Do you know about Presbyopia ?

Question

I know about the Myopia and Hypermetropia but not about the presbyopia. Can you tell me ?

Answer 1

Defects in eye :

1. Myopia -

Myopia is Near-sightedness in which the person is not able to see the far objects clearly, but can see the near objects. In this defect, the image is formed in front of the retina.

It is caused due to the excessive curvature of eye lens or elongation of the eye ball. It can be corrected by the concave lens of suitable power.

2. Hypermetropia -

Hypermetropia is Far-sightedness in which person can see distant objects clearly and is unable to see the near objects. In this defect, the image is formed i=behind the retina.

It is caused when eye  ball is too short or when focal length of eye is too long. It can be corrected by the used of convex lens of appropriate power.

3. Presbyopia -

It is a vision defect which indicates that the power of accommodation of the eye usually increasing with the age of a person. It is a disorder of eye in which person is not able to see near and far objects clearly. It mostly occurs first from the age of 40.

It is not caused due to shape of eyeball rather it is caused by the hardening of lens and weakening of ciliary muscles over time. It can be corrected by using the bifocal lens.