Hammer A.,University of Geneva |
Richoz O.,University of Geneva |
Mosquera S.A.,SCHWIND eye Technology solutions |
Tabibian D.,University of Geneva |
And 3 more authors.
Investigative Ophthalmology and Visual Science | Year: 2014
Purpose. New corneal cross-linking (CXL) devices are capable of using higher UV-A light irradiances than used in original CXL protocols. The Bunsen-Roscoe law states that a photochemical reaction should stay constant if the delivered total energy is kept constant; however, little clinical data are available to support this hypothesis. Methods. We investigated the biomechanical properties of four groups (n = 50 each) of porcine corneas. Three groups were exposed to riboflavin 0.1 % and UV-A irradiation of equal total energy (3 mW/cm2 for 30 minutes, 9 mW/cm2 for 10 minutes, and 18 mW/cm2 for 5 minutes). Controls were exposed to riboflavin 0.1% without irradiation. Young's modulus of 5-mm wide corneal strips was used as an indicator of corneal stiffness. Results. We observed a decreased stiffening effect with increasing UV-A intensity. Young's modulus at 10% strain showed significant differences between 3 mW/cm2 and 9 mW/cm2 (P = 0.002), 3 mW/cm2 and 18 mW/cm2 (P = 0.0002), 3 mW/cm2 and the control group (P < 0.0001), and 9 mW/cm2 and the control group (P = 0.015). There was no difference between 18 mW/cm2 and the control group (P = 0.064) and between 9 mW/cm2 and 18 mW/cm2 (P = 0.503). Conclusions. The biomechanical effect of CXL decreased significantly when using high irradiance/short irradiation time settings. Intrastromal oxygen diffusion capacity and increased oxygen consumption associated with higher irradiances may be a limiting factor leading to reduced treatment efficiency. Our results regarding the efficiency of high-irradiance collagen cross-linking (CXL) raise concerns about the clinical efficiency of the new high-irradiance CXL devices already used in clinical practice without proper validation. © 2014 The Association for Research in Vision and Ophthalmology, Inc.
Baudu P.,Clinique Avicenne |
Penin F.,Schwind France Eye Technology Solutions |
Arba Mosquera S.,SCHWIND eye Technology solutions
American Journal of Ophthalmology | Year: 2013
Purpose: To analyze the uncorrected binocular performance after biaspheric multifocal central presbyopic laser in situ keratomileusis treatments. Design: Retrospective, interventional case series. Methods: setting. Private clinical practice. patient or study population. Three hundred fifty-eight presbyopic patients (43% males, 82 myopic), bilaterally treated, suitable for laser in situ keratomileusis, with monocular corrected distance visual acuity of 20/32 or better. intervention or observation procedure(s). PresbyMAX (Schwind Eye-Tech-Solutions GmbH and Co) biaspheric multifocal ablation. main outcome measures. Binocular uncorrected distance visual acuity (UDVA) and near visual acuity (UNVA) after surgery and their changes compared with corrected distance visual acuity and corrected near visual acuity before surgery. Results: At 6 months, 76% of patients achieved a UDVA of 0.1 logarithm of the minimal angle of resolution (logMAR; Snellen equivalent, 20/25) or better, 91% of patients obtained a UNVA of 0.1 logarithmic of the reading acuity determination (logRAD) (p3) or better, and 99% of patients were within 1 diopter of defocus. Postoperative mean spherical equivalent was -0.17 ± 0.34 diopter. Ninety-six percent of patients achieved a UDVA of 0.2 logMAR (Snellen equivalent, 20/32) or better and a UNVA of 0.2 logRAD (p4) or better. Mean binocular corrected distance visual acuity degraded from 0.00 ± 0.01 logMAR (Snellen equivalent, 20/20) to a UDVA of 0.09 ± 0.07 logMAR (Snellen equivalent, 20/25). Mean binocular corrected near visual acuity degraded from 0.02 ± 0.01 logRAD (p2) to a UNVA of 0.07 ± 0.07 logRAD (p2). Conclusions: Although optically the results are predictable, approximately 17% of the patients did not obtain objectively successful outcomes. In presbyopic patients without symptomatic cataracts, but with refractive errors, the PresbyMAX will decrease the presbyopic symptoms and correct far distance refraction in the same treatment, offering spectacle-free vision in daily life in most of the patients. Further investigation is necessary to evaluate the overall benefit of this procedure. © 2013 BY ELSEVIER INC. ALL RIGHTS RESERVED.
