In the Chapter of Generation of the Five Zang-organs in Suwen, it says: "All blood is related to the eyes", "the heart is associated with the vessels", "all the vessels are related to the eyes". In the Chapter of Pulse Abstruseness in Suwen, it says: "The vessels house blood." The heart governs vessels. The blood in the vessels is propelled by heart qi to circulate throughout the body and into the eyes. That is why the eyes are able to see.

 

Though the spirit is governed by the heart, its outward manifestations are in the eyes. In the Chapter of Treasure of Eyes in Shenshi Yaohan, it says: "The heart spirit displayed in the eyes is vision and the kidney water enables the eyes to see everything."

In the Chapter of Linglan Midian in Suwen, it says: "The small intestine is the organ responsible for reception and transformation." The small intestine separates the lucid from the turbid when food and water are taken into the body. The lucid part is transported to the whole body by the spleen to nourish the eyes. Besides, the heart and the small intestine are internally and externally related to each other.  The functional state of the small intestine not only relates to the heart, but also affects the eyes.