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EYE ANATOMY |
The eye is a complex optical system
allowing us to learn more about the surrounding world.
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| Eye anatomy |
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| The cornea |
The cornea is a front clear window of the eye which is responsible
for focusing light rays to the back of the eye, its function
is protective.
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| The iris |
The iris is a part of the vascular membrane visible through
the clear cornea as the colored disk inside the eye. The color
of the iris is determined by the amount of pigment present
in this eye structure. The pupil is a circular hole in the
midde of the iris which regulates the amount of light passing
through to the retina at the back of the eye.
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| The crystalline
lens |
The lens is a biconvex transparent body situated inside the
eyeball behind the iris and the pupil, constituting part of
the refracting mechanism of the eye. Outside the lens is
covered by the capsule - a clear, membrane-like structure
that is quite elastic. There are the anterior and posterior
lens surfaces; the central points of these surfaces are termed
the anterior and posterior poles; a line connecting the poles
constitutes the axis of the lens, while the marginal circumference
is termed the equator.
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| The vitreous humour |
The vitreous is a clear gel which occupies the posterior compartment
of the eye, located between the crystalline lens and the retina.
Light is transmitted through the vitreous to the retina. In
the adult no blood vessels penetrate the vitreous body.
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| The retina |
The retina is the innermost layer of the eye. It is composed
of nerve tissue which senses the light entering the eye. This
system of nerves sends impulses through the optic nerve back
to the brain which translates these messages into images that
we see. It covers the back of the eye, the ciliary body and
the inner surface of the iris. The beginning of the optic
nerve in the retina is called the optic disk. This area of
the retina cannot respond to light stimulation. As a result,
it is known as the "blind spot". The macula, a yellowish
spot, is located in the central part of the retina. The very
center of the macula is called the fovea centralis. It contains
the highest concentration of cones. The fovea is the point
of the sharpest visual acuity. In the other retinal areas
the number of cones decreases and there are more rods. There
are about 7 million cones and 75-150 million rods in the retina.
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| The optic
nerve |
The optic nerve (also known as cranial nerve II) carries visual
information from the eye to the brain. It enters the central
nervous system at the optic chiasm where the nerve fibers
become the optic tract just prior to entering the brain.
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| The macula |
The macula is a retinal areathat is responsible for central
vision and allows us to perceive colors. It is also called
the " yellow spot".
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| The sclera |
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The sclera, the white part of the eye is a firm, unyielding
membrane that protects the inner workings of the eye. The
sclera is formed of white fibrous tissue intermixed with fine
elastic fibers. The fibers are aggregated into bundles which
are arranged in a longitudinal direction. It is much thicker
behind than in front (about 0,6 mm), the thickness of its
posterior part is 1 mm. In front, the sclera is directly continious
with the cornea, the line of union being termed the sclero-corneal
junction. In the inner part of the sclera close to this junction
is a circular canal or canal of Schlemm (the aqueous humor
drains into this canal). |
