Hyperopia or longsightedness is more difficult to understand.The longsighted individual can not see clearly near or far but distance is better. It is often confused with presbyopia, because people think that when their distance is good but they can’t read that that must be that they have become longsighted.
CAUSE OF HYPEROPIA
In a normal individual, an image of an object that is being looked at is focused onto the retina at the back of the eye.
However in hyperopia the image is focused not on the retina but behind it.
As the object that is being looked at moves closer to the eye, the image that is being focused behind the retina as above, moves further behind the retina making close objects even worse. This is the opposite to the shortsighted individual.
One trick that a long sighted person is able to employ, is that by accommodating, he can compensate for some of his hyperopia. For example, if the degree of longsightedness is say 2 diopters, then he can accommodate an equivalent amount and thus ‘mask’ the hyperopia. This is called ‘latent’ hyperopia. This amount of accommodation which is used to compensate for the hyperopia is thus not available for reading. Thus, the young hyperope may not even know that they are longsighted. However as they age and the ability to accommodate starts to decrease, there come a time when they don't have enough accommodation left and the hyperopia then becomes manifest.
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