Artificial Vision

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Artificial Vision

• By Justin Martin

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Vision Loss

• Affects thousands of people each year
• Retinitis Pigmentosa is the leading cause of
  inherited blindness.
• 1.5 million people are affected worldwide
• Age-related macular degeneration
• Leading cause of vision loss for adults over 65
• 700,000 newly diagnosed patients yearly in the
  United States.

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Prosthetic Replacements

• Components
• Image capturing device
• This is usually an externally worn camera
• Processor
• Takes the pictures and translates them into
  electronic signals, which are then sent to the
  electrode array
• Electrode Array
• The microelectrode array is connected to the
  retina and stimulates any remaining
  photoreceptors. This is done by electrical
  impulses.
• Battery
• The battery is usually externally worn and about
  the size of a pager.

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Intraocular Retinal Prosthesis

• Developed by Dr. Humayun of the University of
  California
• Device consists of external and internal
  components
• External Units
• External camera that is built into a pair of
  lightweight glasses
• External worn battery
• Internal Unit
• A small visual processing unit that is implanted
  behind the patients ear
• Microelectrode Array
• Consisting of 16 platinum microelectrodes that
  vary in size
• Held into place by a small tack that makes sure
  the array stays connected to the retina
• The array is connected to the processor by a cable

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Clinical Trial

• The product was first tested in dogs to see if
  there was any rejection at the implant site
• A 2 to 3 month period showed no inflammation or
  rejection
• The only irritation occurred at the site of the
  tack
• 6 patients suffering from vision loss
• First signals were sent to the processor through
  a computer to simulate light
• This was done to see if the impulses sent to the
  retinal fibers stimulated any brain activity
• Then the external camera was used to send
  pictures to the processor
• After a few months
• Patients were able to detect when lights were on
  or off
• Patients could describe an objects path of
  motion
• Patients could count discrete objects
• Showed that the healthier a patients eyes were,
  the lower the threshold current the electrode
  array needed to operate properly

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Learning Retina Implant

• Similar to the IRP device
• The microelectrode array consists of 50
  electrodes instead of 16
• An externally worn processor takes the
  information from the external camera and
  translates it into data which is then sent
  wirelessly to the microelectrode array inside the
  eye
• The receiver on the microelectrode array has an
  infrared receiver that wirelessly transmits data
  and energy

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Clinical Trial

• 11 patients with retinitis pigmentosa
• The patients were immediately able to distinguish
  between light and dark and recognize the outlines
  of objects
• After a few month of use with the device
• Patients could read letters and form them into
  words
• Patients could recognize different objects, like
  distinguish between a knife, fork and spoon
• The most remarkable thing is the patients could
  tell differences in height and distinguish arm
  movement of people from 20ft away
• After the trials were concluded, the devices were
  removed, but one patients was so pleased with the
  device he kept it in and has been using it for
  years

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Future for Artificial Vision

• Change the external glasses mounted camera into a
  contact lens with a camera incorporated.
• Changing the wired array to a wireless array,
  this will eliminate the need to have wires
  implanted into the patients skull.
• Incorporate solar cells into the chip to convert
  the light entering the eye into energy, this
  would eliminate the need for externally worn
  batteries
• When the technologies becomes available,
  scientists hope to have arrays consisting of
  thousands of microelectrodes, this would increase
  the resolution of images people could see

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References

• Javaheri, Michael, David S. Hahn, Rohit R.
  Lakhanpal, and Mark S. Humayun. "Retinal
  Prostheses for the Blind." Annals Academy of
  Medicine 35.3 (2006). Web
• www.boston.com/news/globe/magazine/articles/2004/1
  2/05/the_bionic_eye/
• www.sciencecodex.com/get_ready_for_a_bionic_eye
• www.revophth.com/archive/newsletter/01_06retina.ht
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