Understanding The Human Eye

The human eye is a delicate and complex organ that converts light waves into impulses that are then interpreted by our brains as images. It is considered by many in the scientific and medical communities to be the most complex organ in our bodies. Below is an overview of the components of the human eye and how the process of sight works.

Parts Of The Eye

  • Cornea: Located at the front of the eye, the cornea is a transparent layer of tissue that focuses light into the pupil.
  • Iris: The colored part of the eye that controls the expansion and contraction of the pupil depending on the amount and intensity of the light that enters the eye.
  • Pupil: Located in the center of the iris, the pupil controls how much light enters the internal structure of the eye. In humans, the pupil is round, and it appears black, because the light that enters the pupil is absorbed by the inner eye.
  • Lens: Located directly behind the pupil, the lens (along with the cornea) helps to focus light onto the retina
  • Retina: A light-sensitive layer of tissue, the retina is a membrane located at the back of the eye that converts light into electrical impulses.
  • Photoreceptors: (sometimes called rods and cones) are specialized cells used by the retina to process and convert light
  • Optic Nerve: Located behind the eye, the optic nerve is a bundle of nerve fibers that transmits the impulses generated by the retina to the vision centers of the brain.
  • Macula: Part of the retina, the macula is responsible for central vision. It's highly specialized structure is responsible for visual acuity .
  • Sclera: The white part of the eye, the Sclera is made of fibrous tissue and is designed to protect the inner workings of the eye.
  • Choroid: Located between the retina and the sclera, the choroid is the vascular layer of the eye.

  • How It All Works

    The ability to see is a complex and delicate process that requires the various parts of the eye as well as the vision centers of the brain to work in concert. The process begins as light waves enter the eye through the cornea. As the primary focusing element of the eye, the cornea bends and focuses the light so it can pass through the pupil and enter the inner structures of the eye.

    The pupil, which is controlled by the ring of muscles known as the iris, contracts and expands to limit the amount/intensity of light that enters the inner eye. In bright conditions, the pupil will contract, and in low light conditions, the pupil will expand.

    Once through the pupil, the light then passes through the eye's secondary focus structure called the lens. Unlike the cornea, which is fixed, the lens has the ability to change shape, which allows the light to be fine tuned to a sharp focus before it passes onto the retina.

    The retina works much like the film in a camera. It's an intricate layer of light-sensitive tissue that lines the inner surface of the eye made up of photoreceptor cells (sometimes called rods and cones). As light hits the retina, it initiates a surge of chemical and electrical events that ultimately trigger nerve impulses. These impulses then travel through the optic nerve, located behind the eye, into the vision centers of the brain which finally get interpreted into the images we see everyday.

    As you can see, it is an extremely delicate system with several working parts. Just a slight defect, like the curvature of the lens, the shape of the cornea, or damage to the retina can cause sometimes significant vision problems. That is why taking care of your eyes is critically important. Buenau's Opticians recommends all patients receive an annual eye exam. Early detection and prevention of several common eye disorders can signigicantly reduce eye damage and prevent vision loss.