PRESENTED BY:
Y. Srujan Reddy

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Organization
Introduction
The Human Eye
The Retina
Causes of Blindness
Retinitis Pigmentosa
Macular Degeneration
Bionic Eye: Two Approaches
MARC – Concept
MARC System
Image Acquisition System
RF Telemetry
Organization
MARC – Concept
Data Recovery
Image Formation
Important Aspects
Artificial Silicon Retina
Retinal Implantation Approaches
Epiretinal Approach
Subretinal Approach
Limitations of ASR
Summary
References
Introduction
Bio-electronic Eye.
Replaces functionality for a part or the whole eye
Chips specifically designed to imitate retina characteristics
Hope for the blind
Huge revolution in the field of medicine
The Human Eye
Human Eye is similar to a camera
Macula provides the highest
resolution
Macula contains maximum cones.
Has nearly 100 million
photoreceptors.
The Retina
Causes of Blindness
Damage to the Retina:
Retinitis Pigmentosa
Macular Degeneration
Damage to the Optic Nerve
Damage to the Brain
Bionic Eye restores vision lost due to retinal damage.
Retinitis Pigmentosa
Hereditary Genetic Disease
Peripheral rods degenerate
Gradually progresses towards center of the eye
Tunnel vision results
Retinitis Pigmentosa
Macular Degeneration
Genetically Related
Cones in the macula region degenerate
Loss of central vision
Peripheral Retina spared
Common among old people
Macular Degeneration
Bionic Eye: Two Approaches
MARC – Concept
MARC System
Image Acquisition System
RF Telemetry
Data Recovery
Low frequency data obtained by low pass filtering
The first RF signal received sets pulse width, height & period
ASK demodulator obtains PWM scheme
Delay Locked Loop (DLL) deciphers PWM to obtain data
Image Formation
Important Aspects
Field of View:
More number of Ganglion cells stimulated, more is the field of view
Large electrodes and area becomes a trade-off
Changing Scene and Real-time vision:
The whole process must be extremely fast for real time vision
Any noticeable lag could stimulate the "vestibular-ocular reflex", making people feel dizzy and sick.

Artificial Silicon Retina
ASR mimics the neural circuitry of a real retina.
Chip contains light sensors and circuitry equivalent to nerves in a real retina.
Current generated in response to light stimulation
Visual sensations or “phosphenes” are evoked by electrical stimulation
Artificial vision created by the controlled electric stimulation of the retina has color
Retinal Implantation Approaches
Epiretinal Approach
ASR chip positioned on the surface
of the retina
Tries to simulate remaining
overlying cells
Subretinal Approach
ASR chip behind the retina
Tries to simulate remaining viable
cells
Epiretinal Approach
Site of Implant:
Implant Structure
Layers
Photodiode Array
Polyimide Strip
Stimulator Chip
Electrodes on end of
Polyimide Strip
Working of System
Laser source hits photodiode array & powers stimulator chip.
Stimulator chip drives current to electrodes facing retina.
This excites the ganglionic cells > axons > optic nerve > visual cortex in occipital lobe of brain.
Brain helps in perceiving image.
Subretinal Approach
Basic Idea – Alter the membrane potential
Single Micro Photodiode Array
No external power supply
Implants are comprised of a doped & ion-implanted silicon substrate disk
Images
Limitations of ASR
ASR is designed to interface & function with partially degenerated retina.
ASR can only be applied when photoreceptor cellular is damaged.
The remaining cellular layers need to be functioning.
Summary
Human Eye & Causes of Blindness
Two approaches used in Bionic Eye
MARC Approach
Artificial Silicon Retina
Epiretinal Approach in ASR
Subretinal Approach in ASR