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Gislin Dagnelie, Michael P Barry, Avi Caspi, Paul Gibson, Arup Roy, Alfred Vinnett, Reem Husseiny, Greg Seifert; Comparing thermal and visible light imaging for the Argus II retinal implant in real-world situations. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4568.
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Users of retinal prosthetic systems such as the Argus II have limited beneft from their restored vision due to poor resolution; in many real-world situations the scene is too cluttered to be understandable to the prosthesis user. We have previously shown benefit of thermal imaging as an input modality for Argus II retinal implant users that can simplify the image by only showing people and warm objects. In this study, advanced thermal imaging was compared to visible light imaging in real-life conditions.
Four end-stage RP patients, aged 55 to 84, with 1-9 years of Argus II user experience, were presented with scene presentations in thermal energy or visble light. To present the former, the video stream of a FLIR Lepton thermal sensor (80x60 pixels) was converted to NTSC video and spliced into the Argus II Video Processing Unit (VPU). Tasks ranged from localizing and counting cups of hot water to locating and counting people seated or walking past. In one person localization task, subjects had to indicate both absolute and relative positions of 3 persons sitting around a conference table
Locating and counting cups with hot water was performed with 90-100% accuracy for thermal, but at chance for visible imaging, due to poor visible contrast between cup and background. Absolute localization of persons using thermal imaging was hampered by lack of references in the background, but relative position was reported with over 90% accuracy, whereas only 60% accuracy was attained with visible imaging. Observing persons walking past, using thermal imaging, was also significantly more accurate than with visible imaging, but was limited by two factors: Body-covering clothing greatly reduced detection, and one participant was unable to perform the task due to many photopsias being reported as events.
These early results confirm that thermal imagery use with retinal implants can have benefits in real-world conditions. Benefits were limited by participants' lack of experience with thermal imagery, and we expect that the benefits of thermal presentation will increase with on-going practice. Continued experiments are in progress and a version of the equipment for home use is under development.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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