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Vision
Conditions:
Myopia
(Nearsighted). This is when the
vision at the distance (further away) is blurry, as in the
photo.
Hyperopia
(Farsighted). This is when the
vision at near, or close, (such as reading) is blurry.
Astigmatism. This is when
the vision at all distances is
blurry. In astigmatism the eye surface is shaped more like a
football (not like a basketball) where the horizontal and vertical
curvatures are different from each other, thus distorting the
vision, somewhat oblong (where a circle looks like an
oval).
Presbyopia is caused
by a slow loss of flexibility within the lens inside your eye. The
typical onset is around age 40 - 45 years old. These changes occur
within the proteins in the lens, making the lens harder and less
elastic with time. Changes also take place in the muscle fibers
surrounding the lens. A prescription with a bifocal or progressive
addition lenses (PALs) are the usual correction for presbyopia.
Bifocal means two points of focus: the main part of the spectacle
lens contains a prescription for distance vision, while the lower
portion of the lens has a different near prescription for close
work. Another alternative is reading glasses, or a prescription
"just for near".
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