Bionic Eyes - Hansma Lab

Bionic Eyes
Sub-Retinal Implants
Michael Hutchins
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.
Retinal Diseases
Retinitis Pigmentosa
•  A genetic disorder
•  Starts with degradation of night vision
followed by tunnel vision.
•  No cure, but can be staved off with Vitamin
Retinal Diseases
Macular Degeneration
•  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.
Photoreceptors
Rods
Cones
Slow
Response
Fast Response
Scattered
Light
Direct Light
One Pigment
Three
Pigments
Greys
Color Vision
Photorecptors
Photorecptors
Retinal Encoding
•  Rods (off center cells)
surround cones (on
center cells).
-1/8 -1/8 -1/8
-1/8 +1 -1/8
-1/8 -1/8 -1/8
Retinal Encoding
Optic Nerve
•  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.
Photodiode
Photodiode
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 usin
electrical stimulation to treat and prevent
visual loss.
ASR Device
•  2mm diameter
•  25µm thick
•  ~5000 negative
intrinsic layerpositive
microphotodiode
pixels
•  Pixels are
electrically isolated
ASR Device
•  Placed subretinally.
•  Photodiodes run solely
off incident light.
•  Electric charge produces
by photodiodes alter
membrane potential of
nearby neurons.
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
Implanting
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Placed 20˚ off axis from th
macula.
Retina is cut and ASR is
implanted beneath it.
The retina is re-flattened
Absorption
ASR in Rats
Post Operative Results
Humphrey Central Visual Field Tests
Post Operative Results
Humphrey Central Visual Field Tests
Subjective Results • 
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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.
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 (t
is what was published in the clinical trial paper).
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.
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.
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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-andwavelength-on-the-retina/
http://misclab.umeoce.maine.edu/boss/classes/SMS_491_2003/Week_10.htm
Questions
The Artificial Silicon Retina cannot:a. see into the infr