Microgravity and Astronauts: Do Spacewalks Cause Optical Abnormalities?


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Microgravity may be damaging our astronauts' vision: Image by Bobrov Alexey

Is exposure to microgravity hurting our astronauts? A new study, published today in the journal Radiology, discusses 27 astronauts’ MRI (Magnetic resonance imaging) results which show that after prolonged time in space, optical abnormalities occur.

Interview With Larry Kramer, M.D.

Decoded Science had the opportunity to interview the professor of diagnostic and interventional imaging at the University of Texas Medical School at Houston, Larry A. Kramer, M.D.

Decoded Science: Were these astronauts affected more by the duration of their exposure to microgravity, or was the effect the same over a span of time with multiple exposures? In other words, if Astronaut A. went on a single spacewalk for 30 days, and Astronaut B. went on 5 spacewalks over the course of 3 years, with a total cumulative microgravity exposure of 30 days, would they suffer similar results?

Dr. Kramer: We only divided astronauts in terms of cumulative days exposure to microgravity and therefore Astronaut A and Astronaut B were coded the same. We did not look at frequency of exposures as a variable, so there is no definitive answer to your excellent question.

Decoded Science: Have the astronauts with these abnormalities, identified on MRI, also suffered noticeable symptoms?

Dr. Kramer: It is difficult for me to answer that question since I did not perform any of the clinical exams, but I can reference a recently published study on the subject. Dr. Tom Mader, a neuro-ophthalmogist, recently published in Ophthalmology (2011) the following results: “300 postflight questionnaires documented that approximately 29% and 60% of astronauts on short and long-duration missions, respectively, experienced a degradation in distant and near visual acuity. Some of these vision changes remain unresolved years after flight“. Dr. Mader also noted that all symptoms occurred after long term exposure to microgravity and disc edema (swelling of the optic nerve) in 2 astronauts was documented by direct observation on board the spacecraft.

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