Pointing at static targets in a virtual reality environment: performance of visually impaired vs. normally-sighted persons

Abstract

Virtual reality (VR) offers innovative perspectives in the field of visual impairment. The general and exploratory goal of this study was to investigate how well the patients performed a pointing task compared to normally-sighted controls. We also assessed whether the characteristics of patients’ scotoma correlated with their performance in our pointing task. Normally-sighted and visually impaired subjects participated in a head contingent task developed with PTVR (https://ptvr.inria.fr/). Subjects had to move their head to point with a gaze-contingent reticle at a static target in the virtual environment. Pointing had to be maintained for 2 seconds to be validated (a timeout occurred after 30 sec without valid pointing). Reticle position in the headset’s viewport was either in the center (centered condition) or 10° from the center at one of the 8 possible half-meridians (eccentric condition). An additional perimetric exam was conducted for patients using a microperimeter (MP-3 Nidek Inc.), thus providing information about the position and shape of the scotoma. Our main dependent variable was the time needed to achieve valid pointing. We also estimated the accuracy of the subjects’ performance. Accuracy is the percentage of trials validated by the subject during the experiment. Linear mixed-effects models were used to analyze the reaction times of all subjects. Our preliminary data (N=8) show that visually impaired subjects are able to perform our head-contingent task. Although the reaction times were longer in the patients’ group (mean, 12.4 sec) than in the control group (mean, 4.6 sec). Patients had lower accuracy (87%) than normally-sighted subjects (100%). For the patients’ group, the results indicate an anisotropy of pointing performance across the reticle’s positions. Microperimetry data will help to understand how this idiosyncratic anisotropy may be related to the characteristics of each subject's scotoma. These data will help us develop rehabilitation tools based on pointing tasks.