Dr. James Tsai at the Yale School of Medicine in New Haven, Conn. -- who is also chairman of the glaucoma education program committee of the National Institutes of Health -- said the eye condition damages the optic nerve that carries information to the brain.
Glaucoma can affect the outer edges of the field of vision -- the side vision. Glaucoma can come on so slowly that, in its early stages, people might not be aware it's happening, Tsai said.
"The eye care professional has to do a dilated exam and carefully look at the optic nerve for signs of glaucoma as well as assess the side vision in that patient," Tsai said in a statement.
Tsai said the risk of glaucoma was higher for African-Americans and older people.