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Principal Investigator:
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Brandon R. Macais
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Organization:
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University of California, San Diego
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These experiments will determine intracranial pressure (ICP), intraocular pressure (IOP), and ocular structures-function using state-of-the-art noninvasive techniques during conditions know to simulate microgravity induced headward fluid shifts in healthy astronaut-aged individuals.
Hypothesis
A headward fluid shift during microgravity exposure causes elevation of translaminar pressures (ICP-IOP) at the optic nerve head, compromising ocular structures-function. We will test proven head-ward fluid shift countermeasures (lower body negative pressure exercise and Braslet) to mitigate elevations of ICP and IOP.
The same device used for pre-, in- and post-flight ICP measures of astronauts will be utilized. These studies will employ a whole body tilt protocol known to induce headward fluid shifts and raise ICP, enabling direct comparisons of IOP, ICP and ocular structures-function. Moreover, these studies will determine the efficacy of lower body negative pressure or Braslet countermeasures to mitigate elevations in ICP and IOP during conditions known to induce head-ward fluid shifts. Briefly, measures of ocular structure will include: optic nerve head and macula tomography, retinal nerve fiber layer thickness, anterior-to-posterior axial length of the eyeball, and retrolaminar subarachnoidal space of cerebrospinal fluid (CSF). Measures of ocular function will include: best corrected visual acuity, total retinal blood flow and capillary blood flows in the optic nerve head and in the macula area.
The NASA Countermeasure Readiness Level may be regarded 2 at the beginning of the study and the level will rise to 6 at the conclusion of the study if the countermeasure of lower body negative pressure or Braslet is successful. These experiments will establish standard tests, methodologies and databases for the assessment of acute changes in ICP and IOP. These low-cost experiments will deliver rapid data that can be used as a foundation for future flight-analog and flight studies.
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