Glaucomas are among the most common neurodegenerative diseases, and a leading cause of blindness in the United States. Many patients with glaucoma have high intraocular pressure (IOP), long believed to be a cause of the degeneration of the optic nerve and nerve cells in the retina that leads to vision loss. The standard treatment for glaucoma is reducing the intraocular pressure by medication or surgery.
However, researchers have also observed that some patients with elevated IOP do not develop optic nerve and retinal damage, while others do incur damage despite relatively normal IOP. "It's increasingly clear," says Dr. Simon W.M. John, leader of the Jackson Laboratory research team and a Howard Hughes Medical Institute Investigator, "that multiple mechanisms are at work in this disease."
John and researchers elsewhere have identified several genes associated with glaucomas. They have also developed inherited mouse glaucoma models that reliably develop glaucoma in mid-life. One of these models is the DBA/2J mouse.
The Jackson research team treated 5- to 8-week-old DBA/2J mice with a single, high dose of gamma radiation, together with bone marrow transfer.
When they examined the mice at 12-14 months--an age at which most DBA/2J mice have advanced glaucoma--the researchers were amazed to find that the vast majority of mice did not have glaucoma. There was no detectable loss of the retinal ganglion cells, which typically degenerate in glaucoma.
"It was very surprising and we had to be very careful," John said. "We repeated the experiment two more times with the same results."