The eye is one of the natures wonders. It is a very sensitive organ of our body. The eye lie in the sockets in the skull. The eye is covered with the you study the internal structure of the human eye. If you see inside the eye from a side, you will observe that the eye has the following parts;
Photoreceptors
They are
also known as visual receptors .Eye is the organ used as photoreceptor in human
body. A pair of eyes is present in human beings whish are present in the orbits
one the face.
An eye is a very complex structure. It is in the form of a ball. Eye
consists of three layers;
sclerotic, the retina, the nervous layer.
The
outer most white, tough, muscular layer is called sclera
which covers the eye outside. Its anterior part is transparent and bulging to
make cornea. The
colorued a small hole called pupil which
control the amount of light entering the eye. It windens when light is dim and
narrows when light is bright. Behind pupil a lens is
present which focus images from different on the retina. Lens is held by ciliary muscles and suspensory
ligament which
control the focusing of lens
automatically. The chamber in betweens lens
and cornea is filled with a fluid called aquous
humour which nourishes cornea, lense…Observations
1: Sclera (sclerotic coat) 2: Choroid 3: Cornea 4: Retina 5: Iris 6: pupil 7: Aqueous humour 8:Vitreous humour 9: Lens 10: Muscles
Choroid is the vascular layer of the eye and provides nourishment to the eye. The third innermost layer of the eye is retina. This layer is composed of special type of neurons called rods and cones. Rods are used to perceive dim light. They give us the image of the object but not colours and detail. Whereas cones are responsible for visualizing colours. The space between retina and lens is filled by a jelly like substance called vitreous humor which is also nutritive in function. Retina is the nervous layer composed of sensory neurons. Lens focuses the image of the object front of the eye on the retina which is transmitted to brain by optic nerve.The image is finally perceived by brain.
BULL EYE
Disorders of
Eye
Eyes send a
huge amount of information to brain. Sometimes a defect occurs in the working
of eyes which causes great disturbance in the life of a person. Some of these
disorders are vary serious and lead to blindness but some disorders are easily
curable. Two disorders generally known as long sightedness and short sightedness
are very common. These defects occur in old age. In these disorders the lens of
the eye is not able to adjust itself to focus the image on the retina. Hence
the vision is disturbed.
Sort sightedness
or near sightedness ,is a common eye disorder in
which a parson can see closer objects clearly but the distant objects are not
clearly visible technically this disorder is known as myopia it
is caused by an unusually long eyeball which makes light rays focus too far in
front of the retina, or the back of the eye, instead of focusing on the surface
of the retina. Because light is focused too early, a blurred image is left on
the retina.
The disorder
is corrected by using a concave lens is glasses. This lens focuses the rays on
the retina and the person is again able to see correctly.
Long sightedness or farsightedness, is a disorder in
which a o person feels difficulty in focusing on near objects but can see
far objects clearly. This is because the
image focuses at a point behind retina. The disorder is caused when the eyeball
is to short or the shape of the lens is not round. Technically this disorder is
known as hypermetropia
or simply hyperopia.
The disorder is corrected by using a convex lens
in glasses. This lens focuses the rays on the retina and the person is again
able to see correctly.
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