3. Conclusions 2. Methods 1. Introduction

Assessing Patients with Central Field Loss Using a Low-Cost Virtual Reality System with Head Tracking

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Giovanni Fusco, Natela Shanidze and Preeti Verghese The Smith-Kettlewell Eye Research Institute {giofusco, natela, preeti}@ski.org

1. Introduction Central visual field loss is a common problem among the elderly, who experience difficulties in performing daily tasks. Low-cost Virtual Reality (VR) could be used as a rehabilitation tool, emulating aspects of daily life in a safe environment. To assess the feasibility of this approach we set out to determine: • Can older adults with poor vision enjoy an immersive virtual reality setup? • Do they perceive depth, given that many of them have poor stereopsis? • Are there adverse effects of using a head-mounted virtual reality system in the elderly? • Can this VR tool be used to assess visual perception and monitor head movements? We introduce a novel testing environment with both monocular and binocular cues to depth, using a low-cost custom handheld VR simulation on an Android smartphone.

2. Methods Using the free 3D game engine (Unity 3D), we designed an immersive environment with robust depth cues (perspective and looming).

3. Participants identified a letter in the center of the wagon wheel.

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Press when Wagon Wheel spotted

User

1. Participants were presented with a looming wagon-wheel and were asked to push a lever when they spotted it. 2. Observers reported the number of spokes (3, 5, 7; number and location randomly assigned)

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Head Movement

The second part of each session consisted of three tasks:

System

At the beginning of each session, we tested the acuity of the pariticipants in the VR headset using a single letter Fig. 1 - 3D environment with an example of stimulus used for acuity assessment. with size controlled by a 2 up - 1 down staircase. The threshold letter size was used for Trials Overview the rest of the experiment. Looming Wagon Wheel

P i t c h

Count spokes

Report letter

Restart

Head stability was recorded using the smartphone’s accelerometer, sampled at 30Hz. Each experiment consisted of 1 acuity assessment and 15 trials. Participant Age Gender P1 P2 P3 P4 P5 C1 C2

87 91 71 68 73 74 70

F M M M F M F

Dx(R/L)

Stereo Acuity (arcsec)

nAMD

1421 1482 1136 960 1368 N/A N/A

aAMD/nAMD & aAMD

---/nAMD OT AMD Control Control

• 3. Conclusions

• All partipants were enthusiastic about the immersive experience and reported perceiveng depth; • Acuity test is limited by screen resolution • Participants did not experience motion sickness, discomfort or fatigue • Head movements can be recorded in real time and resolved to a fraction of a degree

Fig. 2 - Example of recorded head movements for control (C2, top panel) and patient (P5, bottom): each colored dashed line represents a single trial, the average is in solid black, while the dotted vertical line marks when the button press occurred.