[Skip to Content]
[Skip to Content Landing]
Original Investigation
December 26, 2019

Optic Disc Edema and Choroidal Engorgement in Astronauts During Spaceflight and Individuals Exposed to Bed Rest

Author Affiliations
  • 1KBR, Houston, Texas
  • 2College of Optometry, University of Houston, Houston, Texas
  • 3German Aerospace Center, Cologne, Germany
  • 4NASA Johnson Space Center, Houston, Texas
JAMA Ophthalmol. 2020;138(2):165-172. doi:10.1001/jamaophthalmol.2019.5261
Key Points

Question  Are the ocular changes that develop in a ground-based analogue of weightlessness similar to the ocular changes experienced by astronauts during weightlessness?

Findings  Peripapillary total retinal thickness increased to a greater degree among individuals exposed to bed rest than among astronauts during spaceflight, while choroidal thickening developed only among astronauts during spaceflight.

Meaning  Differences in peripapillary total retinal thickness and choroidal thickness observed in astronauts vs individuals exposed to bed rest suggest that the mechanism(s) underlying optic disc edema may differ between those groups.


Importance  Optic disc edema develops in astronauts during long-duration spaceflight and is a risk for all future astronauts during spaceflight. Having a ground-based analogue of weightlessness that reproduces critical features of spaceflight-associated neuro-ocular syndrome will facilitate understanding, preventing, and/or treating this syndrome.

Objective  To determine whether the ocular changes in individuals exposed to an analogue of weightlessness are similar to the ocular changes in astronauts exposed to a duration of spaceflight comparable to this analogue of weightlessness.

Design, Setting, and Participants  This cohort study, conducted from 2012 to 2018, investigated 11 healthy test participants before, during, and after 30 days of strict 6° head-down tilt bed rest as well as 20 astronauts before and during approximately 30 days of spaceflight. Data were collected at NASA Johnson Space Center, the German Aerospace Center, and on board the International Space Station. Statistical analysis was performed from February 13 to April 24, 2019.

Main Outcomes and Measures  Peripapillary total retinal thickness and peripapillary choroid thickness quantified from optical coherence tomography images.

Results  Peripapillary total retinal thickness increased to a greater degree among 11 individuals (6 men and 5 women; mean [SD] age, 33.4 [8.0 years]) exposed to bed rest than among 20 astronauts (17 men and 3 women; mean [SD] age, 46.0 [6.0] years), with a mean difference between groups of 37 μm (95% CI, 13-61 μm; P = .005). Conversely, choroid thickness did not increase among the individuals exposed to bed rest but increased among the astronauts, resulting in a mean difference between groups of 27 μm (95% CI, 14-41 μm; P < .001).

Conclusions and Relevance  These findings suggest that strict head-down tilt bed rest produces a different magnitude of edema than occurs after a similar duration of spaceflight, and no change in choroid thickness. It is possible that a mild, long-term elevation in intracranial pressure experienced by individuals exposed to bed rest is greater than the intracranial pressure experienced by astronauts during spaceflight, which may explain the different severity of optic disc edema between the cohorts. Gravitational gradients that remain present during bed rest may explain the lack of increase in choroid thickness during bed rest, which differs from the lack of gravitational gradients during spaceflight. Despite the possibility that different mechanisms may underlie optic disc edema development in modeled and real spaceflight, use of this terrestrial model of spaceflight-associated neuro-ocular syndrome will be assistive in the development of effective countermeasures that will protect the eyes of astronauts during future space missions.

Limit 200 characters
Limit 25 characters
Conflicts of Interest Disclosure

Identify all potential conflicts of interest that might be relevant to your comment.

Conflicts of interest comprise financial interests, activities, and relationships within the past 3 years including but not limited to employment, affiliation, grants or funding, consultancies, honoraria or payment, speaker's bureaus, stock ownership or options, expert testimony, royalties, donation of medical equipment, or patents planned, pending, or issued.

Err on the side of full disclosure.

If you have no conflicts of interest, check "No potential conflicts of interest" in the box below. The information will be posted with your response.

Not all submitted comments are published. Please see our commenting policy for details.

Limit 140 characters
Limit 3600 characters or approximately 600 words