Abstract
Purpose
Patients in the early stage of retinitis pigmentosa (RP) suffer from night blindness and, therefore, have mobility problems at night. To assist such patients with walking in the dark, we developed a wearable visual aid utilizing a see-through display upon which assistive images from a high-sensitivity video camera are superimposed. We evaluated the efficacy of our new visual aid for RP patients.
Methods
The device is equipped with a camera with a minimum illuminance of 0.08 lux and a view angle of 53° × 40°. The experiment was conducted in a room with dimmed light (illuminance level 0.2–1.2 lux). Eight subjects with RP were instructed to arrive at a goal 16 m away from the starting point, both with and without the device, passing through four 1.5-m-wide gates consisting of pairs of black square carpet pieces, white poles, red and white traffic cones and cardboard boxes with and without the device in a darkened room. Three gates, except for the boxes, which were nearest the goal, were randomly arranged along the x-axis at each trial. The number of trial failures and the time required to walk the course were assessed as outcomes.
Results
Seven of the 8 subjects could walk with the aid of the device without any failure. With the device, the number of trial failures significantly decreased in number (p < 0.05) in all subjects.
Conclusions
This device enabled the subjects to see objects that could not be recognized by the unaided eye. Our visual aid effectively assisted RP patients with night blindness.
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Acknowledgments
This work was supported in part by a grant from the Association for Technical Aids in Japan (2008).
Conflicts of interest
Y. Ikeda, None; E. Suzuki, Employee (Tokai Optical); T. Kuramata, Employee (Tokai Optical); T. Kozaki, Employee (Tokai Optical); T. Koyama, Employee (Tokai Optical); Y. Kato, Employee (Tokai Optical); Y. Murakami, None; H. Enaida, None; T. Ishibashi, None.
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Supplementary material 1 Supplementary Video 1. The walking test without the device (Subject No. 6). The subject (No. 6) walked toward the goal without the device. She stumbled over the first piece of black carpet. She could see the white poles and walk between them; however, she could not see the red and white traffic cones or cardboard boxes. It took her 26 s to arrive at the goal. (MPG 2,882 kb)
Supplementary material 2 Supplementary Video 2. The walking test with the device (Subject No. 6). The same subject (No. 6) walking with the device. She could see all the gates and successfully walk toward the goal. The entire trip took 23 s. (MPG 2,506 kb)
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Ikeda, Y., Suzuki, E., Kuramata, T. et al. Development and evaluation of a visual aid using see-through display for patients with retinitis pigmentosa. Jpn J Ophthalmol 59, 43–47 (2015). https://doi.org/10.1007/s10384-014-0354-0
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DOI: https://doi.org/10.1007/s10384-014-0354-0