This presentation includes the description of human eye - it's parts, defects of human eye and their correction methods, concept of power of accommodation of human eye and care of human eye.

1. Topic- Human eye
By- SHREET MISHRA (K.V. OMTINAGAR,
2ND SHIFT, LUCKNOW)
CONCEPTS EXPLAINED-
1- HUMAN EYE
2- HUMAN EYE PARTS
3- EYE DEFECTS
4- POWER OF ACCOMODATION
5- CARE OF EYE

2. HUMAN EYE

3. RETINAThe 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

4. 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.

5. LENS
During modern cataract surgery the outer membrane of the lens is left in
place. The artificial intraocular lens is placed in this sack

6. 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.

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

8. HYPERMETROPIA
 Hypermetropia, also known as
farsightedness or 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.
Convex lens is used to correct such disease.

9. Image of Hypermetropia

10. 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.
Concave lens is used to correct such
disease.

11. Image of Myopia

12. CATARACT
THE EYE LENS BECOMES OPAQUE.
REMEDY - SURGICAL REMOVAL

13. Presbyopia
A person who is suffering from
nearsightedness or myopia in their
earlier age may develop the defect of
farsightedness or hypermetropia in their
old age due to weakening up of cilliary
muscles. Such person is neither able to
see distant objects clearly nor able to see
nearby objects clearly.

14. Presbyopia
• Cause of Presbyopia
• This defect may arise due to following reasons
• 1. Weakening of cilliary muscles due to age factor.
• 2. Loss of elasticity of eye lens and becoming rigid.
• Cure for Presbyopia
• As in this defect person suffers from farsightedness as well
as nearsightedness he is equipped with the spectacles
having bifocal lenses. The upper part of the lens is concave
in nature to enable him to focus at distant objects and lower
part of the lens is convex in nature to enable him to focus at
nearby objects.

15. Presbyopia
An eye with presbyopia can
neither focus clearly at distant
objects nor at nearby objects .
A normal eye can focus on
distant as well as nearby
situated objects clearly
Spectacles
With
Bifocal
Lens

16. Power of Accommodation
• Power of an eye to form the image of close and far
situated objects on the retina by adjusting the focal
length of crystalline eye lens with the help of cilliary
muscles is known as power of accommodation.
• Light rays coming from the objects situated close to the eye
are more diverging as compared to the objects situated far
away from it. Hence eye lens has to increase its power in
order to converge the more diverging rays and for this
cilliary muscles pushes the cartilaginous eye lens from its
sides to increase its thickness and thereby increase the
power of the lens. But there is a limit of thickening the eye
lens by cilliary muscles and increasing its power. Hence
there is a limit of the closeness of the objects from the eye
up to which an eye can see them clearly and distinctly. The
Minimum distance up to which an eye can see clearly is
known as least distance of distinct vision.

17. 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.

18. THE
END