火车突然冲进黑暗的隧道或突然冲出光明，都会对视力造成极大的损害。

The sudden plunging of a train into the darkness of a tunnel, and the equally sudden rush into full daylight, would cause great damage to eyesight.

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所以当血液流动不到眼睛时，视力就会衰退，黑暗就会从神经末梢蔓延到中心。

So when blood flow does not reach the eye, vision fails, and darkness ensues from the periphery to the center.

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因为他“上帝创世般的勇气”，海伦凯勒写到，布莱叶为那些有视力缺陷的人群铺建了一条坚实的道路，让他们开始从绝望的黑暗中攀登到思想的绝顶。

With his “godlike courage, ” Helen Keller wrote, Braille built a “firm stairway for millions of sense-crippled human beings to climb from hopeless darkness to the Mind Eternal.”

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