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H. Ezelius, H. Gerding; The Minimal Invasive Retinal Implant (miRI) Project: Risk Analysis of Different Retinal Prosthetic Devices and Design of a New Concept . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3176.
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The purpose of this project was threefold: 1. to analyze final results of a large series of experimental retinal prostheses implantations in rabbits, 2. to analyze available risk data on similar implant projects and other references concerning intraocular foreign bodies and implants, and 3. to design and modify a principally new minimal invasive retinal prosthetic technology.
The final outcome in our series of combined anterior–posterior segment or solely posterior epiretinal implantations in rabbit eyes (n=31) was analysed including clinical, electrophysiological, histological, and immunhistochemical data. Data resource (Medline & Current Contents) analysis on similar projects, other intraocular implants and foreign structures was performed. Results of this analytical process were integrated into the design process of the novel minimal invasive retinal prosthetic system.
Experimental testing of epiretinal implants resulted in a favourable outcome in 10/31 eyes (2/8 eyes with combined anterior/posterior segment implants, 8/23 eyes with posterior segment implants). 8 of 10 eyes with favourable outcome were presenting regional retinal damage related to the implantation or implant position. 17 of 31 eyes presented macroscopically detectable PVR with partial or total retinal detachment. The outcome was especially poor in combined anterior/posterior segment implants. The latter were only successful in cases with an anterior implant diameter not extending the size of conventional intraocular lenses. Results of this study and data bank metaanalyses clearly provided evidence that surface area, dimension, and mass of the implant ought to be reduced as far as possible. In addition to that the extend of intraocular surgery seems to be an independent risk factor. On the basis of these results a concept was designed which allows to place all components of the implant outside the globe with the only exception of stimulation electrodes. The latter are designed so that they will penetrate the scleral, choroid, and retina from the outer ocular surface towards the intraocular compartment.
The results of our experimental series and metaanalytical data clearly demonstrate that the implantation and long–term observation of intraocular retinal implants may be accompanied by a high rate of severe complications. Therefore we designed a new minimal invasive retinal prosthesis.
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