Page 14 - The Book Pi in eye

Rajesh Khanna, MD

If the light does not come to focus by the time it crosses the
retina, than it is called hypermetropia or far sightedness. The person
has trouble seeing near and middle distances and even far.
If light comes to focus at different spots, it is termed astigmatism.
In more complicated cases some beams may come to focus in front
of retina and others behind the retina. A person will see blurry at all
distances and may need to squint in an effort to improve vision. This
can give rise to eye pain and headaches.

Figure 1.3 Errors of refraction

These errors of refraction are different from Presbyopia, which is
the inability to see near in old age. Theses anomalies of refraction are
physical limitations whereas as presbyopia is a physiological defect. In
other words, these three errors occur because of a mismatch between
the shape or power of the cornea and the length of the eye.
Presbyopia is due to the weak action of internal eye muscles. With

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