How does the eye work?

In its simplest sense, your eye works like a camera. The variable opening is called the pupil; there is a lens system, including the transparent covering called the cornea; a reusable "film" is called the retina, with its various sets of muscles; these muscles control the size of the opening, as well as the shape of the lens and the movements of the eye. Light passes through the cornea and pupil, is refracted by the lens, and focuses on the retina, which forms the image.

In the retina, rods and cones change the photons of light into electrical signals, which are then sent to and interpreted by the brain. The shapes of the cornea and the lens determine the ability to focus the light on the retina, and not only their shapes, but also elasticity, the shape of the eyeball itself and sets of attached muscles. So, when you are looking at something, muscles attached to the lens must alternately contract and relax to change the shape of the lens system and thereby keep the image focused on the retina, all this even when your eyes are moving; this complex set of muscle movements is controlled automatically by your nervous system.

The eye is a ball covered with a tough outer membrane. The covering in front is clear and curved. This curved area is the cornea, which focuses light while protecting the eye.

After light passes through the cornea, it travels through a space called the anterior chamber (which is filled with a protective fluid called the aqueous humor), through the pupil (which is a hole in the iris, the colored part of the eye), and then through a lens that performs more focusing. Finally, light passes through another fluid-filled chamber in the center of the eye (the vitreous) and strikes the back of the eye, the retina.

Like the film in a camera, the retina records the images focused on it. But unlike film, the retina also converts those images into electrical signals, which the brain receives and decodes.

One part of the retina is specialized for seeing fine detail. This tiny area of extra-sharp vision is called the macula.

The eye is often compared to a camera, but in truth, the organ of sight is far more complex and efficient. Not only does the eye focus and snap pictures, but it also works continuously with the brain and nervous system to process ever-changing images, providing you with the visual information you need for doing everything from hitting a golf ball to preparing your taxes.