Testing Visual Search Performance Using Retinal Light Scanning as a Future Wearable Low Vision Aid

Abstract

For the goal of designing a wearable low vision aid, aspects of both head-mounted display (HMD) design and performance evaluation were integrated into a single study of scanning ability. A head-mounted version of a novel retinal light scanning display known as the virtual retinal display was fabricated for this study. A remote head CCD (charge coupled device) attached approximately at the user's line of sight was used as the input source. Scanning ability was quantified as the time to identify a target in a wide field of distractors while using the HMD design in four different display interface modes (DIMs). Each DIM was tested with respect to their corresponding controls: A (augmented, see-through) and CO (center occluded) DIMs were compared to the augmented control (augmented, retinal display turned off), and CPO (center and periphery occluded) and PO (periphery occluded) DIMs were compared to the periphery occluded control (periphery obstructed, retinal display turned off). Each DIM was tested at high, medium, and low contrast levels. Five subjects were tested without optical correction (visual acuity worse than 20/200), which accurately represented low vision subjects. Results showed that for each DIM, scanning performance decreased as the contrast level decreased. At the lowest contrast level, the PO DIM provided the greatest and most significant improvement in scanning performance. At the medium and highest contrast levels, all DIMs provided equal or worse performance than their controls. Additionally, the subjects' natural visual acuity showed no correlation with scan time. All subjects reported a higher acuity with the retinal display, and showed a diverse range of preference for the most helpful DIM. Based on these results, we realized that low vision applications have unique design requirements unlike those for normally sighted users, and therefore customization of a wearable low vision aid may be an optimal design strategy.