During a recent NASA broadcast, I noticed something in the background:

eye chart?

It looks like a Snellen chart to me, but why would they have that on board? If that's not it, what is it then?

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    $\begingroup$ I love how there is also an "exit" sign. $\endgroup$
    – duzzy
    Commented Jan 31, 2016 at 23:21
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    $\begingroup$ @duzzy: It's an exit into the next section. Perfectly reasonable. $\endgroup$ Commented Feb 1, 2016 at 11:54
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    $\begingroup$ @LightnessRacesinOrbit: anyway funny. Let alone its clear and anyway selfexplanatory enough to make speculations on other reasons reasonable again. $\endgroup$
    – Zaibis
    Commented Feb 1, 2016 at 12:23
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    $\begingroup$ Aside from high-falutin' studies on the effects of weightlessness, I bet that both NASA and Roscosmos are fairly keen to find out about it ASAP if an ISS crew member's vision starts to deteriorate for any reason. Would spotting an eye chart on a naval submarine be grounds to wonder what the reason could possibly be? If it's not just for decoration then it's for testing eyesight :-) $\endgroup$ Commented Feb 2, 2016 at 11:47
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    $\begingroup$ I noticed this on the right hand side but I think it's significant enough to bear repeating in a comment: space.stackexchange.com/questions/219/… $\endgroup$ Commented Feb 2, 2016 at 16:38

2 Answers 2


Eyes do strange things in microgravity (when you consider they're deformable bags of fluid, this isn't too surprising). This report outlines the changes that can be identified after just a short parabolic flight. Eye test charts provide a way to investigate this without requiring heavy equipment or specialists.

This study appears to be an on-going project to study this on the ISS (Mar 13 - Sep 16), and is probably the reason that chart's there...

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    $\begingroup$ Although i question the ability of a printed standard chart to be useful for long... If you are taking the test weekly, for instance, after a while you are going to remember the letters, possibly unconsciously. If your brain has a record of what it is, it will tend to help your eyes out by hinting at that. This is why we can read tiny, blurry letters in our own language - our brains know the patterns of words so well it sort of mentally enhances the image. A simple test program on a laptop would work better. $\endgroup$
    – kim holder
    Commented Mar 23, 2016 at 21:29

NASA has been studying the effects of microgravity on astronauts' eyes for at least a few years. This article from Space.com from 2012 talks about some of the findings from that time.

In a new study, researchers used magnetic resonance imaging (MRI) to study the eyes and brains of 27 astronauts who spent an average of 108 days in space aboard NASA's space shuttle and/or the International Space Station. They found optical abnormalities similar to those that can occur in patients with intracranial hypertension, a potentially serious condition in which pressure builds up inside the skull. - See more at: http://www.space.com/14876-astronaut-spaceflight-vision-problems.html#sthash.h3YPDnGZ.dpuf

For example, nine of the 27 astronauts (33 percent) exhibited expansion of the cerebrospinal fluid space surrounding the optic nerve, and six (22 percent) showed flattening of the back of the eyeball - See more at: http://www.space.com/14876-astronaut-spaceflight-vision-problems.html#sthash.h3YPDnGZ.dpuf

They say it's a high priority, so having the ability to perform tests aboard the ISS makes sense, especially for the astronauts who are up there for a year.


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