Assessing visual acuity in visual prostheses through a virtual-reality system

TL;DR

This study uses virtual reality to simulate prosthetic vision, evaluating how resolution and field of view affect visual acuity, to guide future visual prosthesis development for blind patients.

Contribution

It introduces a VR-based simulation system for testing visual prosthesis parameters, providing new insights into optimal resolution and field of view for artificial vision.

Findings

Optimal field of view of 20° with 1000 phosphenes yields best acuity.

Visual acuity improves with phosphene density but plateaus below 20° FOV.

Simulation system aids in designing better visual prostheses.

Abstract

Current visual implants still provide very low resolution and limited field of view, thus limiting visual acuity in implanted patients. Developments of new strategies of artificial vision simulation systems by harnessing new advancements in technologies are of upmost priorities for the development of new visual devices. In this work, we take advantage of virtual-reality software paired with a portable head-mounted display and evaluated the performance of normally sighted participants under simulated prosthetic vision with variable field of view and number of pixels. Our simulated prosthetic vision system allows simple experimentation in order to study the design parameters of future visual prostheses. Ten normally sighted participants volunteered for a visual acuity study. Subjects were required to identify computer-generated Landolt-C gap orientation and different stimulus based on light perception, time-resolution, light location and motion perception commonly used for visual acuity examination in the sighted. Visual acuity scores were recorded across different conditions of number of electrodes and size of field of view. Our results showed that of all conditions tested, a field of view of 20{\deg} and 1000 phosphenes of resolution proved the best, with a visual acuity of 1.3 logMAR. Furthermore, performance appears to be correlated with phosphene density, but showing a diminishing return when field of view is less than 20{\deg}. The development of new artificial vision simulation systems can be useful to guide the development of new visual devices and the optimization of field of view and resolution to provide a helpful and valuable visual aid to profoundly or totally blind patients.