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.

Treating Vision Problems Induced by Space Travel

"To reduce and better treat spaceflight-induced visual impairment, University of Houston (UH) optometrists are collaborating on a NASA study that examines ocular changes seen in a number of astronauts," according to SpaceRef. "The research, developed by Heidelberg Engineering, uses Spectralis Optical Coherence Tomography (OCT), which is a technique for obtaining subsurface images of translucent or opaque materials at a resolution equivalent to a low-power microscope. OCT effectively images reflections from within tissue to provide cross-sectional views. This technology is being used to investigate changes in visual acuity, intraocular pressure, the optic nerve and retinal structures in astronauts exposed to long-duration microgravity aboard the International Space Station (ISS)." Read more.

Why Do Most Astronauts Return with Eye Problems?

"Those who travel to space are rewarded with a beautiful sight--planet Earth. But the effects of space travel on the human sense of sight aren't so beautiful," reports Medical News Today. "More than 30 percent of astronauts who returned from two-week space shuttle missions and 60 percent who spent six months aboard the International Space Station were diagnosed with eye problems. Two recent investigations examined mechanisms that may explain eye changes in spaceflight, help find ways to minimize this health risk to astronauts and eventually prevent and treat eye diseases on Earth." Read more.

GE Global Developing Probe to Study Astronauts' Eyes in Flight

Over the next three years, GE Global Research will  build and test an ultrasound probe and measurement techniques to monitor how the spaceflight affects astronauts' vision. The probe, smaller than what is on the market, It is being designed to deliver real-time, three-dimensional pictures, showing the entire globe of the eye and any potential changes in the structure and function of the eye. NASA wants a tool that "can be used to monitor astronauts, in-flight, to watch for changes in eye structure and how the eye functions,” said Aaron Dentinger with the Ultrasound Systems Lab at GE Global Research. “The goal is to develop a new ultrasound probe that has the ability to take an entire volume of the eye with a single scan.”

At least seven astronauts, with otherwise healthy eyes, returned to Earth and needed adjustments in their prescription. For some, the vision loss lasts only a few weeks; for others the condition persists much longer and may not resolve. One possible cause for these symptoms is elevated intracranial pressure from exposure to spaceflight.Read more. You can also search the blog (use the word astronauts as your keyword) for more articles about the impact of space travel on vision.

Astronaut Vision Loss Linked to B-12 Deficiency

"Could vision changes experienced by astronauts be linked to a vitamin B-12 or folate deficiency?" asks Science Daily. "While investigating the vision changes recently identified in astronauts, nutritional assessment data showed similarities to symptoms that occur with vitamin deficiencies, according to a new study published in the March edition of The Journal of Nutrition." Read more.

Space Travel Causes Optical Abnormalities

Medical News Today reports that "magnetic resonance imaging (MRI) of the eyes and brains of 27 astronauts who have spent prolonged periods of time in space revealed optical abnormalities similar to those that can occur in intracranial hypertension of unknown cause, a potentially serious condition in which pressure builds within the skull. A retrospective analysis of the MRI data appears online in the journal Radiology." Read more.

Space Travel Hurts the Eyes

"Astronauts experience bone and muscle loss in the weightlessness of space, and now the first study of returning space travelers' eyes suggests that prolonged amounts of time in orbit can take a significant toll on vision, although the long-term effects aren't clear," says a post on Yahoo!News. "The new study, of more than 300 astronauts in the U.S. space program, found that almost 50 percent of those who served on long missions -- six months or more -- reported experiencing new problems with their ability to see objects near to them while in space and for some time after returning to Earth." Read more.