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Yvonne Luo, Indran Davagnanam, Lyndon daCruz; MRI Brain Scan in Argus II Retinal Prosthesis Patients. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1051.
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© ARVO (1962-2015); The Authors (2016-present)
To report the safety and feasibility of MRI brain scanning on 2 blind retinitis pigmentosa patients fitted with Argus II retinal implant for prosthetic vision. To our knowledge, these are the first two patients ever to undergo MRI brain scan in the presence of Argus II device. Being commercially available in Europe and with recent FDA recommendation for marketing approval, it is foreseeable that clinicians will encounter more and more patients with Argus II implants in the near future.
Two Argus II retinal prosthesis patients underwent MRI brain scans at 1.5 Tesla field strength for investigations of unrelated medical conditions. Changes in implant position are assessed by comparing color fundus photographs and OCT scans of the implant taken before and after MRI. Changes in implant function are assessed by comparing the impedances and thresholds of the 60 electrodes. Artifacts produced by the implant on MRI image are estimated. The subjects have been followed-up for 3 months and 15 months respectively and ongoing to report any adverse event.
Visual and quantitative comparison of the fundus photographs and OCT images respectively did not show any positional change of the implant in both patients. The frequency distributions of impedance readings for both implants are comparable before and after MRI indicating no significant change in retinal contact. Some deterioration in electrode thresholds are noted for both patients, but these are no greater than the general trend of threshold deterioration with time observed due to disease progression. The implant produces local moderate artifacts of up to 29mm x 37mm x 40mm (AP x TR x SI) which preclude visualization of intra-orbital contents immediately adjacent to the implant, but interpretation of other orbital and retro-orbital structures are possible. There is no adverse event e.g. implant dislocation, retinal detachment during the follow-up.
MRI brain scans have been performed on 2 patients fitted with Argus II retinal prosthesis to date with no adverse effect on patient safety and implant function. The implant produces a moderate size artifact on MRI to preclude visualization of intra-orbital contents, but interpretations of adjacent structures are reasonable.
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