Low_resolution_Thesis_CDD_221009_public - Visual Optics and ...

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CHAPTER 5 5.3.4. Ablation patterns in cornea We applied the depth conversion factor and the ablation efficiency factor from Eq. 5.3 to the ablation patterns measured on flat surfaces to predict the ablation pattern on corneal tissue. Figure 5.6 shows predictions of the ablation profiles on flat and spherical corneas (Fig. 5.6(b)), from the ablation profiles measured on flat plastic surfaces (Fig. 5.6(a)). The differences in the ablation profiles as measured on Filofocon A between the Alcon and Bausch and Lomb lasers are clear in Fig. 5.6(a). In Filofocon, the Alcon laser (higher fluence) penetrates deeper in the plastic material and has a narrower ablation area while the Bausch & Lomb pattern on plastic is wider and shallower. The large differences in response between lasers are attenuated when the corresponding conversions to corneal tissue are applied (Fig. 5.6(b)). However, the ablation depth is significantly higher in cornea for the Bausch & Lomb laser, and the laser efficiency effects not negligible for this laser. a) b) Fig. 5.6. Ablation profiles measured in Filofocon A flat surfaces (a) and predictions in corneal tissue (b) for flat and spherical surfaces. We also estimated the ablated volume from the predicted 2-dimensional corneal ablation patterns, for the Alcon and the Bausch & Lomb lasers, considering the experimentally measured ablation efficiency factor. Table 5.2 shows the ablation depth measured in Filofocon A, the nominal depth in cornea provided by the laser 148
OPTIMIZED LASER PLATFORMS software, the corresponding depth conversion factor between cornea and Filofocon A, and the estimated ablated volume for the entire ablated area and within the optical zone. It is interesting to note that the Zyoptix Tissue Saving algorithm of the Bausch & Lomb laser penetrates deeper in cornea and removes more material than the Standard optimized algorithm of the Alcon laser. Although the optical zone is the same in both lasers (6.5 mm) the ablated area is very different due to different design of the transition zones. Only 0.5% of the ablated volume is outside the optical zone with the Alcon laser (which has minimum transition zones), as opposed to 6.5% with the Bausch & Lomb laser. These ablated volumes were calculated considering the existing efficiency effects. If the efficiency effects were not considered (i.e. application on flat surfaces of the measured ablation profile, multiplied by the plastic-corneal tissue conversion factor) the ablated volume would be 5% larger for the Bausch & Lomb laser and 1% larger for the Alcon laser (within the optical zone in both cases). 5.3.5. Correction factors for efficiency effects in cornea Figure 5.7 shows the correction factors for efficiency effects (1/K) predicted at each point of the human cornea for the Alcon (A) and the Bausch & Lomb (B) lasers. Figure 5.7(c) shows the radial average for both lasers, and the theoretical predictions. The efficiency effects are important for the Bausch & Lomb laser, as already seen in plastic, but not for the Alcon laser. Therefore, the correction factor increases from one (at the ablation center) to higher values toward the periphery for the Bausch & Lomb laser, but remains almost flat for the Alcon laser. The radial average of the correction factor is well predicted by theory. Table 5.2. Ablation depths, depth conversion factors, and ablated volumes in cornea, for a -9 D correction. Alcon Bausch & Lomb Depth – Filofocon (m) 62 47.8 Nominal Depth –Cornea (m) 120.5 135 Conversion factor 1.94 2.82 Ablated corneal volume (m 3 ) 2.09 · 10 9 2.76 · 10 9 Ablated volume within optical zone (m 3 ) 2.08 · 10 9 2.58 · 10 9 5.3.6. Optical outcomes in cornea Figure 5.8 shows the asphericities obtained by fitting the ablated spheres of Filofocon A to conics, for the Bausch & Lomb (crosses) and the Alcon laser (diamonds). The figure also shows the asphericities found in a previous study (Dorronsoro et al., 2006a) with a previous generation laser (Chiron Technolas 217c with PlanoScan). As the artificial eyes used in that study were made of PMMA, a conversion from PMMA to Filofocon A (considering the theoretical ablation efficiency factors for both materials) was applied to the measured ablation pattern. The post-operative asphericities with the new generation lasers are clearly below those obtained with previous generation lasers. However, the measured post-operative asphericity is still significantly different from zero (and positive). 149
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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 150 and 151: CHAPTER 5 a) b) : 6.5 mm c) Fig. 5.
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
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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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