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Biomechanical corneal changes induced by different flap thickness created by femtosecond laser
Medeiros, Fabricio W.;Sinha-Roy, Abhijit;Alves, Milton R.;Dupps Jr., William J.;
Clinics , 2011, DOI: 10.1590/S1807-59322011000600025
Abstract: objective: to evaluate the impact of the creation of corneal flaps at different thicknesses on the biomechanical properties of swine corneas. method: twelve swine eyes were obtained to form two groups: 100 μm flap thickness and 300 μm flap thickness. each eye was submitted to the following examinations: raster topography to investigate corneal curvature alterations, ocular response analyzer to investigate corneal hysteresis change, optical coherence tomography to measure central corneal and flap thickness and sonic wave propagation velocity as a measure of stiffness, before and immediately after flap creation. after flap amputation, surface wave velocity measurements were repeated. results: measured flap thicknesses were statistically different for thin and thick flap groups, with an average of 108.5 + 6.9 and 307.8 + 11.5 μm respectively. hysteresis and corneal resistance factor did not change significantly after flap creation in the thin flap group. with thicker flaps, both parameters decreased significantly from 8.0 +1.0 to 5.1 +1.5 mmhg and from 8.2 + 1.6 to 4.1 +2.5 mmhg respectively. simulated keratometry values increased in the thick flap group (from 39.5 + 1 d to 45.9+1.2 d) after flap creation but not in the thin flap group (from 40.6 + 0.6 d to 41.4+ 1.0 d). regarding surface wave velocity analysis, the surgical procedures induced statistically lower results in some positions. conclusion: in the experimental conditions established by this model, thicker flaps presented a greater biomechanical impact on the cornea.
Comparison of corneal sensitivity, tear function and corneal staining following laser in situ keratomileusis with two femtosecond laser platforms  [cached]
Petznick A,Chew A,Hall RC,Chan CML
Clinical Ophthalmology , 2013,
Abstract: Andrea Petznick,1 Annabel Chew,2 Reece C Hall,2 Cordelia ML Chan,2 Mohamad Rosman,1,2 Donald Tan,1–3 Louis Tong,1–4 Jodhbir S Mehta1–31Singapore Eye Research Institute, Singapore; 2Singapore National Eye Centre, Singapore; 3Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; 4Duke-NUS Graduate Medical School, SingaporePurpose: To evaluate longitudinal changes in corneal sensitivity, tear function, and corneal staining in patients who underwent laser in situ keratomileusis (LASIK) using two different femtosecond lasers.Methods: In a prospective, randomized clinical trial, contralateral eyes of 45 patients underwent flap creation by either VisuMax or IntraLase femtosecond laser. Corneal sensitivity, tear break up time (TBUT), Schirmer’s test, and corneal fluorescein staining were assessed preoperatively and at 1 week, 1 month, and 3 months postoperatively.Results: There were no statistical differences in any clinical outcome measure between the two femtosecond lasers (P > 0.05), although there was a trend towards slightly lower reductions for corneal sensitivity and TBUT in VisuMax-operated eyes. Overall, corneal sensitivity was significantly reduced at 1 week (P < 0.05), 1 month (P < 0 .001), and 3 months (P < 0.001) postoperatively. A significantly greater reduction of corneal sensitivity was noted in eyes with a myopic spherical equivalent of 6.00 diopters (D) to 11.25 D as compared with eyes that had a relatively lower level of myopia of less than 6.00 D (P < 0.001). TBUT and Schirmer’s test values were significantly diminished at 1 week postoperatively (P < 0.04). Overall, corneal staining was significantly increased at 1 week postoperatively (P < 0.001). The level of myopia did not significantly affect postoperative changes in TBUT, Schirmer’s test values, or corneal staining (P > 0.05).Conclusion: This study showed that changes in corneal sensitivity, tear function, and corneal staining were statistically similar in LASIK using VisuMax and IntraLase femtosecond lasers for flap creation. However, the trend towards faster recovery of corneal sensitivity and TBUT observed in VisuMax-operated eyes may be attributable to improved technical specifications.Keywords: femtosecond laser, corneal sensitivity, tear film break-up time, Schirmer’s, corneal staining
