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S. Friderichs–Gromoll, B. Niggemann, H. Gerding; The Minimal Invasive Retinal Implant (miRI) Project: Histological Results After Long–Term Follow–Up of Implants in the Nonhuman Primate Model . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3163.
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© ARVO (1962-2015); The Authors (2016-present)
The object of this project was the development of a therapeutic method for retinopathy and the concrete aim to develop an implant for the rehabilitation of blind people. The cynomolgus monkey is used as an animal model because the anatomy of the eye is comparable to that of humans.
The eyes of three cynomolgus monkeys were histopathologically examined. Two animals had the extrascleral implants for 3 or 6 months with two electrodes, and the third animal for 6 months with ten electrodes.
Histological investigation showed a formation of a fibrous capsule around the implants. The capsule was relatively thin and inflammatory reactions were normally absent. Only minimal focal inflammatory cell foci were present in both animals with 2 electrodes. The animal with 10 electrodes showed a thicker capsule with slight diffuse inflammation and a mild inflammatory reaction in the muscular and fibrous tissue surrounding the implant capsule. The suture material was well tolerated in all three cases. The invasion of the electrodes through the sclera, chorioidea and retina was visible as an interruption of the three layers and the growth of fibrous tissue from subretinal layers into the retina. Only in the regions of penetration of the electrodes were the retinal layers disorganized, however, without inflammatory reactions. Regarding penetration and structure of the retina there was no difference between two or ten electrodes or 3 or 6 months implantation.
The histopathological results showed that the surgical procedure and the penetration of the retina with electrodes was well tolerated after 3 and 6 months of implantation. The only difference regarding the amount of electrodes was that with more electrodes present the inflammatory reactions of the tissue around the implants were slightly more pronounced.
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