Page 126 - Genius Kidz Prudence Learning Sc-8

Lateral Inversion : Lateral inversion is the cones function best in relatively bright light.
reversion of the object image when seen in the Cones are responsible for colour vision.
mirror. Optic nerve transmits visual information from

retina to brain.

VISION DEFECTS
The minimum distance at which an object can

be distinctively seen by a human eye is known
Lateral inversion as least distance of distinct vision (LDDV) and
HUMAN EYE the maximum distance is infinity. If any one of
Eyes are the organs of vision in the human the following is faulty, the vision defects
body. occurs. It can be of 2 types:

Structure of human eye : An eye is a spherical 1. Shortsightedness (Myopia) : It occurs
structure. It's front transparent part, cornea, when a person is not able to see the far
allows the light to pass through the eye. Just away objects. In this type of defect image is

behind the cornea, iris is present. It is black or formed in front of the retina.
brown in color. In the centre of the iris, there is 2. Farsightedness (Hypermetropia) : It occurs
a small opening called pupil. Pupil controls the when a person is not able to see the nearby
amount of light entering the eye. And the size object. In this type of defect the image is
of the pupil is controlled by the iris. Image is formed beyond the retina.
formed by the help of a convex lens on the Care of the eyes :
retina of the eye. Convex lens is situated
! Wash your eyes frequently with clean
behind the pupil. The adjustment of the size of water.

lens is carried out by the help of ciliary
muscles. When the image is formed on to the ! Looking directly towards a powerful light
retina, its constituting nerve cells passes the source can damage the eyes.
message on the brain via optic nerves. Retina ! Excessive rubbing of the eyes on allergy can
has two types of photo receptor cells called cause unnecessary strain.
rods and cones. ! Vitamin A deficiency can effect the eye

Rods are responsible for night vision whereas vision.
! If you are advised by a doctor use proper
Choroid Vitreous humor
spectacles.
Cornea ! Too little or too much light is bad for eyes.
Iris Retina
Insufficient light causes eyestrain and
Anterior headache.
chamber
BRAILLE SYSTEM
Pupil
Lens
Louis Braille, a French Scientist, developed an
Ciliary body Optic nerve aid for the blind persons so that they could
Sclcra
read and write. This aid came to be known as
Structure of human eye Braille and till date remains the most popular

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