A PROSTHETIC EYE TO TREAT BLINDNESS
It seems that today's scientists are trying hard to
treat blindness. If you happen to have a friend or any member of the family who
are blind, my note could be useful someday. Here's what I got to know from
their research:
1. In the USA itself, there are 10 million who are
blind or facing blindness due to the disease of the retina.
2. There are some drug treatments but they are only
effective on the small population, and only little can be done to fix that.
3. So, for the vast majority, their best hope is
through prosthetic devices.
4. The problem is current prosthetics don't work
very well. Users of these prosthetics can only see bright lights and
high-contrast edges. Not very much more and nothing more than that has been
made possible.
5. Recently, researches and scientist have something
that could be a potential to make a difference and to make it much more
effective.
6. This is how it works:
a) When you look at something, the image of that
object goes into your eye and lands on your retina, which goes through
photoreceptors, retinal circuitry (process the image/information) and trasmits
them into codes (electric signals to the brain).
b) The image/information you see with your eyes work
in codes. What I mean by code is, when you look at a dog, the electric patterns
converted tells the brain that it is a dog. So, when another person looks at
the a dog, he or she will have the similar electric wave patterns sent to the
brain. Different objects/information have different patterns. So these patterns
can be calculated and measured and that's how the brain gets the information
from our eyes.
c) The pattern pulses are changing all the time
because the world you're looking at is changing all the time too. You're
pattern pulses are coming out of your eye every millisecond telling your brain
what it is you're seeing.
d) Example: If a person gets a retinal degenerative
desease like macular degeneration? For those who don't know what is a Macular
Degeneration it is a medical condition which usually affects older adults and
results in a loss of vision in the center of the visual field (the macula)
because of damage to the retina. Meaning, the front end (photoreceptors) cells
die and overtime the cells and the circuits that are connected to them die too.
Scary stuff eh?
e) Until the only thing you have left are only the
output cells, the cells that send the signals to the brain. But, because of the
degeneration, they aren't sending any signals anymore. They get no input so the
brain doesn't get any visual information -- that is he or she is blind.
f) Scientist feels that the solution to that problem
is trying to build a device that could mimic the actions of the front-end
circuitry and send signals to the retina output cells.
g) It could made possible with their recent
prosthetics. The prosthetic is divided into 2 parts; the encoder and the
transducer. And so the encoder mimics the actions of the front-end circuitry --
it takes images in and converts them into the retina's code. The transducer
then makes the output cells send the code on up to the brain and the result is
a prosthetic that can produce normal retinal output.
h) So, a completely blind retina, even one with no
front-end cicuitry at all, no photoreceptors, can now send out normal signals
that the brain can understand.
i) The key part of it is the encoder and what it's
doing. It's replacing the retinal circuitry with a set of equations that we can
implement on a chip, but not literally replacing the components of a retina.
They've just abstracted what the retina is doing with a set of equations. The
equations are serving as sort of a codebook. An image comes in, goes through a
set of equations, and out come streams of electrical pulses, just like a normal
retina would produce.
j) Scientist tested it on a normal animal, a blind
animal treated with encoder-transducer, and a blind animal treated with the
standard prosthetics. They then presented movies of everyday things like
people, babies, park benches, and regular things you see everyday and recorded
the responses from the retinas of these 3 groups of animals. Animals treated
with the encoder-transducer really do very closely match the normal firing
patterns (responses from the retina of a normal animal). It is not perfect but
it's pretty good.
7. How important is this? What's the potential
impact on a patients ability to see? The bottome-line... the reconstruction
esperiment, taking the recordings of firing patterns and asked what was the
retina seeing at that moment? Can they reconstruct what the retina is seeing
from the responses of firing patterns?
8. From the standard method, when the looking at the
image of a baby, the firing is pretty limited and because the firing patterns
aren't in the right code, they're very limited in what they can tell about
what's out there. So, you can see that something is there, but you don't know
what that something is. Which comes back to what I mentioned in the beginning;
only high-contrast edges and light. But with their method of using
encoder-transducer, the firing patterns shows an image of a baby, but not that
perfect as the nomal eye.
9. It is vital to be able to communicate with the
brain in its language, and the potential power of being able to do that. Unlike
the current normal prosthetics where the motorwork is the brain to the device,
instead, we communicate with the outside world into the brain and be understood
by the brain. Understanding the code is really important and when you can
understand the code, the language of the brain, things become possible that
didn't seem obviously possible before.
Inspired by Sheila Nirenberg
#masterfreddy
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