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How
the Eye Works
 The
human eye is like a camera where outside images are focused onto a
piece of film. The cornea and crystalline lens are the lenses that
focus the picture onto the eye's film, the retina. The iris is the
colored circle in the front of the eye. The black pupil, in the center
of the iris, enlarges and contracts to regulate the amount of light
entering the eye. The vitreous is a transparent jelly filling the
inside of the eye. The choroid is a system of blood vessels which
covers the outer retinal surface, providing it with oxygen and nourishment.
The sclera, or white of the eye, is a tough protective outer shell
that corresponds to the body of a camera. The optic nerve carries
the light images to the brain.
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Diagram of the normal
retina and macula.
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Photograph of the macular
region. |
The macula is a small
specialized area of the retina responsible for straight-ahead reading
and driving vision. The retina reacts to light through a chemical
process which then sends nerve impulses directly to the brain where
the "picture" is processed.
Unlike a camera, the image obtained by the retina is not of uniform
clarity or sharpness. Only the macula is sensitive enough to provide
high quality central vision. Any disease that affects the macula,
such as diabetes, macular
degeneration, macular hole, macular
pucker, ocular histoplasmosis,
retinal detachment, or retinal
vein occlusions can cause symptoms such as central blurriness
or distortion. |
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