Simulated prosthetic vision confirms checkerboard as an effective raster pattern for epiretinal implants

TL;DR

This study demonstrates that a checkerboard raster pattern in simulated prosthetic vision improves task performance and perceived ease, suggesting its potential as an effective activation strategy for retinal implants.

Contribution

It provides the first quantitative evaluation of raster patterns in simulated prosthetic vision, identifying checkerboard as superior for functional vision enhancement.

Findings

Checkerboard pattern yields higher accuracy and lower difficulty.

Horizontal and vertical patterns introduce motion biases.

Random patterns result in poorer performance.

Abstract

Spatial scheduling of electrode activation ("rastering") is essential for safely operating high-density retinal implants, yet its perceptual consequences remain poorly understood. This study systematically evaluates the impact of raster patterns, or spatial arrangements of sequential electrode activation, on performance and perceived difficulty in simulated prosthetic vision (SPV). By addressing this gap, we aimed to identify patterns that optimize functional vision in retinal implants. Sighted participants completed letter recognition and motion discrimination tasks under four raster patterns (horizontal, vertical, checkerboard, and random) using an immersive SPV system. The simulations emulated epiretinal implant perception and employed psychophysically validated models of electrode activation, phosphene appearance, nonlinear spatial summation, and temporal dynamics, ensuring realistic representation of prosthetic vision. Performance accuracy and self-reported difficulty were analyzed to assess the effects of raster patterning. The checkerboard pattern consistently outperformed other raster patterns, yielding significantly higher accuracy and lower difficulty ratings across both tasks. The horizontal and vertical patterns introduced biases aligned with apparent motion artifacts, while the checkerboard minimized such effects. Random patterns resulted in the lowest performance, underscoring the importance of structured activation. Notably, checkerboard matched performance in the "No Raster" condition, despite conforming to groupwise safety constraints. This is the first quantitative, task-based evaluation of raster patterns in SPV. Checkerboard-style scheduling enhances perceptual clarity without increasing computational load, offering a low-overhead, clinically relevant strategy for improving usability in next-generation retinal prostheses.