In the Yinhai Jingwei (Essential Subtleties on the Silver Sea), a text on ophthalmology from the time of the Ming Dynasty (1), there is a discussion of floaters, described as "black blurred specks in the eyes resembling fly wings." The pathology is said to be related to the "water of the kidney" refers to the kidney yin, as distinguished from the "fire of the kidney," which corresponds to the kidney yang or mingmen fire.
