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Chen W, Bao F, Roberts CJ, Zhang J, Wang C, Li X, Wang J, Abu Said AZM, Mayopa KN, Chen Y, Zheng X, Eliasy A, Elsheikh A, Chen S. Effect of corneal cross-linking on biomechanical changes following transepithelial photorefractive keratectomy and femtosecond laser-assisted LASIK. Front Bioeng Biotechnol 2024; 12:1323612. [PMID: 38558790 PMCID: PMC10978754 DOI: 10.3389/fbioe.2024.1323612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 01/30/2024] [Indexed: 04/04/2024] Open
Abstract
Purpose: To evaluate the change in corneal biomechanics in patients with postoperative ectasia risk when combining two common laser vision correction procedures (tPRK and FS-LASIK) with cross-linking (in tPRK Xtra and FS-LASIK Xtra). Methods: The study included 143 eyes of 143 myopic, astigmatic patients that were divided into non-cross-linked refractive surgery groups (non-Xtra groups, tPRK and FS-LASIK) and cross-linked groups (Xtra groups, tPRK Xtra and FS-LASIK Xtra) according to an ectasia risk scoring system. The eyes were subjected to measurements including the stress-strain index (SSI), the stiffness parameter at first applanation (SP-A1), the integrated inverse radius (IIR), the deformation amplitude at apex (DA), and the ratio of deformation amplitude between apex and 2 mm from apex (DARatio2mm). The measurements were taken preoperatively and at 1, 3, and 6 months postoperatively (pos1m, pos3m, and pos6m). Posterior demarcation line depth from the endothelium (PDLD) and from the ablation surface (DLA) were recorded at pos1m. Results: SP-A1 significantly decreased, while IIR, deformation amplitude, and DARatio2mm increased significantly postoperatively in all four groups (p < 0.01)-all denoting stiffness decreases. In the FS-LASIK group, the changes in IIR, DA, and DARatio2mm were 32.7 ± 15.1%, 12.9 ± 7.1%, and 27.2 ± 12.0% respectively, which were significantly higher (p < 0.05) compared to 20.1 ± 12.8%, 6.4 ± 8.2%, and 19.7 ± 10.4% in the FS-LASIK Xtra group. In the tPRK group, the change in IIR was 27.3 ± 15.5%, significantly larger than 16.9 ± 13.4% in the tPRK Xtra group. The changes of SSI were minimal in the tPRK (-1.5 ± 21.7%, p = 1.000), tPRK Xtra (8.4 ± 17.9%, p = 0.053), and FS-LASIK Xtra (5.6 ± 12.7%, p = 0.634) groups, but was significant in the FS-LASIK group (-12.1 ± 7.9%, p < 0.01). After correcting for baseline biomechanical metrics, preoperative bIOP and the change in central corneal thickness (△CCT) from pre to pos6m, the changes in the IIR in both FS-LASIK and tPRK groups, as well as DA, DARatio2mm and SSI in the FS-LASIK group remained statistically greater than their corresponding Xtra groups (all p < 0.05). Most importantly, after correcting for these covariates, the changes in DARatio2mm in the FS-LASIK Xtra became statistically smaller than in the tPRK Xtra (p = 0.017). Conclusion: The statistical analysis results indicate that tPRK Xtra and FS-LASIK Xtra effectively reduced the biomechanical losses caused by refractive surgery (tPRK and FS-LASIK). The decrease in corneal overall stiffness was greater in FS-LASIK than in tPRK, and the biomechanical enhancement of CXL was also higher following LASIK than after tPRK.
