Cataracts - Blinding Flashes

They've found that a particular gene, Fibroblast Growth Factor 2 (FGF-2), jumps in activity eight-fold following a radiation dose. FGF-2 normally helps cells respond to stress. In this case, it seems to boost the activity of two other genes called "p21" and "p57." These genes control crucial events in the life cycle of a cell - e.g., when a cell divides to form two daughter cells, or when an epithelial cell transforms into a fiber cell. Blakely suspects that an imbalance of p21 and p57 leads to the formation of abnormal fiber cells and, thus, cataracts.

It takes a while for abnormal fiber cells to accumulate and visibly fog the lens. Years go by after high radiation missions before astronauts notice their cataracts. The time delay complicates research. It's hard to pinpoint the cause when you have to wait years for the effect.

more A simplified cross-section of the lens.

Early detection of cataracts is a goal of Rafat Ansari, a physicist at NASA's Glenn Research Center, working independently of Blakely. He has developed a laser probe that can detect signs of cataracts in humans years before they become visible. It's being clinically tested now at the National Eye Institute. Eventually, astronauts might carry such a probe with them on space missions, checking their eyes as they go.

Another team of researchers, led by Leo Chylack, Jr., MD, of the Center for Ophthalmic Research at Brigham and Women's Hospital in Boston, is comparing cataracts in astronauts, test pilots and members of the ground crew at the Johnson Space Center. They'll take stereoscopic pictures of the subjects' lenses to investigate differences in the type of cataracts these people get - another piece of the puzzle.

Meanwhile, Blakely is going back to the lab to learn more about the molecular underpinnings of it all. "We're still establishing the links between changes in FGF-2 and [the other genes]," she says. And there are other questions. For instance, cataracts usually develop slowly, but could sudden big doses of radiation accelerate the process? Astronauts taking off on a 6-month trip to Mars will want to know.

Her group recently won a four-year extension of their NASA research grant. Stay tuned for updates.

See also A Short History of Contact Lenses