Name: Eye Lens and Ciliary Muscles
Uploaded: 2019-07-19
Duration: 2 min 31 s
Description: Here is an interesting video about the adjustment of focal length in the world's great optical instrument, the human eye. Watch this to explore more.

Question

State reasons for Myopia. With the help of ray diagrams, show the image formation by a myopic eye.

Accepted Answer

Myopia is a defeat of vision in which a person can see objects situated nearby and cannot see objects situated far away. The far point of the eye is not at infinity. Due to this defect, rays coming from a point beyond far points meet at a point short of the retina. So that's why the person suffering from myopia will see a blurred image if the object is beyond the far point.

There are two reasons for this effect

The two causes of myopia are:

(1) Due to some disease or age, the ciliary muscles attached to the lens get weak. They are unable to relax, and hence, focal length of the crystalline lens does not increase. Thus, the image of the far-off object is formed in front of the retina, and hence, appears blurred.

(2) Sometimes the eyeball gets elongated and therefore, the images of far-off objects are formed in front of the retina.

In a myopic eye, the image of a distant object is formed in front of the retina as shown in the below diagram:

State reasons for Myopia. With the help of ray diagrams, show the image formation by a myopic eye.

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