It has been said that the eyes are the windows to the soul. In TCM the eyes are more accurately described as the window to the inner workings of the body, for in TCM the eyes are connected to all of the internal organs. In Chinese medicine each part 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.

TCM 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. This balance between vital Qi and external pathogens forms the basis for all aspects of TCM, with degenerative eye diseases and vision loss being no exception. 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.

Environmental Pathogenic Factors Affecting the Eyes
Heat - Leads to swelling, inflammation, and the redness commonly found in many eye diseases such as conjunctivitis
Cold - Will yield pain and slow vision loss over time, as in chronic degenerative conditions such as macular degeneration and glaucoma
Wind - Results in sudden and dramatic onset of vision loss
Dampness - Causes secretion of mucus, and swelling
Dryness - Results in dry itchy eyes and redness
Summer Heat - Inflammation and mucus discharge