Low_resolution_Thesis_CDD_221009_public - Visual Optics and ...

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$XXX Congress of the European Society of Cataract and Refractive ...$

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. 257
CONCLUSIONS 5We have developed a procedure to experimentally measure the laser efficiency effects on curved surfaces (laser efficiency losses from the center to the periphery of the ablated surface) and also to estimate the effect in cornea. We found important differences across laser platforms, depending on their fluence (6.5% for 120 mJ/cm 2 at 2.5 mm from the corneal apex and almost negligible for 400 mJ/cm 2 ). We obtained correction factors for these effects, to be applied in the clinical units. 6A hybrid porcine plastic model for the calibration of anterior segment imaging systems was developed. This artificial eye shows corneal properties (scattering, refractive index) comparable to those of living eyes, but without biological variability. The model was used to validate a Pentacam Sheimpflug imaging system, nominally corrected of geometrical and optical distortion. We proved that this instrument can reliably measure potential changes in the posterior corneal surface after refractive surgery. 7We found that myopic LASIK refractive surgery (from -1.25 to -8.5 D) did not induce systematic long-term changes in the posterior corneal surface shape. Differences were only significant one-day after surgery, and the changes were more relevant in the vertical than in the horizontal meridian. The amount of individual changes in the posterior cornea (radius of curvature) in post-LASIK patients is similar to that found in normal eyes. Left and right eyes show similar changes, suggesting physiological mechanisms acting bilaterally in the same way. 8We developed another in-vitro model based on artificial plastic eyes, aimed at studying the fitting of soft contact lenses. The model allowed eliminating the biological variability associated with real eyes (movements and decentrations of the lens, ocular aberrations) while simulating a more realistic situation than a standard inmersion measurement. Using this in vitro model we found that soft monofocal spherical lenses reduce total spherical aberration. Multifocal lenses are affected by conformity to the cornea and fitting effects that cancel out the multifocal properties of the design, although the final optical performance depends on the lens power that determines the central thickness. 9We used aberration measurements on real eyes fitted with semirigid (RGP) contact lenses and found this tool useful to understand the fitting process and the optical coupling between the optics of the lens and the optics of the eye. We demonstrated that RGP contact lenses can significantly improve the natural optics of the eye. The internal optics and the lens flexure can impose limits on this compensation. We found a marked correlation between the corneal and ocular aberrations of the same eye measured with and without semirigid (RGP) contact lenses. We were able to measure the aberrations of the tear lens in RGP contact lenses, and reported a compensatory effect on the total spherical aberration. This methodology provides an accurate analysis of CL fitting in individual eyes, and can help to choose the best lens parameters to improve the optics of individual eyes. 258
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Doctoral thesis Corneal Ablation an
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Contents Corneal Ablation and Conta
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2.2.1. Fitting surfaces............
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5.3.3. Ablation efficiency factors
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10.5. DISCUSSION...................
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We thank José Antonio Sánchez-Gil
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BOZR Back Optic Zone Radius BCVA Be
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INTRODUCTION 1.1. MOTIVATION The fr
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INTRODUCTION 1.2. THE OPTICAL SYSTE
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INTRODUCTION Myopia is a very commo
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INTRODUCTION a point focus: the dif
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INTRODUCTION system, and tilt repre
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INTRODUCTION term Z 0 2 stands for
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INTRODUCTION which image was shadow
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INTRODUCTION The defocus Zernike te
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INTRODUCTION 1.4.6.3. Internal Aber
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INTRODUCTION 1.5.2.3. Alternating v
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INTRODUCTION and further-more, at l
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INTRODUCTION alcohol is used to loo
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INTRODUCTION changes in reflectivit
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INTRODUCTION Marcos et al. (Marcos
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INTRODUCTION 1.7.3. Ablation effici
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INTRODUCTION corneal surface may be
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INTRODUCTION Algorithm design: The
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INTRODUCTION contact lenses the fie
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INTRODUCTION 1.10.1. Tear studies A
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INTRODUCTION there are still many u
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INTRODUCTION 6. Evaluation and unde
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METHODS 2Chapter Chapter 2 - Method
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METHODS 2.1. MEASUREMENT OF OPTICAL
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METHODS In both profilometers, cust
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METHODS The measurement method that
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METHODS Fig. 2. 9. Set of points in
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METHODS Slit lamp Scheimpflug Camer
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METHODS representing the deviation
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METHODS 2.2.2.2. Ablation pattern f
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METHODS direction. These calculatio
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METHODS eye through the whole pupil
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METHODS (1993) power thresholds for
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METHODS alignment (frontal-illumina
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METHODS Fig. 2. 24. Example frame f
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METHODS 4) New image processing too
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METHODS Fig. 2. 28. Corrected entra
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METHODS Badal lens, corresponds to
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METHODS Each VA measurement consist
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REFRACTIVE SURGERY PMMA MODEL 3.1.