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Affiliation(s)
- Wen Chen
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - FangJun Bao
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- State Key Laboratory of Ophthalmology, Optometry and Vision Sicence, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- The Institute of Ocular Biomechanics, WenZhou Medical University, Wenzhou, China
| | - Cynthia J. Roberts
- Ophthalmology and Visual Sciences and Biomedical Engineering, The Ohio State University, Columbus, OH, United States
| | - Jia Zhang
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- State Key Laboratory of Ophthalmology, Optometry and Vision Sicence, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - Chong Wang
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - XueFei Li
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - JunJie Wang
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- State Key Laboratory of Ophthalmology, Optometry and Vision Sicence, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- The Institute of Ocular Biomechanics, WenZhou Medical University, Wenzhou, China
| | - Anas Ziad Masoud Abu Said
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - Kevin Nguelemo Mayopa
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - YaNi Chen
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - XiaoBo Zheng
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- State Key Laboratory of Ophthalmology, Optometry and Vision Sicence, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- The Institute of Ocular Biomechanics, WenZhou Medical University, Wenzhou, China
| | - Ashkan Eliasy
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
- National Institute for Health Research (NIHR) Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
- Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China
| | - ShiHao Chen
- National Clinical Research Center for Ocular Diseases, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- National Engineering Research Center of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- State Key Laboratory of Ophthalmology, Optometry and Vision Sicence, Eye Hospital, Wenzhou Medical University, Wenzhou, China
- The Institute of Ocular Biomechanics, WenZhou Medical University, Wenzhou, China
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Torres-Netto EA, Abdshahzadeh H, Lu NJ, Kling S, Abrishamchi R, Hillen M, Hafezi NL, Koppen C, Hafezi F. Corneal crosslinking with riboflavin using sunlight. J Cataract Refract Surg 2023; 49:1049-1055. [PMID: 37343287 DOI: 10.1097/j.jcrs.0000000000001241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2022] [Accepted: 06/14/2023] [Indexed: 06/23/2023]
Abstract
PURPOSE To assess whether sunlight might be used to induce a biomechanical stiffening effect in riboflavin-soaked corneas similar to the effect observed in corneal crosslinking (CXL) using riboflavin and UV-A light. SETTING Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland. DESIGN Experimental study. METHODS 52 porcine eyes were assayed. The concentration of riboflavin in the corneal stroma was estimated using UV-A transmission in a preliminary experiment. Then, the duration of sunlight exposure to achieve a fluence of 7.2/cm 2 was calculated. Finally, de-epithelialized corneas were divided equally into 3 groups and soaked with riboflavin 0.1% (control group and Group 1) or 0.5% (Group 2). Eyes from Groups 1 and 2 were then exposed to sunlight. The elastic modulus was calculated as an indicator of stiffness. RESULTS Riboflavin concentration in Group B was higher by a factor of 2.8 than Group A. According to live illuminance measurements and stromal riboflavin concentration, the sunlight exposure duration varied between 16 minutes and 45 minutes. Groups 1 and 2 had higher elastic modulus than controls ( P < .0001) but did not differ between them ( P = .194). The stiffening effect was 84% and 55%, respectively. CONCLUSIONS Sunlight exposure of ex vivo corneas soaked in both riboflavin 0.1% and 0.5% resulted in increased corneal stiffness. Specifically, riboflavin 0.1% with longer UV-A exposure showed a trend for a greater stiffening effect, which might open new alleys for the use of oral riboflavin and fractioned sunlight exposure as less invasive CXL techniques.
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Affiliation(s)
- Emilio A Torres-Netto
- From the Ocular Cell Biology Group, Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich, Switzerland (Torres-Netto, Abdshahzadeh, Abrishamchi, Hillen, F. Hafezi); ELZA Institute AG, Dietikon, Switzerland (Torres-Netto, Abdshahzadeh, Lu, Abrishamchi, Hillen, N. Hafezi, F. Hafezi); Department of Ophthalmology, Paulista School of Medicine, Federal University of Sao Paulo, Sao Paulo, Brazil (Torres-Netto); Faculty of Medicine, University of Geneva, Geneva, Switzerland (Torres-Netto, N. Hafezi, Koppen, F. Hafezi); Faculty of Medicine and Health Sciences, University of Antwerp, Wilrijk, Belgium (Lu, Koppen); Department of Ophthalmology, Antwerp University Hospital, Edegem, Belgium (Lu); Computer Vision Laboratory, Department of Information Technology and Electrical Engineering, Swiss Federal Institute of Technology, Zurich, Switzerland (Kling); Department of Ophthalmology, University of Southern California, Los Angeles, California (F. Hafezi); School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China (F. Hafezi)
