The Perceptual Experience of Argus II Users

Predicting the Perceptual Experience of Argus II Retinal Prosthesis System Users

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.

Study Overview

• Status: Completed
• Conditions: Retinitis Pigmentosa
• Intervention / Treatment: Device: Argus II

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.

• Study Type: Interventional
• Enrollment (Actual): 6
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • California
    • Santa Barbara, California, United States, 93106
      • University of California, Santa Barbara
  • Maryland
    • Baltimore, Maryland, United States, 21287
      • Johns Hopkins University
  • Michigan
    • Ann Arbor, Michigan, United States, 48109
      • University of Michigan, Ann Arbor

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

Description

Inclusion criteria:

• Subject must be at least 25 years of age;
• Subject has been implanted with the Argus II system;
• Subject's eye has healed from surgery and the surgeon has cleared the subject for programming;
• Subject has the cognitive and communication ability to participate in the study (i.e., follow spoken directions, perform tests, and give feedback);
• Subject is willing to conduct psychophysics testing up to 4-6 hours per day of testing on 3-5 consecutive days;
• Subject is capable of understanding patient information materials and giving written informed consent;
• Subject is able to walk unassisted.

Exclusion criteria:

• Subject is unwilling or unable to travel to testing facility for at least 3 days of testing within a one-week timeframe;
• Sighted controls: Subject has a history of motion sickness or flicker vertigo
• Subject does not speak English;
• Subject has language or hearing impairment

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm

Intervention / Treatment

Experimental: Argus II users; 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.

Device: Argus II; Participants used the Argus II retinal prosthesis system in both experiments to perform visual perception tasks.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of Phosphenes Perceived	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.	during single-session testing

Collaborators and Investigators

• Sponsor: University of California, Santa Barbara
• Collaborators: Johns Hopkins University; National Eye Institute (NEI); University of Michigan
• Investigators: Principal Investigator: Michael Beyeler, PhD, University of California, Santa Barbara

Publications and helpful links

General Publications

• Yucel EI, Sadeghi R, Kartha A, Montezuma SR, Dagnelie G, Rokem A, Boynton GM, Fine I, Beyeler M. Factors affecting two-point discrimination in Argus II patients. Front Neurosci. 2022 Aug 24;16:901337. doi: 10.3389/fnins.2022.901337. eCollection 2022.
• Hou Y, Nanduri D, Granley J, Weiland JD, Beyeler M. Axonal stimulation affects the linear summation of single-point perception in three Argus II users. J Neural Eng. 2024 Apr 8;21(2):026031. doi: 10.1088/1741-2552/ad31c4.

Study record dates

Study Major Dates

• Study Start (Actual): January 11, 2022
• Primary Completion (Actual): August 31, 2023
• Study Completion (Actual): August 31, 2023

Study Registration Dates

• First Submitted: February 4, 2022
• First Submitted That Met QC Criteria: March 14, 2022
• First Posted (Actual): March 17, 2022

Study Record Updates

• Last Update Posted (Actual): March 25, 2025
• Last Update Submitted That Met QC Criteria: December 22, 2024
• Last Verified: December 1, 2024

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Genetic Diseases, Inborn; Eye Diseases; Eye Diseases, Hereditary; Retinal Diseases; Retinal Dystrophies; Retinal Degeneration; Retinitis; Retinitis Pigmentosa
• Other Study ID Numbers: R00EY029329 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Deidentified data will be available from the investigative team, following initial publication of the results
• IPD Sharing Time Frame: Spring 2023 onward
• IPD Sharing Access Criteria: Any researchers with a legitimate reason for wishing to re-analyze the data or compare them to study data collected in similar experiments
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: Yes