Artificial Retina

2. ARTIFICIAL
RETINA USING
THIN FILM
TRANSISTOR
Submitted By : BRIJITH P P

3. RETINA STRUCTURE

4. INTRODUCTION
• The Artificial Retina made using Thin-Film Transistors, which can
be fabricated on transparent and flexible substrates.
• Electronic photo devices and circuits are integrated on the artificial
retina.
• Implanted on the inside surface of the living retina at the back part
of the human eyeballs. Wireless power supply is used

5. Major Diseases of Eye
 Retinitis Pigmentosa
• Hereditary genetic disease.
• Degeneration of the retina
• Gradually progress towards center of eye.
• Tunnel vision results

6.  Macular Degeneration
• Genetically related.
• Cones in macula region degenerate.
• Loss or damage of central vision
• Common among aged people.
 Age Related Macular Degeneration

7. RETINAL IMPLANTATION
• A retinal implant is a biomedical implant technology
• The first application of an implantable stimulator for vision
restoration was developed by Drs. Brindley and Lewin in 1968.
• There are two types of retinal implants namely epiretinal implant and
subretinal implant.

8. EPIRETINAL IMPLANT

9. EPIRETINAL IMPLANT
• Advantages:-
 Minimizes the amount of microelectronics implanted and
upgrades are easy to do on the wearable portion thus avoiding
future surgery
 Heat can be dissipated into the vitreous humor
 External control over image processing allowing for
customizability, possible better clarity
• Disadvantages:-
 Difficulty attaching the implant to the fragile inner retina
 Complicated processing.

10. SUBRETINAL IMPLANT

11. CIRCUIT OPERATION
• It uses the same fabrication processes as conventional poly-Si TFTs
and encapsulated using SiO2
• The retina array includes matrix-like multiple retina pixels
• The retina pixel consists of a photo transistor, current mirror, and load
resistance.
• The retina pix-els irradiated with bright light output a higher Vout,
whereas the retina pixels irradiated with darker light output a lower
Vout.

12. SUBRETINAL IMPLANT
• Advantages
Utilizes the surviving bipolar cells – the next step in the
pathway –Retinal processing can take place
Placing the micro photodiodes between layers on the
retina will allow for it to be held in position next to
functioning cells
• Disadvantages:
Limited space
Ambient light may not be adequate to generate current in
this array
 Additional power supplies can be used to improve the
light intensity.

13. FABRICATION OF THIN FILM
PHOTOTRANSISTORS
• Low temperature poly-Si TFTs have been developed in order to
fabricate active matrix LCDs with integrated drivers on large glass
substrates.
• For integrated drivers, CMOS configurations are necessary.
• Ion implantation is one of the key factors in fabricating

14. ION DOPING TECHNIQUE
• The new I/D system which is one of the non mass separated
implanters. 5 percent Phosphane (PH3) or 5 percent Diborane
(B2H6) diluted by hydrogen is used for the doping gas
• Main features of this system are:
1) A large beam area
(over 300 mm square)
2) A high accelerating voltage
(maximum: 110 KeV)

15. WIRELESS POWER SUPPLY
USING INDUCTIVE COUPLING
• For implanted electrical power to function, either an im-planted
battery or via wireless power transmission used.
• For proper retinal functioning, continuous power transmission is
required.
• Inefficient transmission of power is a performance limiting factor.
• High density electrode array with more than 1000 electrodes will
consume about 45 mW of power.

16. • Chip-25mw
• Neuronal stimulation-20mw
• Based on 64 simultaneously operating electrodes each requiring a
maximum of 0.3 mW at 60 Hz image refresh rate.

17. Disadvantages of power transmission
• Difficulty in placing a large receive coil inside the eye.
• We face are large separation between the coils
• Reduction in power transfer to the device.
Overcome problems:
• Intermediate link between
the primary and secondary coil
• Which are embedded under
the wall of the eye.

18. WORKING
• The power transmitter consists of an ac voltage source(10V,34khz)
and induction coil.

19. CONCLUSIONS
 People suffering from low vision to, people who are
completely blind will benefit from this project.
This technology used by US and economic Europe countries.
Hope in INDIA also will acquire this technology soon….Hope in INDIA also will acquire this technology soon….

20. REFERENCES
 www.researchgate.com
 www.onlinelibrary.wiley.com
 www.electrochem.org
 en.m.wikipedia.org
 www.nano-retina.com