Low_resolution_Thesis_CDD_221009_public - Visual Optics and ...

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

CHAPTER 2 thickness map, the same base sphere (typically the one corresponding to the anterior cornea) has to be substracted from both surfaces. The shape of the lens appears more clearly, as a positive or negative meniscus, depending on the lens power. To study the lens flexure or conformity to the underlying cornea, each of base spheres has to be substracted to each from the corresponding surfaces. 2.2.2.4. Representing surfaces Throughout this thesis we have used different graphical representations for analysing the optical surfaces measured. Three dimensional scattered points plots (as those shown in Figs. 2.16 and 2.17) are often used to represent raw measurement (or deviations from a plane or a sphere). Figure 2.18 shows three other representations used. The same example surface, corresponfing to a highly assymetrical ablation pattern, is shown in a 2-D color-coded map of elevations (a), a 3-D topography (b) and a radial profile where only the radial coordinate of the points is plotted vs their heigh (c). To obtain the representations of Figs. 2.18 (a) and (b) an interpolation of the measured points to a regular grid is needed. Depending on the application and variability of the data Zernike polinominal expansions, splines or exact interpolation was used. As opposed to raw sets of data (scattered points), these interpolated data sets can be directly compared, point by point. To obtain representations as the one shown in Fig. 2.18 (c), the data sets have to be previously transformed to cilindrical coordinates. The position of the origin is critical. In the representation of corneal ablations a biconic fitting was performed to obtain the center of the ablation, which was used as origin of the cylindrical coordinates. The representation of Fig. 2.18 (c) can be used with or without previous interpolation of the poins. In rotationally symetrical ablations this representation provides a thin curve. In assymetrical surfaces, as the one shown in Fig. 2.18 (c), a wide region of scattered poins appears. a) b) c) 10 20 30 40 50 60 70 80 90 0.01 0 0 -0.01 -0.01 -0.02 -0.02 -0.03 -0.03 -0.04 -0.05 -0.04 -0.06 -0.05 0.01 0 -0.01 -0.02 -0.03 -0.04 -0.05 100 20 40 60 80 100 -0.07 -0.06 -5 0 -5 0 5 -0.06 0 1 2 3 4 5 6 Fig. 2. 18. Different representations of the surfaces used in this thesis. a) Colormap of elevations. b) Three-dimensional map. C) Radial profile. 2.2.2.5. Operating with surfaces Calculations are performed on the measured surfaces in different chapters of this thesis, to estimate physical effects or to obtain different predictions. For example, in Chapters 3 and 5 efficiency effects are calculated by comparing ablation maps. Also, theoretical calculations of efficiency effects are applied to ablation patterns in flat surfaces to predict the ablation shape in curved surfaces, or measurements in plastic are used to predict the outcomes in corneal tissue. In Chapter 8 the thickness map of contact lenses is calculated by substracting their base surface, alond the redial 76
METHODS direction. These calculations, performed on interpolated ablation maps, will be described in the corresponding chapters. 2.3. MEASUREMENT OF OPTICAL QUALITY Estimates of optical quality in this thesis are based on measurements of corneal aberration, obtained after processing corneal elevation maps (Section 2.1), and total eye aberrations measured with a Laser Ray Tracing device (Section 2.3.2). This Section will describe the numerical procedures to calculate corneal aberrations (Section 2.3.1), and the experimental and numerical procedures to obtain ocular aberrations (Section 2.3.2). The calculation of the Strehl ratio (a metric of optical quality used in this thesis) and the simulation of retinal images and is also described (2.3.3). 2.3.1. Corneal aberrations There are three steps in evaluating corneal aberrations of the anterior corneal surface: 1) obtaining experimental corneal elevation; 2) representing the corneal surface from these data; 3) evaluating corneal aberrations from the corneal model surface. The corneal aberrations were obtained from videokeratoscopy and profilometry measurements in this thesis. 2.3.1.1. Representing the corneal surface Corneal surface representation is limited by the distribution of videokeratoscopic data. As this distribution is not uniformly spatially sampled in XY coordinates, with no data between rings, and especially within the central clear zone (around 0.4 mm radius), strategies based on local interpolations do not work properly. In general, a smooth global interpolation by polynomial expansion offers better results. Considering the circular symmetry of the data, the Zernike polynomial expansion appears to be a good choice (Schwiegerling et al., 1995). We fitted corneal surfaces with a Zernike polynomial expansion using 37 terms, and a standard least squares optimization by means of the inverse matrix built-in function given in Matlab. Once the surface is modelled by Zernike polynomial expansion, discrete points are evaluated in a XY equi-space grid to be introduced in an optical design program, Zemax V.9 (Focus Software, Tucson, AZ) for the corneal ray tracing evaluation. 2.3.1.2. From corneal surface to corneal wave aberration The technique used in this thesis for the estimation of the corneal wave aberration is based on the work by Barbero and colleagues (Barbero et al., 2002b, Barbero et al., 2002c). It is based on calculations of the exact difference of the ray path between two points in the real and ideal wavefront for each pupil coordinate. The surface in a XY equi-space grid is introduced in Zemax, using a finite difference method to evaluate the normals to the surface –necessary to apply Snell’s law-. The exact virtual ray tracing through the corneal surface is performed setting the index of refraction to that of the aqueous humor (1.3315). The wavelength was usually set to that used in the LRT measurement. Mean corneal Zernike coefficient variability of naked human eyes in vivo measured with Placido disk videokeratoscopy is 0.015 m (averaged across terms). The technique has been validated and extensively used in previous work in the Visual Optics and Biophotonics laboratory (Barbero et al., 2002b, Barbero et al., 2002c, Marcos et al., 2007), as described in Sergio Barbero’s Thesis (Barbero, 2004). 77
