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- Title
Transfer characteristics of subretinal visual implants: corneally recorded implant responses.
- Authors
Stingl, K.; Bartz-Schmidt, K.; Braun, A.; Gekeler, F.; Greppmaier, U.; Schatz, A.; Stett, A.; Strasser, T.; Kitiratschky, V.; Zrenner, E.
- Abstract
Purpose: The subretinal Alpha IMS visual implant is a CE-approved medical device for restoration of visual functions in blind patients with end-stage outer retina degeneration. We present a method to test the function of the implant objectively in vivo using standard electroretinographic equipment and to assess the devices' parameter range for an optimal perception. Methods: Subretinal implant Alpha IMS (Retina Implant AG, Reutlingen, Germany) consists of 1500 photodiode-amplifier-electrode units and is implanted surgically into the subretinal space in blind retinitis pigmentosa patients. The voltages that regulate the amplifiers' sensitivity ( V ) and gain ( V ), related to the perception of contrast and brightness, respectively, are adjusted manually on a handheld power supply device. Corneally recorded implant responses (CRIR) to full-field illumination with long duration flashes in various implant settings for brightness gain ( V ) and amplifiers' sensitivity ( V ) are measured using electroretinographic setup with a Ganzfeld bowl in a protocol of increasing stimulus luminances up to 1000 cd/m. Results: CRIRs are a meaningful tool for assessing the transfer characteristic curves of the electronic implant in vivo monitoring the implants' voltage output as a function of log luminance in a sigmoidal shape. Changing the amplifiers' sensitivity ( V ) shifts the curve left or right along the log luminance axis. Adjustment of the gain ( V ) changes the maximal output. Contrast perception is only possible within the luminance range of the increasing slope of the function. Conclusions: The technical function of subretinal visual implants can be measured objectively using a standard electroretinographic setup. CRIRs help the patient to optimise the perception by adjusting the gain and luminance range of the device and are a useful tool for clinicians to objectively assess the function of subretinal visual implants in vivo.
- Subjects
VISION disorders; ARTIFICIAL implants; ELECTRORETINOGRAPHY; RETINAL degeneration; VISUAL perception; PEOPLE with visual disabilities; MEDICAL equipment; DIAGNOSIS
- Publication
Documenta Ophthalmologica, 2016, Vol 133, Issue 2, p81
- ISSN
0012-4486
- Publication type
Article
- DOI
10.1007/s10633-016-9557-7