The Human Eye Problems, Functions, Structure and Facts

The human eye is the organs which enable us to see. The human eye does not only let us view our surroundings, but also enables us to differentiate between colors.

Human Eyes

Structure Of Eye

Human Eye

When you talk of the eye structure, they exist in pairs, each one being approximately 2.5 cm in diameter. Each eye consists of the following main parts.

  • Scelra: The white part of our eyes is known as scelra. It consists of fibrous tissues and protects the internal parts of the eye.
  • Cornea: The transparent tissue through which light enters the eyes is called cornea. It exists in front of the eye.
  • Iris: Iris is made up of muscles which contract or relax in order to adjust the amount of light which enters the eye.
  • Pupil: Pupil is an aperture controlled by the iris muscles. For instance, when it is dark, the iris muscles relax, causing the pupil to open up wider. Therefore, more light enters they eyes to enable us to see better. On the other hand, the pupil becomes narrow due to the contraction of the iris muscles in the presence of excessive light in order to protect the cells of the eyes.
  • Lens: The lens is present behind the pupil. Light enters the pupil, passes through the lens and is focused on the retina of the eye. The lens is capable of changing its shape in order to help us see near or far off objects.
  • Retina: The retina converts light into electrical signals which are transferred to the brain for processing. The retina contains two types of cells: rods and cones. These cells are sensitive to light. Rods are important for night-time vision when there is little light. On the other hand, cones play an important role in helping us see colors.
  • Optic Nerve: The optic nerve takes electrical signals from the retina of the eye to the brain.

Functions of Eyes

Eye functions are associated to our sense of sight. They convert light into electrical signals which are deciphered by the brain into images. Properly working healthy eyes are able to perform the following functions.

  • They help us view our surroundings.
  • Our eyes enable us to see colors. Certain organisms, such as dogs, cannot see colors and, so, their world is black and white.
  • Eyes help us see near as well as distant objects.

How Eyes Work

There is one of the eye facts that these small organs perform a very complex function. The working mechanism of the eyes can be broken down into the following simple steps.

  • When we see an object, light is reflected off it into our eyes.
  • The light rays entering our eyes first pass through the pupil. The size of the pupil is controlled by muscles, known as the iris.
  • After passing through the pupil, light passes through the transparent lens of the eye. Light rays are refracted and are focused onto the retina.
  • Light sensitive cells, rods and cones, present in the retina covert the light rays into electrical impulses.
  • The optic nerve transfers these electrical impulses from the retina to the brain which then processes these signals and translates them in the form of an image.

Diseases of Eyes

These extremely delicate organs can fall prey to different eye problems due to allergic factors, unhygienic conditions and old age. Mentioned below are some of the most common diseases of eyes.


Conjunctivitis is commonly known as the pink eye disease. It is an inflammation of conjunctiva, the transparent membrane which covers the sclera. Inflammation of tiny blood vessels found in conjunctiva make our eyes appear red.


Cataracts affect the eye lenses. They may be caused due to old age or may exist as a defect by birth. Parts of lenses become opaque, blocking the passage of light to the retina, thereby obstructing our vision.


Glaucoma is a disease which leads to blindness due to a damage to the optic nerve. When the optic nerve fails to transmit electric signals to the brain, an individual is unable to see at all.

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