Light could prevent alcohol poisoning from causing blindness, a new rat study suggests. Shining red light into intoxicated rodents' eyes stops them going blind.

Just one shot glass of neat methanol, a common ingredient in antifreeze and windscreen-washing fluid, can blind a human permanently within days. There are over 5,000 accidental overdoses in the United States alone every year.

Sitting methanol-poisoned rats under a near-infrared light source for two and a half minutes each day for three days reduces swelling in their retinal cells, making them "more responsive to light", says toxicologist Janis Eells at the Medical College of Wisconsin in Milwaukee.

Eells hopes that, in the future, light therapy will be used alongside conventional treatments for methanol poisoning, which include drugs and dialysis. "If we can get to people fast enough, we can save their sight," she says. Light would be shone on a patient's eyes for a couple of minutes each day for four to five days, she envisages.

Ophthalmologist John Forrester of the University of Aberdeen, UK, agrees that the study’s results sound promising, but is cautious about extrapolating too widely from animals to humans.

Eells and her colleagues use a light-emitting diode that produces infrared light with ten times the energy of infrared from the Sun, while remaining cool to the touch.

The diode was developed by NASA and electronics company Quantum Devices, based in Barneveld, Wisconsin, to help plants grow on long space missions. "We were looking for a light source that wasn't the size of two refrigerators," says Quantum Device's founder and president, Ron Ignatius. About the size of a cigarette packet, the device is lightweight and cheap.

Astronauts tending to the plants on the International Space Station noticed that their cuts and bruises healed more quickly under the special light. In clinical trials, the light also helped to clear up diabetic skin ulcers in mice, and painful mouth ulcers in children undergoing chemotherapy. It may work by revving up mitochondria, tiny structures in cells that provide them with power.

Researchers hope that light therapy might also alleviate other retinal diseases, such as age-related macular degeneration, which affects up to 10% of those over 65 and is currently untreatable.

"This is an interesting approach," says retinal-cell biologist Mike Cheetham of London's Institute of Opthalmology. "But it needs to be tested in models that are more relevant to human disease." Human retinal diseases are caused by a variety of factors, so one therapy is unlikely to cure them all.

References

1.Eells, J .T. et al. Therapeutic photobiomodulation for methanol-induced retinal toxicity. Proceedings of the National Academy of Science, doi:10.1073/pnas.0534746100 (2002). |Article|

© Nature News Service / Macmillan Magazines Ltd 2003