According to traditional Chinese medicine (TCM), the eyes relate to the internal organs. In Chinese medicine, each part of the eye is associated with a particular element and corresponding zang organ. The iris is represented by the liver zang. The heart zang relates to the corners of the eyes or the canthi, the upper and lower eyelids correspond to the spleen, the conjunctiva the lung, and the pupil the kidney.
Chinese medicine recognizes six environmental, or external, pathogens that can lead to vision loss. A person's resistance to environmental pathogenic factors is based on how healthy their immune system is, which, in turn, is a function of qi (a person’s energy, similar to a life force). Basically, if a person has strong qi and good resistance, he or she can ward off potential hazards associated with these external factors. According to TCM, a person with poor qi flow or imbalances in qi in any of the zang organs relating to the parts of the eye will have decreased resistance to the six specific environmental pathogens that can influence vision.