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Your eyes are beautifully created to focus the world's images. We start by discussing the basics of eye anatomy. Images start as beams of light that pass through several structures in the eye before falling upon the back of the eye. These structures are listed below from the front surface of the eye to the back of the eye. Please refer to the eye diagram.
You may click on the labeled structures to read an explanation of each structure's function in the visual pathway.
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| Tear Film |
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Your tears are extremely important for good vision. The tear film actually
contains three components, oil, water, and lipid (fat). All of these components
must be present in the proper quantities to properly lubricate the outer
surface of the eye. Disorders of the tear film include
dry eye.
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| Cornea |
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Your tear film adheres to the clear, curved window
of the eye otherwise called the cornea. It has several layers all of which
must remain clear for good vision. Eye diseases may affect one or all
of the layers and thus degrade the quality of an image. In addition to
clarity, the cornea provides focusing power for the eye. Disorders of
the cornea include
abrasions,
ulcers, and
keratoconus.
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| Pupil |
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The pupil is the black spot located in the center of the colored portion of the eye.
It is generally round and can adjust its size.
Pupil size is important because too much or too little light directed at the back of the
eye can distort vision. Disorders of the pupil include
coloboma and
Adie's Tonic Pupil.
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| Lens |
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The lens of the eye which rests behind the colored portion of the eye is a living,
growing structure consisting of proteins that help to focus light.
Unlike the glass or plastic of a camera lens, the human lens can change thickness to allow
us to see near or far objects. People who wear glasses cannot clearly focus images
with their lens alone.
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| Vitreous |
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This name sounds unusual. It describes the jelly-like substance within the
eyeball. The inside of the eye is not filled with air. Instead it is filled
with a clear, vaseline-like substance that supports the growth of the eye
during development. As we age, the vitreous becomes more water-like in
consistency.
Floaters
are diseases involving the vitreous.
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| Retina |
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The retina is similar to the film in a camera. Light is directed toward this layer of the eye which consists of specialized nerve cells called rods and cones. The retina actually has multiple layers all of which are needed to transmit light impulses in an organized manner to the brain.
Retinal detachments
and
diabetic retinopathy
are common diseases of the retina.
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| Macula |
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The macula is a very small, but extremely important portion of the retina.
It has a large number of the cone nerve cells and therefore is responsible for
our central vision.
Macular degeneration
and macular holes are common causes of poor vision in adults.
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| Optic Nerve |
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This large yellow structure gathers the nerve impulses from the retina and transmits
them to the specialized visual portions of the brain. Visual information is organized
very precisely as it is directed from our eyes to the occipital cortex in the back of
the head just above the neck.
Glaucoma
and optic neuritis are examples of eye diseases in this portion of the eye.
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| Sclera |
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The tough protective layer of the eye is the sclera. It is the white of the eye. Inflammation of this layer is known as scleritis.
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| Iris |
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The iris is the colored blue or brown part of the eye. Muscles within the iris control the size of the pupil.
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| Choroid |
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The choroid is a vascular coat of the eye. Tumors and inflamation can damage this layer resulting in diminished vision.
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