Bionic Eyes

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Bionic EyesSub-Retinal Implants Michael Hutchins

Motivation Retinal diseases cannot be xed with normal Vision degradation is a result of age but is There are multiple types of blindness, retinal Retinal implants can greatly improve visionand quality of life. implants cure those involving the retina. not inevitable. corrective procedures.

Retinal DiseasesRetinitis Pigmentosa

A genetic disorder Starts with degradation of night visionfollowed by tunnel vision.

No cure, but can be staved off with Vitamin

Retinal DiseasesMacular Degeneration

Loss of vision in the center of the retina. Major cause of blindness in the elderly. Risks of development linked to certaingenes but not the cause.

PhotoreceptorsRodsSlow Response Scattered Light One Pigment Greys

Cones

Fast Response

Direct Light Three Pigments

Color Vision

Photorecptors

Photorecptors

Retinal Encodingsurround cones (on center cells).-1/8 -1/8 -1/8 -1/8 +1 -1/8 -1/8 -1/8 -1/8

Rods (off center cells)

Retinal EncodingOptic Nerve

The optic nerve has 10^6 nerve bers, the The optic nerve transfers at 8.75 x 10^6 The poor capacity of the optic nerve is stillunexplained. bits/second. eye has roughly 10^8 photoreceptors.

Photodiode

Photodiode

Optobionics Optobionics makes the Articial SiliconRetina. through clinical trials.

The device has been tested in 42 patients

Filed a patent in 2002 for methods of usin

electrical stimulation to treat and prevent visual loss.

ASR Device 2mm diameter 25m thick ~5000 negative

intrinsic layerpositive microphotodiode pixels electrically isolated

Pixels are

ASR Device Placed subretinally. Photodiodes run solelyoff incident light.

Electric charge producesby photodiodes alter membrane potential of nearby neurons.

ASR Device Pixels are 20m square. 9 x 9m iridium oxideelectrode

Pixel current is 8-12nA at800 foot-candles (8611 Lux) of illumination day

1,000 lux is an overcast 10,000 - 25,000 lux is

Implanting

Placed 20 off axis from th macula. Retina is cut and ASR is implanted beneath it. The retina is re-attened

AbsorptionASR in Rats

Post Operative ResultsHumphrey Central Visual Field Tests

Post Operative ResultsHumphrey Central Visual Field Tests

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.

Long Term

No reports of rejection, discomfort or any side-effects. Materials used in the ASR are known to be biocompatiblesilicon, silicon oxide, titanium and iridium oxide. is what was published in the clinical trial paper).

All ASR implants were fully functioning after 18 months (t

Considerations The ASR requires that there is some It cannot work if there is severe retinal It is still being clinically tested, only 47human trials have been done so far. scarring. working parts of the retina.

Summary Articial retinas can There is so far norestore sight lost due to retinal diseases. downside to getting retinal implants confer vision outside our normal range.

Retinal implants may

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

References

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 Articial Silicon Retina cannot:a. see into the infr