Know more about what is your human eye and how it functions

1. SUBJECT- SCIENCE
CLASS- 10TH(2015-2016)
CHAPTER- HUMAN EYE AND THE
COLORFUL WORLD
TOPIC- HUMAN EYE, DEFECTS AND
CORRECTIONS
TEACHER'S NAME- MS. RENU KAMBOJ
CONCEPT-
1- HUMAN EYE
2- HUMAN EYE PARTS
3- EYE DEFECTS
4- CARE OF EYE

2. RETINA
The retina is the film of the eye. It converts light rays into electrical signals and
sends them to the brain through the optic nerve. The sides of the retina are
responsible for our peripheral vision. The center area, called the macula, is used
for our fine central vision and color vision. The retina is where most the
problems leading to vision loss Occur. Three of the leading causes of blindness,
from retina damage, are Retinitis Pimentos, Macular Degeneration and Diabetic
Retinopathy
CORNEA
The cornea is a clear, dome-shaped surface that
covers the front of the eye. It is the first and most
powerful lens in the eye's optical system. To keep
it transparent the cornea contains no blood
vessels. Tears that flow over it and aqueous
humor in the chamber behind it keep it
nourished. When you hear of eye banks and eye
transplants, it is the cornea that is being
replaced. The cornea can be damaged from:
accidents, infections, and genetic defects.

3. IRIS
This is the colored part of the eye: brown, green, blue, etc. It is a ring of muscle
fibers located behind the cornea and in front of the lens. It contracts and expands,
opening and closing the pupil, in response to the brightness of surrounding light.
Just as the aperture in a camera protects the film from over exposure, the iris of the
eye helps protect the sensitive retina.
LENS
During modern cataract surgery the outer
membrane of the lens is left in place. The
artificial intraocular lens is placed in this sack

4. EYE DEFECTS
1- MYOPIA
2- HYPERMETROPIA
3- CATARACT
4- PRESBYOPIA
5- ASTIGMATISM

5. HYPERMETROPIA
 Hypermetropia, also known as farsightedness,
long-sightedness,
is a defect of vision caused by an imperfection in the
eye (often when the eyeball is too short or the lens
cannot become round enough), causing difficulty
focusing on near objects, and in extreme cases
causing a sufferer to be unable to focus on objects at
any distance. As an object moves toward the eye, the
eye must increase its optical power to keep the
image in focus on the retina. If the power of the
cornea and lens is insufficient, as in hyperopia, the
image will appear blurred.

6. IMAGE OF HYPERMETROPIA
 Hypermetropia can be cured by using an convex
lens of appropriate focal length.

7. MYOPIA
Myopia, commonly known as being nearsighted or
shortsighted, is a condition of the eye where the
light that comes in does not directly focus on the
retina but in front of it. This causes the image that
one sees when looking at a distant object to be out
of focus, but in focus when looking at a close
object.

8. IMAGE OF MYOPIA
 Myopia can be cured by using an concave lens of
appropriate focal length.

9. CATARACT
THE EYE LENS BECOMES OPAQUE.
Cure- SURGICAL REMOVAL

10. CARE OF EYE
1- DO NOT SEE VERY BRIGHT SOURCE OF LIGHT
2- DO NOT READ IN VERY DIM LIGHT
3- WASH EYES WITH COLD WATER
4- DO NOT RUB EYES IN CASE ANY THING HAS
FALLEN IN.
5- CONSULT EYE DOCTOR IN CASE OF EYE
PROBLEM.

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