Femtosecond Laser Versus Mechanical Microkeratome in Thin-Flap Laser in Situ Keratomileusis (Lasik) for Correction of Refractive Errors an Evidence-Based Effectiveness and Cost Analysis  [cached]
Ali Mostafaie,Alireza Mahboub Ahari,Fatemeh Sadeghi Ghyassi,Sakineh Hajebrahimi
Journal of Lasers in Medical Sciences , 2011,
Abstract: INTRODUCTION: To compare the efficacy and cost-effectiveness of Femtosecond laser versus mechanical Microkeratome corneal flap creation in correction of refractive errors. METHODS: I this review, a comprehensive search of Medline, SCOPUS, Cochrane, TRIP database, supplemented by HTA and economic databases was performed. We searched for randomized controlled trials (RCTs) of Femtosecond laser which included mechanical Microkeratome in other arm. The quality of the retrieved studies was appraised by two independent reviewers and appropriate articles were finalized. RESULTS: A total of 1142 articles were identified, of which, 1059 were excluded after review of the titles and abstracts and 83 articles remained. Systematic reviews and RCTs were evaluated through CASP international worksheet. Eventually, 61 titles were excluded, leaving 22 articles to be reviewed. Safety: There was no individual evidence to cover all safety components about Femtosecond laser, but in summary, this modality seems a safe method for corneal flap creation. Effectiveness: No statistically significant difference was shown in visual acuity and refractive errors. The important secondary end point of this review was diffuse Lamellar keratitis in 17% of the femtosecond group versus 5% in mechanical Microkeratome. Inflammation was low-grade and improved during the first 3 months of follow-up period with a low dose medication without corneal scarring. The two groups was comparable in all clinical outcomes including Unorrected Visual Acuity (UCVA), Best Special Corrected Visual Acuity (BSCVA), manifest refraction, wave front aberrometry, Schirmer test, and Tear Break up time (TBUT). Cost Analysis: Results showed that marginal cost incurred due to Femtosecond technology adoption may vary from 27 to 117 € (resulted from sensitivity analysis). It is clear that additional cost may be a small proportion of LASIK procedure total cost. CONCLUSION: Although Femtosecond flap creation is a modern method with a good quality of corneal flap, but, there is no high-quality evidence to show superiority of Femtosecond laser in clinical outcomes. Although the efficacy and cost of the systems is almost equal, traditional method still remains as the standard approach.
Effect of Corneal Hydration on the Quality of the Femtosecond Laser Anterior Lamellar Cut  [PDF]
Ossama Nada, Anca Marian, Nicolas Tran-Khanh, Michael Buschmann, Michel Podtetenev, Fran?ois Vidal, Santiago Costantino, Isabelle Brunette
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0098852
Abstract: The goal of this study was to assess the effect of corneal hydration on the quality of the femtosecond laser (FSL) anterior lamellar cut. The Visumax FSL was used to dissect an 8-mm-diameter corneal flap in 22 eye bank corneas showing various levels of hydration. The intended ablation depth was 220 μm in all eyes, which corresponded to the maximal depth available with this laser. After the cut, the achieved ablation depth was measured using optical coherence tomography images, flap separability was assessed by measuring the mean force generated to detach the flap, and stromal bed roughness was assessed by measuring the Haralick contrast level on the 1000× scanning electron microscopy images of the ablated surfaces. The preoperative central corneal thickness ranged from 547 to 1104 μm (mean ± SEM: 833±30 μm). A negative correlation was found between the level of corneal hydration and the ablation depth measured in the mid-peripheral cornea (r = ?0.626, p = 0.003), the ablation being more superficial in more edematous corneas. The Haralick contrast also tended to increase as a function of corneal hydration (r = 0.416, p = 0.061), suggesting that laser ablation in edematous corneas results in rougher stromal surfaces. These results support the hypothesis that the quality of the FSL lamellar cut decreases as the level of corneal hydration increases. Although FSL is still considered in the field as the tool of the future for corneal dissection, a better understanding of the limits of this tool will be needed before it can replace manual or automated stromal dissection techniques in hydrated corneas.
