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Zhao Yangkui stated: The *Classic of Internal Medicine* (*Huangdi Neijing*) records that the essence of the five zang and six fu organs all ascend to the eyes, thereby forming the essence of vision. The Kidney stores essence; therefore, in treating eye diseases, emphasis is placed on the Kidney. Although the eyes are the orifice of the Liver, due to the mutual generation between mother (Kidney) and child (Liver), the treatment of the Kidney and Liver is unified. Hua Tuo said: The shape of the eye resembles a sphere, with the pupil located centrally and protruding forward, similar to how the sun and moon shine upon the southeast while the northwest remains dim. Within the eye exist Shen Gao (Divine Paste), Shen Shui (Divine Water), Shen Guang (Divine Light), Zhen Qi (True Qi), Zhen Xue (True Blood), and Zhen Jing (True Essence); these are the source fluids that nourish the eye.

Shen Gao refers to the paste-like fluid contained within the eyeball, formed by the seepage and moistening of essence juice from the Gallbladder, which can nourish and protect the pupil; if deficient, it causes damage. Shen Shui originates from the San Jiao (Triple Burner), transformed from the primordial True One Yuan Qi, serving as the water that moistens the surface of the eye. If Shen Shui is deficient, there is a risk of excessive fire causing dryness and agitation; if exhausted, it leads to disorders of the eyelids' size; if consumed and dry, it brings the danger of visual obscurity. Since loss exceeds gain, there are no perfectly clear eyes in the world.

Shen Guang originates from the Mingmen (Gate of Life), connects to the Gallbladder, issues from the Heart, and pertains to the function of Fire. If Fire is deficient, there is a risk of dizziness and blindness; if Fire flares up, there is the disaster of burning and dryness. Although there are two "Hearts" (referring to Ministerial Fire and Sovereign Fire), there is no central wheel. The Heart is the Sovereign, connecting to the large collaterals; thus, redness in the large collaterals indicates Excess Fire. The Mingmen is the Small Fire, i.e., Ministerial Fire, acting on behalf of the Sovereign, connecting to the small collaterals; thus, redness in the small collaterals indicates Deficient Fire. If the Sovereign remains still and silent, Ministerial Fire naturally becomes clear and tranquil.

Zhen Xue is the blood rising and transporting from the Liver to nourish the eye collaterals; this blood differs from the easily flowing blood in muscles, being generated from the Water of Tian Yi (One), hence called "True." Zhen Qi is the qi circulating and functioning within the eye's meridians, which is the primordial Yang of the innate True One. Zhen Jing is the essence juice transformed from innate Yuan Qi, starting from the Kidney, applied to the Gallbladder, and then reaching the pupil. If any of these are damaged, eye disease ensues.

Generally, the eye is round and elongated, surrounded externally by several layers of hard shell, internally containing soft meat wrapping the black, thick Shen Gao. Outside the paste is white, thick Shen Shui, which nourishes the paste; outside the water is blood, which nourishes the water. The single point of black brilliance within the paste is the refined essence gathered by the Kidney and Gallbladder. Only this point illuminates and inspects infinite space, known as the Water Wheel, corresponding internally to the Kidney and the Water of Ren-Gui Hai-Zi in the North. Among the Five Wheels, only the pupil has the function of illumination. Some ask: Is the pupil water? Qi? Blood? Paste? The answer is: It is neither Qi, nor Blood, nor Water, nor Paste. It is generated by innate Qi, completed by acquired Qi, embodying the subtle mystery of Yin and Yang, and the essence of Water and Fire. Blood nourishes Water, Water nourishes Paste, and Paste protects the Pupil. Qi governs operation, and Spirit maintains stability. Using the Sun and Moon as an analogy, the principle is identical. In men, the right eye is less refined than the left; in women, the left eye is less brilliant than the right. This is because each obtains the correct balance of Yin and Yang Qi distribution.

Scholar Xu stated: The *Classic* says that when the Foot Shaoyin (Kidney) meridian moves, the disease manifests as sitting but wanting to rise, with eyes appearing blurry (*KT KT*, indicating blurred vision) as if unable to see. It also states: What Shaoyin calls "rising leads to blurry vision" occurs because Yin is internally depleted, leading to inability to see clearly. This is likely eye dimness caused by sexual exhaustion. For Left Kidney Yin deficiency, use Yiyin Dihuang Wan (Benefit-Yin Rehmannia Pill) or Liuwei Wan (Six-Ingredient Pill). For Right Kidney Yang deficiency, use Bawei Wan (Eight-Ingredient Pill) or Bushen Wan (Tonify-Kidney Pill).

