Let's take a closer look at one of the examples of lenses given earlier. This would be your eyes or optics. The main focusing parts of your eyes are the lens and cornea. Your lens, which is connected to the optic nerve, bends light so that it is "able to focus the image directly on the retina."

Basically what happens is the light bounces off objects and is reflected into your eyes. The lens then focuses the object to your retina, which is made of cells. The image is projected upside down, so your brain must flip the image right side up. After this occurs, you are able to see what you see.

To completely understand the eye, let's discuss each significant part. The sclera is the tough and slippery white part of your eye. The cornea protects the sensitive part of your eyes. It is the "window" of the eye. Light must pass through this fibrous tunic before entering the inner structures. The sclera also helps focus light. The iris has a job as well. It opens and closes to let different amounts of light into your eye. It is also responsible for the color of your eyes. The two pieces that help your eyes see are the rods and cones. Rods and cones can see two different colors. Rods see black and white, and cones see in color. The brain is what combines both images, so that you see all colors.

Other parts of the eye carrying significance are the lateral rectus, medial rectus, superior rectus, inferior rectus, inferior oblique and superior oblique. Each one of these has a job. Lateral rectus moves the eye vertically. Medial rectus moves the eye medially. The superior rectus rolls the eye upward, while the inferior rectus rolls the eye downward. The inferior oblique turns the eye laterally, and the superior oblique turns the eye to each side. Working together these parts help you see.

Depth is a very important topic as well when discussing the eye. You have spaces between your eyes. Due to that, your eyes see two different worlds. Now, because each eye is seeing two different worlds, the brain must combine the images the eyes take in, so that what you are seeing is not blurry. For further understanding of depth, go to the experiment section.

The view of light is probably the most complex sensory system of the body. Of all sensory receptors in the body, nearly 7/10 are photoreceptors which lie within objects of sight, the eyes or eyeballs. Finally, our eyelids, too have a specific function, to protect the inferior surface of the eyes.

Please see the illustration below for a more detailed description of the eye.