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Moshirfar M, Parsons MT, Chartrand NA, Lau CK, Stapley S, Bundogji N, Ronquillo YC, Hoopes PC. Photorefractive Keratectomy Enhancement (PRK) After Small-Incision Lenticule Extraction (SMILE). Clin Ophthalmol 2022; 16:3033-3042. [PMID: 36119391 PMCID: PMC9480579 DOI: 10.2147/opth.s381319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 08/29/2022] [Indexed: 11/23/2022] Open
Abstract
Purpose To determine rates of enhancement and visual prognosis following photorefractive keratectomy (PRK) enhancement of small-incision lenticule extraction (SMILE). Patients and Methods This retrospective, single-site study reviewed all cases of primary SMILE at Hoopes Vision in Draper, Utah between March 14, 2017 and April 8, 2022 to identify any cases that required follow-up enhancement. Primary SMILE was performed using Visumax 500 kHz femtosecond laser (Carl Zeiss Meditec, Jena, Germany). All enhancements were performed with alcohol-assisted PRK, using a WaveLight EX500 excimer laser (Alcon Laboratories, Inc., Fort Worth, TX). Results Four hundred and five eyes underwent primary SMILE, of which 15 later underwent PRK enhancement (enhancement rate of 3.7%). No significant difference in pre-SMILE data was identified between the enhancement and non-enhancement groups. The average age of those who underwent PRK enhancement was 33.8±6.3 years old and ranged from 25 to 45. Following primary SMILE, 13 eyes (87%) had an uncorrected distance visual acuity (UDVA) of 20/40 or better, and none had a UDVA of 20/20 or better. After one year of post-enhancement follow-up, all eyes had a UDVA of 20/40 or better, and 13 eyes (87%) had a UDVA of 20/20 or better (Figure 1). All were within one diopter of target spherical equivalent (SEQ), 13 (87%) were within 0.50 D, and 10 (67%) were within 0.25 D. Of those with 12-month follow-up data, none had UDVA worse than corrected distance visual acuity (CDVA), and none had lost lines of CDVA. Efficacy and safety indices were 1.03 and 0.99, respectively. Conclusion Following SMILE, ophthalmologists may anticipate an enhancement rate of one to seven percent. In these cases, PRK is a safe and effective procedure for enhancement of SMILE.
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Affiliation(s)
- Majid Moshirfar
- Hoopes Vision Research Center, Hoopes Vision, Draper, UT, USA
- John A. Moran Eye Center, University of Utah School of Medicine, Salt Lake City, UT, USA
- Utah Lions Eye Bank, Murray, UT, USA
- Correspondence: Majid Moshirfar, Hoopes Vision Research Center, 11820 S. State Street Suite #200, Draper, UT, 84020, USA, Tel +1 801-568-0200, Fax +1 801-563-0200, Email
| | - Mark T Parsons
- University of Arizona College of Medicine – Phoenix, Phoenix, AZ, USA
| | | | - Chap-Kay Lau
- University of Arizona College of Medicine – Phoenix, Phoenix, AZ, USA
| | - Seth Stapley
- Arizona College of Osteopathic Medicine, Midwestern University, Glendale, AZ, USA
| | - Nour Bundogji
- John A. Moran Eye Center, University of Utah School of Medicine, Salt Lake City, UT, USA
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Torres-Netto EA, Abdshahzadeh H, Abrishamchi R, Hafezi NL, Hillen M, Ambrósio R, Randleman JB, Spoerl E, Gatinel D, Hafezi F. The Impact of Repetitive and Prolonged Eye Rubbing on Corneal Biomechanics. J Refract Surg 2022; 38:610-616. [PMID: 36098386 DOI: 10.3928/1081597x-20220715-03] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate the effect of simulated repetitive eye rubbing on the corneal biomechanics of porcine eyes using an ex vivo model system. METHODS The average rubbing force that patients with keratoconus apply to their eyelids was previously determined. Fresh porcine eyes with eyelids were either exposed to 10,500 rub cycles from a custom-built eye rubbing machine that rubbed with a similar force to knuckle human eye rubbing (n = 33) or no rubbing at all (control; n = 37). A total of 10,500 rubs are equivalent to 1 year of rubbing six times daily, five movements per rub. The corneal biomechanical properties of these eyes were then tested by measuring the elastic modulus of 5-mm strips. RESULTS The elastic modulus at the range of 1% and 5% of strain was 1.219 ± 0.284 and 1.218 ± 0.304 N/mm2 in the eye rubbing group and the no-rub control group, respectively. Corneal stiffness was similar in both groups (P = .984). CONCLUSIONS The threshold to induce biomechanical changes (purely by eye rubbing) must be higher than 10,500 rubbing movements, suggesting that occasional eye rubbing may not affect corneal biomechanics in normal eyes, and likely only triggers keratoconus progression in predisposed corneas. Further in vivo studies assessing the impact eye rubbing has on inflammatory activity and the biomechanical properties of weakened corneas is warranted. [J Refract Surg. 2022;38(9):610-616.].
