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Brightness as a function of current amplitude in human retinal electrical stimulation
Scott H Greenwald1, Alan Horsager, Mark S Humayun
1Second Sight Medical Products, Inc., Sylmar, California, USA.
Investigative Ophthalmology & Visual Science
|July 18, 2009
Summary
Visual prostheses use electrical stimulation to create phosphenes for blind patients. This study found that phosphene brightness scales with stimulation intensity, enabling consistent visual perception across the electrode array.
Area of Science:
- Biomedical Engineering
- Neuroscience
- Ophthalmology
Background:
- Retinal degenerative diseases cause vision loss.
- Epiretinal prostheses aim to restore vision by stimulating the retina.
- Consistent phosphene brightness is crucial for visual scene representation.
Purpose of the Study:
- To investigate how apparent phosphene brightness changes with electrical stimulation intensity.
- To determine if brightness perception is consistent across different electrodes in a visual prosthesis.
Main Methods:
- Electrical stimulation of the retina using a prototype epiretinal prosthesis (4x4 array).
- Measurement of apparent brightness using subjective magnitude ratings and brightness-matching procedures.
- Inclusion of chronically implanted human subjects with retinitis pigmentosa.
Main Results:
- Apparent phosphene brightness follows a power function of stimulation intensity.
- A single model accurately predicts brightness matching across the electrode array.
- Consistent brightness perception is achievable with appropriate current scaling.
Conclusions:
- A simple model for current scaling can achieve uniform phosphene brightness.
- This finding supports the development of more effective visual prostheses.
- Further research can refine models for optimal visual perception restoration.
