{"id":5870,"date":"2015-11-03T14:21:12","date_gmt":"2015-11-03T19:21:12","guid":{"rendered":"http:\/\/geiselmed.dartmouth.edu\/news\/?p=5870"},"modified":"2015-11-13T15:50:57","modified_gmt":"2015-11-13T20:50:57","slug":"an-eye-on-microgravity","status":"publish","type":"post","link":"https:\/\/geiselmed.dartmouth.edu\/news\/2015\/an-eye-on-microgravity\/","title":{"rendered":"An Eye on Microgravity"},"content":{"rendered":"

As fun as weightlessness may appear to be, microgravity poses health challenges for astronauts. Eyes are among the organs affected, and some astronauts on long-duration missions are returning to Earth with permanent changes in their vision.<\/p>\n

\u201cIt\u2019s not just vision that\u2019s altered. The structure of the eye changes,\u201d says Jay Buckey, MD, a professor of medicine and head of the Space Medicine Innovations Lab at Geisel. \u201cThe eye\u2019s a bit shorter and looks as though it\u2019s been pushed from the back. This is something usually seen in people who have elevated pressure in the fluids surrounding the brain\u2014a condition called idiopathic intercranial hypertension.\u201d<\/p>\n

Astronauts, however, don\u2019t show any of the other signs of elevated pressure in the head and the reason for the flattening of the eyeball is mysterious. Though the vision change is not a major problem\u2014it results in farsightedness and can be corrected with glasses\u2014it can be permanent. What concerns Buckey is that it\u2019s happening at all, and he\u2019s driven to understand why. A former astronaut, Buckey flew in 1998 as a Payload Specialist aboard the Space Shuttle Columbia\u2019s Neurolab Mission, and has written a textbook on space physiology and the adaptation to microgravity.<\/p>\n

Buckey\u2019s interdisciplinary \u201cSpace Eyes\u201d team has been investigating the detrimental effect of microgravity on eyes for the past three years. In his lab at Geisel, they study the effects of changes in the direction of gravity on the eye by taking measurements from individuals in different body postures.<\/p>\n

\"Buckey's
Buckey's team conducted their research on a NASA C-9 aircraft. Photo courtesy of NASA.<\/figcaption><\/figure>\n

But studying the eye in weightlessness requires simulating space flight. And where better to experience microgravity than on a NASA C-9 aircraft that produces short periods of weightlessness during parabolic flight. This year the team, which includes Michael Zegans, MD, an ophthalmologist and professor of surgery at Geisel, traveled to Johnson Space Center in Houston, Texas to collect data in microgravity.<\/p>\n

Performing the experiments required moving the lab\u2019s equipment to Houston, qualifying it to fly on the aircraft, and training the team to make the microgravity measurements. Abigail Fellows, a research coordinator in the lab, and Allison Anderson, a post-doctoral fellow, transferred the lab to Ellington Field in Houston. There, the team gathered detailed baseline measurements and data from the test subjects in upright, supine, and prone positions both prior to and during parabolic flight. The researchers used a Spectralis Optical Coherence Tomography (OCT) device, and a Lenstar Optical Biometer to view the eye\u2019s structure.<\/p>\n

On the flights, Gautam Babu \u201816, a Dartmouth undergraduate, operated the OCT device during all four segments of microgravity. He recorded the thickness of the choroid, which assists in focusing the eye, along with the anterior chamber angles\u2014an important structure for regulating eye pressure\u2014of the test subjects. Babu and fellow Dartmouth undergraduate Helen Gu \u201818, who was also a test subject, collected data, ensured the equipment was operational for each flight, and taught test subjects what they needed to do during flight.<\/p>\n

Experiencing microgravity for 20 seconds on each of the 40 daily parabolas was an experience like no other, Babu recalls. \u201cIt was exhilarating and satisfyingly tiring, but it was also gratifying when everyone worked together to overcome challenges,\u201d he says. \u201cIt was great working together with the doctors, engineers, and students\u2014seeing how we all made meaningful contributions.\u201d<\/p>\n

Back in the lab, the team is analyzing the data on how the thickness of the choroid, length of the eye, and pressure in the eye change in microgravity, and in different body postures. It\u2019s tempting to wonder how data gathered after a mere 20 seconds of cumulative weightlessness contributes to understanding the affect of microgravity experienced by astronauts over several months.<\/p>\n