Theses and Dissertations Collection

Extended visits to microgravity have resulted in many ophthalmic abnormalities in some long-duration spaceflight astronauts. In combination these symptoms define the spaceflight associated neuro-ocular syndrome (SANS). Theorized to be a result of increased intracranial pressure (ICP) due to headward fluid shifts, these issues often persist for some time after return to Earth and will likely worsen on extended spaceflight ventures such as visits to Mars. In particular, changes to the optic nerve, optic nerve sheath, and the posterior optic globe may have an underlying impact on ocular function. The following studies provide reliable, automated, and quantitative analysis of ON and ONS tortuosity and cross-sectional area as well as volumetric globe deformation in long-duration spaceflight astronauts. High resolution MR images were collected pre-flight as well and at five recovery timepoints post-flight for (n = 10) astronauts, extending to one year after return for 6-month missions to the international space station. Methods were developed, reliability tested, and applied to assess ON tortuosity, ON and ONS cross-sectional areas, and volumetric globe deformation in all subjects. There were no spaceflight-associated changes in tortuosity or cross-sectional areas while changes to globe deformation were quantified. The average and percent change in tortuosity, ON area, ONS area, and volumetric globe deformation immediately post-flight was -0.06 ± 0.42 mm (-0.9%), 0.58 ± 2.53 mm2 (6.7%), -0.88 ± 2.35 mm2 (-3.7%), and 10.76 ± 11.93 mm3 respectively. Tortuosity and ON/ONS area values at recovery timepoints were relatively consistent over time. Globe deformation values generally decreased across these timepoints indicating recovery after return to Earth. Quantitative highly automated MRI based assessment of the ocular structures could help our understanding of SANS and assist its prevention.