera seemed to induce an adverse reaction of the retina that resembles a toxic degeneration. The surgical procedure itself seems to be a feasible concept for implantation of a device onto the sclera.
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