Double vision · shi qi

In brief

Double vision is chapter 80’s account of why a man sees one thing as two. The eye is the meeting of the five depots’ essence: 精之窠爲眼，骨之精爲瞳子，筋之精爲黑眼，血之精爲絡其窠，氣之精爲白眼，肌肉之精爲約束. These are wrapped and knotted with the essence of sinew, bone, blood and qi, and the whole is tied to the brain by the eye connection. Let evil strike the back of the neck when the body is empty, and it follows that connection into the brain; the brain turns, the connection is drawn tight, and 目系急則目眩以轉矣. Then 邪其精，其精所中不相比也，則精散，精散則視歧，視歧見兩物 — the essence is scattered, and scattered essence sees double. The explanation is mechanical throughout: two images are not a disease of the eye but a failure of the tie that makes the two eyes one.