Low_resolution_Thesis_CDD_221009_public - Visual Optics and ...

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

CHAPTER 5 a) b) : 6.5 mm c) Fig. 5.7. Correction factor for effciency effects in cornea estimated from the experimental measurements in Filofocon A. a) Alcon. b) Bausch & Lomb. c) Radial plots. The average asphericity in post-operative Filofocon A for a -9 D correction was 0.23 for the Alcon laser, and 0.19 for the Bausch & Lomb laser. When the ablation pattern was transferred to the cornea (considering the corresponding efficiency effects) we obtained a post-operative asphericity of 0.40 for the Alcon laser and 0.71 for the Bausch and Lomb. The corresponding spherical aberration in cornea (Barbero et al., 2002b) was 0.47 m for the Alcon laser, and 0.61 m for the Bausch & Lomb laser. . The spherical aberration of an ideal spherical cornea of 7.8 mm is 0.49 microns. Fig. 5.8. Post-operative asphericities from Filofocon A ablated spheres for the Alcon (diamonds) and Bausch & Lomb lasers (crosses). The asphericities found in a previous study (Dorronsoro et al., 2006a) with a previous generation laser (Chiron Technolas 217c with PlanoScan) are also shown (squares). 150
OPTIMIZED LASER PLATFORMS 5.4. DISCUSSION This work further develops the use of plastic model corneas, introduced in Chapter 3, to obtain precise quantitative evaluation of the ablation patterns provided by refractive surgery laser systems (Dorronsoro et al., 2006a). The depth patterns are measured on plastic, which can provide an accurate calibration of the laser system. Furthermore, the combination of precise profilometric measurements on plastic surfaces, and knowledge of the ablation and optical properties of the plastic material provides estimations of the ablation pattern on cornea, considering all physical effects, and excluding biomechanical factors. In the study of the ablation properties of Filofocon A (Dorronsoro et al., 2008b) we showed (Chapter 4) that a depth pattern measured on this material can be transformed into a laser spot distribution (considering the fluence of the laser), which can be used to predict depth patterns in cornea, provided that the number of pulses is sufficiently high -as is it the case within the optical zone (see discussion of Chapter 4 for details)-. The fact that the ablation response of Filofocon A is well predicted by the Beer- Lambert law, for the range fluences and number of pulses used in refractive surgery (Dorronsoro et al., 2008b) allows an accurate characterization of the ablation pattern on plastic. On the other hand, the estimations of the ablation pattern on cornea are accurate within the limitations of the blow-off model in corneal tissue (Beer-Lambert Law) and the accuracy of the optical and ablation parameters. The estimation of the ablation profile on cornea from the measurement of the ablation profile on plastic could be further sophisticated using more complex ablation models (Arba-Mosquera and de Ortueta, 2008, Kwon et al., 2008), or parameters for the cornea, as dynamic coefficients (Fisher and Hahn, 2007). The geometrical efficiency effects depend on the geometry of the surface on which the corrected ablation pattern is going to be applied. Therefore, strictly speaking, the estimated correction factor to be applied on a spherical surface would be different to that estimated for a conic surface. We performed simulations to quantify the error induced by considering a correction factor calculated for spherical corneas on conic corneas. We found, for a cornea of asphericity -0.4 (upper bound of asphericity in normal corneas) a mean underestimation of 0.21% in the energy applied to the cornea, and a maximum deviation (in the periphery of a 6.5-mm optical zone) of - 1.01%. These values are of negligible clinical relevance. In the case of a retreatment of a highly aspherical post-surgical cornea (asphericity = 1), the correction factor for spherical surfaces overestimates the energy applied to the conic cornea (mean 0.63%, maximum 3.31% in the periphery of the ablation). Equation 5.1 considers all the possible efficiency effects of the laser in plastic (K P ), and an accurate characterizations of the lasers, as the geometry of the plastic surfaces used (and therefore R P ) are well known. The maximum accuracy of the correction factors in cornea (K C ) can obtained when the geometry of individual corneas are taken into account (and not only a generic corneal geometry) in the reflection coefficient R C used in the conversion from plastic to cornea. Previous studies (including Chapter 3) were limited by the use of videokeratoscopy to assess the elevation maps of pre- and post-operative spherical surfaces from which the ablation patterns are computed. The use of high resolution non-contact optical profilometry (Section 2.1.1.2) allows mapping both flat and spherical surfaces with the same instrument and with high accuracy (less than 1 micron), without the need of the slight polishing of post-ablated surfaces, required to 151
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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
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
Page 133: ABLATION PROPERTIES OF FILOFOCON A
Page 137: OPTIMIZED LASER PLATFORMS 5.1 ABSTR
Page 140 and 141: CHAPTER 5 pulses. Fluence, repetiti
Page 142 and 143: CHAPTER 5 ablations. The slit-confo
Page 144 and 145: CHAPTER 5 (Anera et al., 2003): d S
Page 146 and 147: CHAPTER 5 asymmetries also appeared
Page 148 and 149: CHAPTER 5 5.3.4. Ablation patterns
Page 152 and 153: CHAPTER 5 achieve proper reflection
Page 154 and 155: CHAPTER 5 Both the ablation algorit
Page 157: HYBRID PORCINE/PLASTIC MODEL 6.1. A
Page 160 and 161: CHAPTER 6 6.3.1. Hybrid porcine-pla
Page 162 and 163: CHAPTER 6 is detected. Therefore, i
Page 164 and 165: CHAPTER 6 no preferential orientati
Page 167: ANTERIOR AND POSTERIOR CORNEAL ELEV
Page 171 and 172: ANTERIOR AND POSTERIOR CORNEAL ELEV
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Page 187: SOFT CONTACT LENS FITTING USING MOD
Page 191 and 192: SOFT CONTACT LENS FITTING USING MOD
Page 194: ON-EYE OPTICAL PERFORMANCE OF RIGID
Page 198 and 199: ON-EYE OPTICAL PERFORMANCE OF RIGID
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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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