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Diagram of the Eye
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Images courtesy of the National Eye Institute
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- Cornea
The outer, transparent, dome-like structure that covers the iris, pupil, and anterior chamber. The cornea provides approximately two-thirds
of the optical power of the eye. Light passes into the eye through the cornea allowing vision. Light also passes out of the eye allowing the
iris and pupil of the eye to be seen. The cornea can be considered to have five layers:
- The corneal epithelium
- Bowman's layer
- Corneal stroma
- Descemet's layer
- The corneal endothelium
- Fovea
The concave center of the retina. The region of highest visual acuity and cone cell density.
The fovea is a small area located on the retina in the back of the eye which allows us to see details clearly, sharply and with rich color when
the light focuses there correctly. In a normal visual system the fovea of the left and right eye are directed at the same point in space at the
same time giving us a better image than either eye alone.
- Iris
The colored ring of tissue suspended behind the cornea and immediately in front of the lens. It regulates the amount of light entering the eye by adjusting the size of the pupil.
- Lens
The lens is a clear part of the eye that helps to focus light, or an image, on the retina. The retina is the light-sensitive tissue at the back of the eye.
In a normal eye, light passes through the transparent lens to the retina. Once it reaches the retina, light is changed into nerve signals that are sent to the brain.
The lens must be clear for the retina to receive a sharp image. If the lens is cloudy from a cataract, the image you see will be blurred.
- Macula
The macula is located in the center of the retina, the light-sensitive tissue at the back of the eye. The retina instantly converts light, or an
image, into electrical impulses. The retina then sends these impulses, or nerve signals, to the brain.
- Optic Nerve
The optic nerve is a bundle of more than 1 million nerve fibers. It connects the retina to the brain. A healthy optic nerve is necessary for good vision.
- Pupil
Often compared with the shutter of a camera, the pupil is the black, circular "hole" in the iris that regulates the amount of light entering the eye.
The pupil appears black and the contents beyond it dark because of the absence of light inside the eye, similar to the way a dark room looks
when viewed from a lighted one. By using a special instrument called an ophthalmoscope, eye doctors are able to examine the inside of the eye.
- Retina
The nerve tissue that lives at the back of the eye, similar to the film in a camera, which takes the image you are looking at and transmits it to the brain
through the optic nerve. This area is nourished by a web of very fine blood vessels. The layers of cells in the back of the eye that are responsible for
sensing light and transmitting light-induced signals to the brain.
- Vitreous Gel
The transparent, colorless mass of gel that lies behind the lens and in front of the retina. Small semi-transparent or cloudy particles floating in the vitreous are
called spots or floaters.
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