Changes in Optic Nerve Head and Retinal Morphology During Spaceflight and Acute Fluid Shift Reversal

Abstract

IMPORTANCECountermeasures that reverse the headward fluid shift experienced in weightlessness have the potential to mitigate spaceflight-associated neuro-ocular syndrome. This study investigated whether use of the countermeasure lower-body negative pressure during spaceflight was associated with changes in ocular structure.OBJECTIVE To determine whether changes to the optic nerve head and retina during spaceflight can be mitigated by brief in-flight application of 25-mm Hg lower-body negative pressure. DESIGN, SETTING, AND PARTICIPANTSIn the National Aeronautics and Space Administration's "Fluid Shifts Study," a prospective cohort study, optical coherence tomography scans of the optic nerve head and macula were obtained from US and international crew members before flight, in-flight, and up to 180 days after return to Earth. In-flight scans were obtained both under normal weightless conditions and 10 to 20 minutes into lower-body negative pressure exposure. Preflight and postflight data were collected in the seated, supine, and head-down tilt postures. Crew members completed 6-to 12-month missions that took place on the International Space Station. Data were analyzed from 2016 to 2021. INTERVENTIONS OR EXPOSURESSpaceflight and lower-body negative pressure. MAIN OUTCOMES AND MEASURESChanges in minimum rim width, optic cup volume, Bruch membrane opening height, peripapillary total retinal thickness, and macular thickness.RESULTS Mean (SD) flight duration for the 14 crew members (mean [SD] age, 45 [6] years; 11 male crew members [79%]) was 214 (72) days. Ocular changes on flight day 150, as compared with preflight seated, included an increase in minimum rim width (33.8 μm; 95% CI, 27.9-39.7 μm; P < .001), decrease in cup volume (0.038 mm 3 ; 95% CI, 0.030-0.046 mm 3 ; P < .001), posterior displacement of Bruch membrane opening (−9.0 μm; 95% CI, −15.7 to −2.2 μm; P = .009), and decrease in macular thickness (fovea to 500 μm, 5.1 μm; 95% CI, 3.5-6.8 μm; P < .001). Brief exposure to lower-body negative pressure did not affect these parameters.CONCLUSIONS AND RELEVANCE Results of this cohort study suggest that peripapillary tissue thickening, decreased cup volume, and mild central macular thinning were associated with long-duration spaceflight. Acute exposure to 25-mm Hg lower-body negative pressure did not alter optic nerve head or retinal morphology, suggesting that longer durations of a fluid shift reversal may be needed to mitigate spaceflight-induced changes and/or other factors are involved.

Peripapillary hyperreflective ovoid mass‐like structures: Multimodal imaging—A review

“…It has been hypothesized that PHOMS may also be observed in astronauts returning from long‐duration missions to the International Space Station due to impaired glymphatic efflux of ocular fluid into the optic nerve 45 . However, PHOMS were not reported in a previous series of spaceflight associated neuro‐ocular syndromes 46–48 …”

Altmetric Attention Scores in Ophthalmology Journals

“…Through the findings of our study, 1 we believe that it is essential for authors to disseminate their work on all the various platforms that are linked to the Altmetric system and are integrated into the calculation of the AAS (eg, policy documents, news outlets, blogs, Twitter, postpublication peerreviewers, Facebook, Sina Weibo, Syllabi, Wikipedia, Google+, LinkedIn, Reddit, research highlight platforms, Stack Overflow, YouTube, Pinterest, and patents). With the age of social media, the scientific community is accessing articles in evolving ways.…”

“…To the Editor In a recent issue of JAMA Ophthalmology, Djulbegovic et al 1 describe the correlation of Altmetric Attention Score (AAS) and citation number for articles published between 2018 and 2019 in 3 major ophthalmology journals, the American Journal of Ophthalmology, JAMA Ophthalmology, and Ophthalmology. 1 The AAS is a weighted average based on the number of social media website mentions.…”

“…To the Editor In a recent issue of JAMA Ophthalmology, Djulbegovic et al 1 describe the correlation of Altmetric Attention Score (AAS) and citation number for articles published between 2018 and 2019 in 3 major ophthalmology journals, the American Journal of Ophthalmology, JAMA Ophthalmology, and Ophthalmology. 1 The AAS is a weighted average based on the number of social media website mentions. 2 One advantage of AAS is that it can be used to more immediately observe the perceived impact of recent articles, whereas it may take years for citation counts to grow to a meaningful level for comparative analysis.…”

“…To the Editor We read with great interest the article recently published in JAMA Ophthalmology by Pardon et al 1 We are grateful to the authors for sharing their valuable research findings with the scientific community, and we would appreciate the opportunity to comment on the authors' discussion of the possible reason for the observed posterior displacement of the Bruch membrane opening (BMO) during spaceflight.…”