Low_resolution_Thesis_CDD_221009_public - Visual Optics and ...

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

CHAPTER 7 LASIK refractive for intended myopic spherical corrections ranging from -1.25 to - 8.50 D (mean, std -4 ± 2.0 D). Cylinder ranged from 0 to -2.5 D (-0.84 ± 0.7). Patients were tested before and at various times after the procedure. Nine subjects (18 eyes), with ages ranging from 24 to 43 years (mean, std 32.5 ± 7 years), were not operated and acted as control subjects. The control subjects were measured at the Instituto de Óptica “Daza de Valdés”, with the same Pentacam unit as the patients (see section 2.1.3). Experimental protocols were approved by an Institutional Review Board and met the tenets of the Declaration of Helsinki. All patients signed the informed consent. 7.3.2. Surgical procedure We conducted standard LASIK surgery using a narrow-beam, flying-spot excimer laser (Chiron Technolas 217-C equipped with the PlanoScan program; Bausch & Lomb Surgical). This laser has an emission wavelength of 193 nm, a fixed pulse repetition rate of 50 Hz, and a radiance exposure of 120 mJ/cm 2 . The procedure was assisted by an eye tracker. Flaps were performed with suction rings of 8.5-mm (3 eyes) or 9.5-mm (24 eyes) diameter. We used a Hansatome microkeratome (Bausch & Lomb) programmed for 160 m (22 eyes) or 180 m (5 eyes) depth. Photoablation was applied to an optical zone of diameter ranging from 5.2 to 7 mm (6.6 ± 0.6 mm). The LASIK procedures were conducted at the Instituto de Oftalmobiología Aplicada, Universidad de Valladolid, Spain. Pre-operative central pachymetry (measured by Pentacam) ranged from 510 to 643 m (572 ± 33 m). Residual bed thickness one day after surgery (computed as central pachymetry one day after surgery minus programmed flap depth) ranged between 271 m and 421 m (329 ± 41 m). 7.3.3. Measurements: patients and control eyes We collected corneal topographies with the Pentacam system of both eyes of each patient before and several times after surgery. Thirteen eyes were measured at three different time points post-operatively: 1.3±0.5, 10.5±3.2 and 33.4±5.5 days after surgery, which we will refer as “1 day”, “1 week” and “1 month” post-operatively. Another eye was measured post-operatively only one day after surgery, 6 eyes were measured only one week after surgery, 2 eyes were measured one week and one month after surgery and 5 eyes were measured only one month after surgery. Average measurement times for the whole group of eyes are 1.3, 10.8 and 33.4 days. In control subjects, we acquired several consecutive topographies of both eyes separated by 1 day and 1 week. These data were used as baseline for normal short and mid-term changes in the posterior corneal shape. The time of the measurement across subjects varied between 9:00 am and 16:00 pm, but for each subject measurements were conducted around the same time of the day (within 3.4±1.4 hours) in all days of measurements. We acquired 3-6 valid topographies per session. One of the control eyes was measured 23 consecutive times to study the instrument repeatability. 7.3.4. Data Analysis We exported topographic maps of anterior and posterior corneal surfaces from Pentacam (Fig. 7.1 (A)), and used Matlab for the data analysis, in order to have a greater freedom for data manipulation than that permitted by Pentacam’s software, and to ensure that the definitions of apical radius of curvature and asphericity complied with known equations. 172
ANTERIOR AND POSTERIOR CORNEAL ELEVATION MAPS AFTER REFRACTIVE SURGERY We computed apical radii and asphericities by fitting the central 6 mm of the corneal elevation maps to bi-elliptical surfaces (ellipsoids). Unless clearly stated otherwise, the data presented in this paper will be referred to a rotationally symmetric ellipsoid. Fig. 7.1. (A) Elevation data exported from Pentacam. Each corneal surface is represented by a cloud of points arranged in x-y on a 100x100 m square grid. Distance between both corneal surfaces reflects the central pachymetry measured by Pentacam. (B) Difference maps, obtained after alignment as described in the text. Distance between anterior and posterior difference maps is arbitrary, chosen for optimal visualization. 7.3.4.1. Difference maps and corneal elevation We subtracted pre- and post-operative posterior corneal elevation maps to obtain difference elevation maps (see Fig. 7.1 (B)). Proper alignment of these surfaces is critical to prevent misalignment artifacts from affecting the difference maps. In principle, we should align the topographies both in axis (rotation) and position (translation). We found that the raw topographies are already aligned in axis as we performed the analysis both with and without rotation in the alignment (Navarro et al., 2006), and we did not observe statistically significant differences between the results obtained with either method. In order to align the two measurements in position, we used the fit without rotation to achieve the alignment in the XY plane (where Z is the line of sight). Thus, we translated both topographies so that the center of their best-fit ellipsoids fell in the origin. Then, we translated the post-operative measurement in Z until the differences between both topographies were minimal. For a study of repeatability of Pentacam, we used the whole surface for alignment. For 173
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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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CHAPTER 3 3.5.3 Impact of correctio
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ABLATION PROPERTIES OF FILOFOCON A
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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
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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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Page 220 and 221: CORRELATION BETWEEN RADIUS AND ASPH
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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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