Implanted chip 'allows blind people to detect objects'
November 07 BBC
A man with an inherited form of blindness has been able to identify
letters and a clock face using a pioneering implant, researchers say.
Miikka Terho, 46, from Finland, was fitted with an experimental chip
behind his retina in Germany. Success was also reported in other
patients.
The chip allows a patient to detect objects with their eyes, unlike a
rival approach that uses an external camera.
Details of the work are in the journal Proceedings of the Royal
Society B.
Professor Eberhart Zrenner, of Germany's University of Tuebingen, and
colleagues at private company Retina Implant AG initially tested their
sub-retinal chip on 11 people. Some noticed no improvement as their
condition was too advanced to benefit from the implant, but a majority
were able to pick out bright objects, Prof Zrenner told the BBC.
However, it was only when the chip was placed further behind the
retina, in the central macular area in three people, that they achieved
the best results.
Two of these had lost their vision because of the inherited condition
retinitis pigmentosa, or RP, the other because of a related inherited
condition called choroideraemia.
RP leads to the progressive degeneration of cells in the eye's
retina, resulting in night blindness, tunnel vision and then usually
permanent blindness. The symptoms can begin from early childhood.
The best results were achieved with Mr Terho, who was able to
recognise cutlery and a mug on a table, a clock face and discern seven
different shades of grey. He was also able to move around a room
independently and approach people. In further tests he read large
letters set out before him, including his name, which had been
deliberately misspelled. He soon noticed it had been spelt in the same
way as the Finnish racing driver Mika Hakkinnen.
"Three or four days after the implantation, when everything was
healed, I was like wow, there's activity," he told the BBC from his home
in Finland. "Right after that, if my eye hit the light, then I was able
to see flashes, some activity which I hadn't had.
"Then day after day when we started working with it, practising, then
I started seeing better and better all the time."
Soon Mr Terho was able to read letters by training his mind to bring
the component lines that comprised the letters together. The prototype
implant has now been removed, but he has been promised an upgraded
version soon. He says it can make a difference to his life.
"What I realised in those days was that it was such a great feeling
to focus on something," he says.
"Even having a limited ability to see with the chip, it will be good
for orientation, either walking somewhere or being able to see that
something is before you even if you don't see all the tiny details of
the object."
The chip works by converting light that enters the eye into
electrical impulses which are fed into the optic nerve behind the eye.
It is externally powered and in the initial study was connected to a
cable which protruded from the skin behind the ear to connect with a
battery. The team are now testing an upgrade in which the device is all
contained beneath the skin, with power delivered though the skin via an
external device that clips behind the ear.
This is by no means the only approach being taken by scientists to
try to restore some visual ability to people with retinal dysfunction -
what's called retinal dystrophy. |