From: Dickey, Michael F (firstname.lastname@example.org)
Date: Fri Jan 04 2002 - 09:45:56 MST
Kurzweill in 'Age of spiritual machines' talks of how technology merging
with biology will slowly be accepted by the masses by starting out as curing
ailments and disabilities, then moving to mere annoyances and then onto
augmentation. Here is an article from Nasa science news that talks about
artificial photoreceptors, a possible first step in visual related
Using space technology, scientists have developed extraordinary ceramic
photocells that could repair malfunctioning human eyes.
Listen to this story via streaming audio, a downloadable file, or get help.
January 3, 2002: Rods and Cones. Millions of them are in the back of every
healthy human eye. They are biological solar cells in the retina that
convert light to electrical impulses -- impulses that travel along the optic
nerve to the brain where images are formed.
Without them, we're blind.
Indeed, many people are blind -- or going blind -- because of malfunctioning
rods and cones. Retinitis pigmentosa and macular degeneration are examples
of two such disorders. Retinitis pigmentosa tends to be hereditary and may
strike at an early age, while macular degeneration mostly affects the
elderly. Together, these diseases afflict millions of Americans; both occur
gradually and can result in total blindness.
Above: "Eye chart with eyes." Copyright Philip Kaake. All rights reserved.
"If we could only replace those damaged rods and cones with artificial
ones," says Dr. Alex Ignatiev, a professor at the University of Houston,
"then a person who is retinally-blind might be able to regain some of their
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Years ago such thoughts were merely wishful. But no longer. Scientists at
the Space Vacuum Epitaxy Center (SVEC) in Houston are experimenting with
thin, photosensitive ceramic films that respond to light much as rods and
cones do. Arrays of such films, they believe, could be implanted in human
eyes to restore lost vision.
"There are some diseases where the sensors in the eye, the rods and cones,
have deteriorated but all the wiring is still in place," says Ignatiev, who
directs the SVEC. In such cases, thin-film ceramic sensors could serve as
substitutes for bad rods and cones. The result would be a "bionic eye."
The Space Vacuum Epitaxy Center is a NASA-sponsored Commercial Space Center
(CSC) at the University of Houston. NASA's Space Product Development (SPD)
program, located at the Marshall Space Flight Center, encourages the
commercialization of space by industry through 17 such CSCs. At the SVEC,
researchers apply knowledge gained from experiments done in space to develop
better lasers, photocells, and thin films -- technologies with both
commercial and human promise.
Below: A schematic diagram of the retina -- a light-sensitive layer that
covers 65% of the interior surface of the eye. SVEC scientists hope to
replace damaged rods and cones in the retina with ceramic microdetector
arrays. Image courtesy A. Ignatiev.
Scientists at Johns Hopkins University, MIT, and elsewhere have tried to
build artificial rods and cones before, notes Ignatiev. Most of those
earlier efforts involved silicon-based photodetectors. But silicon is toxic
to the human body and reacts unfavorably with fluids in the eye -- problems
that SVEC's ceramic detectors do not share.
"We are conducting preliminary tests on the ceramic detectors for
biocompatibility, and they appear to be totally stable" he says. "In other
words, the detector does not deteriorate and [neither does] the eye."
"These detectors are thin films, grown atom-by-atom and layer-by-layer on a
background substrate -- a technique called epitaxy," continues Ignatiev.
"Well-ordered, 'epitaxally-grown' films have [the best] optical properties."
Crafting such films is a skill SVEC scientists learned from experiments
conducted using the Wake Shield Facility (WSF) -- a 12-foot diameter
disk-shaped platform launched from the space shuttle. The WSF was designed
by SVEC engineers to study epitaxial film growth in the ultra-vacuum of
space. "We grew thin oxide films using atomic oxygen in low-Earth orbit as a
natural oxidizing agent," says Ignatiev. "Those experiments helped us
develop the oxide (ceramic) detectors we're using now for the Bionic Eye
Right: In 1996, during shuttle mission STS-80, astronauts use Columbia's
robotic arm to deploy the Space Vacuum Epitaxy Center's Wake Shield
The ceramic detectors are much like ultra-thin films found in modern
computer chips, "so we can use our semiconductor expertise and make them in
arrays -- like chips in a computer factory," he added. The arrays are
stacked in a hexagonal structure mimicking the arrangement of rods and cones
they are designed to replace.
The natural layout of the detectors solves another problem that plagued
earlier silicon research: blockage of nutrient flow to the eye.
"All of the nutrients feeding the eye flow from the back to the front," says
Ignatiev. "If you implant a large, impervious structure [like the silicon
detectors] in the eye, nutrients can't flow" and the eye will atrophy. The
ceramic detectors are individual, five-micron-size units (the exact size of
cones) that allow nutrients to flow around them.
Artificial retinas constructed at SVEC consist of 100,000 tiny ceramic
detectors, each 1/20 the size of a human hair. The assemblage is so small
that surgeons can't safely handle it. So, the arrays are attached to a
polymer film one millimeter by one millimeter in size. A couple of weeks
after insertion into an eyeball, the polymer film will simply dissolve
leaving only the array behind.
The first human trials of such detectors will begin in 2002. Dr. Charles
Garcia of the University of Texas Medical School in Houston will be the
surgeon in charge.
"An incision is made in the white portion of the eye and the retina is
elevated by injecting fluid underneath," explains Garcia, comparing the
space to a blister forming on the skin after a burn. "Within that little
blister, we place the artificial retina."
Left: These first-generation ceramic thin film microdetectors, each about 30
microns in size, are attached to a polymer carrier, which helps surgeons
handle them. The background image shows human cones 5-10 microns in size in
a hexagonal array. Image courtesy A. Ignatiev.
Scientists aren't yet certain how the brain will interpret
unfamiliar voltages from the artificial rods and cones. They believe the
brain will eventually adapt, although a slow learning process might be
necessary -- something akin to the way an infant learns shapes and colors
for the first time.
"It's a long way from the lab to the clinic," notes Garcia. "Will they work?
For how long? And at what level of resolution? We won't know until we
implant the receptors in patients. The technology is in its infancy."
Ignatiev has received over 200 requests from patients who learned of the
studies from earlier press reports. "I'm extremely excited about this," he
says. He cautions that much more research is needed, but "it's very
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