bionic eyes

25
Bionic Eyes Sub-Retinal Implants Michael Hutchins

Upload: krithika-chowdary

Post on 13-Apr-2015

41 views

Category:

Documents


3 download

DESCRIPTION

bionic eyes are useful for

TRANSCRIPT

Page 1: Bionic Eyes

Bionic Eyes Sub-Retinal Implants

Michael Hutchins

Page 2: Bionic Eyes

Motivation •  Retinal diseases cannot be fixed with normal

corrective procedures.

•  Vision degradation is a result of age but is not inevitable.

•  There are multiple types of blindness, retinal implants cure those involving the retina.

•  Retinal implants can greatly improve vision and quality of life.

Page 3: Bionic Eyes

Retinal Diseases

•  A genetic disorder

•  Starts with degradation of night vision followed by tunnel vision.

• No cure, but can be staved off with Vitamin A.

Retinitis Pigmentosa

Page 4: Bionic Eyes

Retinal Diseases

•  Loss of vision in the center of the retina.

• Major cause of blindness in the elderly.

•  Risks of development linked to certain genes but not the cause.

•  Can be treated with painful drug injections

Macular Degeneration

Page 5: Bionic Eyes

Photoreceptors Rods Cones

Slow Response

Fast Response

Scattered Light

Direct Light

One Pigment Three

Pigments

Greys Color Vision

20x More

Page 6: Bionic Eyes

Photorecptors

Page 7: Bionic Eyes

Photorecptors

Page 8: Bionic Eyes

•  Rods (off center cells) surround cones (on center cells).

Retinal Encoding

-1/8 -1/8 -1/8

-1/8 +1 -1/8

-1/8 -1/8 -1/8

Page 9: Bionic Eyes

Retinal Encoding

•  The optic nerve has 10^6 nerve fibers, the eye has roughly 10^8 photoreceptors.

•  The optic nerve transfers at 8.75 x 10^6 bits/second.

•  The poor capacity of the optic nerve is still unexplained.

Optic Nerve

Page 10: Bionic Eyes

Photodiode

Page 11: Bionic Eyes

Photodiode

Page 12: Bionic Eyes

Optobionics

•  Optobionics makes the Artificial Silicon Retina.

•  The device has been tested in 42 patients through clinical trials.

•  Filed a patent in 2002 for methods of using electrical stimulation to treat and prevent visual loss.

Page 13: Bionic Eyes

ASR Device

•  2mm diameter

•  25µm thick

•  ~5000 negative intrinsic layer-positive microphotodiode pixels

•  Pixels are electrically isolated

Page 14: Bionic Eyes

ASR Device

•  Placed subretinally.

•  Photodiodes run solely off incident light.

•  Electric charge produces by photodiodes alter membrane potential of nearby neurons.

Page 15: Bionic Eyes

ASR Device •  Pixels are 20µm square.

•  9 x 9µm iridium oxide electrode

•  Pixel current is 8-12nA at 800 foot-candles (8611 Lux) of illumination

•  1,000 lux is an overcast day

•  10,000 - 25,000 lux is

Page 16: Bionic Eyes

Implanting

•  Placed 20˚ off axis from the macula.

•  Retina is cut and ASR is implanted beneath it.

•  The retina is re-flattened after implanting.

Page 17: Bionic Eyes

Absorption ASR in Rats

Page 18: Bionic Eyes

Post Operative Results Humphrey Central Visual Field Tests

Page 19: Bionic Eyes

Post Operative Results Humphrey Central Visual Field Tests

Page 20: Bionic Eyes

Subjective Results •  After implanting some could recognize faces, they could not do

this for ten years.

•  One patient could only see brightness, contrast and shape, afterwards could see the shadows of people.

•  Post-operatively others could sometimes make out streetlight colors and navigate without a cane.

•  Some reported unexpected improvements in areas distant from the implant.

•  Two reported perception of sensation to infrared light.

Page 21: Bionic Eyes

Long Term

•  No reports of rejection, discomfort or any side-effects.

•  Materials used in the ASR are known to be biocompatible: silicon, silicon oxide, titanium and iridium oxide.

•  All ASR implants were fully functioning after 18 months (this is what was published in the clinical trial paper).

Page 22: Bionic Eyes

Considerations

•  The ASR requires that there is some working parts of the retina.

•  It cannot work if there is severe retinal scarring.

•  It is still being clinically tested, only 47 human trials have been done so far.

Page 23: Bionic Eyes

Summary •  Artificial retinas can

restore sight lost due to retinal diseases.

•  There is so far no downside to getting retinal implants

•  Retinal implants may confer vision outside our normal range.

Page 24: Bionic Eyes

References •  Wikipedia Articles on: Retina, Retinitis Pigmentosa, Macular Degeneration,

Photoreceptors, Optic Nerve, Photodiode

•  http://optobionics.com/

•  “How Much the Eye Tells the Brain” Current Biology, Volume 16, Issue 14, 1428-1434, 25 July 2006.

•  "The Artificial Silicon Retina Microchip for the Treatment of Vision Loss From Retinitis Pigmentosa" Arch Ophthalmol. 2004;122:460-469.

•  “Jonas JB, Schneider U, Naumann GOH (1992) Count and density of human retinal photoreceptors. Graefe's Arch Clin Exp Ophthalmol 230:505-510.”

•  "Stimulation via a Subretinally Placed Prosthetic Elicits Central Activity and Induces a Trophic Effect on Visual Response" — IOVS Feb 2007, Vol 48 no.2

•  http://www.ghuth.com/2008/05/29/relationship-of-geometry-and-wavelength-on-the-retina/

•  http://misclab.umeoce.maine.edu/boss/classes/SMS_491_2003/Week_10.htm

Page 25: Bionic Eyes

Questions

The Artificial Silicon Retina cannot:a. see into the infrared.b. improve vision due to retinal disease.c. last longer then a year.d. be placed sub-retinally.e. none of the above.An unknown aspect of the retina is:a. how rods and cones interact.b. how light is transfered to the neurons.c. the signal encoding in the optic nerve.d. the number of photoreceptors.e. the ratio of rods and cones.