What are the different components to eyes & what role do they play in vision? like, eyelids create a barrier between the eye and the world. what else?

Complex: The lids spread tears to moisten the eyes. The cornea is the front window behind which is the iris opening to let light in and the lens to focus light through the back chamber (vitreous) onto the retina which translates the light image into an electrical signal which goes up the optic nerve into the brain which is the computer that makes the conscious picture. A wonderful circuit.

Eyeball: From outside to inside, you have the eyelid, cornea, iris, lens, and retina. The cornea is a clear protective coating to the eye, which bend the light toward the retina. The iris regulates the amount of light getting into the eye. The lens further bends the light to land on the retina. The retina receives the light and changes the light information into electrical impulses and the brain.