Shraiki M.,FH Darmstadt |
Arba-Mosquera S.,SCHWIND eye Technology solutions |
Arba-Mosquera S.,University of Valladolid
Investigative Ophthalmology and Visual Science | Year: 2011
Purpose. To evaluate ablation algorithms and temperature changes in laser refractive surgery. Methods. The model (virtual laser system [VLS]) simulates different physical effects of an entire surgical process, simulating the shot-by-shot ablation process based on a modeled beam profile. The model is comprehensive and directly considers applied correction; corneal geometry, including astigmatism; laser beam characteristics; and ablative spot properties. Results. Pulse lists collected from actual treatments were used to simulate the temperature increase during the ablation process. Ablation efficiency reduction in the periphery resulted in a lower peripheral temperature increase. Steep corneas had lesser temperature increases than flat ones. The maximum rise in temperature depends on the spatial density of the ablation pulses. For the same number of ablative pulses, myopic corrections showed the highest temperature increase, followed by myopic astigmatism, mixed astigmatism, phototherapeutic keratectomy (PTK), hyperopic astigmatism, and hyperopic treatments. Conclusions. The proposed model can be used, at relatively low cost, for calibration, verification, and validation of the laser systems used for ablation processes and would directly improve the quality of the results. © 2011 The Association for Research in Vision and Ophthalmology, Inc.
Arba-Mosquera S.,University of Valladolid |
Triefenbach N.,SCHWIND eye Technology solutions
Journal of Modern Optics | Year: 2012
The relative ablation efficiency at different materials (in particular human cornea and poly(methyl methacrylate) (PMMA)) was analysed. A comprehensive model, which directly considers applied correction, including astigmatism, as well as laser beam characteristics and ablative spot properties has been developed. The model further provides a method to convert the deviations in achieved ablation observed in PMMA to equivalent deviations in the cornea. Radiant exposures from about 90mJ/cm 2 to about 500mJ/cm 2 correspond to cornea-to-PMMA ablation ratios of about 9 and about 1.7, respectively (about 7 and 1.3 optically). Super-Gaussian order from simple Gaussian profile to flat-top profile, and for a radiant exposure of 250mJ/cm 2, correspond to cornea-to-PMMA ratios of about 2.3 and about 1.6, respectively (about 1.7 and about 1.2 optically). For a Gaussian beam of 160mJ/cm 2 radiant exposure, a severe overcorrection of +50% in PMMA corresponds only to an overcorrection of +29% on corneal tissue, whereas a moderate overcorrection of +20% in PMMA corresponds to an overcorrection of +12% on corneal tissue. For a severe undercorrection of 50% ablation observed in PMMA, the range for radiant exposures from about 90mJ/cm 2 to about 500mJ/cm 2 correspond to corneal undercorrections of about 14% to about 40%, respectively. The proposed model can be used for calibration, ablation pattern test and development, verification and validation purposes of laser systems used for ablation processes at relatively low cost and would directly improve the quality of results. © 2012 Copyright Taylor and Francis Group, LLC.
Luger M.H.A.,VisionClinics |
Ewering T.,SCHWIND eye Technology solutions |
Arba-Mosquera S.,SCHWIND eye Technology solutions
Journal of Cataract and Refractive Surgery | Year: 2012
Purpose: To compare the postoperative efficacy, safety, and higher-order-aberrations (HOAs) between transepithelial photorefractive keratectomy (PRK) and alcohol-assisted PRK in contralateral eyes. Setting: Private clinic, Utrecht, The Netherlands. Design: Comparative case series. Methods: Consecutive patients were randomized to have transepithelial PRK in 1 eye and alcohol-assisted PRK in the contralateral eye. In both eyes, aspheric treatments were planned with Custom Ablation Manager software and ablations performed with the Schwind Amaris system. Clinical outcomes were predictability, refraction, visual acuity, wavefront aberrations, and contrast and glare sensitivity. Paired t tests were applied for statistics. Results: The study evaluated 66 eyes (33 patients). All patients completed the 1-year follow-up. At 1-year, 97% of eyes in both groups achieved an uncorrected distance visual acuity (UDVA) of 0.1 logMAR or better. No eye lost 2 or more lines of corrected distance visual acuity (CDVA); 97% of transepithelial PRK eyes and 91% of alcohol-assisted PRK eyes were within ±0.50 diopter (D) of the targeted refraction. The postoperative mean spherical equivalent was +0.07 D ± 0.23 (SD) and +0.01 ± 0.27 D, respectively. Conclusions: The CDVA, UDVA, and safety outcomes between transepithelial PRK and alcohol-assisted PRK were comparable. Profiles for both techniques applied to regular corneas preserved the eye's natural HOAs. Transepithelial PRK is faster to perform and it is an all-laser procedure, which might be less stressful for the patient. Financial Disclosure: Mr. Ewering and Mr. Arba-Mosquera are employees of Schwind eye-tech-solutions. Dr. Luger has no financial or proprietary interest in any material or method mentioned. © 2012 ASCRS and ESCRS.