Comparison of corneal sensitivity, tear function and corneal staining following laser in situ keratomileusis with two femtosecond laser platforms
Petznick A, Chew A, Hall RC, Chan CML, Rosman M, Tan D, Tong L, Mehta JS
Clinical Ophthalmology , 2013, DOI: http://dx.doi.org/10.2147/OPTH.S42266
Abstract: mparison of corneal sensitivity, tear function and corneal staining following laser in situ keratomileusis with two femtosecond laser platforms Original Research (171) Total Article Views Authors: Petznick A, Chew A, Hall RC, Chan CML, Rosman M, Tan D, Tong L, Mehta JS Published Date March 2013 Volume 2013:7 Pages 591 - 598 DOI: http://dx.doi.org/10.2147/OPTH.S42266 Received: 03 January 2013 Accepted: 26 January 2013 Published: 25 March 2013 Andrea Petznick,1 Annabel Chew,2 Reece C Hall,2 Cordelia ML Chan,2 Mohamad Rosman,1,2 Donald Tan,1–3 Louis Tong,1–4 Jodhbir S Mehta1–3 1Singapore Eye Research Institute, Singapore; 2Singapore National Eye Centre, Singapore; 3Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; 4Duke-NUS Graduate Medical School, Singapore Purpose: To evaluate longitudinal changes in corneal sensitivity, tear function, and corneal staining in patients who underwent laser in situ keratomileusis (LASIK) using two different femtosecond lasers. Methods: In a prospective, randomized clinical trial, contralateral eyes of 45 patients underwent flap creation by either VisuMax or IntraLase femtosecond laser. Corneal sensitivity, tear break up time (TBUT), Schirmer’s test, and corneal fluorescein staining were assessed preoperatively and at 1 week, 1 month, and 3 months postoperatively. Results: There were no statistical differences in any clinical outcome measure between the two femtosecond lasers (P > 0.05), although there was a trend towards slightly lower reductions for corneal sensitivity and TBUT in VisuMax-operated eyes. Overall, corneal sensitivity was significantly reduced at 1 week (P < 0.05), 1 month (P < 0 .001), and 3 months (P < 0.001) postoperatively. A significantly greater reduction of corneal sensitivity was noted in eyes with a myopic spherical equivalent of 6.00 diopters (D) to 11.25 D as compared with eyes that had a relatively lower level of myopia of less than 6.00 D (P < 0.001). TBUT and Schirmer’s test values were significantly diminished at 1 week postoperatively (P < 0.04). Overall, corneal staining was significantly increased at 1 week postoperatively (P < 0.001). The level of myopia did not significantly affect postoperative changes in TBUT, Schirmer’s test values, or corneal staining (P > 0.05). Conclusion: This study showed that changes in corneal sensitivity, tear function, and corneal staining were statistically similar in LASIK using VisuMax and IntraLase femtosecond lasers for flap creation. However, the trend towards faster recovery of corneal sensitivity and TBUT observed in VisuMax-operated eyes may be attributable to improved technical specifications.
