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Eye Anatomy & Vision

The eye is our window to the world around us. Light entering the eye passes through our tear film, cornea, pupil, and lens and focuses on a small area of our retina called the macula. This is the area responsible for clear or 20/20 vision. The tear film, as the first surface that light passes through is actually the most important refracting or focusing surface of the eye. The cornea is the clear tissue below the tear film and is the most anterior portion of the eye. Behind the cornea is a space called the anterior chamber that is filled with clear fluid and behind the anterior chamber is the iris. This is the pigmented layer of muscle that determines eye color. The iris acts to adjust the size of the pupil making it larger at night to allow more light to enter the eye and smaller during the day to reduce glare. The lens of the eye sits behind the iris and adjusts its shape to focus light when the visual focus moves from a distant object to a near object. The part of the eye essential for the transmission of visual information to the brain is the retina and optic nerve. These two structures are actually extra cranial brain and are the only opportunity to directly view the brain. There are two types of light receptors in the retina: rods, for receiving and transmitting light intensity, located mainly in the peripheral retina; and cones, for receiving and transmitting colors, most responsible for 20/20 vision. The outside of the eye is called the sclera and consists of collagen. It is a protective covering for the internal eye structures. There are six muscles that help the eye move and six cranial nerves responsible for eye and eyelid movement, vision and corneal and eyelid sensation. The eye sits in a bony cavity called the orbit which surrounds and protects all but the most anterior aspect of the eye. The anterior aspect of the eye is covered and protected by the eyelids which act to keep the cornea moist, remove debris and prevent particles from damaging the cornea. The back of the eyelids and most of the anterior of the eye is covered by a moist membrane called the conjunctiva.