The Eye, Nose, Ears, and Throat

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visual acuity.
* Iris - the colored ring of tissue behind the cornea that regulates the amount of light entering the eye by adjusting the size of the pupil.
* Lens - the transparent structure suspended behind the iris that helps to focus light on the retina; it primarily provides a fine-tuning adjustment to the primary focusing structure of the eye, which is the cornea.
* Macula - the portion of the eye at the center of the retina that processes sharp, clear straight-ahead vision.
* Optic nerve - the bundle of nerve fibers at the back of the eye that carry visual messages from the retina to the brain.
* Photoreceptors - the light sensing nerve cells (rods and cones) located in the retina.
* Pupil - the adjustable opening at the center of the iris through which light enters the eye.
* Retina - the light sensitive layer of tissue that lines the back of the eye.
* Retinal Pigmented Epithelium (RPE) - a layer of cells that protects and nourishes the retina, removes ...

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light rays then pass through the lens, which actually changes shape so it can further bend the rays and focus them on the retina at the back of the eye. The retina is a thin layer of tissue at the back of the eye that contains millions of tiny light-sensing nerve cells called rods and cones, which are named for their distinct shapes. Cones are concentrated in the center of the retina, in an area called the macula. In bright light conditions, cones provide clear, sharp central vision and detect colors and fine details. Rods are located outside the macula and extend all the way to the outer edge of the retina. They provide peripheral or side vision. Rods also allow the eyes to detect motion ...

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