Among the five sense organs of the human body, the eyes and ears are particularly important. Beyond hearing, nothing is more crucial than vision. Although the eyes open into the Liver (Gan), the essence and fluids of all five Zang organs (Wu Zang) ascend to the eyes to form their luster. Therefore, practitioners of health preservation emphasize the quiet practice of "inner vision" (Nei Shi) and the concept of gaze being as bright as a candle flame. Only when internal nourishment is sufficient and external pathogenic factors do not disturb will the pupils remain clear and bright. However, who can avoid the mental and physical exertion inherent in worldly life? Some suffer external injury from wind, cold, or summer-heat invasion; others suffer internal damage from depression and anger injuring the Liver, leading to the depletion of Ying Blood (Ying Xue). Thus, regarding medical treatment for illness, the key to lifelong sight or blindness lies in the hands of physicians; how can one not be cautious? Yet, who among the world is capable of clearing the clouds and fog to reveal the blue sky? Who else but Master Deng of Qingjiang?

I have read *The Complete Book of Ophthalmology at Yicaoting*. In his preface, he explains the origin of his medical practice, which is based on the Song Neo-Confucian argument that children must understand medicine. This shows his filial piety. Furthermore, adhering to the principle of Fan Zhongyan, a righteous official of the Northern Song Dynasty, who stated, "If one cannot serve as a good prime minister, one should become a good physician," he set high standards for himself, demonstrating his benevolence. A person who is both benevolent and filial, dedicating their utmost energy to medicine, would inevitably reach a realm of divine proficiency. Consequently, his theoretical discussions and prescriptions analyze internal injuries and external causes in meticulous detail, with precise and complete formulations for odd and even formulas. Moreover, his teachings far surpass ordinary methods by ten thousandfold; thus, using his prescriptions always yields effective results. It is a pity that the woodblocks were damaged, causing the book to fall out of circulation. I obtained this book and kept it safely for a long time. Now, daring not to keep it to myself, I have arranged for its re-printing and publication to the world. This is not only to praise the painstaking efforts of this benevolent and filial author but also to provide future generations suffering from eye diseases with selected prescriptions for treatment, enabling them to restore their vision. Without needing the practice of inner vision, they can naturally preserve the most critical of the five sense organs, free from the harm of wind, cold, anger, and depression. In that case, what could be the measure of the merit of Master Deng's *Yicaoting*? This is the preface.

Written by Nian Xiyao of Guangning at the government office in Jinling, in the ninth lunar month of the Dingyou year of the Kangxi reign.