As light enters to the eye, it would pass first through three (3) structures or main layers/tunics:
1. Fibrous tunic - outermost layer of the eye. Consists of cornea and sclera which gives the eye white color and protect the inner parts of the eye.
2. Vascular tunic - middle layer of the eye. Consists of iris and choroid which gives the dark color of the eye and inhibits disorderly reflections inside the eye.
3. Nervous tunic - inner layer of the eye. Consist of retina which is responsible for vision
