The document discusses several common eye defects: myopia (nearsightedness) which causes light to focus in front of the retina, hypermetropia (farsightedness) which causes light to focus behind the retina, presbyopia which causes blurred near vision due to a thickening and loss of flexibility of the lens usually beginning at age 40, and cataracts where the lens becomes progressively cloudy resulting in blurred vision and potentially total vision loss if not corrected through surgery.

1. Eye defects

2. What you mean by vision?
• the ability to see is called vision, eyesight or drishti.
1. Lens
2. Film
3. wires
1. Lens
2. Retina
3. Nerves

3. Working of a lens

4. How do we see things?

5. MYOPIA or SHORTSIGHT
• Myopia occurs when the eyeball is too long, relative to the focusing
power of the cornea and lens of the eye. This causes light rays to
focus at a point in front of the retina, rather than directly on its
surface.

7. HYPERMETROPIA or LONG SIGHT
• This vision problem occurs when light rays entering the eye focus
behind the retina, rather than directly on it. The eyeball of a
farsighted person is shorter than normal farsightedness can be
corrected with glasses to change the way light rays bend into the
eyes.

9. PRESBYOPIA
• Presbyopia generally is believed to stem from a gradual thickening
and loss of flexibility of the natural lens inside your eye
Presbyopia usually occurs beginning at around age 40, when people
experience blurred near vision when reading, sewing or working at
the computer. Everyone becomes presbyopic.

11. Cataract:
• A yet another defect of the eye which usually comes in old age is
the cataract. The medical condition in which the lens of the eye of a
person becomes progressively cloudy resulting in blurred vision. It
develops when the eye-lens of a person becomes cloudy due to the
formation of a membrane over it. It decreases the vision of the eye
gradually and can lead to total loss of vision of the eye. It can be
restored after getting surgery .The opaque lens is removed and
artificial lens is inserted in its place via operation. This defect cannot
be corrected by any type of spectacle lenses.