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Spiru B, Torres-Netto EA, Kling S, Hafezi F, Sekundo W. Hyperopic SMILE Versus FS-LASIK: A Biomechanical Comparison in Human Fellow Corneas. J Refract Surg 2021; 37:810-815. [PMID: 34914557 DOI: 10.3928/1081597x-20210830-02] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To investigate the biomechanical properties of ex vivo human paired corneas after hyperopic correction via cap-based versus flap-based laser-assisted refractive surgery. METHODS In this prospective experimental study, 13 pairs of human corneas unsuitable for transplantation were equally divided into two groups. The pachymetry was performed in each eye just before the laser procedure. Corneas from the right eye were treated with small incision lenticule extraction (SMILE), whereas corneas from the left eye of the same donor were treated with femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK). All corneas were subjected to a refractive correction of +6.00 diopters (D) sphere with a 6.5-mm zone under a 120-µm cap (SMILE) or a 7-mm zone under a 110-µm flap (FS-LASIK). For two-dimensional biomechanical measurements, the corneoscleral buttons underwent two testing cycles (preconditioning stress-strain curve from 0.03 to 9.0 N and stress-relaxation at 9.0 N during 120 seconds) to analyze the elastic and viscoelastic material properties. The effective elastic modulus was calculated. Statistical analysis was performed with a confidence interval of 95%. RESULTS In stress-strain measurements, the effective elastic modulus was not significantly different (P > .311) between SMILE (13.5 ± 12.8 MPa) and FS-LASIK (7.56 ± 17.9 MPa). In stress-relaxation measurements, the remaining stress was not significantly different (P = .841) between SMILE (124 ± 20 kPa) and FS-LASIK (126 ± 21 kPa). CONCLUSIONS Unlike myopic correction, after hyperopic correction the cap-based procedure (SMILE) and the flap-based technique (FS-LASIK) may be considered equivalent in terms of biomechanical stability when measured experimentally in ex vivo human fellow eye corneas. [J Refract Surg. 2021;37(12):810-815.].
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Bao F, Chen W, Zheng X, Miao Y, Zhu M, Akiti S, Li Y, Weng Z, Wang J, Zhang P, Chen S, Elsheikh A. Changes in Corneal Biomechanical Properties in PRK Followed by Two Accelerated CXL Energy Doses in Rabbit Eyes. J Refract Surg 2021; 37:853-860. [PMID: 34914559 DOI: 10.3928/1081597x-20210830-03] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate whether photorefractive keratectomy (PRK) combined with the two commonly delivered energy doses in accelerated corneal cross-linking (A-CXL) could help the cornea maintain its preoperative stiffness level. METHODS A total of 72 corneas of 36 healthy white Japanese rabbits were randomly divided into four equal groups. The groups included an untreated control group and three that had undergone PRK. After tissue ablation, one of the latter three groups (PRK group) was left untreated, whereas the other two were exposed to riboflavin (0.22% concentration by volume) and ultraviolet-A (370 nm) with the same irradiation (30 mW/cm2) but different CXL energy doses of 1.8 J/cm2 (PXL group) and 2.7 J/cm2 (PXH group). Dynamic Scheimpflug analyzer (Corvis ST; Oculus Optikgeräte GmbH) measurements of stiffness parameter at first applanation (SP-A1), Stress-Strain Index (SSI), and other dynamic corneal response parameters were taken 3 days preoperatively and 1 month postoperatively. Subsequently, ex vivo inflation testing was performed and the tangent modulus of each specimen was estimated using an inverse analysis process. RESULTS In comparison to the control group, the tangent modulus at a stress of 10 kPa decreased by 8.9% in the PRK group and increased by 10.6% and 22.4% in the PXL and PXH groups, respectively. SP-A1 decreased postoperatively in the PRK group (P < .05), indicating an overall stiffness reduction of -7.4, -3.5, and -5.3 mm Hg/mm in PRK, PXL, and PXH groups, respectively. The material stiffness parameter SSI remained almost unchanged in the PRK group (P = .989), increased slightly in the PXL group (8.3%, P = .077), and increased significantly in the PXH group (11.1%) (P < .05). CONCLUSIONS Biomechanical deterioration following PRK was significant and could not be fully compensated for by ACXL with either 1.8 or 2.7 J/cm2 doses. The increased value of corneal overall stiffness was higher in A-CXL with 2.7 J/cm2 energy than with 1.8 J/cm2 energy. [J Refract Surg. 2021;37(12):853-860.].
