Once the optic nerve that’s responsible for sight is damaged, it’s impossible to see again. At least that’s been the dogma. But a group of U.S. scientists has upended that thinking and helped mice with destroyed optic nerves to see again. It does not have immediate implications for humans yet, but it points researchers in promising new directions.

Andrew Huberman, an associate professor of neurobiology at Stanford University, and his team describe their advance in a study published in Nature Neuroscience. To learn about the way vision nerves grow, they crushed the optic nerve in one eye of mice. Once destroyed, the long finger-like extensions sent out by nerve cells from the eye to the brain start to shrivel, eventually severing any connection to the brain and resulting in blindness. Huberman and his colleagues, however, found that a combination of visual stimulation of the nerve, along with nerve-growing chemicals, can rescue these extensions, called axons, and coax them to stretch out again. Not only that, but the axons are able to find their appropriate connections to the correct sight-dedicated parts of the brain to restore vision. Mice with similar damage to the nerve that didn’t receive the treatment did not show much regrowth of the axons.

About three weeks after the optic nerves in the mice were damaged, the researchers saw evidence of axons extending back into the brain from the eye, something that previous efforts to regenerate eye nerves haven’t done with much reliability. The combination of keeping the damaged but remaining axons stimulated, by exposing the mice to bars on a screen that are moving in different directions, and the nerve growth factors lead to a 500-fold increase in axon regrowth. Granted, not all of the axons managed to sprout again, but those that did were able to do so with impressive speed and distance to reach the brain.

When the researchers conducted four different tests to verify how much of the regrowth contributed to actual restoration of vision in the animals, the animals passed two of the tests that detected large objects and movement.

“For the longest time people in the field wondered if neurons could regenerate and form the correct patterns to connect to the brain, and we found that they did,” says Huberman.

The most compelling finding is that the study suggest that once nerves are coaxed to grow again, they retain the instructions to find their proper connections in the brain’s visual center. If nerves growing toward the brain are like visitors to New York’s Grand Central Station, these nerves are like well-equipped travelers with maps and specific instructions for finding their destination. “It means that neurons remember the way home; they never forget,” says Huberman.

That’s encouraging him and his team to start considering how to translate the results to treat blindness in people. Keeping the axons stimulated by exposing them to stimuli is an easy first step; if these axons are kept alive, then they have a chance of regrowing again, as the mouse study showed…

The summer’s no vacation for blood banks, and this one has been especially hard: Just after the fourth of July, the American Red Cross issued an emergency call for blood and platelet donations. This time of year, “blood donors are typically out of town and unable to give," explains Justin Kreuter, MD, medical director of the Mayo Clinic Blood Donor Center in Rochester, Minnesota; or they may not be eligible to donate after traveling to certain areas outside the United States. “It really hits us in the summer months,” Dr. Kreuter says. Your community needs your help now; here’s what you should know about pitching in.

Eligibility is always changing, and Zika’s a concern this year

The Red Cross maintains an alphabetical list of eligibility criteria for potential donors—from acupuncture (thumbs up) to Zika (thumbs down)—and can give you the latest information on whether or not you’re good to give. There have been no reported cases of Zika transmission via blood transfusion so far, according to the Centers for Disease Control and Prevention (CDC), but there’s a strong possibility that the virus can be transmitted that way. “What we’re doing now, per the FDA, is deferring [donors who may have been exposed to Zika] for 28 days, which is twice the known period of infectivity,” Dr. Kreuter says. Because Zika can be transmitted by sexual contact (via semen) as well, women with male partners who have visited Zika-affected areas are deferred for three additional months.

RELATED: 4 Unexpected Benefits of Donating Blood

The FDA regulates donor blood just as aggressively as it regulates drugs

“It takes a lot of money to do the infectious-disease testing that we do [on donor blood], and when we create blood products out of the donation, that’s done to the same standards as any drug manufactured in this country. The FDA holds us to those same standards, so it’s a very high level of quality and also resources that are invested,” Dr. Kreuter explains. “These tests and high standards are what’s keeping the blood supply safe, so that if my wife or one of my daughters needs a blood transfusion, I can feel assured that I can just sit at their bedside and hold their hand rather than worry about what that might result [in] for them later down the road.”  

You’ll get a mini-physical before you donate

The flip side of donor blood screening (which ensures that it’s safe for the eventual recipient) is confirming the donor’s health (which ensures that the blood draw won’t have a negative effect on them). “We check blood pressure and pulse, we do a pinprick to check red blood cells to make sure they’re safe—we don’t want to make our donors iron deficient,” Dr. Kreuter says. He makes no specific suggestions about what you eat and drink prior to donation; just be sure you have breakfast and lunch under your belt, and take it easy on caffeine…