Peter drew a circle on the paper and also
marked its diameter. But when Peter saw, Peter could only see the horizontal line,
he could not see the entire circle. Not only near objects even in case of far
objects, like the television and this wall hanging, Peter could only focus on few objects
which were at a distance. Till now, we’ve spoken about near sightedness
where near objects seem clear but far objects are unclear and blurry
and farsightedness where far objects are clear but near objects are not prominent.
So in normal human eyes, the image gets focused on the retina.
Now, let us see what happens in case of Peter’s eyes.
See the entire image is not getting focused on the yellow spot, but on different parts
of the retina. And so he could not focus properly on all
the objects present in the room. He could only see the objects which were getting
focused on the yellow spot and the other images that were getting focused on the other area
of the retina became not prominent and hazy. Well this was happening because Peter’s
lens was uneven. And since the lens was uneven, the lens wasn’t
being able to focus the entire image on the yellow spot.
The image was getting scattered all over the retina.
This condition is known as Astigmatism. A’ means without and ‘Stigma’ means a
spot. So astigmatism is a condition that arises
when the image does not get focused on the yellow spot, hence without spot.
Now another condition arises with old age when things become blurry.
Well this happens because of the accumulation of protein granules on the lens.
This condition is known as cataract. See the lens turns opaque.
And this cataract can be treated surgically. The lens can be replaced surgically and normal
vision is again regained after that.