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Gab-Alla AA. SmartSurfACE transepithelial photorefractive keratectomy with mitomycin C enhancement after small incision lenticule extraction. EYE AND VISION 2021; 8:28. [PMID: 34963489 PMCID: PMC8895781 DOI: 10.1186/s40662-021-00254-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 07/27/2021] [Indexed: 11/16/2022]
Abstract
Background To evaluate predictability, stability, efficacy, and safety of transepithelial photorefractive keratectomy (TPRK) using smart pulse technology (SPT) (SmartSurface procedure) of Schwind Amaris with mitomycin C for correction of post small incision lenticule extraction (SMILE) myopic residual refractive errors. Method This study is a prospective, non-comparative case series conducted at a private eye centre in Ismailia, Egypt, on eyes with post-SMILE myopic residual refractive errors because of undercorrection or suction loss (suction loss occurred after the posterior lenticular cut and the creation of side-cuts; redocking was attempted, and the treatment was completed in the same session with the same parameters) with myopia or myopic astigmatism. The patients were followed up post-SMILE for six months before the SmartSurface procedure, and then they were followed up for one year after that. TPRK were performed using Amaris excimer laser at 500 kHz. The main outcomes included refractive predictability, stability, efficacy, safety and any reported complications. Results This study included 68 eyes of 40 patients out of 1920 total eyes (3.5%) with post-SMILE technique myopic residual refractive errors. The average duration between the SMILE surgery and TPRK was 6.7 ± 0.4 months (range 6 to 8 months). The mean refractive spherical equivalent (SE) was within ± 0.50 D of plano correction in 100% of the eyes at 12 months post-TPRK. Astigmatism of < 0.50 D was achieved in 100% of the eyes. The mean of the residual SE error showed statistically significant improvement from preoperative − 1.42 ± 0.52 D to 0.23 ± 0.10 D (P < 0.0001). Uncorrected distance visual acuity (UDVA) (measured by Snellen's chart and averaged in logMAR units) was improved significantly to 0.1 ± 0.07 (P < 0.0001). UDVA was 0.2 logMAR or better in 100% of the eyes, 0.1 logMAR or better in 91.2% of the eyes, and 0.0 logMAR in 20.6% of the eyes. Corrected distance visual acuity (CDVA) remained unchanged in 79.4% of eyes. 14.7% of eyes gained one line of CDVA (Snellen). 5.9% of eyes gained two lines of CDVA (Snellen). Conclusion Transepithelial photorefractive keratectomy using smart pulse technology with mitomycin C enhancement after SMILE is a safe, predictable, stable, and effective technique.
