VOA标准英语2010年-Early Signs of Glaucoma Show up in Bra（在线收听）

Glaucoma is the leading cause of irreversible loss of vision worldwide and now doctors believe the devastating disease begins in the brain and not in the eye as has long been thought.

Dr. David Calkins, director of research at the Vanderbilt Eye Institute in Tennessee, quotes estimates that by the year 2020, there will be 80 million cases of glaucoma worldwide.

Glaucoma is called the 'silent thief of sight,' since most people with the disease don't notice a change in their vision. It happens gradually, as increased fluid pressure inside the eye, known as ocular pressure, damages the optic nerve, which sends visual images to the brain. Damaged nerve cells cannot be replaced or repaired.

There is currently just one treatment for glaucoma, which is to reduce ocular pressure. Doctors test for glaucoma by measuring pressure inside the eye and checking peripheral vision.

But Calkins and his colleagues have discovered that the earliest signs of glaucoma are not in the eye, but in the brain.

A new understanding of the disease progression

"We don't really understand why it is that there is a loss of communication at the brain first," Calkins says, adding that it is now clear the degeneration of vision starts in the brain and works its way back to the retina, rather than the other way around.

The finding suggests that glaucoma may be reversible in the early stages, since the nerve structures between the brain and the optic nerve do not degenerate right away. "The structure that allows the communication remains in place for a very, very long time," Calkins says.

And that, he says, opens up new ways to treat glaucoma and puts it in an entirely new perspective.

"Instead of treating it just as a disease of the eye, we now understand that it is really a neurological disease that involves loss of communication between the optic nerve and the brain." And, by studying glaucoma as a neurological disease, Calkins says researchers may be able to learn more about other age-related neuro-degenerative disorders like Alzheimer's and Parkinson's disease.

The study appeared in the "Proceedings of the National Academy of Sciences."