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Crisp vision is achieved when
light rays are focused and processed by the
many parts of the eye.
Incoming light rays are
focused on the retina by both the cornea and
lens. The cornea is the transparent "window"
located at the front of the eye. |
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It is responsible for 2/3 of the
"bending" of light rays. Inside the eye the lens
provides the additional 1/3 of the bending of the
image.
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 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. Back to Top
 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. Back to Top
 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. Back to Top
 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. Back to Top
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