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Results of thin-cap small-incision lenticule extraction. J Cataract Refract Surg 2021; 47:439-444. [PMID: 33149046 DOI: 10.1097/j.jcrs.0000000000000470] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 09/21/2020] [Indexed: 11/27/2022]
Abstract
PURPOSE To evaluate the influence of a thin cap in small-incision lenticule extraction (SMILE) for the correction of myopia or myopic astigmatism. SETTING Tertiary care private practice. METHODS A chart review of 102 eyes of 51 patients was performed. The effect of 120 µm vs 100 μm cap thickness on postoperative spherical equivalent refraction (SEQ), cylinder, corrected and uncorrected visual acuities, and ease of lenticule separation was assessed in a contralateral manner, whereas all other parameters were identical between eyes (including optical zone, minimum lenticule thickness, incision size, and energy and spot settings) using paired t test. RESULTS At 3 months postoperatively, SMILE with 120 μm cap thickness was undercorrected in SEQ relative to SMILE with 100 μm cap thickness in a cohort of 102 eyes of 51 consecutive patients. The difference of 0.06 ± 0.39 diopter (or 0.7% ± 5.7%) did not reach statistical significance. Postoperative cylinder was not statistically different in both groups. Visual acuity was similar in both groups. Ease of lenticule separation was identical in both groups. Suction time was shorter with a 100 μm cap (P < .005). Postoperative central residual stromal thickness was 20 ± 15 μm thicker with a 100 μm cap (P < .0001). Adverse events were comparable. CONCLUSIONS Postoperative refraction, visual acuity, ease of lenticule separation, and incidence of adverse events were not significantly affected by cap thickness. Surgeons might safely use 100 μm instead of 120 μm caps without nomogram adjustment. Alternatively, after suction loss during the lenticule cut, a second docking with a programmed cap thickness of 100 μm (and a larger optical zone) might be a rescue technique enabling surgeons to still perform the intended SMILE procedure.
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Contribution of Bowman layer to corneal biomechanics. J Cataract Refract Surg 2021; 47:927-932. [PMID: 33315734 DOI: 10.1097/j.jcrs.0000000000000543] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 11/23/2020] [Indexed: 11/26/2022]
Abstract
PURPOSE To compare the elastic modulus of thin corneal lamellas using 2D stress-strain extensometry in healthy ex vivo human corneal lamellas with or without the presence of Bowman layer. SETTING Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Switzerland; ELZA Institute, Dietikon, Switzerland; Department of Ophthalmology, Philipps University of Marburg, Germany. DESIGN Prospective experimental laboratory study. METHODS Healthy human corneas were stripped of Descemet membrane and the endothelium for Descemet membrane endothelial keratoplasty. After epithelium removal, corneas were divided into 2 groups. In Group 1, Bowman layer was ablated with an excimer laser (20 μm thick, 10 mm). In Group 2, Bowman layer was left intact. Then, a lamella was cut from the anterior cornea with an automated microkeratome. Elastic and viscoelastic material properties were analyzed by 2D stress-strain extensometry between 0.03 and 0.70 N. RESULTS Twenty-six human corneas were analyzed. The mean lamella thickness was 160 ± 37 μm in corneas with Bowman layer and 155 ± 22 μm in corneas without. No statistically significant differences between flaps with and without Bowman layer were observed in the tangential elastic modulus between 5% and 20% strain (11.5 ± 2.9 kPa vs 10.8 ± 3.7 kPa, P > .278). CONCLUSIONS The presence or absence of Bowman layer did not reveal a measurable difference in corneal stiffness. This may indicate that the removal of Bowman layer during photorefractive keratectomy does not represent a disadvantage to corneal biomechanics.
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Torres-Netto EA, Spiru B, Kling S, Gilardoni F, Lazaridis A, Sekundo W, Hafezi F. Similar Biomechanical Cross-linking Effect After SMILE and PRK in Human Corneas in an Ex Vivo Model for Postoperative Ectasia. J Refract Surg 2020; 36:49-54. [PMID: 31917851 DOI: 10.3928/1081597x-20191211-01] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 12/10/2019] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate the biomechanical effect of corneal cross-linking (CXL) in paired human corneas following small incision lenticule extraction (SMILE) or photorefractive keratectomy (PRK) in an ex vivo model for postoperative ectasia. METHODS Twenty-six paired human corneas preserved in tissue culture medium were equally divided into two groups: right and left corneas were treated with PRK and SMILE, respectively. Corneal thickness was measured in all eyes before surgery. Corneas were stretched using an extensometer with two cycles of up to 9 N (570 kPA stress), followed by accelerated CXL with irradiance of 9 mW/cm2 for 10 minutes (fluence 5.4 J/cm2) in both groups. The elastic modulus was evaluated using two-dimensional stress-strain extensometry. RESULTS Following accelerated CXL, the ectatic cornea model showed a mean effective elastic modulus of 17.2 ± 5.3 MPa after PRK and 14.1 ± 5.0 MPa after SMILE. Although the elastic modulus in corneas previously subjected to PRK was higher, there was no significant biomechanical difference between the two groups (P = .093). CONCLUSIONS Under similar conditions, both experimental groups (PRK followed by CXL and SMILE followed by CXL) were characterized by similar biomechanical stability as measured experimentally on ex vivo human fellow corneas. The data suggest that, in the event of postoperative ectasia, the biomechanical improvement achieved by CXL may be similar after PRK and SMILE. [J Refract Surg. 2020;36(1):49-54].
