NASA最新一项研究表明，在太空上呆超过6个月以上的的宇航员，他们的眼睛结构会有所变化，视力会变的模糊。
研究人员发现这些变化是由于在微重力环境下迁延照射的结果，而且会影响到去火星或其他载人太空飞行计划。
研究合著者之一Thomas Mader博士在新发表的论文中提出，40岁以上的宇航员中，和同龄非宇航员一样，他们的眼睛“镜头”已经失去了某些改变聚焦的能力。在早年的太空计划中，大多数宇航员都很年轻，军队体检视力都很好。今天的宇航员差不多是40岁以上，这也可能是视力问题上升的一个原因。而且我们认为年轻的宇航员可能更能忍受他们所面临的问题，而不是报告问题。
论文发表在10月出版的Ophthalmology杂志上。研究人员检查了7位年龄都在50岁左右的宇航员，他们在太空上持续度过了至少6个月的时间。结果发现所有宇航员在太空站上都有视力模糊的问题，而且这些变化在6周后更加严重，甚至他们返还地球后还持续了很长时间。
研究人员还发现，这些宇航员在组织、血液、神经和其他结构也有些变化。由于视觉问题只影响了在太空上度过较长时间的宇航员有关，而且他们当中没有人有与颅内压增加有关的症状（慢性头痛、复视、耳鸣）。因此研究人员将宇航员视力的变化原因归结于微重力。
论文作者们表明微重力对视觉的影响因人而异，需要更多的研究来解释为什么为这样或者为什么有些宇航员更能适应太空长时间飞行。
研究人员指出NASA已经知道宇航员视觉问题的原因，当前他们给宇航员提供特制“像差”眼镜来改善他们的视力。当然宇航员也要接受复杂的眼睛检查和视力测试。（生物探索译）
相关英文论文摘要：
Optic disc edema, globe flattening, choroidal folds, and hyperopic shifts observed in astronauts after long-duration space flight.
To describe the history, clinical findings, and possible etiologies of ophthalmic findings discovered in 7 astronauts after long-duration space flight, and document vision changes in approximately 300 additional astronauts.
DESIGN:
Retrospective, observational examination of ophthalmic findings in 7 astronauts and analysis of postflight questionnaires regarding in-flight vision changes in approximately 300 additional astronauts.
PARTICIPANTS:
Seven astronauts with ophthalmic anomalies upon return from long-duration space missions to the International Space Station and 300 additional astronauts who completed postflight questionnaires regarding in-flight vision changes.
METHODS:
Before and after long-duration space flight, all 7 subjects underwent complete eye examinations, including cycloplegic and/or manifest refraction and fundus photography. Six underwent postmission optical coherence tomography (OCT) and magnetic resonance imaging (MRI); 4 had lumbar punctures (LP). Approximately 300 astronauts were queried regarding visual changes during space missions.
MAIN OUTCOME MEASURES:
Refractive change, fundus photograph examination, retina OCT, orbital MRI, LP opening pressures, and examination of visual acuity data.
RESULTS:
After 6 months of space flight, 7 astronauts had ophthalmic findings, consisting of disc edema in 5, globe flattening in 5, choroidal folds in 5, cotton wool spots (CWS) in 3, nerve fiber layer thickening by OCT in 6, and decreased near vision in 6 astronauts. Five of 7 with near vision complaints had a hyperopic shift ≥+0.50 diopters (D) between pre/postmission spherical equivalent refraction in 1 or both eyes (range, +0.50 to +1.75 D). These 5 showed globe flattening on MRI. Lumbar punctures performed in the 4 with disc edema documented opening pressures of 22, 21, 28, and 28.5 cm H(2)O performed 60, 19, 12, and 57 days postmission, respectively. The 300 postflight questionnaires documented that approximately 29% and 60% of astronauts on short and long-duration missions, respectively, experienced a degradation in distant and near visual acuity. Some of these vision changes remain unresolved years after flight.
CONCLUSIONS:
We hypothesize that the optic nerve and ocular changes we describe may result from cephalad fluid shifts brought about by prolonged microgravity exposure. The findings we report may represent parts of a spectrum of ocular and cerebral responses to extended microgravity exposure.
