The third eye chakra relates to our ability to visualize and process mental concepts. How we "see" the world is determined by the state of this chakra. If it's blocked, then our perception will be distorted and often negative. Through this chakra we can see into the subtle realms, remote view, increase our extra sensory perception, posses greater intuition, and hold a superior insight into people's motives.
A section through the choroid layer of the eye. A pigment cell (red) is at upper center. The choroid layer lies behind the sclera (white of the eye) and in front of the retina. It is highly vascular and supplies blood to the back of the eye. It is pigmented to absorb excessive light, preventing internal reflections that would form multiple images on the retina.