Trade-off between field-of-view and resolution in the thermal-integrated Argus II system

Abstract

Purpose : This study aims to investigate the effect of a wider field-of-view (FOV) of a thermal sensor camera integrated with Argus II retinal prosthesis system (Argus II) on Argus II wearers’ accuracy and response time in finding heat- emitting objects.

Methods : Four subjects who were blind due to end-stage retinitis pigmentosa and had been implanted with Argus II were recruited for this study. A thermal sensor camera is used to provide thermal imaging input which was eventually converted to electrical stimulation from the retinal prosthesis to the retina. The subject was sitting in front of a table and asked to perform two functional tasks. The first task was to identify the locations of two cups of hot water, which could be located either together or separately at one or two of the three locations: right, center, or left, respectively. The second task was to reach for a cup of hot water that is located at one of the three locations: right, center, and left (Figure 1). Two different FOV mappings were used for both tasks: a normal 1:1 mapping (no zoom) which provided 18° of FOV and a 3:1 mapping (zoom out) which had a FOV of about 50 °. Each task was repeated for twenty trials. The locations of the cups were randomized and pre- scheduled. The accuracy and response time were recorded and compared for the two different FOV mappings.

Results : All subjects showed either significantly higher accuracy (Wilcoxon test, ps < 0.001) or significantly shorter response time (ps < 0.05) to locate the two cups using the 1:1 mapping in comparison to the 3x wider FOV. One subject was also significantly faster (p < 0.001) and more accurate (p < 0.01) to reach for the cup with the 1:1 mapping.

Conclusions : The results suggested that a wider FOV mapping of the integrated thermal sensor camera with Argus II system made objects appeared smaller, which made more challenging for subjects to locate the targets. Argus II wearers can efficiently find heat-emitting objects using the integrated thermal sensor with the natural field-of-view.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Figure 1. Task 1 with 1:3 mapping (zoom out) which shows a wider field of view and smaller thermal targets, which are shown on the laptop screen.

 

Figure 1. Task 2 with 1:1 mapping (no zoom) which shows a large thermal target, demonstrated on the laptop screen.