Myopia- Myopia is also known as short sightedness. In this defect a person can see nearby objects clearly but cannot see distant objects clearly. In this case image forms before the retina not on the retina.
Causes- A person with this defect has the far point near then Infinity this defect arises due to the decrease in focal length of the lens either
•due to either excessive curvature of eyes lenses.
•along its action of the eyeball
As a result the images formed before retina.
Hypermetropia- Hypermetropia is also known as long sightedness. In this defect a person can see distance objects clearly but cannot see nearby objects clearly. A person with this defect has the near point farther away from normal near point. In this, image is formed beyond retina.
Causes- This effect rise due to following reasons
• Focal length of eye lens become large
Eyeball become too short so that the image is formed behind retina.