Development and evaluation of a visual aid using see-through display for patients with retinitis pigmentosa

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.

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.

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.

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.