Importance Countermeasures 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 Participants In 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 Exposures Spaceflight and lower-body negative pressure. Main Outcomes and Measures Changes 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 mm3; 95% CI, 0.030-0.046 mm3; 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.

中文翻译：

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太空飞行和急性流体转移逆转期间视神经乳头和视网膜形态的变化。

重要的是，逆转失重状态下流体向前方移动的对策有可能减轻与太空飞行相关的神经眼综合症。本研究调查了在太空飞行期间使用对抗措施下半身负压是否与眼部结构的变化有关。目的 确定在飞行期间短暂施加 25 毫米汞柱下半身负压是否可以减轻视神经乳头和视网膜的变化。设计、设置和参与者 在美国国家航空航天局的“流体转移研究”中，这是一项前瞻性队列研究，美国和国际机组人员在飞行前、飞行中、返回地球后最多 180 天。在正常失重条件下和下半身负压暴露 10 至 20 分钟后获得飞行中扫描。在坐姿、仰卧和低头倾斜姿势下收集飞行前和飞行后数据。机组成员完成了在国际空间站进行的 6 到 12 个月的任务。分析了 2016 年至 2021 年的数据。干预或暴露 太空飞行和下半身负压。主要结果和测量 最小边缘宽度、视杯体积、刷膜开口高度、视盘周围总视网膜厚度和黄斑厚度的变化。结果 14 名机组成员（平均 [SD] 年龄，45 [6] 岁；11 名男性机组成员 [79%]）的平均 (SD) 飞行时间为 214 (72) 天。与飞行前就座相比，飞行第 150 天的眼部变化，包括最小边缘宽度的增加（33.8 μm；95% CI，27.9-39.7 μm；P < .001），杯体积减少（0.038 mm3；95% CI，0.030-0.046 mm3；P < .001），后部Bruch 膜开口位移（-9.0 μm；95% CI，-15.7 至 -2.2 μm；P = .009）和黄斑厚度减少（中央凹至 500 μm，5.1 μm；95% CI，3.5-6.8 μm； P <.001）。短暂暴露于下半身负压不会影响这些参数。该队列研究的结论和相关性结果表明，视乳头周围组织增厚、视杯体积减小和中央黄斑部轻度变薄与长时间太空飞行有关。急性暴露于 25-mm Hg 下半身负压不会改变视神经乳头或视网膜形态，