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Among the thirteen departments of medicine, ophthalmology is the most difficult, yet it is often underestimated by laypeople. Not only do laypeople underestimate it, but even specialists in this field tend to do so. This stems from a lack of clarity in reasoning and insufficient dedication; some are unfamiliar with Confucian classics, others have superficial knowledge of medicine, and some cannot even read a single character. They may obtain a prescription or method, test it with slight success, and then boast that no one surpasses them in ophthalmology, proceeding to treat patients. The ignorant public suffers repeatedly from such practitioners without realizing it. Such individuals are indeed like looking at the sky through a tube, seeing only a narrow view. However, since ancient times, following Huangdi (Yellow Emperor) and Qibo, renowned physicians have emerged continuously. For example, Zhang Zhongjing (Zhang Changsha) treated *Shanghan* (Cold Damage), Li Dongyuan treated miscellaneous diseases, Liu Wansu treated fire-heat disorders, and Zhu Danxi treated yin deficiency. Besides these four masters, there were many other experts who wrote treatises and formulated prescriptions for miscellaneous diseases to transmit to posterity and guide future learners. Thus, later students had a foundation to rely on; by examining pulses and symptoms, diagnosing diseases, and applying formulas appropriately, they achieved miraculous results, gaining fame far and wide, all relying on the formulas established by the ancients.

Why is ophthalmology considered easy only by modern people? I suspect that Zhang, Li, Zhu, and Liu also had only superficial understanding of it, as no detailed and refined discussions from them on this subject have survived, leaving later generations without a basis. They merely mentioned blood deficiency, mental fatigue, kidney deficiency, and wind-heat. If treatment is rigidly confined to these four aspects, few would avoid bias.

Regarding internal obstructions (*Neizhang*), the eyes are neither red nor purple, neither painful nor itchy, but feel dim and blurred. Vision may be obscured like being covered by thin gauze, seen through fog or dew, seeing black spots, seeing flies flying, seeing spider webs hanging, pain in the supraorbital ridge, dizziness, and darkening of vision. All these are termed internal obstructions. "Obstruction" means blocking, as if an object blocks the view. Internal and external obstructions are collective terms for 108 types of symptoms. External obstructions (*Waizhang*) refer to the eye surface being blocked by nebulae or opacities, hence the name. External obstructions are treatable because there are visible signs to guide intervention. Internal obstructions are difficult to treat because there are no external manifestations, making it hard to find a point of entry. Patients with internal obstructions often have bright gaze similar to healthy individuals, making differentiation difficult; only by observing whether the eyeball moves freely can one distinguish them slightly. Ancient sages stated that brain fluid descends and blocks the pupil, causing blindness. Only gold needles could displace the opacity downward, restoring vision instantly.

I have deeply reflected on this: the eyes are the essence of the five zang and six fu organs, ascending to the eyes to provide brightness, like skylights in a house. They originate from the Liver and Gallbladder, with meridians and orifices connecting upwards to the eyes, akin to underground springs flowing. If blocked, water flow stops. The eyes belong to the Liver; the Liver governs anger. Anger causes fire to stir and phlegm to generate. Phlegm-fire obstructs the Liver-Gallbladder meridians, blocking the orifices of light transmission, resulting in dim vision like smoke or fog. Once vision blurs, depression increases, hence "long illness generates stagnation, long stagnation generates illness."

Current practitioners fail to understand this principle, adhering to biased theories that attribute everything to Liver-Kidney deficiency, using only tonifying herbs for the Liver and Kidney. This exacerbates the pathogenic factors in the Liver-Gallbladder meridians, leading to worsening vision and ineffective treatment, truly due to the blockage of light-transmitting meridians. I compare this to a well spring: if the channel is blocked, water does not flow. If one insists it is merely Liver-Kidney deficiency, consider consumption disease (*Laozhi*); even when patients are near death, they can still see fine details. Thus, if the Liver and Kidneys have no pathogenic factors, the eyes will not become diseased. Specialists must investigate whether the deficiency is due to absence of pathogens or presence of pathogens. If pure deficiency, use tonics; if righteous qi is deficient and pathogenic factors excess, first expel the pathogens, then tonify the righteous qi, avoiding the harm of aiding pathogens. In this way, even difficult internal obstructions can be managed.

For external obstructions, one must examine symptoms according to the Five Wheels theory (*Wulun*) to determine the deficiency or excess of the five zang organs. Among them, the Kidney Water and Divine Light reside deep within, being the most spiritual and precious, capable of distinguishing all things. However, if Kidney Water is insufficient while Fire of the five zang is excessive, Fire becomes too strong and Water too weak. Further depletion of Kidney Water intensifies the fires, leading to nebulae, pterygium (*Pan Jing*), and fleshy growths. Although severe, these are treatable, unlike internal obstructions. Yet, current practitioners use cold-cooling decoctions to suppress fire for temporary effect, and apply arsenic-containing drops to remove opacities, caring only for immediate results. Neither approach is balanced or benevolent. While bitter-cold herbs can subdue fire, overuse damages Stomach Qi and loses warmth-nourishing functions, causing chronic eye issues. Harsh drugs attack the eyes, which are organs of utmost purity and emptiness; although opacities may clear, infinite sequelae may follow, which is lamentable.

I practice medicine under my father's guidance. Prescribing decoctions and drops based on my limited insight, though not perfectly balanced, adheres to principles. Decoctions focus on relaxing the middle jiao, resolving stagnation, regulating qi, eliminating phlegm, nourishing yin, descending fire, tonifying the Kidney, and dispersing wind. Drops prioritize removing opacities and brightening the eyes, using only the qi of herbs rather than their substance. Though slow, they have no aftereffects. Their subtlety is unknown to the secular world. Medicines are family secrets, refined through years of thought. In emergencies, arsenic may be used sparingly (one part in ten), strictly controlled to mitigate toxicity. This reflects my cautious attitude. Patients must also be careful, avoiding mental strain, alcohol, sexual indulgence, and anger. Otherwise, vision may not last, and prolonged viewing may cause dull eye pain and future damage. Mental strain should be avoided because the Heart houses the Spirit and projects light to the eyes. Activities requiring intense focus (reading, writing, embroidery, carving) keep the mind engaged. The Heart governs Fire; continuous mental engagement stirs Heart Fire, causing eye pain and initiating disease.

Everyone tends to deplete the Kidneys. The Kidney belongs to Water, which controls Fire. If the Kidney is not depleted, Water ascends to control Fire; Water ascends, Fire descends, achieving the state of "Water and Fire both complete" (*Shui Huo Ji Ji*). Thus, even with mental strain, sufficient Yuan Qi prevents major harm. However, those with weak Kidney Water are hard to treat; adding mental strain prevents Water ascent, leading to permanent eye damage. Therefore, treating eye diseases requires first assessing the deficiency or excess of pathogenic and righteous factors. One must first expel excess pathogens, then tonify deficient righteous qi. With proper treatment, recovery follows. This is the sequence of treatment. Clinical flexibility and divine illumination depend on individual wisdom; specialists should study this diligently.