Eye Anatomy

By: Dr. Levinger

The sense of sight is our most important sense. Five million nerve fibers reach our brain from our five senses combined, half of which originate from our eyes. Our eyes receive an enormous amount of information, which in turn, is transmitted to our brains for processing and application. The eye has an extremely complex structure, composed of a multiplicity of units. Each unit has its own specific function. These elements blend together to create a" whole" affording us the sense of sight.

Cornea The transparent front portion of the eye. Rays of light pass through the cornea and are refracted through the lens toward the retina, located in the posterior portion of the eye. Therefore, the tiniest alteration of the cornea will significantly affect the focus of light. The cornea is transparent and covered with a layer of tears that maintain its moisture level and protect it from infection.

Pupil A small hole through which light enters the eye. The diameter changes depending upon the amount of environmental light. The less light there is, the larger the size of the pupil, and conversely. For example, at night our pupils dilate and permit a greater amount of light to enter the eye. This mechanism makes it possible to see in dim light as well.

Iris Tissue that contains pigment and encompasses the pupil. The muscles of the iris act like a camera shutter. They dilate or contract the pupil according to the amount of environmental light present, thus controlling the amount of light that will enter the eye.

Lens Approximately 8 mm in diameter and approx. 2.7 mm thick. It is located behind the pupil and its function is to concentrate all the light rays that arrive from the cornea to the retina. The lens is flexible and has the ability to change its curvature, and subsequently its optic strength, which makes it possible to focus at different distances.

Vitreous A gel-like transparent fluid that fills the eye cavity. The vitreous supports the eyeball and creates its round shape.

Retina Composed of millions of nerve cells that cover the inner posterior wall of the eye. These nerve cells are sensitive to light stimulus, and are responsible for converting light energy into electrical energy transmitted through nerve fibers to the brain, for the purpose of processing this information.

Optic Nerve Composed of a bundle of nerve fibers that transmit the information that arrives from the retina to the brain, which completes the final processing of a visual image that arrives to the eye.

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