Hi. I'm Ashley, and I'm in grade nine. And my question is how does being in space for so long affect your body. 
Hi. It affects us a lot of different ways. 
It affects your bones, your muscles. 
But one of the ways that we're learning recently is it affects your vision. 
We don't understand why, but it makes some people's vision worse, 
and we're studying it and trying to figure it out. 
So we have a lot of new equipment on board just to test and understand our vision. 
One of the things we have is a tonometer. 
This is actually like a pressure gage that you touch to your eyeball. 
We put drops just - it's weird to put drops in your eyes with no gravity. 
You sort of touch the little drop thing to your eyeball. It spreads over your eye. 
And then one of the other astronauts will just tap the centre of my eyeball really carefully about ten times, 
and this lovely little tonometer will figure out the pressure inside my eyeball. 
That's one way to measure our eyes. 
Another is to look into the back of them. 
And so we put those drops in your eyes that dilate your eye, 
and then I actually put this up against my eye 
and plug this into a computer, and then I can look into the back of my eyeball. 
And there are expert doctors on the ground who are looking at my eyeball while I'm doing it. 
And we can take photographs and videos of the optic nerve and - or at least where it comes into my eyeball, 
and the veins and the stuff that's inside my eye. 
So we can do it that way. 
And then also, we actually do ultrasounds of our eyeballs. 
And that's in order to see how our eyeballs are changing, 
what's going on with the optic nerves. 
And so we have a full ultrasound machine onboard, but we don't need gel. 
You just put a ball of water in your eye, and then you touch the ultrasound to your eyeball, 
or just to the water above your eyeball, and move it back and forth. 
And with that, we can see our whole optic nerve, 
we can see the lens and the cornea and everything in beautiful resolution. 
It's something we've just started doing. 
And we have experts on the ground who are helping us do it. 
But with all of these things, we're trying to figure out how the human body works and what controls vision, 
and how it changes when you take away something as simple as gravity. 
We're learning more about eyeballs, 
but we're also learning more about how to stay in space permanently, 
so if you go to Mars, you won't show up there with bad vision. 
