Laurie SS, Lee SMC, Macias BR, et al. - In view of the observation that astronauts develop optic disc edema during long-duration spaceflight and this is a risk for all future astronauts during spaceflight, researchers sought to determine if the ocular changes developing in a ground-based analog of weightlessness are similar to the ocular changes experienced by astronauts during weightlessness. From 2012 to 2018, they examined 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 nearly 30 days of spaceflight. Individuals exposed to bed rest had a greater degree increase in peripapillary total retinal thickness than astronauts during spaceflight, while only astronauts during spaceflight developed choroidal thickening. Given these differences in astronauts vs individuals exposed to bed rest, it appears that these groups differ in the mechanism(s) underlying optic disc edema. Nevertheless, the use of the terrestrial model of the spaceflight-associated neuro-ocular syndrome may aid in the development of efficient countermeasures that may protect the eyes of astronauts during future space missions.