Eye
The eye are sensitive organs of sight. Eyes help us in seeing the world around us.
They are small in size, but are one of the most complex organs of the human body.
The eye is approximately 2.54 cm wide, 2.5 cm deep, and 2.3 cm tall.
The eye is like a camera. A camera has a lens and a film to produce an image. Similerly, the eye also has its own lens and film.
Thecornea, lens and vitreous help to bend and focus the light. The retina is the film on which the light is focused. The lens and vitreous help in focusing the light on to the retina.
The retina forms an upsidedown image of the object. It converts the light rays into electrical impulses, which are then transmitted to the brain through the optic nerve.
The brain then translated and perceives the image in an upright position.
Vitreous:-
The vitreous is a transparent, thick substance in the large back section of the eye. It gives form and shape to the eye.
It is mainly made of water. The vitreous gradually thins with age and takes a liquid form.
Iris and pupil:-
Theiris is the coloured membrane lying behind the cornea and in front of the lens. It is a sheet of muscle that determines the amount of light entering the eye.
Dilatorand sphincter are the tiny muscle in the iris. The movement of these muscle widen and nerrow the size of the pupil, thus determining the amount of light.
The iris separates the front of the eye from the back of the eye. It contains microscopic pigment cells containing melanin that provides colour to the iris. The pupil is the round opening at the centre of the iris.
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Cornea, lens and retina:-
The cornea is a transparent covering of the eye. It covers the iris and the pupil. The cornea has a clear and shiny surface and helps in the refraction of light.
It provides two-thirds of the total focusing power of the eye. The lens is also a transparent structure in the eye. It is located just behind the iris.
The lens helps in the refraction of light and focuses light on the retina. It has one-fourth of the total refracting power of the eye. The lens can change shape to focus on objects at different distances.
This is known as accommodation. This ability gradually slows with age. The retina is a tissue lining the back of the eye. It has millions of light sensitive cells to catch light rays and convert them into electrical impulses.
These impulses are transferred to the brain to turn them into electrical impulses. These impulses are transferred to the brain to turn them into images. Rods and cones are two types of cells in the retina.
Rods are sensitive to light whereas cones are sensitive to colour. The retina contains about 6 million cones.
Macula:-
The macula is a small and sensitive part of the retina. It is located in the centre of the retina.
The macula is responsible for detailed central vision required for activities like reading. The center of the macula is called the fovea.
Myopia:-
Myopia is an eye condition in which a person can see near objects clearly but distant vision is unclear.
It is also known as short-sightedness or near-sightedness. The defected usually develops in childhood and adolescence and is thought to be hereditary.
Myopia is caused when the cornea becomes too long. It can be corrected by using a concave lens. Redial keratotomy is a surgical process to correct myopia by reshaping the cornea. It was developed in the mind- 1970s.
Hypermetropia:-
Hypermetropia is an abnormal condition of vision in which a person can see distant objects but cannot see near objects clearly. It is also known as long-sightedness or far-sightedness.
Hypermetropia is caused by the shortening of the eyeball that disables the eye to focus on near objects. It can be corrected by using a convex lens.
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