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CHAPTER 3 optimization of refractiv
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CHAPTER 3 These data demonstrate th
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CHAPTER 3 regression line, since it
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CHAPTER 3 Figure 3.3 shows one of t
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CHAPTER 3 Ablation efficiency facto
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CHAPTER 3 considering the same set
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CHAPTER 3 3.5.3 Impact of correctio
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ABLATION PROPERTIES OF FILOFOCON A
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OPTIMIZED LASER PLATFORMS 5.1 ABSTR
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CHAPTER 5 pulses. Fluence, repetiti
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CHAPTER 5 ablations. The slit-confo
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CHAPTER 5 (Anera et al., 2003): d S
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CHAPTER 5 asymmetries also appeared
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CHAPTER 5 5.3.4. Ablation patterns
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CHAPTER 5 a) b) : 6.5 mm c) Fig. 5.
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CHAPTER 5 achieve proper reflection
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CHAPTER 5 Both the ablation algorit
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HYBRID PORCINE/PLASTIC MODEL 6.1. A
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CHAPTER 6 6.3.1. Hybrid porcine-pla
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CHAPTER 6 is detected. Therefore, i
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CHAPTER 6 no preferential orientati
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ANTERIOR AND POSTERIOR CORNEAL ELEV
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Page 181 and 182: ANTERIOR AND POSTERIOR CORNEAL ELEV
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Page 187: SOFT CONTACT LENS FITTING USING MOD
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Page 194: ON-EYE OPTICAL PERFORMANCE OF RIGID
Page 198 and 199: ON-EYE OPTICAL PERFORMANCE OF RIGID
Page 212: SOFT MONOFOCAL AND MULTIFOCAL CONTA
Page 216: SOFT MONOFOCAL AND MULTIFOCAL CONTA
Page 220 and 221: CORRELATION BETWEEN RADIUS AND ASPH
Page 230: CONCLUSIONS Conclusions This thesis
Page 236: CONCLUSIONS LIST OF METHODOLOGICAL
Page 240 and 241: CONCLUSIONS FUTURE RESEARCH LINES T
Page 242 and 243: CONCLUSIONS LIST OF PUBLICATIONS AN
Page 244 and 245: REFERENCES References AIZAWA, D., S
Page 246 and 247: REFERENCES PHOTODECOMPOSITION (APD)
Page 248 and 249: REFERENCES DORRONSORO, C., CANO, D.
Page 250 and 251: REFERENCES GISPETS, J., ARJONA, M.
Page 252 and 253: REFERENCES KOPF, M., YI, F., ISKAND
Page 254 and 255: REFERENCES MARCOS, S., DORRONSORO,
Page 256 and 257: REFERENCES NOVO, A., PAVLOPOULOS, G
Page 258 and 259: REFERENCES SAKIMOTO, T., ROSENBLATT
Page 260: REFERENCES WANG, L., DAI, E., KOCH,
Page 263 and 264: RESÚMENES pacientes reales fue com
Page 265 and 266: RESÚMENES experimentales de cirug
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Page 269 and 270: RESÚMENES plástico medidas anteri
Page 272 and 273: RESÚMENES 8 Evaluación óptica de
Page 274 and 275: RESÚMENES 9 Prestaciones ópticas
Page 276 and 277: RESÚMENES 10 Calidad óptica y cal
Page 278: RESÚMENES A Correlación entre rad
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CONCLUSIONES clínicos. La descripc
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CONCLUSIONES 12 Las superficies ocu
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CONCLUSIONES IMPLICACIONES DE ESTA
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CONCLUSIONES contribuyen a la compr
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(y muchísimo más difícil). Me da
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