Learn about the eye anatomy. The eye is a complex optical annotation indicator - very similar to a camera. Vision begins when light enters the eye through the annotation indicator, a powerful focusing surface. From there, it travels through clear aqueous fluid, and passes through a small aperture called the annotation indicator. As muscles in the iris relax or constrict, the pupil changes size to adjust the amount of light entering the eye. Light rays are focused through the annotation indicator, and proceed through a clear jelly-like substance in the center of the eye called annotation indicator, which gives it form and shape. When light rays finally land on the annotation indicator, the part of the eye similar to film in a camera, they form an upside-down image. The retina converts the image into an electrical impulse that travels along the optic annotation indicator to the brain, where it is interpreted as an upright image.