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many astronauts are coming back from

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long duration missions to iss with

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diminished vision and station science is

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working to understand why station crew

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members take part in the ocular health

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experiment gathering data on the eyes

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and weightlessness so scientists can

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determine what's causing the vision loss

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and develop counter measures

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last week my colleague brandi dean

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showed us how the crew members conduct

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an examination using a tonometer and

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today she reports on eye exams using an

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ultrasound

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hi welcome back to the medical

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simulation laboratory just off site at

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johnson space center in houston where we

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have learned recently a little bit about

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some of the different ways that we're

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finding out about what happens to

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astronauts eyesight when they're in

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space we're back today to learn

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specifically about the ultrasound that

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the crews perform to learn more about

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that and we have with us today dr ashat

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sargissian who is an ultrasound imaging

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expert and also one of the investigators

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on several of the studies that are

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looking into that

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so thank you so much for joining us

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pleasure to be here all right well so

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why don't we start with why do we do

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ultrasounds on astronauts eyes in space

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well sound is one of the

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imaging modalities that we use on

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astronauts before during and after

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missions and this modality is very good

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for portability

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non-invasiveness and

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it's very informative while looking at a

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specific organ we're talking about the

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eye it was one of the first devices that

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we used for this problem and

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the reason being

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it is just best suited to look at

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certain areas of the eye and best with

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it for some measurements

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that we can conduct and in general

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ultrasound is easily

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easily transmittable so we can get a

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real-time video from the space station

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we can guide the crew members during the

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procedure actually we do not use too

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much time doing it but most importantly

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again is the information that we derive

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out of those images what kind of

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information do you get

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the information

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received by ultrasound imaging

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is twofold one aspect of it is structure

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or anatomy

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using the eye model here i can

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demonstrate

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we measure for example the distance

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between the very front of the eye and

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the back of the eye

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this way

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we can monitor this distance and turns

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out in some crew members this distance

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becomes shorter during the mission

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progressively shorter and if this

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distance makes becomes shorter the

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subject needs to wear the reading

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glasses to to see well and some subjects

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who

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use glasses for distant vision have to

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throw them away because they don't need

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them anymore because this distance is

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naturally shorter so there is some

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silver lining in some crew members but

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generally it's a sign of concern so i

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know you've done a number of these exams

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or had the crew do a number of the exams

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on orbit have you been able to collect

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some good data so far besides looking at

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the anatomy and structure we also look

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at physiology

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in broader term specifically we look at

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at the

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flow of blood in and out of the globe we

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have multiple vessels as you can see on

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this model

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and the reds are arteries and the

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yellows are nerves actually but there

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are four veins coming out of the globe

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and then there is a pair of vessels that

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comes out of through the optic nerve

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right in the central canal of the optic

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nerve so these are tiny tiny vessels

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those are now less than a millimeter in

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diameter however this technology allows

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us to not accurately describe the

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character of the flow inside of those

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vessels and the

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actual velocities of flow of the blood

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um

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this is

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more a scientific aspect of sound

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imaging where we're we're trying to tie

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the changes in the eye to the

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changes that body in the body in general

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undergoes including shift of fluids

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including some swelling of the upper

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part of the body and difficulty in

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venous drainage from some parts of the

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body including the eye so that's one of

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the hypotheses that one of the multiple

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factors we're dealing with is the

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changes in the blood flow

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can you tell us what we're looking at

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here

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this is the ultrasound scanner actually

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an exa exact copy of what we have on the

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international space station it's one of

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the most used research hardware actually

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we fly these days

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you can notice that the keyboard is uh

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unlike most medical devices it's very

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colorful there's a reason for that we

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have made it

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color coded so that we can remotely

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guide the crew members to the right

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button more easily for example this

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would be a purple two up this would be a

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pink two this would be a green four and

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so on okay so it makes the remote

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guidance much easier to perform why

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don't you show me what we do with this

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all right you're in a position similar

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to an astronaut about to be examined on

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the international space station and

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there will be a second astronaut uh to

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assist with the machine and uh so on so

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i will be the assisting okay remember in

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this case i'm handing you a probe

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already with gel all right i think layer

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of gel

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and you take off your glasses and

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center yourself relative to the screen

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okay do a chin up

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position with

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the probe going on to your upper eyelid

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okay gently ease it on the upper eyelid

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once you apply the probe we can see the

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circle the black circle on the screen

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that takes up most of the image is the

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eye globe actually okay you can

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appreciate the curvature of the back of

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the eye and now if you're a tilt the

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probe with the cable end of the probe

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towards your feet very very slowly

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there we go that's a that's a very good

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view the optic nerve coming and meeting

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the eye here is where the 1.2 million uh

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nerve fibers are located in the bundle

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here inside the central part of this

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tribe but we're very interested in the

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gray zone in both sides of this dark

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stripe which is the space that

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communicates with the intracranial space

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and pressure inside the skull propagates

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all the way to reach the globe here so

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this diameter is very important also

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important is the distance between the

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front of the eye and the back

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respectively for these uh three values

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tell us that something's going not

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perfect with the given subject well how

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does my eye look all right it looks

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perfect gorgeous and unchanged

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all right

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so have you been able to draw some some

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conclusions based on what you've learned

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so far

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we do see changes in the structure we do

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see some

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progression and regression as the

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mission

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continues and

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gets completed eventually

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most of the changes return back to their

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pre-applied levels

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we do see for example

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changing the curvature of the back of

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the eye that's we call it flattening

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although it's not really flat flat in

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most cases but it's flattening over the

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back of the eye which may be an

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indicator that there is a disbalance

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between the pressures inside the globe

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and behind the globe

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the thing is uh the fact is that the

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space between the sheet and the nerve

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itself is pressurized and the pressure

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equals the pressure inside the skull so

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if the intracranial pressure rises that

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reflects the pressure propagates all the

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way to the globe

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and therefore changes the balance of

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pressures right at this interface

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so one of those things that we can

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describe well with ultrasound is that

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shape of the back of the globe and the

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diameter of the

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nerve so those things together combined

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tell us something is happening okay so

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based on that what you've already

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learned what do you do next you keep

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gathering the same data or add to it or

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we do this and produce data for flight

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surgeons to use immediately so the

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immediate use for the data at least some

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of the data

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is part of the clinical practice of

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space medicine nowadays so the flight

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surgeon looks at those numbers and looks

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at the trends

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and

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somehow modifies the surveillance

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intensity how frequently they look uh do

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they do

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additional testing in shorter time

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intervals and so on so that's the

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immediate clinical monitoring of the

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crew member however

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the long-term analysis of the cohort as

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a whole will give us more information

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about

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factors of predisposition why do some

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crew members develop vision changes and

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others don't and

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finally we correlate our ultrasound

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imaging data with other data so we have

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a suite of different diagnostic methods

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so we have the luxury of statistical

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analysis that tells us

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um

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pretty individualized

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picture of what's going on we do need

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more subjects though so that scientific

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aspect of of this work

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will take some time

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but picture

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papers are already coming out

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all right well thank you so much for

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talking with us again this was dr ashto

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sargusian who is an ultrasound imaging

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expert and one of the principal

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investigators of several of the studies