Object identification by retinitis pigmentosa patients in dim light, using a Head Mounted Display

Abstract

Purpose: Retinitis pigmentosa (RP) results in peripheral vision loss and reduced, delayed dark-adaptation. In this study we assessed with affected individuals in dim light, the value of enhanced luminance image processing using a Head Mounted Display (HMD), to locate and identify objects.

Methods: We enrolled 12 patients with RP, complaining of night blindness to various degrees, (23 to 81 years old, mean = 43; visual acuity (VA) = -0.1 to +0.5 logMAR, mean = +0.15; horizontal visual field = 20° to 180°, mean = 52°). Dark-adaptation threshold was assessed with Goldmann-Weekers adaptometer. We used a non-immersive HMD (Lumus, Israel; Essilor Int. and Institut de la Vision, Paris) which provides a luminance-enhanced video image, displayed through transparent lenses. The experiment took place in a living room, including regular furniture. Before starting the evaluation, the tested subject viewed the furniture setting in photopic lighting condition (700 lux). Then, the subject turned his back on the scene, and the experimenter placed nine objects on various locations. Eventually lighting was abruptly reduced to 3 lux, and the, subject was asked to identify all added objects as quickly as possible. Trials were repeated three times, with and without the HMD. Between two consecutive trials, object locations were changed, and the subject was exposed to photopic condition during 5 minutes to prevent dark adaptation. The number of objects and the detection time were recorded.

Results: To identify the presented objects, four of 12 patients performed better using the HMD than without it (F(1,54) = 8.05; p < .01). In this group, three subjects had time-savings of mean 45.6 s with the HMD and two subjects were able to recognize more objects with the HMD (mean= 4.7). For these four subjects, alteration in dark adaptation and reduction in VA were more pronounced than for the remaining patients.

Conclusions: The luminance-enhanced image provided by the HMD improved object identification, following sudden reduction in lighting for patients with advanced RP. It may prove valuable in daily life, in such lighting conditions. Less affected Individual might also benefit from the HMD in dark environments if a more light-sensitive camera is used.

Keywords: 549 image processing • 719 scene perception • 702 retinitis