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BIONIC EYE
A Look into Current Research and Future Prospects
WHAT’S BIONIC EYE ?
 Bio-electronic eye
 Electronic device which replaces functionality of a part or whole of the eye.
 Used for replacing functionality (or)
 Adding functionality to the eye.
Causes of Blindness:
Damage to:
 Clear Structures in the eye, that allow the light to pass through
 The nerves within the eye
 Optic Nerve
 Brain
Why we should be optimistic?
The Success of :
 Cardiac pacemakers as neural prosthesis
 Cochlear implants to restore hearing to the deaf.
Rapid developments in :
 VLSI design
 Micro- fabrication technology
MIT-Harvard device:
Features
 Epi-Retinal Approach
 Microelectrode array replaces damaged photoreceptors
 Power source – Laser(820nm wavelength)
 Image Acquisition - Using CCD Camera
 Patient spectacle holds the camera and power source
Implant Structure:
 Layers
1- Photodiode Array
2- Polyimide strip
3- Stimulator chip
 Electrodes on other end of Polyimide strip
The Eye:
 Human Eye is similar to a camera
 Macula provides the highest resolution of the image which we see.
 Macula is comprised of multiple layers of cells which process the initial “analog "light energy entering the eye into “digital”
electrochemical impulses.
 Human eye has nearly 100 million photoreceptors.
Fundamental idea behind ASR
 ASR is a solid state biocompatible chip which contains an array of photo receptors ,and is implanted to replace the functionality of the defective photoreceptors .
 Current generated by the device in response to light stimulation will alter the membrane potential of the overlying neurons and thereby activate the visual system.
 Visual sensations or “phosphenes” can be evoked by electrical stimulation of the different levels of the visual pathway.
 Phosphenes are evoked by the stimulation of the eyeball or the visual cortex.
 Artificial vision created by the controlled electric stimulation of the retina has color.
Post Implant function and Inference:
 Measurement procedure:
 IR stimulation at 940nm on the ASR chip
 Recorded at the corneal surface using contact lens electrode
 Comparison of responses of gold, platinum and iridium electrodes
 Iridium based device has a longer persistence
 Stability of these electrodes