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The retina, located in the back of the eye, is the portion
of the eye that receives focused images and translates
them into vision.
All
of the eye's parts must be correctly shaped for images
to be clearly focused on the retina. The eye's shape is
important in determining clear vision. If the eye is either
too short or too long, light rays are not focused properly
on the retina. Images will also be blurry if the cornea
has an uneven shape.
Nearsightedness
(Myopia)
 Nearsightedness
is the most common focusing problem in the United States,
affecting 25-30% of our population. Nearsighted individuals
can see things better up close than they can in the distance.
The most common reason for nearsightedness is the eye
is too long in relation to its focusing parts, or the
cornea is to steep. As a result, the cornea and lens focus
light rays from distant objects too quickly, and they
are blurred by the time they reach the retina.
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Farsightedness
(Hyperopia)
Farsightedness affects about 10% of the U.S. population.
Farsightedness is a focusing problem  usually
resulting from an eye that is too small, or a cornea that
is too flat. As a result, the cornea and lens cannot focus
the light rays quickly enough to achieve a focused image
on the retina. The effects of hyperopia vary with age
because of the loss of flexibility of the natural lens.
Young people may not notice any effects until their thirties,
but as they begin to age, near objects begin to become
blurry. Over time, farsighted individuals usually have
blurry vision for both near and far objects.
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Astigmatism
Astigmatism is an inability of the eye to clearly focus
images from any distance. This can occur because the shape
of the cornea is not perfectly spherical. Instead of being
spherical, corneas with astigmatism have a steeper curvature
in one direction than another. This results in two different
radii of curvatures. Corneas with pronounced astigmatism
are shaped more  like
a football (with a steeper curvature in one direction
and a flatter curvature in the other) than a well-rounded
basketball (with the same curvature in all directions).
Most individuals have some degree of astigmatism that
is usually small enough not to significantly affect the
quality of vision. However, if the amount of astigmatism
is greater it can cause a focusing problem. It is common
to see astigmatism associated with both nearsightedness
and farsightedness.
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Presbyopia
Presbyopia is a focusing problem that occurs in most people
when they reach their mid-forties. In younger individuals
the  natural
lens of the eye is soft and pliable. This flexibility
permits the natural lens to change its shape, allowing
it to focus on objects up close. However, as we age the
lens loses its flexibility and can no longer focus clearly
on near objects. Even people with perfect distance vision
will need reading glasses when presbyopia develops. Therefore
even if you achieve excellent distance vision through
surgery, reading glasses are usually necessary beginning
around 45 years of age. The effects of presbyopia can
be masked with LASIK surgery by a procedure know as monovision.
Monovision can offer both near and distance vision to
a person with presbyopia, and this option should be discussed
with our staff.
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