January 15, 2020
1 min read

Ocular changes differ in ground-based analogue of weightlessness

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Subjects who underwent a ground-based analogue of weightlessness experienced greater peripapillary total retinal thickness but less choroidal thickening compared with astronauts during approximately 30 days of spaceflight, according to a study.

“NASA is studying why some astronauts develop optic disc edema during long-duration spaceflight. This experiment used optical coherence tomography imaging to quantify the onset and resolution of optic disc edema in healthy volunteer subjects exposed to strict head-down tilt bed rest for 30 days. Using this bed rest model, NASA will be able to test treatment options or countermeasures that someday can be used to prevent optic disc edema from developing in astronauts traveling to the moon or Mars,” study co-author Steven S. Laurie, PhD, told Healio/OSN.

The cohort study, conducted from 2012 to 2018, included 20 astronauts before and during approximately 30 days of spaceflight and 11 healthy test participants before, during and after 30 days of 6° head-down tilt bed rest. Investigators evaluated peripapillary total retinal thickness and peripapillary choroid thickness based on OCT images. Participants in the bedrest cohort had a greater proportion of women and were younger and weighed less than those in the astronaut cohort.

The bedrest cohort experienced a statistically significant increase in peripapillary total retinal thickness from head-down tilt day 1 of 8.1 µm to 53.9 µm at head-down tilt day 30 (P < .001). By day 13 after bedrest, the total retinal thickness was 33.4 µm (P = .003). However, compared with before bedrest, the mean change in choroid thickness was not statistically significant during bedrest. The choroid, though, was significantly thinner than baseline during bedrest. At day 13 after bedrest, the choroid was 9.9 µm thinner compared with its baseline measurement (P = .01).

Peripapillary total retinal thickness increased to a greater degree in participants in bedrest compared with astronauts experiencing similar durations. The mean difference between the groups was 37 µm (P = .005). Choroid thickness, however, increased in astronauts, resulting in a mean difference between the cohorts of 27 µm (P < .001). – by Robert Linnehan

Disclosure: Laurie reports receiving grants from NASA during the conduct of the study.