Li Dongyuan stated: Those who can see far but not near have Excess Yang and Insufficient Yin. With insufficient Yin essence and excess Solar Light, the pathology lies in Water. The brilliance scatters and cannot converge for near vision. Treatment focuses on the Heart and Kidney; when balanced, Water and Fire harmonize, and Yin and Yang equilibrate. Water transforms into Blood, serves as Jin Ye (Body Fluids) in the body, and as Gao Zhi (Paste Juice) in the eyes. If one indulges in lust, suffers irregular eating, experiences severe physical/meridian fatigue, or excessive weeping, it damages True Yin. When Yin essence is deficient, Yang Fire flourishes. Due to its flaming nature, it disperses outward, and since Yin cannot restrain it, the light projects far outward, preventing near vision. Treatment should strengthen the Master of Water to control Solar Light.

Those who can see near but not far have Insufficient Yang and Excess Yin. With Yang deficiency and Yin excess, the pathology lies in Fire. Thus, brilliance cannot project outward and is constrained for near vision. Treatment focuses on the Gallbladder and Kidney; when sufficient, Wood and Fire become bright, Shen Qi flows freely, and essence reaches far. The Heart's function is Qi, manifesting as demeanor in the body and Shen Guang in the eyes. If one indulges in lust, losing Yuan Yang, and Yuan Yang becomes exhausted, cloud-like haze and shadow appear. The Yin Water in the Kidney is only enough to reflect light inward; it cannot vigorously transport essence juice to nourish the Gallbladder, nor allow the Fire within Water to spread far into the sky. Treatment should benefit the Source of Fire to dissipate Yin shadows.

All the above syndromes involve Yin weakness failing to match Yang, constituting internal cataract diseases. These present without discharge, tearing, pain, itching, photophobia, or tightness/dryness. Initially, vision is like walking through fog or dew; gradually, black spots appear in the air; then objects appear double; finally, light does not gather, resulting in disability. Patients should nourish the root of Innate Constitution and treat early. This disease is difficult to cure; medication requires years. One must abstain from alcohol and sex, avoid irregular eating and overwork, and dispel the Seven Emotions and Five Thieves. Otherwise, recovery is unlikely. People fail to realize that eye dimness is harmless initially; once cataracts form, they mistakenly attribute it to Heat, using cooling medicines that damage the Stomach. Since Cooling corresponds to Autumn Metal and the Liver to Spring Wood, this further injures the Liver, often leading to permanent disability. How sad!

There are also cases where Yang deficiency fails to resist Yin. Due to irregular diet and overwork, Spleen-Stomach weakness causes Qi to sink into the Kidney and Liver. Turbid Yin fails to descend, and Clear Yang fails to ascend. Like the sun and moon obscured at dawn, pathogenic factors harm the orifices, causing deafness and blindness. The essence of the five zang and six fu organs relies on the Spleen-Stomach and ascends to the eyes. The Spleen is the head of Yin, and the eyes are the congregation of Blood and Qi. Thus, Spleen deficiency causes the essence of all organs to lose control, failing to clarify the eyes. Furthermore, if Stomach Qi sinks into the Kidney-Liver, termed "Chong Qiang" (Heavy Rigidity), Ministerial Fire carries Heart Fire to run wild, boiling the vessels, causing Qi and Blood to rebel upward, leading to eye disease.

For dim vision in both eyes with non-fatigued limbs, use Li Dongyuan's Yiqi Congming Tang (Qi-Supplementing Brilliance-Decoction). For eyes that feel tight/small, fear sunlight even when slightly bright, or have weak vision, limb fatigue, or numbness in hands/feet, indicating Spleen-Lung Qi deficiency failing to ascend, use Shenxiao Huangqi Tang (Miraculous Astragalus Decoction). For post-illness vision loss, or inability to see at dusk or under lamplight, indicating Yang deficiency sinking, use Jueming Yeguang Wan (Clear-Bright Night-Light Pill) or Shengma Zhenyin Tang (Cimicifuga Subduing-Yin Decoction).

Zhang Zihe stated: Eye diseases arise from Fire. Redness of the White Wheel (Sclera) indicates Fire invading the Lung; redness and swelling of the Meat Wheel (Eyelids) indicate Fire invading the Spleen; obstruction of the Black Water and Divine Light indicates Fire invading the Liver and Spleen; red vessels penetrating the eye indicate extreme Fire. Treating Fire can be summarized in one sentence. However, Zhang Zihe used only cold-cooling herbs to treat Fire. I alone use tonifying Water to balance Fire, which is also one sentence. For complex syndromes of Six Evils and Seven Emotions, see *Yuanji Qiwei*. Xue Lizhai supplemented this, deeply clarifying methods of strengthening Water and benefiting Fire. His expertise in treating eye diseases was profound and rooted in ancient wisdom.