Low_resolution_Thesis_CDD_221009_public - Visual Optics and ...

CONCLUSIONS
ACHIEVED GOALS AND SPECIFIC CONCLUSIONS
1We have developed different instrument implementations, measurement
procedures and processing algorithms for the accurate study of the geometry of
optical surfaces. These techniques include Placido disk corneal topography,
Scheimpflug imaging and profilometry. The technology has proved useful to measure
both artificial and real eyes, to measure the changes induced by different procedures
(refractive surgery and corneal lens fitting), and to obtain anterior and posterior
surface shape differences across conditions, as well as the optical consequences of
these changes.
2We have developed a compact and versatile Laser Ray Tracing aberrometer, to
measure the optical aberrations of the eye with high dynamic range and
configurable parameters (for example the number of samples in the wavefront or
their spatial distribution). It has proved capable of achieving the demanding
requirements of the measurement of multifocal contact lenses with high aberrations.
The system has been validated (against corneal wavefront measurements on artificial
eyes). The system has also been applied in other studies of the Visual Optics and
Biophotonics Laboratory (Llorente et al., 2004a) (Llorente et al., 2007).
3We have reported the optical and ablation properties of two polymer materials
(PMMA and Filofocon A) for their use in refractive surgery research. The
absence of ablation artifacts (central islands), a lower number of incubation
pulses, a lower pulse-number dependence of the ablation threshold, and a good
correspondence between the effective absoption coefficient of the ablation and the
absorption coefficient estimated from spectroscopic measurements make Filofocon A
a more appropriate material than PMMA for experimental models in refractive surgery
and for calibration of clinical lasers. The accurate description of the physical
properties obtained in a laboratory laser is essential to analyze the outputs from
clinical lasers and for correct estimations in corneal tissue.
4We have developed (and later evolved) an experimental model eye for the study
of the physical effects involved in refractive surgery that allowed us to measure
experimentally the ablation patterns of four different clinical platforms. The
outputs of three state of the art algorithms were compared with one of previous
generation. We concluded that the new algorithms have been optimized to reduce the
induction of spherical aberration in non-biological materials, although the induced
spherical aberration is still not negligible (up to 0.7 microns). We have shown that
physical effects can explain most of the increase in asphericity found clinically (70 %
in a non-optimized laser). However, and particularly for high corrections, there is still
some room for biomechanical effects.
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