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Spiru B, Torres-Netto EA, Kling S, Lazaridis A, Hafezi F, Sekundo W. Biomechanical Properties of Human Cornea Tested by Two-Dimensional Extensiometry Ex Vivo in Fellow Eyes: PRK Versus SMILE. J Refract Surg 2020; 35:501-505. [PMID: 31393988 DOI: 10.3928/1081597x-20190730-02] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2019] [Accepted: 07/30/2019] [Indexed: 11/20/2022]
Abstract
PURPOSE To investigate the biomechanical properties of the ex vivo human paired corneas after completion of photorefractive keratectomy (PRK) versus small incision lenticule extraction (SMILE) in the same donor. METHODS In this experimental study, 13 pairs of human corneas unsuitable for transplantation were equally divided into two groups. Corneal thickness was measured in each eye directly before laser refractive surgery. Corneas from the right eye were treated with PRK and corneas from the left eye with SMILE. All corneas were subjected to a refractive correction of -10.00 diopters (D) sphere and -0.75 D cylinder at 0° with a 7 mm zone, using either surface ablation (PRK) or 130 µm cap (SMILE). For two-dimensional biomechanical measurements, corneoscleral buttons underwent two testing cycles (preconditioning stress-strain curve from 0.03 to 9.0 N and stress-relaxation at 9.0 N during 120 seconds) to analyze the elastic and viscoelastic material properties. The effective elastic modulus was calculated. Statistical analysis was performed with a confidence interval of 95%. RESULTS In stress-strain measurements, the effective elastic modulus was not significantly different (P = .081) between SMILE (9.58 ± 4.26 MPa) and PRK (11.9 ± 4.90 MPa). The effect size was medium (Cohen's d = 0.58). In stress-relaxation measurements, the remaining stress was not significantly different (P = .878) between SMILE (122 ± 33 kPa) and PRK (123 ± 30 kPa). CONCLUSIONS The lenticule extraction procedure (SMILE) and the surface ablation technique (PRK) may be considered equivalent in terms of biomechanical stability when measured experimentally in ex vivo human fellow eye corneas. [J Refract Surg. 2019;35(8):501-505.].
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Moshirfar M, Shah TJ, Masud M, Linn SH, Ronquillo Y, Hoopes PC. Surgical options for retreatment after small-incision lenticule extraction: Advantages and disadvantages. J Cataract Refract Surg 2019; 44:1384-1389. [PMID: 30368350 DOI: 10.1016/j.jcrs.2018.07.047] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 07/19/2018] [Accepted: 07/21/2018] [Indexed: 10/28/2022]
Abstract
Since the inception of small-incision lenticule extraction (SMILE), many surgeons have speculated the lack of an adequate and standard retreatment procedure will impede its popularity. However, more than 1 million patients worldwide have had this surgery, with visual outcomes nearly equivalent to current laser in situ keratomileusis (LASIK) results. With the procedure's growing popularity, some patients will inevitably have a postoperative residual refractive error from regression, overcorrection, undercorrection, and astigmatic induction and will require retreatment. To our knowledge, literature reviewing major retreatment options is limited. Options include surface ablation, thin-flap LASIK, secondary small-incision lenticule extraction, and a cap-to-flap procedure (CIRCLE) in which a femtosecond laser is use to create cuts that convert the small-incision lenticule extraction cap into a LASIK flap. This review discusses major advantages and disadvantages of these options and compares the visual outcomes based on the existing literature. An algorithmic approach created from this analysis is presented to guide retreatment decision-making.