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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
Page 25 and 26: INTRODUCTION a point focus: the dif
Page 27 and 28: INTRODUCTION system, and tilt repre
Page 29 and 30: INTRODUCTION term Z 0 2 stands for
Page 31 and 32: INTRODUCTION which image was shadow
Page 33 and 34: INTRODUCTION The defocus Zernike te
Page 35 and 36: INTRODUCTION 1.4.6.3. Internal Aber
Page 37 and 38: INTRODUCTION 1.5.2.3. Alternating v
Page 39 and 40: INTRODUCTION and further-more, at l
Page 41 and 42: INTRODUCTION alcohol is used to loo
Page 43 and 44: INTRODUCTION changes in reflectivit
Page 45 and 46: INTRODUCTION Marcos et al. (Marcos
Page 47 and 48: INTRODUCTION 1.7.3. Ablation effici
Page 49 and 50: INTRODUCTION corneal surface may be
Page 51 and 52: INTRODUCTION Algorithm design: The
Page 53 and 54: INTRODUCTION contact lenses the fie
Page 55 and 56: INTRODUCTION 1.10.1. Tear studies A
Page 57 and 58: INTRODUCTION there are still many u
Page 59 and 60: INTRODUCTION 6. Evaluation and unde
Page 61 and 62: METHODS 2Chapter Chapter 2 - Method
Page 63 and 64: METHODS 2.1. MEASUREMENT OF OPTICAL
Page 65 and 66: METHODS In both profilometers, cust
Page 67 and 68: METHODS The measurement method that
Page 69 and 70: METHODS Fig. 2. 9. Set of points in
Page 71 and 72: METHODS Slit lamp Scheimpflug Camer
Page 73 and 74: METHODS representing the deviation
Page 75: METHODS 2.2.2.2. Ablation pattern f
Page 79 and 80: METHODS eye through the whole pupil
Page 81 and 82: METHODS (1993) power thresholds for
Page 83 and 84: METHODS alignment (frontal-illumina
Page 85 and 86: METHODS Fig. 2. 24. Example frame f
Page 87 and 88: METHODS 4) New image processing too
Page 89 and 90: METHODS Fig. 2. 28. Corrected entra
Page 91 and 92: METHODS Badal lens, corresponds to
Page 93: METHODS Each VA measurement consist
Page 99: REFRACTIVE SURGERY PMMA MODEL 3.1.
Page 102 and 103: CHAPTER 3 optimization of refractiv
Page 104 and 105: CHAPTER 3 These data demonstrate th
Page 106 and 107: CHAPTER 3 regression line, since it
Page 108 and 109: CHAPTER 3 Figure 3.3 shows one of t
Page 110 and 111: CHAPTER 3 Ablation efficiency facto
Page 112 and 113: CHAPTER 3 considering the same set
Page 114 and 115: CHAPTER 3 3.5.3 Impact of correctio
Page 117: ABLATION PROPERTIES OF FILOFOCON A
Page 121 and 122: ABLATION PROPERTIES OF FILOFOCON A
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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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SOFT CONTACT LENS FITTING USING MOD
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SOFT CONTACT LENS FITTING USING MOD
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ON-EYE OPTICAL PERFORMANCE OF RIGID
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SOFT MONOFOCAL AND MULTIFOCAL CONTA
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SOFT MONOFOCAL AND MULTIFOCAL CONTA
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CORRELATION BETWEEN RADIUS AND ASPH
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CONCLUSIONS Conclusions This thesis
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CONCLUSIONS 5We have developed a pr
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CONCLUSIONS LIST OF METHODOLOGICAL
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CONCLUSIONS FUTURE RESEARCH LINES T
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CONCLUSIONS LIST OF PUBLICATIONS AN
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REFERENCES References AIZAWA, D., S
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REFERENCES PHOTODECOMPOSITION (APD)
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REFERENCES DORRONSORO, C., CANO, D.
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REFERENCES GISPETS, J., ARJONA, M.
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REFERENCES KOPF, M., YI, F., ISKAND
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REFERENCES MARCOS, S., DORRONSORO,
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REFERENCES NOVO, A., PAVLOPOULOS, G
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REFERENCES SAKIMOTO, T., ROSENBLATT
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REFERENCES WANG, L., DAI, E., KOCH,
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RESÚMENES pacientes reales fue com
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RESÚMENES experimentales de cirug
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RESÚMENES cada punto de las cornea
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RESÚMENES plástico medidas anteri
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RESÚMENES 8 Evaluación óptica de
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RESÚMENES 9 Prestaciones ópticas
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RESÚMENES 10 Calidad óptica y cal
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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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