The Perceptual Experience of Argus II Users

Not Applicable

Completed

Brief Summary: This Basic Experimental Studies Involving Humans (BESH) study investigates phosphene perception and performance factors in blind participants implanted with the Argus II retinal prosthesis system. Using paired-electrode stimulation, we analyze how phosphene shape and number are influenced by neuroanatomical factors, stimulus parameters, and spatial offsets. Additionally, we examine the causes of high current thresholds and limited spatial resolution, which impede pattern vision in Argus II devices. This research aims to provide insights for optimizing stimulation strategies and improving retinal prosthesis design.

Detailed Description: This study focuses on two experiments involving blind participants implanted with the Argus II retinal prosthesis:

Experiment 1: Paired-Electrode Phosphene Perception The study retrospectively analyzes 3548 phosphene drawings made by three participants. We investigate the impact of single- and paired-electrode stimulation on phosphene shape (area, perimeter, major/minor axis length) and the number of perceived phosphenes. Neuroanatomical parameters, including electrode-retina distance, electrode-fovea distance, and electrode-electrode distance (both along-axon and between-axon), are correlated with these outcomes. Statistical analyses include linear regression and partial correlation to examine the relationship between stimulation parameters and phosphene perception.

Experiment 2: Performance Factors in Argus II Prostheses This study explores the factors contributing to high current amplitude thresholds and poor spatial resolution in three participants. We measure current amplitude thresholds and two-point discrimination (the ability to distinguish stimulation on one versus two electrodes). Data from psychophysical experiments and simulations are analyzed to identify the roles of axonal stimulation, electrode lift, and retinal damage in limiting device performance.

These experiments aim to advance the understanding of epiretinal stimulation and inform the development of future retinal prostheses with improved spatial resolution and sensitivity.

Recruitment & Eligibility

Inclusion Criteria

Not provided

Exclusion Criteria

Not provided

Arm && Interventions

Group	Intervention	Description
Predicting the perceptual experience of retinal prosthesis patients	Argus II	This intervention will assess the effect of different stimulation strategies on the perceptual experience of retinal prosthesis patients. We will produce visual percepts in patients either by directly stimulating electrodes (using FDA-approved pulse trains) or by asking them to view a computer or projector screen and using standard FDA-approved stimulation protocols (as is standardly used for their devices) to convert the computer or projector screen image into pulse trains on their electrodes. Existing blind users of the Argus II will be recruited for this study. Performance of Argus II users will be compared to performance of sighted subjects viewing a prosthetic vision simulation in virtual reality.

Primary Outcome Measures

Name	Time	Method
Number of Phosphenes Perceived	during single-session testing	Number of phosphenes perceived in response to paired-electrode stimulation across 5 spatial distances and 7 temporal interpulse delays. Phosphenes are brief sensations of light or visual flashes that occur in the absence of an external light source. A response is counted as a phosphene if the participant reports any visual sensation consistent with a flash of light.

Secondary Outcome Measures

Name	Time	Method

Locations (3): University of California, Santa Barbara
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Santa Barbara, California, United States
Johns Hopkins University
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Baltimore, Maryland, United States
University of Michigan, Ann Arbor
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Ann Arbor, Michigan, United States