《灵枢·大惑论》帝曰∶予尝上清冷之台，中 而顾，匍匐而前，则惑。予私异
之，窃内怪之，独瞑独视，安心定气，久而不解，独抟独眩，披发长跪，俯而视之，后久而
不已也。卒然自上，何气使然？岐伯曰∶五脏六腑之精气皆注于目，而为之精，精之窠为眼
骨之精为瞳子，筋之精为黑眼，血之精为络，其窠气之精为白眼，肌肉之精为约束，裹撷
筋骨血气之精，而与脉并为系，上属于脑，后出于项中。故邪中于项，因逢身之虚，其入深
则随眼系以入于脑，入于脑则脑转，脑转则引目系急，目系急则目眩以转矣。邪中其精，其
精所中，不相比也，则精散，精散则视歧，故见两物。又云∶目者，五脏六腑之精也，荣卫
魂魄之常营也，而神气之所生也。故神劳则魂魄散，志意乱。是故瞳子黑睛法于阴，白睛赤
脉法于阳也，故阴阳合转而睛明也。目者心之使也，心者神之舍也，故神精乱而不转，卒然
见非常处，精神魂魄，散不相得，故曰惑也。帝曰∶予疑其然，予每之东苑，未曾不惑，去
之则复，予唯独为东苑劳神乎？何其异也。岐伯曰∶不然也。心有所喜，神有所恶，卒然相
惑，则精气乱，视误故惑，神移乃复，是故闻者为迷，甚者为惑。《素问》云∶睛明者，所
以视万物，别白黑，审长短，以长为短，以白为黑，颠倒错乱，神光暗 ，则精衰而视变矣
宜分虚实治之可也。
黄帝问道：我曾经登上清冷之台，中途回头张望，又匍匐向前行进，便产生了眩晕迷惑之感。我私下对此感到诧异，内心暗自奇怪，独自闭眼或睁眼，安心定气，长时间无法解除这种状态，独自专注凝视时出现头晕目眩，披散头发长跪不起，俯身向下看，许久之后仍不停止。这种症状突然从上方袭来，是什么气导致的呢？
岐伯回答说：五脏六腑的精气都汇聚于眼睛，形成眼的精气。其中，骨之精表现为瞳子（瞳孔），筋之精表现为黑眼（虹膜/角膜部分），血之精表现为络脉（眼内血管），气之精表现为白眼（巩膜），肌肉之精表现为约束（眼睑）。这些精气包裹着筋骨血气，与经脉并行为目系，向上连接于脑，向后出于项中。所以，邪气侵袭项部，如果恰逢身体虚弱，邪气深入就会随着目系进入脑部。进入脑部则引起脑转（头脑旋转感），脑转牵引目系紧张，目系紧张则导致目眩和视物旋转。邪气侵入其精气之中，被邪气所中的精气不能相互协调，就会导致精气涣散，精气涣散则视物成双，所以看见两个物体。
又说：眼睛是五脏六腑精气的汇聚处，也是营卫、魂魄经常循行的地方，更是神气产生的地方。所以精神过度劳累会导致魂魄涣散，意志混乱。因此，瞳子和黑睛属于阴，白睛和赤脉属于阳，阴阳协调转动则目光明亮。眼睛是心的使者，心是神的居所，所以如果神精混乱不能正常转动，突然看到不寻常的地方，精神魂魄分散而不能相合，这就叫做“惑”。
黄帝问道：我怀疑正是如此，我每次去东苑，没有不发生迷惑的，离开那里就恢复了，难道只有我去东苑才劳神吗？为什么这么奇怪呢？
岐伯回答说：不是这样的。心中有所喜好，神有所厌恶，突然相互干扰，导致精气紊乱，看错了所以产生迷惑，神志转移后就能恢复。所以，轻微的叫“迷”，严重的叫“惑”。《素问》说：眼睛之所以能看清万物，辨别黑白，审察长短，如果把长的看成短的，把白的看成黑的，颠倒错乱，神光昏暗，就是精气衰弱而视觉改变，应当分辨虚实进行治疗即可。
Yellow Emperor asked: I once ascended the Qingleng Terrace. Looking back midway and crawling forward, I experienced dizziness and confusion. I privately found this strange and wondered within myself. Whether closing or opening my eyes alone, calming my mind and regulating my qi, the state persisted for a long time without resolving. Gazing intently alone caused vertigo; with hair disheveled, kneeling for a long time, looking down, it continued for an extended period. This sensation suddenly arose from above; what qi causes this?
Qibo replied: The essence of the five zang organs and six fu organs all converge into the eyes, forming the eye's essence. The essence of bone manifests as the pupil (tongzi); the essence of sinew manifests as the black eye (heiyan, referring to the iris/cornea area); the essence of blood manifests as the collaterals (luo, intraocular vessels); the essence of qi manifests as the white eye (baiyan, sclera); the essence of muscle manifests as the constraints (yueshu, eyelids). These essences envelop the sinews, bones, blood, and qi, merging with the meridians to form the optic nerve system (muxi), which connects upward to the brain and exits posteriorly at the neck. Therefore, when pathogenic factors invade the neck, especially if accompanied by bodily deficiency, deep invasion allows them to follow the optic nerve system into the brain. Once in the brain, it causes cerebral rotation (naozhuan); cerebral rotation pulls the optic nerve system taut; tautness of the optic nerve system leads to vertigo and spinning vision. If pathogenic factors invade the essence itself, the affected essence fails to coordinate with others, leading to the dispersion of essence. Dispersion of essence results in diplopia (shiqi), hence seeing double objects.
It is also said: The eyes are the convergence of the essence of the five zang and six fu organs, the regular circulation site of Ying-Wei (Nutritive and Defensive) qi and Hun-Po (Ethereal and Corporeal Souls), and the birthplace of Shen (Spirit). Thus, mental overexertion causes Hun and Po to scatter and Zhi (Will) to become chaotic. Consequently, the pupils and black parts correspond to Yin, while the whites and red vessels correspond to Yang; when Yin and Yang harmonize and rotate, vision becomes clear. The eyes are the messengers of the Heart, and the Heart is the residence of Shen. Therefore, if Shen Jing (Spiritual Essence) becomes chaotic and fails to rotate properly, and one suddenly sees unusual scenes, the Spirit, Jing, Hun, and Po scatter and fail to integrate, which is termed "Huo" (Confusion/Delusion).
The Yellow Emperor asked: I suspect this is true. Every time I go to Dongyuan, I invariably experience confusion; leaving there restores me. Am I the only one whose spirit is taxed by Dongyuan? Why is it so peculiar?
Qibo replied: Not so. If the Heart has preferences and the Spirit has aversions, sudden mutual interference causes Qi and Essence to become chaotic, leading to visual errors and thus confusion. When the Shen shifts focus, recovery occurs. Hence, mild cases are called "Mi" (Muddled), and severe cases are called "Huo" (Confused). The Suwen states: The eyes enable us to see all things, distinguish black from white, and judge length. If long appears short, and white appears black, resulting in inversion and chaos, with dimming of Shen Guang (Spiritual Light), it indicates depletion of Essence and alteration of vision. Treatment should differentiate between Deficiency and Excess patterns.