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The *Huangdi Neijing* (Yellow Emperor's Inner Canon) states: When the Foot-Shaoyin Kidney Meridian (Kidney Channel of Foot-Shaoyin) is disturbed, disease arises, and the eyes appear blurred as if unable to see. It further states: In Shaoyin disease, when one cannot see due to blurred vision, it is because Yin essence is depleted internally; thus, the eyes fail to see clearly. This is likely dimness of vision caused by sexual exhaustion. The left Kidney suffers from Yin deficiency, while the right Kidney suffers from Yang deficiency.

Liu Wansu stated: Blurred vision is caused by heat. However, the "Xuanfu" (Mysterious Pores/Orifices) exists everywhere—in the human viscera, skin, hair, muscles, fascia, bone marrow, nails, and teeth, as well as in all things in the world. They are the pathways and gates for the entry and exit, ascent and descent of Qi. The reason why the human senses—eyes, ears, nose, tongue, body, and mind—and consciousness can function is that the ascent, descent, entry, and exit of Qi are smooth and unobstructed. If there is any blockage, function is lost. Inability to see with the eyes, hear with the ears, smell odors with the nose, taste flavors with the tongue, flaccidity of sinews, bi-syndrome of bones, falling nails, rotting teeth, falling hair, insensitivity of the skin, and inability of the intestines and stomach to excrete—all these result from the stagnation of heat and the closure of the Xuanfu, preventing Qi, fluids, blood, vessels, Ying-Wei (Defensive and Nutritive Qi), and spirit from ascending, descending, entering, and exiting. Depending on the severity of the stagnation, the severity of the disease varies. Therefore, knowing that heat stagnates in the eyes leads to blindness. Thus, those with slight blurring of vision find it harder to distinguish objects when looking closely, because the Xuanfu of the eyes are narrowed, resembling the effect of viewing objects through a curtain. Or seeing spots like fly wings indicates that the Xuanfu are partially closed. Or experiencing blurriness with floating black spots is due to excessive heat manifesting in the eyes. According to the principle "Excess leads to harm, and control follows" (Kang ze hai, cheng nai zhi), tears and fluid secretions may obscure vision. Because these are very close to the eye, even minute particles are visible like black flowers.

Lou Quanshan said: "Indeed! Liu Wansu's words are true. Blindness, deafness, inability to smell, inability to taste, and inability to move hands and feet are all caused by the closure of the Xuanfu, blocking the pathways for the entry, exit, ascent, and descent of Shen-Qi (Spiritual Qi)." Therefore, ancient sages treated blurred vision, such as using Yanggan Wan (Sheep Liver Pill), employing sheep liver as a guiding herb to direct herbs like Huanglian (Coptis Rhizome) into the Liver to resolve various stagnations in the Liver. Since the Liver opens into the eyes, resolving Liver stagnation allows the Xuanfu of the eyes to become clear and bright. Thus, Huanglian-type herbs resolve heat stagnation; Jiaomu (Sichuan Pepper Seed) type herbs resolve damp-heat stagnation; Chongwei Cao (Leonurus Herba) type herbs resolve Qi stagnation; Xionggui (Ligusticum Chuanxiong and Angelica Sinensis) type herbs resolve Blood stagnation; Muzei (Equisetum Hiemale) type herbs resolve accumulated stagnation; Qianghuo (Notopterygium Root) type herbs resolve meridian stagnation; Cishi (Magnetitum) type herbs resolve head-and-eye stagnation, weighing down evil Qi to make it descend; Manjing (Brassica Pekinensis) directs Qi downward and unblocks the middle, following the same logic. All these formulas are methods for treating blurred vision caused by Qi and Blood stagnation, confirming that Liu Wansu's statements are not unfounded. As for Li Dongyuan and Zhu Danxi treating blurred vision, they used Renshen (Panax Ginseng) and Huangqi (Astragalus Membranaceus) to tonify Qi and Blood, which also restores clarity. There must be an explanation involving unblocking. Since vision primarily relies on Qi, abundant Blood allows the Xuanfu to be patent, enabling normal ascent/descent and entry/exit for clear vision; deficiency prevents the Xuanfu from functioning normally, leading to blurriness. In such cases, one must use formulas like Renshen combined with Siwu Tang (Four Substance Decoction) to assist the circulation and operation of Qi and Blood to restore clarity.