The eyes are the convergence of the essence and brilliance of the five zang organs and six fu organs, much like the sun and moon hanging in the sky, shining brightly and unobscured. Redness at the inner and outer canthus belongs to Heart pathology; redness of the entire sclera (white part of the eye) belongs to Lung pathology; the round and large cornea (black pupil/wu jing) belongs to Liver pathology; the upper and lower eyelids belong to Spleen pathology; and the small black pupil in the center, dark as lacquer, is governed by the Kidney. Therefore, corresponding syndromes arise with each of the five zang organs. However, in discussing their primary relationships, the pupil holds the most significant connection. Why is this so? Because the eyes are the external manifestation of the Liver. The Liver corresponds to Wood, and the Kidney corresponds to Water; Water generates Wood, making the Liver the child and the Kidney the mother. How can a mother and child be separated? Thus, when the qi of the Liver and Kidney is abundant, vision is bright and clear; when it is deficient, vision becomes dim, dizzy, with red halos around the cornea, stinging pain, and floating turbidity, which indicates Liver Heat. If bile secretes clear tears but they become withered and yellow, circling the eyes, this indicates Liver Deficiency. If the pupil dilates and appears pale white or deviated, this indicates Kidney Deficiency. If the pupil shrinks, becomes scorched, or has a slight yellow tint, this indicates Kidney Heat. All eye diseases can be verified by these signs.

However, people generally know that the qi of the Liver and Kidney acts in mutual dependence, but few realize that the Heart is the master of Shen (Spirit/Mind), serving as an assistant to the Liver and Kidney. This is what is meant by "one becoming two, and two becoming one." Why? The Heart governs Blood, and the Liver stores Blood. Blood can generate Heat. Whenever heat rushes to the eyes, one must clear Heart Fire and cool Liver Blood. Yet, one should not rigidly adhere to the theory that Water generates Wood. It must be understood that the eye is wrapped in a thin membrane containing fluid, capable of illuminating all directions. Tracing back to the source, if it were not the innate Tianyi Water (Primordial Water), who would be its master?

Analyzing in detail: Tension and pulling sensations, aversion to wind, cyanotic pupils, white eyelids, itching with clear tears, without redness or pain, is called Wind Eye. Protrusion of the cornea, hard and swollen red eyelids, excessive discharge and tearing, internal heat and stinging pain, is called Heat Eye. Turbid eyes with tearing, swollen and soft eyelids, upper obstruction causing blurriness, soreness, dryness, and slight redness, is called Qi Eye. If Wind and Heat combine, there is itching and fluctuating redness; if Wind and Qi contend, there is itching, dryness, and heaviness/blurriness; if Blood Heat aggregates, conditions such as pterygium (fleshy growths) and hordeolum (stye) arise. When Qi and Blood do not reach the area, symptoms such as diminished vision, ptosis, and amblyopia occur. A pale purple hue suggests Deficient Heat, while a fresh, intense red suggests Excess Heat. Pterygium growing from the canthi indicates Heart Blood Heat and fullness; a red membrane on the sclera resembling a paper umbrella indicates Qi Stagnation and Blood Congestion with Heat. Bulging within the pupil, stagnation and dampness in the sclera, with a floating and red color, indicate cold pain leading to cyanotic-green pupils, withered sclera, sinking and turbid Qi. If eye heat persists for a long time and is invaded by Wind-Cold, it becomes red and ulcerated. If the eye is not red but painful due to Phlegm-Fluid accumulation, and if Liver Qi is unsmooth and carries Heat, photophobia occurs. Heat accumulation damaging the eyelids causes them to close tightly. Alas, these are the general external manifestations. However, the five zang organs cannot lack any one; why are the Spleen and Lung seemingly excluded? The answer is: Redness or red veins in the sclera indicate Heat in the Lung; lesions like acne spots on the upper/lower eyelids or corners of the mouth indicate Heat in the Spleen. The Spleen governs taste; the essence of the five flavors nourishes the interior, allowing brilliance to manifest externally. The Lung governs Qi; the ascent and descent of Water and Fire, and the circulation of Ying and Wei (Nutritive and Defensive Qi), rely on Qi. The aforementioned principle that each zang organ has corresponding syndromes can be deduced from this.

Although eye ailments mostly arise from Heat, medication generally prioritizes clearing Heart Fire, cooling Liver Blood, regulating Blood, and smoothing Qi. Since the Spleen dislikes dryness, in cases of deficiency, herbs like Dang Gui (Angelicae Sinensis Radix) and Di Huang (Rehmanniae Radix) are used for moistening and nourishing; mild use of warm herbs is inadvisable. Moreover, the Lung can induce dryness, and the Liver prefers moisture. Ancient formulas often use Xing Ren (Armeniacae Semen Amarum), dried persimmon, yi tang (maltose), sha mi (rock sugar/honey) as adjuncts, clearly intending to moisten and benefit. Regarding the removal of nebula (corneal opacity), this is particularly critical. Nebula originating from the Lung, if caused by mild heat, appears blurry; if severe, actual nebula forms. True spider nebula, resembling broken rice grains, is easy to dissipate; plum blossom nebula, resembling plum blossoms, is difficult to eliminate. Although nebula arises from Heat, treatment should remove nebula before clearing Heat, because extreme Heat generates nebula. If one removes redness and heat first, blood turns to water, and the nebula cannot be removed. Those with red eyes given too many cooling medicines, and washed with water, will see their eyes freeze like ice in an instant, becoming merely a mass of water. Water nature is clear and pure; thus, one should not rigidly stick to topical washing treatments. Irregular emotions, excessive desires, overuse of eyesight, excessive crying, exposure to cold and wind, enduring summer heat and sun, ignoring smoke and fire, and consuming too much hot/spicy food—all these cause disease originating from the zang-fu organs. Can topical treatment alone suffice? One who can sit quietly, clarify the spirit, protect eyesight, relax the mind, cease anxious thoughts, enjoy mental ease and daily rest, harmonize diet for nourishment, and carefully select medicine for balance, will surely achieve clear vision and peace of mind.