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If you are a person who is suffering from a
chronic disease, the future is already here. Biology and electronics are
working together to treat eye diseases, hearing loss, and even creating bionic
limbs for amputees.
Bionic Vision
Retinitis pigmentosa is an inherited disease that affects about 1.5
million people worldwide, while 10 percent of people over the age of 55 suffer
from various stages of macular degeneration. Both diseases damage the
eyes' photoreceptors. Photoreceptors are the cells at the back of the retina that receive light and pass it to the
brain in the form of nerve pulses, where the received signals are then interpreted as images.
A bionic eye device to restore vision to people
suffering from these two diseases is now on the market. The bionic vision system consists of a camera attached to a pair of
glasses which transmits high-frequency radio signals to a microchip implanted
in the eye. Electrodes on the implanted chip convert these signals into
electrical impulses to stimulate cells in the retina that connect to the optic
nerve. These impulses are then passed down along the optic nerve to the vision
processing centres of the brain, where they are interpreted as an image. This
part of the process is still facing obstacles, for example, what the patients
can actually see are patterns of light and darkness. One way around it is to
train the patients to interpret these patterns according to what they represent
in reality. Another method is to increase the number of electrodes that could
be implanted in the retina.
Bionic Hearing
In terms of treating hearing loss, a cochlear implant is a small,
complex electronic device that can help to provide a sense of sound to a person
who is profoundly deaf or severely hard-of-hearing. The implant consists of an
external portion that sits behind the ear and a second portion that is surgically
placed under the skin (see image below).
An implant has the following parts:
- A microphone,
which picks up sound from the environment
- A speech
processor, which selects and arranges sounds picked up by the microphone
- A transmitter
and receiver/stimulator, which
receive signals from the speech processor and convert them into electric
impulses
- An electrode
array, which is a group of electrodes that collects the impulses from the
stimulator and sends them to different regions of the auditory nerve.
The implant does not restore normal hearing. Instead, it can give a deaf
person a useful representation of sounds in the environment and help him or her
to understand speech.
The external part on the left side of the image above is worn above the ear and it consists of a
receiver unit that takes the ear shape and a transmitter unit which is fixed on
the skull. The internal parts is the receiver parts that ends with electrodes
that are positioned in the cochlea.
Bionic Hands
Most hand prosthetics use moving digits to allow the hand to bend at the
joints and give the patient a compliant grip so that the hand accurately
conforms around the shape of the object being grasped. One challenge in the
design of this prosthetic is to allow the patient to exert the right amount of
force for doing different tasks, from grasping large objects like a ball or a
box to small ones like coins. The tricky part is that the type of force should
be proportional to the material and to the use, for example grasping a water
glass with so much force can break it, while having low force on a big object
can make it fall. This is classically controlled by a micro controller that
takes the input from an electrode positioned in the rudimentary nerve of the
patient, where different nerve signals are interpreted by the device to mean
different degrees of force and various degrees of freedom.
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