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 measurements of anterior and posterior radius of curvature using either fitting the best sphere, or horizontal and vertical apical radii, asphericity and astigmatism fitting a biconic surface (see Section 2.2.1). Raw elevation maps are also provided, which can be used for further quantitative analysis in Matlab, Mathworks (see Data analysis section). The technique had been used in previous studies (Rosales et al., 2006, de Castro et al., 2007, Rosales and Marcos, 2009) in the Visual Optics and Biophotonics Laboratory, and therefore many software routines were available to retrieve and process the data obtained with this instrument. One of the major contributions of previous work is the development of optical and geometrical distortion correction algorithms for this system. A detailed description of the technique, calibrations and corrections can be found in Patricia Rosales’s thesis (Rosales, 2008), and in (Rosales and Marcos, 2009). In Chapter 6 of this thesis the accuracy of the measurements of the back surface of the cornea, including the geometrical and optical distortion corrections, will be tested, by using a model cornea of known posterior surface. In Chapter 7 we applied this instrument (validated in Chapter 6) for the study of changes in the posterior cornea after refractive surgery. Fig. 2. 14. Pentacam Scheimpflug imaging system. 2.2. SURFACE ELEVATION ANALYSIS TOOLS During this thesis, different tools for the analysis of the measured optical surfaces have been developed. In the following sections the different tools will be described, and their use illustrated with examples. The specific use of each tool will be described in the results chapters (Chapters 3 to 10). 2.2.1. Fitting surfaces The optical surfaces of the eye (anterior and posterior surfaces of the cornea and the lens) are often described by surfaces whose profiles are conic sections. The general equation of a conic curve is x 2 2 2Ry (1 Q) y (2.1) where R and Q are the apical radius and asphericity, respectively. Any conic is described in terms of these two parameters, the radius R representing the radius of the circumference that best fits a small region around the apex, and the asphericity Q 72
METHODS representing the deviation of the conic with respect to a circumference. Conic curves are classified in circumferences (Q=0), hyperbolas (Q-1). Figure Fig. 2. 15 graphically describes the effect of asphericity on conic sections, as all the curves shown have the same apical radius. Therefore, the surfaces of the ocular components (cornea and crystalline lens) can also be described in terms of their radius and asphericity. Fig. 2. 15. The effect of asphericity on the shape of a conicoid. All the curves have the same apical radius of curvature (Atchison and Smith, 2000). The three-dimensional extension of this description based on conic sections can be made in terms of quadrics (rigorous extension of conic sections to three dimensions), conicoids (surfaces with revolution symmetry in which all the longitudinal sections are conic sections, as in Section 1.2.1 and Equation 1.1) and biconics (asymmetric surfaces with two preferential axes, which are conics). Consequently the surfaces of the eye are usually be described in terms of conics. A single apical radius of curvature and one single asphericity for conics, and two radii and two asphericities for biconics. The representation of ocular surfaces in terms of conic-based surfaces, although very useful in many cases, constitutes only a coarse approximation of the real cornea. A point by point numerical description of the surface is often impractical. In these cases, fittings to a base of Zernike polinomials (Section 1.4.4) can be a good compromise (Schwiegerling et al., 1995). In all cases, but specially with conic-based surfaces, it is important to choose the correct number of free parameters in the fitting to achieve the maximum accuracy. If the surface is (or could be) tilted or decentered, it is desirable to include two tilting and two centering parameters. In the studies presented in this thesis, many of the surfaces show a prioritary center (abation patters or multifocal designs). We found optimal results when the fitting was accomplished in two phases: one to locate the center and tilt of the surface (for example, after fitting an sphere) and another one (after removing tilt and decentration) to retrieve the radius and asphericity. As the optimal approach depends on the specific application and the characteristics of the surface, the procedures will be described in detail in the corresponding Chapter. Annex A will analyse the existing correlation between radius and asphericity appearing when fitting different corneal surfaces to conics. 2.2.2. Comparing surfaces In many of the studies of this thesis, the outcome results from the comparison of two or more surfaces. For example, the ablation pattern appears after comparing the 73
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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
Page 21 and 22: INTRODUCTION 1.2. THE OPTICAL SYSTE
Page 23 and 24: 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: METHODS Slit lamp Scheimpflug Camer
Page 75 and 76: METHODS 2.2.2.2. Ablation pattern f
Page 77 and 78: METHODS direction. These calculatio
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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183
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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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