The International Space Station (ISS) Ocular Surveillance protocol aims to systematically gather physiological data to characterize the Risk of Microgravity-Induced Visual Impairment and Intracranial Pressure (VIIP) on crewmembers assigned to a six month ISS Increment. The data collected will mirror Medical Requirements Integration Documents (MRID) requirements and testing performed during annual medical exams. The frequency of in-flight and post flight testing will be increased to more accurately assess changes that occur in the visual, vascular, and central nervous systems upon exposure to microgravity and induction of fluid shifting. Monitoring in-flight changes, in addition to post flight recovery, which is the main focus of this protocol.
The overall objectives of this study include the following:
- Characterize the nature of in-flight visual, vascular, and central nervous system changes during six months of exposure to microgravity.
- Document changes from pre- to post flight.
- Document changes post-flight, including the post flight time course for recovery to baseline.
This investigation hypothesizes that some crewmembers will experience meaningful and detectable changes before, during, and after space flight in at least one or more of the following measurements: visual acuity, intraocular pressure, optic disc edema, choroidal folds, optic nerve sheath distention, optic nerve tortuosity, optic nerve to sheath ratio, globe flattening, and retinal “cotton-wool spots.” Moreover, it is expected that crewmembers will have changes before and after in the Cerebrospinal fluid (CSF) velocity through the aqueduct of Sylvius and the retinal nerve fiber layer. It is further anticipated that measures observed during and after space flight will deviate from the baseline measurements, which may prolonged the recovery period to return to the baseline values.
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Preflight, in-flight and post flight measures include: tonometry, ocular ultrasound, fundoscopy, and visual acuity; contrast sensitivity and threshold visual fields. While, Magnetic Resonance Imaging (MRI), Optical Coherence Tomography (OCT), refraction, pupil reflexes and bio-microscopy will be captured preflight and post flight exclusively. Two additional, research measures being investigated include blood pressure and cardiac output, which will be collected preflight, in-flight and post flight to assess vascular compliance.
Data collection will begin one year prior to flight, continue in-flight approximately every 30 days, and through to one year post flight. In circumstances where abnormalities may persist beyond one year, post flight data will continue to be collected, but per the MRID requirements and Visual Impairment/Intracranial Pressure (VIIP) clinical practice guidelines.
This experiment is in progress. Results will be available at a later date.
Giovanni T, Cromwell RL, Zanello SB, Yarbough PO, Ploutz-Snyder RJ, Bernard F. Godley BF, and Vizzeri G. Ocular outcomes comparison between 14- and 70-day head-down-tilt bed rest. Investigative Ophthalmology and Visual Science.
2016. February; 57(2): 495–501. [DOI]
Mader TH, Gibson CR, Otto CA, Sargsyan AE, Miller NR, Subramanian PS, et al. Persistent Asymmetric Optic Disc Swelling After Long-duration Space Flight: Implications for Pathogenesis. Journal of Neuro-ophthalmology.
2017. June 1; 37(2):133–9.
Anterior chamber depth
Cerebral blood flow velocity
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Diffusion tensor imaging
Extra ocular muscle balance
Inflight intraocular pressure
Optic nerve diameter
Optic nerve sheath diameter
Optic nerve tortuosity
Optical axial length
Optical coherence tomography
Retinal nerve fiber layer thickness
Slit lamp test
Threshold Visual Field
Crew health and performance is critical to successful human exploration beyond low Earth orbit.
The Human Research Program (HRP) investigates and mitigates the highest risks to human health
and performance, providing essential countermeasures and technologies for human space exploration.
Risks include physiological and performance effects from hazards such as radiation, altered gravity,
and hostile environments, as well as unique challenges in medical support, human factors,
and behavioral health support. The HRP utilizes an Integrated Research Plan (IRP) to identify
the approach and research activities planned to address these risks, which are assigned to specific
Elements within the program. The Human Research Roadmap is the web-based tool for communicating the IRP content.
The Human Research Roadmap is located at: https://humanresearchroadmap.nasa.gov/
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for information of how this experiment is contributing to the HRP's path for risk reduction.