Digital analysis of flap parameter accuracy and objective assessment of opaque bubble layer in femtosecond laser-assisted LASIK: a novel technique  [cached]
Kanellopoulos AJ,Asimellis G
Clinical Ophthalmology , 2013,
Abstract: A John Kanellopoulos,1,2 George Asimellis11Laservision Eye Institute, Athens, Greece; 2New York University School of Medicine, New York, NY, USABackground: The purpose of this study was to determine flap parameter accuracy, extent of the opaque bubble layer, and incidence of skip lines in femtosecond laser-assisted stromal in situ keratomileusis (LASIK) using the WaveLight FS200 laser and optoelectronic clinical measurements.Methods: Images from 101 flaps were automatically recorded during consecutive routine LASIK procedures performed using the WaveLight FS200 femtosecond laser and the EX500 excimer laser. Digital processing of these images was used to evaluate objectively the diameter of FS200-created flaps, by comparing planned versus achieved procedures and to evaluate the incidence and extent (area) of the opaque bubble layer.Results: The intended flap diameters were between 8.00 mm and 9.50 mm. The achieved flap diameters showed extremely high precision, and were on average -0.16 ± 0.04 mm smaller for a 8.00 mm intended flap diameter, -0.12 ± 0.03 mm smaller for a 8.50 mm flap, and up +0.06 ± 0.06 mm wider for a 9.50 mm flap. With an average flap area of 72.4 mm2, the mean area of the opaque bubble layer (4.1 ± 4.3 [range 0–14.34] mm2) corresponded to a 6% opaque bubble layer-to-flap area. Specifically, 80% of the femtosecond-created flaps had an essentially zero opaque bubble layer (<2.7% of the flap area).Conclusion: In our clinical experience, flaps created using FS200 and this novel highly objective assessment technique demonstrate both precision and reproducibility. The incidence of opaque bubble layer was minimal.Keywords: femtosecond laser precision, bladeless laser-assisted stromal in situ keratomileusis, corneal flap diameter, opaque bubble layer, skip lines, WaveLight FS200
Intraoperative and postoperative complications of laser in situ keratomileusis flap creation using intralase femtosecond laser and mechanical microkeratomes  [cached]
Espandar Ladan,Meyer Jay
Middle East African Journal of Ophthalmology , 2010,
Abstract: An essential step of laser in situ keratomileusis surgery is corneal flap creation, Femtosecond (FS)-assisted or mechanical microkeratome. Each type has rare intraoperative and postoperative complication rates. Several recent studies have identified risk factors and guidelines to help manage these complications. Fortunately, studies have shown no loss of best-corrected visual acuity (BCVA) after the management of intraoperative and postoperative complications in IntraLase FS and mechanical microkeratome. Refractive surgeons need to be aware of the types of complications that can occur, how to avoid them and how to manage them to ensure the best possible outcomes.
Analysis of corneal endothelial cell density and morphology after laser in situ keratomileusis using two types of femtosecond lasers
Tomita M, Waring GO IV, Watabe M
Clinical Ophthalmology , 2012, DOI: http://dx.doi.org/10.2147/OPTH.S35887
Abstract: nalysis of corneal endothelial cell density and morphology after laser in situ keratomileusis using two types of femtosecond lasers Original Research (1325) Total Article Views Authors: Tomita M, Waring GO IV, Watabe M Published Date September 2012 Volume 2012:6 Pages 1567 - 1572 DOI: http://dx.doi.org/10.2147/OPTH.S35887 Received: 12 July 2012 Accepted: 05 August 2012 Published: 24 September 2012 Minoru Tomita,1,2,* George O Waring IV,3,4 Miyuki Watabe,1,* 1Shinagawa LASIK Center, Chiyoda-ku, Tokyo, Japan; 2Department of Ophthalmology, Wenzhou Medical College, Wenzhou, China; 3Medical University of South Carolina, Storm Eye Institute, Charleston, SC, USA; 4Magill Laser Center, Charleston, SC, USA *These authors contributed equally to this study Purpose: To compare two different femtosecond lasers used for flap creation during laser-assisted in situ keratomileusis (LASIK) surgery in terms of their effects on the corneal endothelium. Methods: We performed LASIK surgery on 254 eyes of 131 patients using IntraLase FS60 (Abbott Medical Optics, Inc, Irvine, CA; IntraLase group) and 254 eyes of 136 patients using Femto LDV (Ziemer Group AG, Port, Switzerland; LDV group) for corneal flap creation. The mean cell density, coefficient of variation, and hexagonality of the corneal endothelial cells were determined and the results were statistically compared. Results: There were no statistically significant differences in the corneal morphology between pre and post LASIK results in each group, nor were there significant differences between the results of both groups at 3 months post LASIK. Conclusions: Both IntraLase FS60 and Ziemer Femto LDV are able to create flaps without significant adverse effects on the corneal endothelial morphology through 3 months after LASIK surgery.
