Question

collect information about different types of eye defects from your nearest eye specialist or optical shop

Answer 1

The normal vision of eye is 25cm to infinity. But sometimes the eye cannot focus the image of object on retina , so in such cases person is said to suffer from eye defect.

There are three common eye defects:
--> Myopia
--> Hypermetropia.
--> Presbyopia.
---> Cataract.

Myopia : 
Person suffering with Myopia can see the near distances comfortably but finds difficulty in seeing far off things .Hence it  is also  called as Near Nearsightedness.
Parallel rays from distant object converge in front of retina

Reason For eye defect :
-->Elongated eye ball
-->Due to short focal length.

Corrective measures :
 Myopia eye defect is corrected by using spectacles containing concave lenses.

Hypermetropia:
Person suffering from hypermetropia can see far objects clearly but finds difficulty in seeing near objects . Hence it is also called as Farsightedness.

The Diverging rays from near object converge behind retina.

Reason for defect :
-->Due to eye ball too short
--->Due to larger focal length.

Corrective measures:
Hypermetropia eye defect is corrected by using spectacles containing convex lens.

Presbyopia:
In old age due to ciliary muscles becoming weak and eye lens becoming inflexible the eye loses its power of accommodation.
Presbyopia is special kind of hypermetropia.
Its possible that same person suffering hypermetropia can also suffer with myopia. In old age, person cannot see near as well as far.

Corrective measure :
A bifocal lens is used in spectacles in which upper part is concave and lower part of lens is convex.

Cataract :
The medical condition in which the lens of the eye of person becomes cloudy resulting in blurred  vision.
It can be cured only by surgery.

Answer 2

Explanation:

Myopia Hypermetropi a