Low_resolution_Thesis_CDD_221009_public - Visual Optics and ...

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

CHAPTER 6 no preferential orientation. These retrieved values of astigmatism of the posterior corneal surfaces conformed to spherical plastic surfaces are similar to those found in the calibrations of spherical model eyes (anterior surfaces) in the previous section. There was no correlation between the astigmatism of the anterior and posterior corneal surface (p=0.57 for all eyes). 6.4.3.3. Asphericities Finally, there was no correlation between the anterior and posterior corneal asphericities (p=0.28 for all the eyes), as shown in Fig. 6.5, where anterior asphericities are plotted vs posterior asphericities (ideally zero). However, the posterior corneal asphericity differed from zero, and was quite variable (-0.33 ± 0.44) for the back surface). Fig. 6.5. Measurements of Asphericities. Each point is the average across repeated measurements in the same conditions. 6.5. DISCUSSION In this chapter we have presented a validation of the Pentacam Scheimpflug system to measure the posterior corneal surface geometry. The experiments using a hybrid porcine/plastic eye model indicate that the posterior corneal radius can be obtained with high repeatability and that the reconstructed posterior surface is not affected by changes or asymmetries in the anterior cornea. Posterior corneal radius seems to be slightly underestimated and asphericity overestimated in comparison to the nominal values of the posterior cornea in the model eye used for calibration. While studies on the repeatability of this system had been published before (particularly of the anterior radius of curvature and pachymetry (Lackner et al., 2005, Jain et al., 2007)) this is, to our knowledge, the first time that the accuracy (both for anterior and posterior surface) is studied. 6.6. CONCLUSIONS We have developed an artificial eye model that shows corneal properties (scattering, refractive index) comparable to those of living eyes and can be used for calibration of anterior segment imaging systems. The accuracy of the posterior corneal geometry data provided by the Pentacam Imaging System was verified using our model. The independence of the retrieved data from the anterior corneal topography indicates 164
HYBRID PORCINE/PLASTIC MODEL proper correction of optical distorsion in the posterior. These results have implications on the study of posterior cornea, specially in changes after refractive surgery and the assessment of biomechanical properties (Perez-Escudero et al., 2008, Kling et al., 2009) by Scheimpflug Imaging. 6.7. OUTLOOK The Scheimpflug-based system has proved to be an appropriate technique to measure reliably potential changes on the posterior corneal surface, as we have shown that the posterior corneal shape measurements are not affected by changes on the anterior cornea. In Chapter 7 we will present a study where the instrument validated here, was used to measure posterior corneal shape changes after standard myopic LASIK surgery, and to evaluate potential longitudinal changes after the procedure. 165
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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
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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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Page 117: ABLATION PROPERTIES OF FILOFOCON A
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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 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
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Page 194: ON-EYE OPTICAL PERFORMANCE OF RIGID
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Page 212: 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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