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Spaceflight induced visual impairment is hypothesized to be a result of increased intracranial pressure. The study of visual changes and intracranial pressure (ICP) in astronauts on long-duration flights is a relatively recent topic of interest to Space Medicine professionals. Although reported signs and symptoms have not appeared to be severe enough to cause blindness in the near term, long term consequences of chronically elevated intracranial pressure is unknown.〔 NASA has reported that fifteen long-duration male astronauts (45–55 years of age) have experienced confirmed visual and anatomical changes during or after long-duration flights. (Optic disc edema ), globe flattening, (choroidal folds ), (hyperopic shifts ) and an increased intracranial pressure have been documented in these astronauts. Some individuals experienced transient changes post-flight while others have reported persistent changes with varying degrees of severity. Although the exact cause is not known at this time, it is suspected that microgravity-induced cephalad fluid shift and comparable physiological changes play a significant role in these changes.〔 Other contributing factors may include pockets of increased CO2 and an increase in sodium intake. It seems unlikely that resistive or aerobic exercise are contributing factors, but they may be potential countermeasures to reduce intraocular pressure (IOP) or intracranial pressure (ICP) in-flight.〔 ==Causes and current studies== Although a definitive cause (or set of causes) for the symptoms outlined in the Existing Long-Duration Flight Occurrences section is unknown, it is thought that venous congestion in the brain brought about by cephalad-fluid shifts may be a unifying pathologic mechanism. As part of the effort to elucidate the cause(s), NASA has initiated an enhanced occupational monitoring program for all mission astronauts with special attention to signs and symptoms related to ICP. Similar findings have been reported among Russian Cosmonauts who flew long-duration missions on MIR. The findings were published by Mayasnikov and Stepanova in 2008. Animal research from the Russian Bion-M1 mission indicates duress of the cerebral arteries may induce reduced blood flow, thereby contributing to impaired vision. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Visual impairment due to intracranial pressure」の詳細全文を読む スポンサード リンク
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