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U. Thelen, B. Niggemann, H. Gerding; The Minimal Invasive Retina Implant (miri) Project: Long-Term External Stabilization and Tissue Integration of Episcleral Implants. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2559.
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To analyze mechanical stabilization, tissue reaction and integration of episclerally sutured miRI prototypes with penetrating stimulation microelectrodes in a long-term experiment.
Implants with penetrating electrodes were episclerally sutured in 5 cynomolgus monkeys and clinically observed during a follow-up period of 3 (n=1) and 6 months (n=4). Each implant was stabilized by two intrascleral sutures running through fixation holes within the electrode carrier. The analyses included clinical evaluation, final passive eye motility test, biomicroscopy, and histological analyses of tissue reaction and integration.
Postoperative follow-up was uneventful in all cases without signs of prolonged (>4 weeks) anterior or posterior segment inflammation. At the time of explantation eyes were presenting free motility. All implants were embedded by a thin tissue capsule which was gliding within tenon's capsule. Implants were found in a stable position at the site of primary implantation. The inner surface of implants was directly in touch to the scleral surface. Histological examination presented a thin fibrous encapsulation of microelectrode carriers, and in some locations a very minor sheet of newly formed interfacial tissue between implant and scleral surface. The sclera was intact in all eyes. Secondary proliferation was not extending the implant area. Fibrocellular proliferation was forming a thin band along stabilizing sutures through the fixation holes forming bridges between sclera and implant capsule. In combination with the embedding capsule these proliferations were providing mechanical stabilization of implants. Stabilizing intrascleral sutures were running through the inner scleral lamellar layers without signs of tissue injury or inflammation. Signs of minor cellular reaction were found in two eyes (1x granuloma, 1x cellular infiltration of adjacent eye musle).
Episcleral suturing of implants provides a stable and biologically very well tolerated way of device implantation. Secondary proliferation contributes to a stable episcleral implant position. Relevant inferface proliferations between outer scleral surfaces and implants were not observed in this series. Email: firstname.lastname@example.org
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