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Our eyes are the doorway to the
external environment, and clearly, the most important of the sense
organs. They play a pivotal role in our day-to-day existence. The eye
receives light from the outside world, and converts it into
electrical signals that are transported to the brain and perceived as
an image. The eye is a slightly asymmetrical globe, about an inch in
diameter.
Main Parts of the Human Eye
Sclera:
The sclera is the white part of the eye that surrounds the cornea. It
is made up of fibrous tissues, and provides protection to the inner
parts of the eye. This is the tissue that is commonly called the
white of the eye.
Cornea: The cornea is the transparent
tissue at the front of the eyes through which light coming from an
object enters the eye. It also helps in focusing the light on the
retina.
Aqueous Humor: It is a clear transparent fluid
that fills the space between the cornea and the eye lens. It also
supplies nutrients and oxygen to these parts.
Iris: The
iris is a ring of muscles in the central part of the eye, that is
helpful in regulating the amount of light entering the eye by
controlling the size of the pupil.
Pupil: This is an
opening in the center of the iris through which light passes and
falls on the eye lens. Its size is controlled by the iris.
Eye
Lens: The lens of the eye is situated directly behind the pupil.
It helps in focusing the light on the retina. The eye lens is capable
of changing its shape so as to enable us to see objects near and
far.
Ciliary Muscles: This is a ring-shaped tissue that
holds and controls the movement of the eye lens, and therefore, helps
in controlling the shape of the lens.
Vitreous Humor:
It acts as a filler and covers the space between the eye lens and
retina. It also provides protection to the lens. It makes up for
about two-thirds of the total volume of the eye, and is composed
mainly of water.
Retina: It is a membrane responsible
for converting the light falling on it into electrical impulses that
can be sent to the brain. The retina contains light-sensitive
photoreceptor cells called rods and cones. The rods help in black and
white vision and for seeing in dim light, while the cones help in
daytime and color vision.
Optic Nerve: It is a bundle
of nerve fibers that serve as a cable that connects the eye to the
brain. This optic nerve helps in transmitting signals from the retina
to the visual center of the brain.
Yellow Spot or Macula:
Situated at the center of the retina, this yellow spot helps in
absorbing excess light that enters the eye. The macula is responsible
for our reading vision, and helping us to see objects right in front
of us.
Eyelids: The eyelids help in the protection and
lubrication of our eyes. They also help in controlling the amount of
light falling onto our eyes.
Muscles of the Eye: The
eyeball is held in its place by the help of several eye muscles. The
eye muscles are responsible for the up and down, as well as the left
and right movement of the eye.
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