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The *Huangdi Neijing* (Yellow Emperor's Inner Canon) states: "When Qi (vital energy) escapes, vision becomes unclear." Qi refers to the Clear Yang Qi. If Clear Yang Qi fails to ascend, then Turbid Yin cannot descend, and how can the eyes shine like a candle, seeing everything without omission? Humans exist within heaven and earth, nowhere is there not the circulation of Qi transformation. When the Qi in the Zang-Fu organs and meridians is correct, all actions will be auspicious. If Qi loses its correctness, harm ensues everywhere. Thus it is said: "All diseases arise from Qi." Recently, Wang Yingzhen stated: "If a practitioner does not understand Qi, from where should one approach treating disease? This is laughable for those in the profession who have not yet reached the level of true understanding." These words are profound; they represent the primary principle for preserving health and treating illness. The function of Qi reaches everywhere; once disordered, it causes various ailments. It manifests as deficiency or excess, cold or heat, with transformations too numerous to describe. Wherever Qi is disordered, that is where the root of the disease lies. A skilled practitioner grasps this to regulate it, much like untying a knot, achieving immediate relief with a single movement. Therefore, what originates from Heaven is Heavenly Qi; what originates from Earth is Earthly Qi. Human Qi responds accordingly. Excess Yang Qi leads to redness and swelling of the eyes. Excess Yin Qi leads to aching, dryness, and photophobia. Deficiency of Middle Qi leads to laxity and ptosis of the eyelids. Stagnation of Qi failing to move results in goiter-like nodules on the Spleen meridian. For excess patterns, use breaking methods; for deficiency patterns, use tonifying methods. For stagnation, promote movement; for depression, vent and reach. For cold, warm; for heat, cool. For disharmony, harmonize and diffuse. All Five Elements, Five Emotions, Zang-Fu organs rely on Qi for their functions. In normalcy, there is peace; in change, there is disease. Hence, the Sages state that all diseases stem from Qi, let alone eye diseases. Therefore, physicians must observe comprehensively and cross-verify, prescribing suitable treatments, thereby remaining worthy of the Dao.

The *Huangdi Neijing* states: "The eyes see when nourished by Blood; Blood is transformed from Qi." Thus, abundant Blood leads to a strong physique, which is what life relies upon. It moistens the meridians, nourishes the Zang-Fu, sustains sinews and bones, fills the whole body, and the eyes benefit from its shade. Naturally, it should flow freely and not stagnate. However, at birth, life begins with Essence (Jing). Although Jing and Blood seem different, Daoist alchemists say: "Tears, saliva, sweat, fluids, essence, marrow, and blood—these seven spiritual substances are all Yin." Thus, anything belonging to the Water category is transformed by Tian Yi and Di Liu, and Blood is a type of Essence. Essence is stored in the Kidney, and its accumulation is limited. If sexual activity is excessive, Essence deficiency leads to Blood deficiency, causing the seven orifices to lose sensitivity. Blood belongs to the Yin category; its movement is usually due to Fire. Whether external pathogens remain unresolved, causing Fire to stagnate in the meridians, or indulgence in alcohol and diet causes Fire to stir in the Stomach, resulting in Heat-Blood acting recklessly, leading to red eyes and ulcers. The treatment method focuses on cooling Blood and clearing Fire. If stasis obstructs the meridians, the eyeball feels distended and stuffy. If depression accumulates in the Spleen (eyelids), pterygium may protrude. If Wind-Heat is contracted, conditions like trachoma (pepper sores) or follicular conjunctivitis (millet sores) may occur. The general treatment is to invigorate and disperse Blood. If there are depressed scars after injury or white opacities covering the cornea, these belong to Blood deficiency with pathogenic invasion; treatment should prioritize invigorating and tonifying Blood. The Taiyang Meridian starts at the inner canthus, having more Blood and less Qi. The Shaoyang Meridian starts at the outer canthus, having less Blood and more Qi. The Yangming Meridian starts at both sides of the eyes meeting at the forehead, having abundant Blood and Qi. Only the Jueyin Meridian connects to the eye system. Therefore, excess Blood indicates an Excess pattern in the Taiyang and Yangming meridians. Insufficient Blood indicates a Deficiency pattern in the Jueyin and Shaoyang meridians. By distinguishing between excess and insufficiency, attack and tonification can be applied appropriately. From this, we know Blood is transformed by Qi and is also a form of Essence. Yang deficiency cannot generate Blood, so Blood should be warmed, not cooled. Yang hyperactivity damages Yin most severely, so Blood should be still, not active. Understanding this and mastering the way to nourish Ying (Nutritive) Qi ensures bright vision, leaving no reason to fear Blood diseases.