Some people cannot see objects at long distances but can see nearby objects clearly. This type of defect in vision is called 'Myopia". It is also called 'near sightedness'. For these people the maximum focal length is less than 2.5 cm. In such cases the rays coming from distant objects, after refraction through the eye lens, form an image before the retina as shown in figures 5(a) and (b).
A healthy person can see objects at all distances more than 25 cm clearly but a person with myopia can see objects clearly up to a certain distance. Let the extreme point from where an object appears clearly to a person with myopia be 'M' (shown in figure 5(c).
If the object is at M or in between M and point of least distance of distinct vision (L), the eye lens can form an image on the retina (see figure 5(c) and 5(d)). This point M is called 'far point".
The point of maximum distance at which the eye lens can form an image on the retina is called 'far point".
The defect, in which people cannot see objects beyond far point is called 'Myopia'
The eye lens can form clear image on the retina, when an object is placed between far point and point of least distance of distinct vision. If we are able to bring the image of the object kept beyond far point, between the far point and the point of least distance of distinct vision using a lens, this image acts as an object for the eye lens.
