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Customized Laser Vision Correction
Excimer lasers have been used to correct the nearsightedness, farsightedness and
astigmatism of over six million people worldwide. An estimated 98% of these patients are
now seeing 20/20 to 20/40 without glasses. With such impressive results, how could you
expect laser vision correction to improve?
Since the mid-1800s doctors have measured vision by having patients read letters
on a standard Snellen Eye Chart. Doctors consider your vision "normal" if you can identify the
small letters on the 20/20 line from a distance of 20 feet. But scoring 20/20 on your vision
test doesn't necessarily mean you have excellent vision, especially if the letters you are able
to identify are not crisp and clear.
Until now, laser vision correction, like glasses and contacts, could only correct the
visual distortions caused by nearsightedness, farsightedness and astigmatism. However,
these three common types of vision distortions, called "lower order aberrations," are only
responsible for 85-90% of the overall quality of your vision. There are other imperfections on
your eye's optical system that may affect the clarity of your vision and how well you see at
night or in low light. Doctors call these visual distortions "higher order aberrations" and they
can cause a glare, shadows, halos and other annoying visual effects. Unless these higher
order aberrations are addressed along with the lower order aberrations, the quality of your
vision may not be ideal, even if you have measurable vision of 20/20.
Now, thanks to advanced wavefront technology, it's possible to measure and
address both lower and higher order aberrations. Here's how it works: First, flat waves of
light are passed through your eye using a computerized wavefront-measuring instrument,
and as the light waves travel through your eye's optical system, the distortions in your vision
are measured. The diagnostic unit captures the distorted waves as they exit your eye and
compares them to the perfectly flat light waves that would have been reflected if your optical
system were perfect. Next, a map is generated representing your unique visual distortions,
including both lower and higher order aberrations. This map is a guide for the laser, telling it
how and where to reshape the cornea to correct your vision.
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