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New LASIK treatment uses the same kind of laser used in
PRK or photorefractive keratectomy. PRK is the first surgical procedure
developed to reshape the cornea by sculpting using the laser. It was only
later that new LASIK was developed.
The major difference between the two
surgeries lies in the way that the stroma, the middle layer of the cornea is
exposed before vaporized with the laser. In PRK, the top layer of the
cornea called epithelium is scraped away to expose the stromal layer. In
new LASIK, a flap is cut in the stromal layer and then the flap is folded
back.
The first refractive laser systems approved by the FDA were excimer
lasers for use in PRK to treat myopia and later on to treat astigmatism.
Later, doctors began using these lasers for new LASIK to treat other
refractive errors. Over the last several years, new LASIK treatment has been
used by doctors to treat myopia, hyperopia and astigmatism.
Over the past ten years, there have been major
developments in laser vision correction technology and the understanding of
the procedure. The improvements include improved eye tracking systems during
the laser procedure, larger treatment zones, and improved mechanical and
laser microkeratomes which reduce flap complications. However no development
has caused more excitement than the recent FDA approval (June, 2003) of
CustomVue LASIK from VISX
utilizing wavefront guided treatment. This will be the predominant
form of new LASIK treatment.
Wavefront guided custom new LASIK differs from
conventional LASIK treatment in the way the eye's optics is measured.
Accurate measurement of the optics of each eye is essential for a good
visual outcome from the new LASIK procedure. It is this series of
numbers/calculations that is used to program the laser for reshaping the
cornea.
Before wavefront guided new LASIK, the surgeon objectively measured
the eye with a handheld instrument or an automated measuring device then
asked the patient to subjectively refine the measurement. The reality is
that the eye's optical system is not uniform throughout the central 6mm of
measurement. The new LASIK wavefront can precisely measure the optics of
light from minute areas over the central 6mm of the cornea.
While conventional LASIK was and still is very
effective treatment, the wavefront guided new LASIK procedure has given
surgeons the ability to provide patients with improved visual results over
those of
conventional LASIK.
Custom wavefront guided new LASIK uses a waveprint of
the eye's optical system as the guide for laser reshaping. The waveprint is
25 times more precise than an averaged measurement because data about the
eye's optical system is collected from hundreds of separate points over the
central 6mm area of the cornea. Rather than using an averaged measurement
from the central 6mm to reshape the entire cornea, the cornea reshaping is
customized at each of the hundreds of points from which measurements are
taken.
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