The eyes are the external manifestation of the liver, the essence of the viscera, the gathering place of the ancestral meridians, and the pathway for the upper fluids. If sorrow stirs the viscera internally, the fluid pathways open and tears fall; if the fluids are exhausted, the eyes become dry. Additionally, if wind evils invade the viscera internally and transmit to the fluid pathways externally, it also causes tears to fall and frequent yawning; if the tears are exhausted, the eyes become dry. If the viscera are overworked and heat arises, the heat energy attacks the liver and rushes to the eyes, causing the eyes to become hot and dry, and in severe cases, red and painful.