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Shenguang (visual function or light in the eye) manifests from within oneself, initially resembling a lightning flash. This occurs because Jingyin (Yin essence, the nourishing and quieting substance of the body) is mixed with Pure Yang, causing Yangguang (Yang qi / deficient fire) to fly and transform, resulting in only seeing a vast, chaotic blur. Why resort to empty lamentation?

This condition refers to the spontaneous appearance of Shenguang before the eyes, often flashing like electric light, and in severe cases, appearing bright like flames or rosy clouds. Since it comes and goes intermittently, it differs from the fixed vision of colored objects. It is caused by the depletion of Yin essence, stagnation of clear Qi, severe damage to Xuanfu (fine pores in the eye regulating the flow of Qi, blood, and fluids), and the flight of solitary Yang, leading to the scattering of light. This is a severe form of internal cataract (Neizhang), distinct from milder conditions such as "firefly stars" or phlegm-fire. The appropriate prescription is:

Bushui Ningshen Tang (Water-Nourishing Spirit-Calming Decoction): Tonifying Kidney Water prevents erratic movement of fire; calming the Heart spirit causes the Shenguang to dissipate naturally.
Prepared Rehmanniae Radix (Shu Dihuang) and Raw Rehmanniae Radix (Shengdi) (each 2 qian), White Peony Root (Baishao), Angelica Sinensis (Danggui), Ophiopogon Tuber (Maimendong, dehearted), Spirit of Poria (Fushen) (each 1.5 qian), Schisandra Berry (Wuweizi) (30 berries), Licorice Root (Gancao, use raw, 6 fen).
Chop the herbs into pieces. Add two zhong of water, decoct until reduced to eight-tenths, strain, and take warm on an empty stomach.

Since Kidney Water is deficient and True Yin is insufficient, Prepared Rehmanniae Radix is used. As a formula based on "Heaven generates One [Water]," it greatly tonifies True Yin. Raw Rehmanniae Radix has the effect of nourishing Yin and retreating heat. Ophiopogon Tuber clears the Heart and descends fire. To tonify Blood and nourish Yin, Angelica Sinensis and White Peony Root are essential. The fluctuation of Shenguang, restless day and night, is due to the erratic movement of formless fire between thoughts and consciousness. Therefore, Fushen and Wuweizi must be used to nourish Essence, calm the Spirit, and stabilize Will, preventing the loss of Yuanjing (Primordial Essence) Qi. Finely sliced Gancao descends the fire within the Spirit; without these, the condition cannot be cured. If treated thus, Kidney Water ascends, Heart Fire descends, the Spirit becomes tranquil, and the Shenguang stabilizes.

Seeing objects suddenly in the dark should not be mistaken for the gathering of essence; rather, it is a sign that disaster is imminent. This indicates the mechanism of Yangqi (Yang light) about to collapse, a disease of Water and Fire being contrary. If ignored, loss is certain.

Commentary: In humans, corresponding to Heaven and Earth, brightness during the day and darkness at night is natural. Seeing clearly in the dark contradicts Yin-Yang principles. It必然 indicates that Water and Fire do not interact, Essence and Qi are blocked and obstructed, and disharmony is extreme. The harm of flying Yang prevents the preservation of Yin Essence, leaving Yang uncontrolled. Instead of worrying, one might mistakenly believe essence is abundant, often suffering harm and leaving great regret. The appropriate prescription is:

Jiajian Bawei Wan (Modified Eight-Ingredient Pill): Treats insufficient Kidney Water and rising deficient fire, causing disorder of Shenguang in the eyes, depletion of Yin Essence unable to control Yang, accompanied by fever and thirst, sores in the mouth and tongue, or ulcerated gums, sore throat, emaciation, night sweats with fever, damage to all five Zang organs, and fire rejecting the Upper Jiao.
Prepared Rehmanniae Radix (8 liang, avoid iron, boil in wine until soft, mash into paste), Yam (Shanyao, dried), Cornus Fruit (Shanzhuyu, washed in wine, baked, each 4 liang), White Poria (Baifuling, steamed with milk, sun-dried), Alisma Rhizome (Zexie, washed in wine, baked dry), Moutan Bark (Mudanpi, washed in wine, baked, each 3 liang), Liaoning Schisandra Berry (Liaowumei, dried, 1.5 liang), Cinnamon Bark (Rougui, peeled, avoid fire, 1 liang).
Except for the Rehmanniae paste which is added separately, grind the rest into fine powder. Make pills with refined honey, sized like paulownia seeds. Take 3 qian per dose, with weak salt soup on an empty stomach. Avoid radishes.

Due to insufficient Kidney Water, deficient Yang rebels upward. If Kidney Water is not nourished to benefit True Yin, Water will not ascend and Fire will not descend, causing Shenguang to lose order and fail to store. Thus, in the dark when the eyes are clear, Seven-Ingredient Pill plus Wuweizi is used. Wuweizi is a key herb for nourishing Kidney Water. Once fluids are generated, Kidney Water strengthens naturally. When Water is sufficient, Shenguang turns inward, eliminating the risk of disorder. Rougui, being acrid and hot, guides fire back to its source, ensuring recovery. For Junhuo (Monarch Fire), it can be subdued by dampness or directly suppressed; for Xianghuo (Minister Fire), one must follow its nature to subdue it. Rougui is hot, sharing the same nature as fire. Mixed with drugs strengthening Water in the Lower Jiao, it guides rootless deficient fire down to its meridian, following the principle of "gathering by similarity." Moreover, the quality of Rougui lies in the middle-lower part, so its action specifically targets the lower part of the Kidney Meridian, following the principle that "what is of the earth tends downward." Furthermore, Minister Fire resides between Jia and Yi (Liver and Gallbladder). When Liver-Gallbladder Wood is excessive, strange winds move and fierce flames blaze. Ancients said the North should not be purged; purging the Liver is purging the Kidney. *Bencao* states: "Wood withers when meeting Cinnamon," making it a key drug for suppressing the Liver. The Classics say: "Treating heat with heat" is the wonderful method of following treatment (Congzhi). This aligns perfectly with following its nature to subdue it. Some fear its heat and discard it; do they not understand the subtleties of creation's ascent and descent? Huangbai (Phellodendron Bark) and Zhimu (Anemarrhena Rhizome) treat Minister Fire but are only suitable for temporary use in robust individuals. If misused for deficient fire, the Kidney becomes more deficient through purging, and the deficient fire becomes even more intense. Have you not heard the saying in *Suwen*: "Qi increases and conquers," and the explanation that long-term use of cold medicines transforms into fire?