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Susana Marcos, Sergio Barbero, Lourdes Llorente, Jesús Merayo-Lloves; Optical Response to LASIK Surgery for Myopia from Total and Corneal Aberration Measurements. Invest. Ophthalmol. Vis. Sci. 2001;42(13):3349-3356.
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purpose. To evaluate the optical aberrations induced by LASIK refractive surgery
for myopia on the anterior surface of the cornea and the entire optical
system of the eye.
methods. Total and corneal aberrations were measured in a group of 14 eyes
(preoperative myopia ranging from −2.5 to −13 D) before and after
LASIK surgery. Total aberrations were measured using a laser
ray-tracing technique. Corneal aberrations were obtained from corneal
elevation maps measured using a corneal system and custom software.
Corneal and total wave aberrations were described as Zernike polynomial
expansions. Root-mean-square (RMS) wavefront error was used as a global
optical quality metric.
results. Total and corneal aberrations (third-order and higher) showed a
statistically significant increase after LASIK myopia surgery, by a
factor of 1.92 (total) and 3.72 (corneal), on average. This increase
was more pronounced in patients with the highest preoperative myopia.
There is a good correlation (r = 0.97, P < 0.0001) between the aberrations induced in the
entire optical system and those induced in the anterior corneal
surface. However, the anterior corneal spherical aberration increased
more than the total spherical aberration, suggesting also a change in
the spherical aberration of the posterior corneal surface. Pupil
centration and internal optical aberrations, which are not accounted
for in corneal topography, play an important role in evaluating
individual surgical outcomes.
conclusions. Because LASIK surgery induces changes in the anterior corneal
surface, most changes in the total aberration pattern can be attributed
to changes in the anterior corneal aberrations. However, because of
individual interactions of the aberrations in the ocular components, a
combination of corneal and total aberration measurements is
critical to understanding individual outcomes, and by extension, to
designing custom ablation algorithms. This comparison also reveals
changes in the internal aberrations, consistent with the posterior
corneal changes reported using scanning slit corneal
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