Low_resolution_Thesis_CDD_221009_public - Visual Optics and ...

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

CHAPTER 1 1.7.2. Influence of the ablation profile Several studies have estimated the changes in corneal asphericity expected from the theoretical application of the standard ablation pattern, using both the formula reported by Munnerlyn et al. (Munnerlyn et al., 1988), which assumes that both pre- and postoperative corneal shapes are spherical, or a parabolic approximation of the Munnerlyn formula. In Fig. 1.15 (already explained in Section 1.6.6) the different asphericity of both profiles, for an ablation of the same power (-3 D), is apparent, as both profiles are similar in the center but different in the periphery. Numerical analysis performed by Gatinel et al. (Gatinel et al., 2001) demonstrates that the Munnerlyn pattern should not increase the asphericity of corneas with typical preoperative asphericities, in contrast to clinical findings. Jiménez et al. (Jiménez et al., 2003) carried out analytical calculations and found that the parabolic approximation of the Munnerlyn function should produce some increase in corneal asphericity after myopic corneal ablation. In recent studies (Marcos et al., 2003, Cano et al., 2004), Marcos et colleagues simulated post-operative corneal surfaces by subtracting the standard Munnerlyn ablation pattern and a parabolic approximation of the Munnerlyn pattern from real preoperative corneas, and compared the estimated post-operative asphericity (Q) and spherical aberration with the real post-operative values. They found that while the actual surgical procedure increased asphericity from -0.14±0.14 to 1.1±1.3 on average, for treatments ranging between -2.0 to -11.5 D, corneal asphericities expected from the computer simulations with the standard Munnerlyn pattern did not increase (mean post-operative asphericity = -0.21±0.19). Simulations with the parabolic approximation of the Munnerlyn formula only increased slightly the corneal asphericities (mean post-operative asphericity = 0.3±0.4). These results, shown in Fig. 1.18 indicate that the increase in corneal asphericity is not due to an inappropriate design of these ablation patterns, or the assumptions upon which these patterns are based. Fig 1.18. Post operative asphericity for postoperative real corneal topographies and for simulated post-operative corneas (with the Munnerlyn algorithm and with its parabolic approximation, and with and without efficiency effects (Section 1.7.3)). Patients are sorted by increasing correction. From Cano et al. (Cano et al., 2004). 46
INTRODUCTION 1.7.3. Ablation efficiency Mrochen and Seiler (Mrochen and Seiler, 2001) proposed that the increase of asphericity with the refractive surgery procedure is due to changes in the ablation efficiency as the laser spot moves from the center to the periphery of the cornea. As the angle of incidence increases, both the reflected energy and the illuminated area increase and therefore, the ablation depth per pulse decreases (Fig 1.19). F =F 0. cos (1- R) Fig 1.19. As the laser spot moves from the center to the periphery of the cornea the angle of incidence increases. The ablation depth per pulse decreases in the periphery because both the reflected energy and the illuminated area increase. Ablation efficiency can be defined as the ratio of the amount of removed material when the angle of incidence is (namely d p corr ) to the amount of removed material when the illumination is perpendicular to the corneal surface (d p ). Jiménez et al. (Jimenez et al., 2002, Anera et al., 2003) estimated theoretically the corneal ablation efficiency (K() in this study) using Fresnel equations and taking corneal curvature into account. They provided an equation (Eq. 1.10) that relies on several assumptions regarding the laser properties and laser-tissue interactions. These assumptions include: 1) homogeneous laser beam intensity; 2) non-polarized light; and 3) Beer-Lambert’s law, i.e. logarithmic dependence of the ablation depth on the absorbed energy density. In Jiménez’s model, the resultant corneal shape after ablation depends not only on the laser fluence pattern but also on the corneal radius of curvature and on the tissue properties (ablation fluence threshold and refractive index) at 193nm. (1.10) where is the reflectivity that can be obtained from Fresnel equations: (1.11) and cos ´ can be obtained from the Snell law. Figure 1.20 shows graphically the ablation efficiency effects obtained with Eq. 1.10, for three different materials used in this thesis: corneal tissue, PMMA and 47
Page 1: Doctoral thesis Corneal Ablation an
Page 5 and 6: Contents Corneal Ablation and Conta
Page 7 and 8: 2.2.1. Fitting surfaces............
Page 9 and 10: 5.3.3. Ablation efficiency factors
Page 11: 10.5. DISCUSSION...................
Page 14 and 15: We thank José Antonio Sánchez-Gil
Page 16 and 17: BOZR Back Optic Zone Radius BCVA Be
Page 19 and 20: 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: INTRODUCTION Marcos et al. (Marcos
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 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
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REFRACTIVE SURGERY PMMA MODEL 3.1.
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CHAPTER 3 optimization of refractiv
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CHAPTER 3 These data demonstrate th
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CHAPTER 3 regression line, since it
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CHAPTER 3 Figure 3.3 shows one of t
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CHAPTER 3 Ablation efficiency facto
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CHAPTER 3 considering the same set
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CHAPTER 3 3.5.3 Impact of correctio
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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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