Retinal Prosthesis Electrode Array for Phosphene Shape Control
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Solution Overview
Problem
Existing retinal prosthetic devices are bulky and unable to produce adequate simulated vision for the visually impaired, and there is a need for a more precise method to stimulate visual neurons to create artificial vision, particularly in cases of blindness due to photoreceptor degenerative diseases.
Innovation Solution
An electrode array with alternating large and small electrodes at a 45-degree angle is used to minimize interference between electrical fields, allowing for varying current levels to control phosphene shape, size, and brightness, and a retinal prosthesis system that bypasses photoreceptors to directly stimulate retinal ganglion cells, with a method for correcting array rotation to ensure accurate image shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional electrode arrays are used for retinal stimulation, then the device structure is simple, but the device is bulky and cannot produce adequate simulated vision
Solution Approach 1:
The electrode array is segmented into alternating large and small electrodes arranged in a checkerboard pattern. This segmentation allows different electrode sizes to produce phosphenes of different sizes and brightness levels, thereby improving vision quality through more nuanced neural stimulation patterns.
Solution Approach 2:
Different regions of the electrode array have different electrode sizes (large vs. small electrodes), creating local quality variations. This enables spatially differentiated stimulation effects where large electrodes produce larger, brighter phosphenes and small electrodes produce smaller, dimmer phosphenes, improving overall vision simulation.
2Reliability
If uniform electrode sizes are used in the array, then the device structure is simple, but electrical field interference between adjacent electrodes cannot be minimized
Solution Approach 1:
The electrode array employs asymmetric electrode sizes in a checkerboard pattern, with alternating large and small electrodes. This asymmetry ensures that adjacent electrodes have different spatial footprints, minimizing electrical field interference between them and improving reliability of individual electrode stimulation.
3Measurement precision
If varying current levels are applied to control phosphene attributes, then phosphene shape and size control is improved, but the system requires more complex control mechanisms
Solution Approach 1:
The system controls phosphene attributes by changing electrical stimulation parameters, specifically current amplitude. By varying the current level applied to each electrode, the system precisely controls phosphene brightness and size, with higher currents producing larger, brighter phosphenes and lower currents producing smaller, dimmer phosphenes.
4Measurement precision
If the electrode array is implanted without rotation correction, then the implantation process is simpler, but the image shape accuracy deteriorates
Solution Approach 1:
The system incorporates feedback mechanisms to detect and correct rotation of the electrode array after implantation. By monitoring the actual orientation of the array and comparing it to the desired orientation, the system can apply rotational corrections to the stimulation pattern, ensuring accurate image shape reconstruction despite implantation variations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables repeatable and significant changes in phosphene shape and size with increasing stimulation amplitude, providing more accurate video preproduction and improved perception capabilities for the visually impaired.
Implementation Method 1
Neural tissue can be artificially stimulated and activated by prosthetic devices that pass pulses of electrical current through electrodes on such a device. The passage of current causes changes in electrical potentials across visual neuronal membranes, which can initiate visual neuron action potentials
Data Source
AI summary
The present invention is an improved method of stimulating visual neurons to create artificial vision. It has been found that varying current of visual stimulation can create varying percept brightness, varying percept size, and varying percept shape. By determining the attributes of predetermined current levels, and using those attributes to program a video processor, more accurate video preproduction can be obtained.The present invention also includes an electrode array having alternating large and small electrodes in rows at a 45 degree angle to horizontal in the visual field.