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one of the goals of the space station is

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to help prepare humankind for future

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exploration out into the solar system as

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well as to mars and including to mars

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and other destinations

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through it we've already learned that

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some of the crew members who have been

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in a weightless environment for a long

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period of time come home with diminished

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vision

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an experiment called ocular health is

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underway to find out why and the recent

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conclusion of expedition 47 marked the

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end of its on-orbit data gathering

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recently my colleague pat ryan talked

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with the principal investigator of the

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experiment dr christian otto to find out

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where they stand and he started by

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asking otto to characterize the vision

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changes that have been noticed in

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astronauts after shuttle flights and

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after six months on the space station

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that's a really interesting question pat

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and it really goes back many years in

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fact

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in shuttle it was noticed that crew

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members had changes in their vision and

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and they were often prescribed uh

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glasses uh space anticipation glasses

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that they could wear in flight as that

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vision changed and

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this was also noted in the iss era to a

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greater degree so there was this change

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in vision

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we think that has to do with changes in

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the structural nature of the eye

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we also know from

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shuttle flights there was a change in

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the intraocular pressure usually early

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in flight in the first seven to ten days

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and that

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tended to normalize but it wasn't until

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the mid 2000s 2005 that a crew member

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returned with swelling of the optic disc

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we call that disc edema and then

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critical care emergency medicine papal

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edema if it's caused by raised

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intracranial pressure so

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this appeared a bit strange at the time

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and then a second and then a third crew

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member returned with dyskidemia and

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space medicine knew that they were

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dealing with something here that was uh

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concerning and why are we getting crew

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members returning with optic disk edema

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and there are many causes of optic disc

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edema

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and investigations with those initial

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crew members

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determined there were some structural

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changes with the eyes and over the past

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several years it's been clear there's a

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constellation of signs and symptoms that

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has been formalized into the visual

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impairment intracranial pressure risk

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and so this is a risk that's been stood

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up by nasa and the ocular health

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experiment is the first on-board

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experiment in the portfolio symptoms

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such as

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so

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clearly the one you've mentioned is a

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change in vision typically uh near

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vision would degrade and far vision

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would remain intact or even get better

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we see changes in the shape of the globe

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it gets somewhat compressed the optic

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nerve that runs from the brain to the

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eye is surrounded in a sheath and has

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cerebral spinal fluid within that sheath

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around the optic nerve and if

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intracranial pressure goes up that

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sheath diameter can can increase

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suggestive of elevated pressure and

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we've seen significant changes

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in that parameter as well

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and the the disk edema in 2012 a an

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ocular coherence tomography machine

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which is a sophisticated device used in

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ophthalmology and optometry to look at

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how much swelling occurs

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in the retina was launched to the space

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station as a significant capability on

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space station now and we were able to

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measure to the micron level changes in

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this disk edema

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and clearly

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the crew members there are different

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severities we have individuals who reach

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clinical significance if you will

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with clinical grade discidema and then

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there are others who

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either don't get very much swelling or

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have a very mild amount of swelling do

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any of them improve spontaneously once

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they come back to work

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yeah so in the ocular health experiment

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we've been able to again we're getting

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this categorization of subjects

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in 10 subjects that we've tested so far

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one has become a clinical is a clinical

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vip case so they have the edema to the

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point that it's clinically concerning

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all the others would be considered

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non-cases

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some of those again are sub-clinical but

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they're not clinical cases

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and what we're seeing is certainly in

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the case these symptoms are persisting

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not all of them but many of the symptoms

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are persisting

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through one year post flight and that's

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the length of time that the ocular

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health study is testing individuals we

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test five times post flight

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as soon as the crew member returns

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flight day 30 90 180 and then 365.

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and in other individuals the non-cases

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we see the symptoms abate

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rapidly and without consequence when

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you're first considering this

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what sort of were the options about what

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may be causing the problem

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so

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initially a lot of the work done in the

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space program has clearly shown that

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fluid shift is a is a major change that

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occurs in the physiological system one

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to two liters of fluid tends to move

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from the lower limbs

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towards the head into the thorax in the

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chest etc so that really was one of the

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first hypotheses the primary hypothesis

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that this may be

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causing some changes in the the pressure

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in the head clearly in weightlessness

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there's no acceleration due to gravity

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we do think that there may be some

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congestion of blood in in the head and

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in the brain because we don't have that

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assistance due to gravity like we have

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here on earth helping to drain the

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venous blood

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uh

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other hypotheses that we're still

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investigating

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there may be

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an underlying genetic propensity

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the

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dr smith is investigating

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we've identified that crew members who

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have an elevated cardiovascular risk

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seem to be more susceptible to the vip

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syndrome we think that may be due to the

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elasticity or what we call the

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compliance of the blood vessels and the

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ability to accommodate that fluid shift

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so if your vessels are stiffer you'll

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move more of that

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fluid towards

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the head

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a couple of minutes ago you mentioned

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a couple of different ways that you were

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getting data from the crew on orbit

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different kinds of examinations i i'm

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guessing that that relates to the

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several different possible causes that

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you're just talking about as well yeah

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pat this is an incredibly complex

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problem um that involves the ocular

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system itself is incredibly complex so

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we need to understand the changes that

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are happening in the structure

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structural anatomy we have to understand

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the functional changes so we use ocular

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ultrasound to understand what's going on

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behind the eye i mentioned the optic

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nerve sheath and changes with

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intracranial pressure

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there's the globe of the eye if you will

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appears to be compressed we're measuring

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how much compression that occurs in each

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individual so we use ocular ultrasound

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for that we want to know what's

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happening with the pressure inside the

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eye intraocular pressure which is very

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important for example in glaucoma

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patients we don't want the pressure to

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be too high or too low it appears with

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most of the crew members on station it's

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staying nominal very very comparable to

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preflight i mentioned the oct device on

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station so we can

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determine what's happening with the

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optic disc edema

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we're also using ocular ultrasound to

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look at blood flow in the eye is are the

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is the blood flow being altered and

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changing pressures and we're also

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looking at other aspects of in other

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systems that may be interacting with the

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ocular system so for example we're using

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transcranial doppler to look at changes

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in blood flow in the brain can that give

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us an indication of what's happening to

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intracranial pressure because it's that

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pressure that may be changing uh the

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pressures behind the eye do you do the

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same sort of examinations with the crew

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members after they come home to you you

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mentioned that you're going to do tests

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maybe out to a year are you doing all of

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these different kinds of tests over that

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time

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yeah we are and so it's really important

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to understand

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what is happening to the crew member

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pre-flight what are the changes in

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flight but how are they recovering post

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flight and so that was one of the

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designs of the ocular health experiment

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to follow the crew member for that

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one year post flight

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so over the entire duration of the

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experiments three year commitment for

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for the the subjects and so we are

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following them with all of the tests and

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in fact we add some tests that can't be

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done in in

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on the iss for example uh

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we do the mri magnetic resonance imaging

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in the brain pre-flight and also five

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times post flight and what we're trying

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to characterize is the recovery how fast

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is the recovery in crew members is it

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complete at one year

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and for example is it not complete and

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in the cases

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what is the recovery pattern for those

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individuals and this information will

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help us understand the

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interrelationships of the different

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systems not just the ocular system but

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potentially the cardiovascular and the

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central nervous system but help us

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understand

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what the roles are of each of these in

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in precipitating what we're seeing with

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the ocular changes and ultimately

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help us

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design countermeasures to prevent

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the vip syndrome from occurring good

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luck with the analysis

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wait to hear what happens thanks very

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much it's great to be with you dr

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christian otto is the principal

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investigator of the ocular health