When light enters the eye, it passes through most of the key structures of the eye.
The ray of light travels first through the cornea, a transparent, protective window which bends (or refracts) light as it passes through.
The light then traverses the pupil, a dark hole in the center of the iris which is the colored part of the eye.
Once light passes through the pupil, it enters the lens, which bends the rays of light so they are properly focused on the rear of the eye.
The light then reaches the retina where the electromagnetic energy is converted into the neural codes used by the brain.
The retina consists of a thin layer of nerve cells at the back of the eyeball
There are two kinds of light-sensitive receptor cells.
Rods are thin, cylindrical receptor cells highly sensitive to light.
Cones are cone-shaped, light-sensitive receptor cells that are responsible for sharp focus and color perception, particularly in bright light.
The rods and cones play different roles in vision.
Cones are primarily responsible for the sharply focused perception of color, particularly in brightly lit situations.
Rods are related to vision in dimly lit situations and are largely insensitive to color and to details as sharp as those the cones are capable of recognizing.
