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L. Wang, L. Yang, D. Duval, G. Dagnelie; Pursuit Eye Movement Initiation and Accuracy Are Affected by Implant Location in Simulated Prosthetic Vision. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2565.
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© ARVO (1962-2015); The Authors (2016-present)
Pursuit eye movement (EM) is an important oculomotor function to be rehabilitated in prosthetic vision (PV). A retinal prosthesis may be implanted extrafoveally and is of low resolution. We investigated the effects of implant location on pursuit initiation and accuracy in simulated PV.
PV was simulated as a grid of 10x10 dots. Each dot subtended visual angles of 0.94° x 0.92° with a Gaussian luminance profile. The PV covered a visual field of 9.4° x 9.2°, projected to a retinal area of the left eye via eye tracking. Two normally-sighted subjects (w51, w52) participated in the study. Ss were seated in front of a display and performed eye-tracking of a target moving horizontally from the central fixation point to the periphery and back at a constant velocity. Target movement direction and distance were randomized. Ss were required to press a button as soon as the target jumped. Each S performed the task in 4 viewing conditions: Normal vision, PV projected to the fovea, to 8° superior to fovea, and 8° right of fovea. Under each viewing condition, Ss tracked the target in two 40-trial sessions with target velocities of 4°/s and 8°/s, respectively. EM were assessed with initiation, measured by Latency defined as EM onset time minus target movement onset time, and accuracy, measured by horizontal Error defined as (Σ | eye position - target position |) / (Σ| target position |).
Ss showed (Table) longer mean Latency with PV than with normal vision (p<0.01) as well as larger mean Error (p<0.01). EM with the prosthesis implanted at 8° right of fovea had longest latency and greatest error. In PV conditions, EM showed saccade-like stepwise waveforms.
The results suggest that PV’s lower spatial resolution and extrafoveal implantation may have addictive effects on pursuit EM initiation and accuracy. If extrafoveal implantation is necessary, a retinal location superior to the fovea appears preferable over a location lateral to the fovea.
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