Scotty, Beam Me Up Some Presbyopic Lenses

What happens to your body--even your vision--after spending a year in zero gravity? That's what scientists are trying to understand, according to a New York Times article about astronaut Scott Kelly. "One of the unanswered concerns is how much astronauts could be expected to do right after landing on Mars as they readjust to gravity. Mr. Kelly, 52, now holds the record for the longest single stay in space for a NASA astronaut, and the most time overall: 520 days over four missions. (A Russian, Valeri Polyakov, holds the overall record for the longest single spaceflight: nearly 438 days.) NASA and the Russian space agency collaborated on a series of scientific studies to examine how extended weightlessness changes bones, muscles, nerves and the cardiovascular system. 'You name it, we’re interested in all of it," Dr. Charles said. In addition, NASA aims to compare changes, including genetic mutations, between Mr. Kelly and his twin brother, Mark, a retired NASA astronaut," goes the article.

Zero gravity affects the eyes: "One experiment looked at 'fluid shift' — the movement of water from the lower body toward the head when there is no gravity to hold things down. Increased pressure in the skull could cause the flattening of the eyeballs seen in some astronauts, pushing their vision toward farsightedness." Read more.

According to the website AmeritasInsight, "During extended space travel, astronauts live in microgravity, which scientists believe creates excessive pressure inside the head and impacts an astronaut’s fluid level in the eyes. According to the American Academy of Ophthalmology, these specific changes to the eyes were noticed:

• Flattening in the back of the eyeball
• Swelling of the optic nerve
• Creases in the tissue behind the retina

"Through the study, medical professionals learned that many astronauts experience correctable near and distance vision problems following space travel. This included about 23 percent of those participating in brief missions and 48 percent of those in an extended space program of at least six months. Although most reported that these were short-term issues, some continued to experience problems for several months or years following space travel. Decades ago, after documenting incidences of near-vision problems, NASA started equipping astronauts with space anticipation glasses to improve vision sharpness during aeronautical missions." Read more.

And there's more. "Pirates saw green flashes at sunset; many space-flight crew members see light flashes at night during a mission. For space crew, these flashes  are thought to come from high-energy particles interacting with the eyes and brain. The Anomalous Long Term Effects of Astronauts (ALTEA) investigation measured the effect of exposure to radiation in space, particularly on the central nervous system. One part of the study relates the light flashes to the radiation passing through the spacecraft. This knowledge helps to more accurately determine the risk and  the specific type of radiation exposure of ISS crew members, and to develop ways to protect future crews," according to a NASA website. Read more.