Light therapy tackles eye injuries
19:00 12 July 02
People blinded by light could be treated with more light. Researchers
have found that shining near-infrared radiation on damaged retinal
cells can keep them alive and prevent permanent blindness.
(Photo: Corbis Sygma)
(Photo: Corbis Sygma)
The US Defense Advance Research Projects Agency is funding research
into the method and hopes to use it to treat people whose eyes are
damaged by lasers. A number of US military personnel, including a
helicopter pilot over Bosnia in 1998, have suffered laser eye
injuries.
If the infrared technique works in people, it could be used to treat a
wide range of eye injuries and diseases. And it does not stop there.
Other studies have shown that infrared light can help heal all sorts
of injuries and sores, and it is already being used to treat severe
mouth ulcers in children undergoing chemotherapy.
Cell powerhouses
In the late 1990s, lab studies on cells showed that near-infrared
wavelengths can boost the activity of mitochondria, the crucial
powerhouses in cells. That caught the attention of NASA, which hoped
it could use the technique to treat astronauts in space, where
injuries heal more slowly than on Earth, possibly because mitochondria
do not function properly.
The treatment requires high-intensity light, but instead of lasers,
NASA has developed powerful light-emitting diodes for the job. Lasers
tend to damage cells, whereas LEDs can deliver light in a way that is
less harmful to tissue (New Scientist magazine, 25 September 1999, p
20). Now Harry Whelan, a neurologist at the Medical College of
Wisconsin in Milwaukee, and his colleagues have put the LEDs to the
test on eye injuries.
In a study that will appear in Proceedings of the National Academy of
Sciences, Whelan blinded rats by giving them high doses of methanol,
or wood alcohol. This is converted by the body into formic acid, a
toxic chemical that inhibits the activity of mitochondria. Within
hours, the rats' energy-hungry retinal cells and optic nerves began to
die, and the animals went completely blind within one to two days.
But if the rats were treated with LED light with a wavelength of 670
nanometres for 105 seconds at 5, 25 and 50 hours after being dosed
with methanol, they recovered 95 per cent of their sight. Remarkably,
the retinas of these rats looked indistinguishable from those of
normal rats. "There was some tissue regeneration, and neurons, axons
and dendrites may also be reconnecting," says Whelan.
Painful sores
The results have raised the hope that the LED technique could be used
to treat people for a range of eye diseases known to be caused by
mitochondrial problems. Whelan also thinks it will help treat laser
injuries to the retina, apart from areas where cells have been
completely destroyed.
Whelan has already tested the LEDs on 30 children suffering from
mucositis, a painful side effect of cancer chemotherapy. The children
had painful sores in their mouths and throats and were unable to eat
or drink, he says.
The LED treatment eliminated the mucositis and is now being used to
prevent it. "It's a night and day difference in the children's floor,"
he says. The results appeared in the Journal of Clinical Laser
Medicine and Surgery in December last year. The Food and Drug
Administration has now approved further trials in hospitals, which
will use LEDs donated by NASA.
What is not yet clear is exactly how the light stimulates healing. But
Britton Chance of the University of Pennsylvania has shown that about
50 per cent of the near-infrared light is absorbed by mitochondrial
proteins called chromophores. Whelan and his colleagues think the
light boosts the activity of a chromophore called cytochrome c
oxidase, a key component of the energy-generating machinery.
VICUG-L is the Visually Impaired Computer User Group List.
To join or leave the list, send a message to
[log in to unmask] In the body of the message, simply type
"subscribe vicug-l" or "unsubscribe vicug-l" without the quotations.
VICUG-L is archived on the World Wide Web at
http://maelstrom.stjohns.edu/archives/vicug-l.html
|