Analysis of corneal endothelial cell density and morphology after laser in situ keratomileusis using two types of femtosecond lasers  [cached]
Tomita M,Waring GO IV,Watabe M
Clinical Ophthalmology , 2012,
Abstract: Minoru Tomita,1,2,* George O Waring IV,3,4 Miyuki Watabe,1,* 1Shinagawa LASIK Center, Chiyoda-ku, Tokyo, Japan; 2Department of Ophthalmology, Wenzhou Medical College, Wenzhou, China; 3Medical University of South Carolina, Storm Eye Institute, Charleston, SC, USA; 4Magill Laser Center, Charleston, SC, USA*These authors contributed equally to this studyPurpose: To compare two different femtosecond lasers used for flap creation during laser-assisted in situ keratomileusis (LASIK) surgery in terms of their effects on the corneal endothelium.Methods: We performed LASIK surgery on 254 eyes of 131 patients using IntraLase FS60 (Abbott Medical Optics, Inc, Irvine, CA; IntraLase group) and 254 eyes of 136 patients using Femto LDV (Ziemer Group AG, Port, Switzerland; LDV group) for corneal flap creation. The mean cell density, coefficient of variation, and hexagonality of the corneal endothelial cells were determined and the results were statistically compared.Results: There were no statistically significant differences in the corneal morphology between pre and post LASIK results in each group, nor were there significant differences between the results of both groups at 3 months post LASIK.Conclusions: Both IntraLase FS60 and Ziemer Femto LDV are able to create flaps without significant adverse effects on the corneal endothelial morphology through 3 months after LASIK surgery.Keywords: LASIK, corneal endothelium, femtosecond laser, IntraLase FS60, Ziemer LDV
Three-dimensional LASIK flap thickness variability: topographic central, paracentral and peripheral assessment, in flaps created by a mechanical microkeratome (M2) and two different femtosecond lasers (FS60 and FS200)  [cached]
Kanellopoulos AJ,Asimellis G
Clinical Ophthalmology , 2013,
Abstract: A John Kanellopoulos,1,2 George Asimellis1 1Laservision.gr Institute, Athens, Greece; 2NYU Medical School, New York, USA Purpose: To evaluate programmed versus achieved laser-assisted in situ keratomileusis (LASIK) flap central thickness and investigate topographic flap thickness variability, as well as the effect of potential epithelial remodeling interference on flap thickness variability. Patients and methods: Flap thickness was investigated in 110 eyes that had had bilateral myopic LASIK several years ago (average 4.5 ± 2.7 years; range 2–7 years). Three age-matched study groups were formed, based on the method of primary flap creation: Group A (flaps made by the Moria Surgical M2 microkeratome [Antony, France]), Group B (flaps made by the Abbott Medical Optics IntraLase FS60 femtosecond laser [Santa Ana, CA, USA]), and Group C (flaps made by the Alcon WaveLight FS200 femtosecond laser [Fort Worth, TX, USA]). Whole-cornea topographic maps of flap and epithelial thickness were obtained by scanning high-frequency ultrasound biomicroscopy. On each eye, topographic flap and epithelial thickness variability was computed by the standard deviation of thickness corresponding to 21 equally spaced points over the entire corneal area imaged. Results: The average central flap thickness for each group was 138.33 ± 12.38 μm (mean ± standard deviation) in Group A, 128.46 ± 5.72 μm in Group B, and 122.00 ± 5.64 μm in Group C. Topographic flap thickness variability was 9.73 ± 4.93 μm for Group A, 8.48 ± 4.23 μm for Group B, and 4.84 ± 1.88 μm for Group C. The smaller topographic flap thickness variability of Group C (FS200) was statistically significant compared with that of Group A (M2) (P = 0.004), indicating improved topographic flap thickness consistency – that is, improved precision – over the entire flap area affected. Conclusions: The two femtosecond lasers produced a smaller flap thickness and reduced variability than the mechanical microkeratome. In addition, our study suggests that there may be a significant difference in topographic flap thickness variability between the results achieved by the two femtosecond lasers examined. Keywords: Moria M2, IntraLase FS60, WaveLight FS200, Allegretto Wave Eye-Q, 400 Hz excimer, ultrasound biomicroscopy
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