| For the farsighted
eye, objects at a close distance are out of focus.
The refractive power of the cornea is too low or the eye itself is
too short. The light rays are focused behind the retina, and the retina
itself will only receive a blurry image of the environment.
Figure: Anatomy of a Farsighted Eye
Please use the Freevis
Simulator
for demonstration of your refractive error!
As opposed to the nearsighted eye, farsightedness can be compensated
by the lens of the lens of the eye, at least in part, and up to a certain
age only. The eye lens can change shape, therefore increasing the refractive
power which, in turn, balances the reduced refractive power of the farsighted
eye for distance vision.
Distance vision of farsighted people generally remains good even at
an older age. Eyeglasses need to be worn at a younger age only at a
very high level of farsightedness. On the other hand, for the farsighted
person, the ability to read decreases at a younger age. For the purpose
of reading, the eye lens needs to change shape as well (see "presbyopia").
The farsighted eye requires part of the ability of the eye lens to
change shape even for distance vision. Only a reduced ability to change
shape remains for reading. Since the ability of the eye lens to change
shape is reduced with increased age, the farsighted person will need
reading glasses sooner than the person with normal vision. At a later
stage in life, correction for distance vision will be necessary as well
since the ability of the eye lens to change shape will decrease to a
point that sharp images for distance vision will no longer be produced.
|