Tuesday, May 29, 2012
Damage to the optic nerve robs people of their eyesight and it's long been considered an irreversible loss. But maybe it isn't.
A team of researchers at Boston Children's Hospital has not only grown new optic nerve fibers in mice, but also restored some basic elements of vision.
The researchers, led by Larry Benowitz, showed that mice with severe optic nerve damage can regain some depth perception, the ability to detect overall movement of the visual field, and perceive light, allowing them to synchronize their sleep/wake cycles.
Findings were published online by the Proceedings of the National Academy of Sciences.
What does that mean for humans? The researchers are hopeful that patients blinded by optic nerve damage from trauma or from glaucoma, estimated to affect more than 4 million Americans, might be able to regain at least some visual function.
In other forms of vision loss, such as macular degeneration, people can sometimes regain visual acuity, but there is currently no way to recover from damage to the optic nerve.
Big step forward
Previous studies, including many by the Benowitz lab, have demonstrated that optic nerve fibers can regenerate some distance through the optic nerve. This development, however, takes it another big step.
"Dr. Benowitz and his group have, for the first time, established proof-of-concept that a damaged optic nerve can regenerate and attain lost function," said Nareej Agarwal, PhD, of the National Eye Institute, which supported the study. "This is an important advance in an effort to reverse vision loss in glaucoma and other neurodegenerative diseases."
Benowitz cautions, however, that the vision the mice regained was limited, and probably didn't restore the ability to discriminate objects.
"What lies behind what we call seeing is very complicated – so many subsystems contribute to seeing," he said. "We're in a sense just scratching the surface about functional recovery."