Wearable Technology With Head-Mounted Displays and Visual Function
Authors: Tsontcho Ianchulev, Donald S. Minckler, H. Dunbar Hoskins, Mark Packer, Robert Stamper, Ravinder D. Pamnani, Edward Y. Koo
Journal: JAMA (2014)

Letters RESEARCH LETTER Wearable Technology With Head-Mounted Displays and Visual Function Interest in wearable head-mounted display systems for gen- eral consumers is increasing, with multiple models in production. 1 However, their effect on vision is largely un- known. Peripheral visual field is a main component of vision and essential for daily activities such as driving, pedestrian safety, and sports. Conventional spectacle frames can reduce visual field, sometimes causing absolute scotomas (blind spots), 2 and head- mounted devices have even more pronounced frames. To quantify their effect on visual function, we compared perfor- mance on perimetric visual field tests with a head-mounted device vs regular eyewear. Methods | Three healthy emmetropic or refractively corrected individuals with 20/20 best-corrected visual acuity and nor- mal baseline visual fields were tested in April 2014. Partici- pants used a wearable device (Google Glass, Google Inc), fol- lowing manufacturer’s instructions, for a 60-minute acclimation period. Participants required minor adjustments to optimize screen visibility. To assess obstruction potential, the display prism’s position relative to the right eye pupillary axis was graded as (1) over central pupillary axis; (2) above cen- tral pupillary axis but inferior to superior limbus; or (3) above superior limbus. Immediately thereafter, participants underwent 30-2 and 60-4 threshold perimetric (visual field) testing with the Hum- phrey Visual Field Analyzer II-750i (Carl Zeiss Meditec). Test- ing was performed first with the device (with software deac- tivated to avoid distractions), followed by a control frame of similar color and temple width. The University of California, San Francisco, determined the study was exempt from insti- tutional review board review. To assess how the devices are worn by general consum- ers, photographs of people wearing the product and facing the camera, obtained from an Internet search conducted on May 1, 2014, were analyzed. 3 The image search included the term Google Glass. The full output of images was reviewed, includ- ing images posted by companies and individuals. Photo- graphs were assessed for prism position relative to the pupil with the grading system described above. Results | Figure 1 shows the baseline characteristics of partici- pants. Visual field testing demonstrated significant scotomas in all 3 participants while wearing the device (Figure 2; note variations in wearing and head position). In all 3 cases, more than 10° of visual field in the horizontal axis were subtended. Scotoma was absent with control perimetry testing with the regular frame. For the image analysis, 311 images were found, with 132 eli- gible for evaluation. The prism covered the pupillary axis in 29.5%, covered the eye but not the axis in 29.5%, and was su- perior to the limbus in 41%. Therefore, 59% had the prism in a position likely to interfere with vision. Discussion | To our knowledge, this is the first evaluation of the effect of wearable electronics with head-mounted display on vision. The device created a clinically meaningful visual field obstruction in the upper right quadrant. Defects were in- duced by the frame hardware design only and were not re- lated to a distracting effect of software-related interference. Image analysis further demonstrated that many people wear the device near or overlapping their pupillary axis, which may induce scotomas and interfere with daily function. This study is limited by the small number of participants, who may not be representative of all users. Even though the scotomas were easily identifiable, a larger sample is needed to identify factors that influence scotoma size and depth. The Figure 1. Baseline Characteristics of Participants Age, y Participant 1 Participant 2 Participant 3 Sex Male Male Male Race White Pacific Islander Asian Refraction oculus dexter (OD) a Plano Plano Best corrected visual acuity OD a Prism placed over the central pupillary axis Prism cleared the central pupillary axis but was inferior to the superior limbus Prism placed over the central pupillary axis Pupillary distance, mm Wearable device prism position a jama.com jamanetwork/2014/jama/05nov2014/jld140032 Indicates the right eye. JAMA November 5, 2014 Volume 312, Number 17 PAGE: right 1 SESS: 24 OUTPUT: Oct 17 11:34 2014