Friday, 26 July 2013

Contact lenses bestow telescopic vision

Contact lenses bestow telescopic
vision
By Mark Ward
Technology correspondent, BBC News
2 July 2013 Last updated at 12:56
The lens has a telescopic element
that focuses light on to the retina
Researchers have created contact
lenses which, when paired with
special spectacles, bestow
telescopic vision on their wearers.
The contact-lens-and-spectacles
combination magnifies scene details
by 2.8 times.
Polarising filters in the spectacles
allow wearers to switch between
normal and telescopic vision.
The telescopic sight system has been
developed to help people suffering
age-related blindness.
Age-related macular degeneration is
one of the most common forms of
blindness and damages the part of
the eye, the macula, that handles
fine detail. As this area degenerates,
sufferers lose the ability to recognise
faces and perform tasks, such as
driving and reading, that rely on
picking up details.
Precise control
The contact lens created by the
researchers
has a central region that lets light
through for normal vision. The
telescopic element sits in a ring
around this central region. Tiny
aluminium mirrors scored with a
specific pattern act as a magnifier as
they bounce the light around four
times within the ring before directing
it towards the retina.
In ordinary use, the magnified image
is not seen as it is blocked by
polarising filters set in a companion
pair of spectacles. Wearers can
switch it on by changing the filters
on the spectacles so the only light
falling on their retina comes from
the magnified stream.
For their filtering system, the
researchers, led by Joseph Ford at
UC San Diego and Eric Tremblay at
Switzerland's EPFL, adapted a pair of
glasses that Samsung produces for
some of its 3D TV sets. In normal
use, these spectacles create a 3D
effect by alternately blocking the
right or left lens.
The prototype contact lens produced
by the team is 8mm in diameter,
1mm thick at its centre and 1.17mm
thick in its magnifying ring.
"The most difficult part of the project
was making the lens breathable," Dr
Tremblay told the BBC. "If you want
to wear the lens for more than 30
minutes you need to make it
breathable."
The contact lenses might find a role
on the battlefield to help soldiers
Gases have to be able to penetrate
the lens to keep the parts of the eye
covered by the contact, especially the
cornea, supplied with oxygen, he
said.
The team has solved this problem by
producing lenses riddled with tiny
channels that let oxygen flow
through.
However, said Dr Tremblay, this
made manufacturing the lenses much
more difficult.
"The fabrication tolerances are quite
challenging because everything has to
be so precise," he said.
Despite this, gas-permeable versions
of the telescopic lens are being
prepared that will be used in clinical
trials in November, he said.
Eventually it should be possible for
those with age-related sight problems
to wear the telescopic lenses all day.
The lenses are an improvement on
other ways these sight problems have
been tackled which has included
surgery to implant a telescopic lens
or wearing bulky spectacles that have
telescopic lenses forming part of the
main lens.
Clara Eaglen, eye health campaigns
manager at the RNIB said the
research looked "interesting" and
praised its focus on macular
degeneration.
"It is encouraging that innovative
products such as these telescopic
contact lenses are being developed,
especially as they aim to make the
most of a person's existing vision,"
she said. ""Anything that helps to
maximise functioning vision is very
important as this helps people with
sight loss to regain some
independence and get out and about
again, helping to reduce isolation."
The lenses may one day find their
way into other areas as the research
was being funded by Darpa, the
research arm of the US military.
"They are not so concerned about
macular degeneration," he said.
"They are concerned with super
vision which is a much harder
problem.
"That's because the standard is much
higher if you are trying to improve
vision rather than helping someone
whose eyesight has deteriorated," he
said.

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