The eye is arguably one of the most complicated organs in our body. It is unique in its ability to transmit light rays and images through the pupil, focus the image clearly through the vitreous humor and onto the retina and finally converting it into electrical signals that are carried to the brain via the optic nerve. It is all quite extraordinary. With all of this happening seamlessly, what are the basic parts of the eye that contribute to this effort? What are their respective roles of each of the parts and how do they function? Let's look at the various components contributing to the whole vision experience that we sometimes take for granted.

Iris

The iris is heavily pigmented and defines the color of the eye based on the concentration and distribution of its pigments. The iris also has a sphincter muscle that controls the amount of light allowed into the eye through contraction and dilation. This function is similar to a camera aperture.

Cornea

The clear bulging surface in front of the eye is the cornea. It is transparent in nature and is the primary refractive surface of the eye. With its sensitivity to foreign debris and irritants such as chemicals and even cold air, it is the eye's primary defensive structure. Tears help the cornea maintain its hydration, anti-bacterial integrity, water content and extensive oxygen exchange.

Lens

The eye's natural lens is a transparent body enclosed in an elastic capsule made up of protein and water which can change shapes as one focuses on near or distant objects. As one ages the cells that form the lens age and become less pliable and flexible leading to presbyopia. This condition is the reason why people look to use bifocal glasses or reading glasses. This lens can also become cloudy, the prime indicator that cataracts are forming.

Optic Nerve

The location where the optic nerve is bundled at the back surface of the eye is known as the optic disk. Oddly enough there are no photoreceptor at the anatomical location of the optic disk therefore creating a blind spot. Below is a demonstration of the natural permanent blind spot:

Close your left eye. Fixate on the cross with your right eye. Adjust the viewing distance until the black spot disappears. When this happens, the image of the spot is falling on your blind spot.

Pupil

The pupil is a hole approximately 3 to 7 millimeters in diameter through which light passes.

Retina

The retina is a layer of tissue at the back of the eyeball that essentially acts like the film of a camera. It contains cells that are sensitive to light, both black and white as well as colored, and converts these light stimuli into electrical nerve impulses that travel along the optic nerve and onward to the brain where these are converted to images that we can see.

Sclera

The sclera is the white of the eye, with a smooth exterior and grooved interior. The sheath of the sclera continues with the sheath that covers the optic nerve. The scelra is the housing of the eye and is incredibly flexible and durable. This part of the eye also serves as a base for tendons to attach to. These tendons are involved in the active movement of the eye.

Vitreous

This is the clear gelatinous substance that fills the space between the lens and retina. This fluid helps to maintain the eye shape.

With a better understanding of the eye and its structures one can appreciate its true complexity. Taking sight for granted is easy to do. However no one can avoid admiring the eye for its wonders once its secrets are discovered.