Low_resolution_Thesis_CDD_221009_public - Visual Optics and ...

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

CHAPTER 4 4.5.3. Central islands in PMMA Central islands are systematically observed in the ablation spot profiles in PMMA (Fig. 4.1), but not in Filofocon A. Our results reveal that it is a multipulse effect, not appearing with single pulses. This suggests that defect accumulation during the first pulses can play a role in the island formation. AFM images (Fig. 4.7) also suggest different ablation mechanisms in Filofocon A and PMMA. The droplets observed in PMMA may be indicative a more explosive mechanism than in Filofocon A, where a dense worm-like structure appears after the ablation. These are also found to be multipulse effects. As the number of pulses increase, the droplet density increase in PMMA, while the worm thickness decreases in Filofocon A. Central islands have been extensively reported in corneal tissue as isolated areas within the optical zone where the laser ablated tissue less efficiently. Central islands have been associated to shockwaves in water, shielding effects due to the plume and particle redeposition (Noack et al., 1997, Munnerlyn et al., 2006). Central islands have been also been observed in PMMA (Noack et al., 1997, Munnerlyn et al., 2006). It is remarkable that it is not observed in Filofocon A, indicating that the effect is not inherent to the laser energy distribution. In any case, as was previously reported in corneas (Munnerlyn et al., 2006), the use of flying spot lasers in refractive surgery, and the associated averaging effect, reduces the impact of inhomogeneities in the laser spot. 4.5.4. Absorption coefficient It is enlightening to compare the absorption coefficient determined from low intensity ellipsometric measurements (Table 4.1) to the effective absorption coefficient eff estimated from the slope of the Beer-Lambert representation and plotted in Fig. 4.5. The corresponding values differ strongly for PMMA, with eff always being much higher than even for a low number of pulses. This is consistent to what is reported in the literature for PMMA (Srinivasan et al., 1986, Kuper and Stuke, 1987). In contrast, we observe a perfect agreement for Filofocon A in the stationary saturation regime at high pulse numbers ( 10 pulses). This agreement points to a fundamentally different absorption mechanism in Filofocon A, truly following a Beer-Lambert law in the multipulse regime as opposed to PMMA. As a consequence, the ablation behavior is expected to be also influenced, as evidenced by the different surface morphology/topography shown in Figs. 4.6 and 4.7. 4.6. CONCLUSIONS We have presented the ablation properties of Filofocon A and PMMA in the operational range of refractive surgery excimer lasers. PMMA is often used as an ablation material in the calibration of clinical lasers, and in model eyes (as that presented in Chapter 3). Filofocon A has been identified as appropriate material for refractive surgery research, and we will present an experimental model based on Filofocon A in the next chapter. We have learned that the ablation properties of Filofocon A make it a better material than PMMA for laser ablation refractive surgery research and for the development of calibration protocols. Filofocon A provides a more accurate energy-to-depth conversion (with no central islands and other ablation artifacts), has a predictive absorption coefficient, and shows 132
ABLATION PROPERTIES OF FILOFOCON A lower number of incubation pulses and ablation parameters less dependent on the number of pulses. These findings are useful to design calibration and validation procedures for the refractive surgery excimer lasers, and to improve the outcomes and predictability of new ablation profile designs. 4.7. OUTLOOK The optical and ablation properties of a new material, Filofocon A, have been measured for the first time. Knowledge of these properties is essential to establish accurate plastic models for refractive surgery. In the next chapter, we will use Filofocon A into a new refractive surgery model to predict experimentally the optical outcomes of state-of-the art laser refractive surgery laser platforms 133
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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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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
Page 131: 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 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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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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