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The *Treatise on the Correspondence of Yin and Yang* states: "All meridians connect to the eyes." The eyes are able to see when they receive nourishment from blood. The essence of the five zang organs and six fu organs all ascend to the eyes, thereby forming visual function. The gathering place of essence is called the eye; the essence of bone manifests as the pupil (pupil); the essence of sinew manifests as the black eye (iris); the essence of blood manifests as the collaterals (intraocular vessels); the essence of qi manifests as the white eye (sclera); and the essence of muscle manifests as the eyelids (constraints). These essences derived from sinews, bones, blood, and qi combine with the meridians to form the optic nerve system (optic pathway), which ascends to connect with the back of the brain and emerges from the nape. Therefore, when pathogenic factors invade the nape, especially if accompanied by a deficiency in the body's healthy qi, the pathogens may penetrate deeply and follow the optic pathway into the brain. Pathogens entering the brain cause dizziness, which pulls on the optic pathway causing tension; tension in the optic pathway leads to vertigo and rotational visual disturbances.

If pathogenic factors invade the essence of the eye, and the invaded sites are not coordinated, the essence will scatter. Scattered essence results in diplopia (seeing double objects). The eyes are the gathering place of the essence of the five zang organs and six fu organs, the site where Ying-Qi (nutritive and defensive qi) and Hun-Po (ethereal and corporeal souls) frequently circulate, and the seat governed by Shen (spirit). Therefore, excessive mental labor causes Hun and Po to scatter and Yi (will/intention) to become chaotic. Thus, the pupils and black eyes originate from Yin, while the white eyes and red vessels originate from Yang; the harmonious interaction of Yin and Yang produces clear vision. The eyes are the messengers of the Heart, and the Heart is the residence of Shen. If Shen and Jing (essence) become disordered and fail to function normally, sudden perception of abnormal phenomena occurs, causing Shen, Jing, Hun, and Po to scatter and lose coordination; this state is called "Huo" (delusion/confusion).

The twelve primary meridians and 365 acupoints have their blood and qi ascending to the face and penetrating all orifices. Clear Yang qi ascends and disperses into the eyes to form vision, while turbid Qi descends to the ears to form hearing. If mental distress, irregular diet, or overwork leads to Spleen-Stomach weakness and excessive Heart Fire, the hundred meridians will boil, blood vessels will flow retrograde, and pathogenic factors will damage the orifices, much like the sun and moon losing brightness at dawn. The essence of the five zang organs and six fu organs is derived from the Spleen and ascends to the eyes. The Spleen is the head of all Yin meridians, and the eyes are the congregation of blood vessels. Therefore, Spleen deficiency causes the essence of the five zang organs to lose control, failing to clarify vision. The Heart is the Ministerial Fire (Jun Huo), governing the spirit, which should remain calm and peaceful. The Assistant Fire (Xiang Huo) executes commands; the Assistant Fire refers to the Pericardium (Pericardium Meridian), which governs the hundred meridians that nourish the eyes. Since physical exertion causes the Assistant Fire to act recklessly, and pathogenic factors further damage the blood vessels, various diseases arise. Physicians who do not regulate the Spleen and Stomach, nourish blood, and calm the spirit, but only treat symptoms without addressing the root, fail to understand the correct principles.

The meridian of the Pericardium originates from the Heart, acting on behalf of the Heart Monarch, and is exterior-interior related to the Shaoyang (Gallbladder) meridian. Dilated pupils indicate that the Shaoyin (Heart) meridian's qi supports the optic pathway; the Jueyin (Liver) meridian connects to the optic pathway. The Heart governs Fire, and the Liver governs Wood; this represents an excess of Wood-Fire energy. Dietary tastes should be bitter, sour, and cool, strictly avoiding pungent and hot foods to prevent aiding the Wood-Fire pathogenic factors. Understanding this principle in daily diet is advisable. Pungent flavors dissipate heat but aid Fire, so they should not be consumed. Sour flavors promote consolidation, drain Heart Qi, and subdue Wood-Fire. Bitter flavors drain Heat-Fire, thereby benefiting Water. Cold water and excessively cold foods are particularly contraindicated, as they damage Stomach Qi, obstruct Qi mechanism, and prevent the generation of Yuan Qi (Primary Qi). If Yuan Qi fails to generate, Stomach Qi sinks, allowing Fire of the Sanjiao (Triple Burner) and Heart Fire to counterflow upward, invading the Lungs, entering the brain, and burning the marrow. Fire promotes dispersion, leading to dilated pupils. Hot foods further aid Fire pathogenic factors; these are verified reasons for dietary restrictions.

Regarding herbal medicine, texts such as *Yao Xing Lun* state: Elsholtzia Fructus (Chongwei Zi) has a pungent nature and primarily benefits the eyes. However, since pungency aids Fire, it is removed. Instead, Scutellariae Radix (Huang Qin) and Coptidis Rhizoma (Huang Lian) are added to drain Middle Jiao Fire; Scutellariae Radix drains Upper Jiao Lung Fire, prepared with wine washing, employing the method of "treating cold with heat" (Han Yin Re Yong). Semen Celosiae (Qingxiang Zi) is removed because it aids Yang Fire. Schisandrae Fructus (Wuweizi) is added to astringe the pupils. In human physiology, Fire and Qi cannot coexist in excess; thus, the *Neijing* states: "Strong Fire consumes Qi, Qi feeds mild Fire; mild Fire generates Qi, strong Fire scatters Qi." Various sour foods assist Yuan Qi. Sun Simiao stated: "In the fifth month, regularly consume Wuweizi to assist the Qi of the five zang organs." The supplementation method states: "Supplement with sour, drain with pungent." Pungency drains Qi, thereby clarifying vision. One might ask: Dang Gui (Angelica Sinensis) in prescriptions also has a pungent and sweet flavor; why is it not removed? Because the combination of pungent and sweet is the supreme remedy for harmonizing blood, and furthermore, the sweet flavor acts as a guide and envoy for the other herbs.