1. Superabundance of kidney Essence Enables Eyes 

In the Chapter of Genuine Discussion in the Antique in Suwen, it says: "The kidney controls water and receives and stores essence from the five zang-organs and six fu-organs." That is why the eyes are in close relationship with the kidney essence.

In the Chapter of the Manifestations of Yin and Yang in Suwen, it says:" The kidney produces cerebral marrow." In the Chapter of Sea Discussion in Lingshu, it says: "The brain is the sea of marrow." In Elucidation on Major Problems in Lingshu, it says: "The ocular system pertains to the brain in the upper and comes out from the middle of the nape.  The brain and marrow are different in name but both transformed from kidney essence. The ocular system is connected with the brain and is related to the function of the kidney to store essence and produce cerebral marrow. If the kidney essence and marrow are abundant, the eyes are sharp in vision. If the kidney essence and marrow are deficient, tinnitus, vertigo and dim eyesight will be caused.

In the Chapter of Reverse Regulation in Suwen, it says: "The kidney is a water organ and controls fluid." In the Chapter of Differentiation of Five Kinds of Retention and Fluid in Lingshu, it says: "Fluid from the five zang-organs and six fu-organs all comes into eyes." In the eyes, fluid transforms into tears to moisten the eyes and vital liquids to nourish the eyes.

The qi transformation in bladder depends on the state of kidney qi.  If kidney qi is insufficient or if damp-heat is accumulated, it will lead to dysfunction of the kidney in transforming qi, resulting in retention of fluid and invasion of fluid into the eyes. Besides, the bladder meridian controls the surface of the whole body and is subject to attack by exogenous pathogenic factors which causes eye disorders.