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Affiliation(s)
- Majid Moshirfar
- From the John A. Moran Eye Center (Moshirfar, Hoopes) and the University of Utah (Masud), Salt Lake City, Utah Lions Eye Bank (Moshirfar), Murray, and the HDR Research Center (Moshirfar, Linn, Ronquillo, Hoopes), Hoopes Vision, Draper, Utah; Department of Ophthalmology, University of Arizona College of Medicine-Phoenix (Shah), Phoenix, Arizona, USA.
| | - Tirth J Shah
- From the John A. Moran Eye Center (Moshirfar, Hoopes) and the University of Utah (Masud), Salt Lake City, Utah Lions Eye Bank (Moshirfar), Murray, and the HDR Research Center (Moshirfar, Linn, Ronquillo, Hoopes), Hoopes Vision, Draper, Utah; Department of Ophthalmology, University of Arizona College of Medicine-Phoenix (Shah), Phoenix, Arizona, USA
| | - Maliha Masud
- From the John A. Moran Eye Center (Moshirfar, Hoopes) and the University of Utah (Masud), Salt Lake City, Utah Lions Eye Bank (Moshirfar), Murray, and the HDR Research Center (Moshirfar, Linn, Ronquillo, Hoopes), Hoopes Vision, Draper, Utah; Department of Ophthalmology, University of Arizona College of Medicine-Phoenix (Shah), Phoenix, Arizona, USA
| | - Steven H Linn
- From the John A. Moran Eye Center (Moshirfar, Hoopes) and the University of Utah (Masud), Salt Lake City, Utah Lions Eye Bank (Moshirfar), Murray, and the HDR Research Center (Moshirfar, Linn, Ronquillo, Hoopes), Hoopes Vision, Draper, Utah; Department of Ophthalmology, University of Arizona College of Medicine-Phoenix (Shah), Phoenix, Arizona, USA
| | - Yasmyne Ronquillo
- From the John A. Moran Eye Center (Moshirfar, Hoopes) and the University of Utah (Masud), Salt Lake City, Utah Lions Eye Bank (Moshirfar), Murray, and the HDR Research Center (Moshirfar, Linn, Ronquillo, Hoopes), Hoopes Vision, Draper, Utah; Department of Ophthalmology, University of Arizona College of Medicine-Phoenix (Shah), Phoenix, Arizona, USA
| | - Phillip C Hoopes
- From the John A. Moran Eye Center (Moshirfar, Hoopes) and the University of Utah (Masud), Salt Lake City, Utah Lions Eye Bank (Moshirfar), Murray, and the HDR Research Center (Moshirfar, Linn, Ronquillo, Hoopes), Hoopes Vision, Draper, Utah; Department of Ophthalmology, University of Arizona College of Medicine-Phoenix (Shah), Phoenix, Arizona, USA
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Siedlecki J, Luft N, Priglinger SG, Dirisamer M. Enhancement Options After Myopic Small-Incision Lenticule Extraction (SMILE): A Review. Asia Pac J Ophthalmol (Phila) 2019; 8:406-411. [PMID: 31513041 PMCID: PMC6784780 DOI: 10.1097/apo.0000000000000259] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Accepted: 08/06/2019] [Indexed: 11/29/2022] Open
Abstract
PURPOSE To provide an overview of the currently available retreatment methods after myopic small-incision lenticule extraction (SMILE). DESIGN Systematic literature review. METHODS The PubMed library was searched for articles containing the terms "small-incision lenticule extraction" and "enhancement" or "retreatment". The last search was performed on May 1, 2019. RESULTS In contrast to laser in-situ keratomileusis (LASIK), which can be retreated by a flap relift, repeat SMILE retreatment is currently not approved and only seldomly performed. As substitutes, surface ablation, cap-to-flap conversion using the CIRCLE program in the VisuMax platform, and thin-flap LASIK have been recently established. While all options offer safety and efficacy comparable to LASIK retreatments, each has its patient-specific advantages and disadvantages. While surface ablation preserves the flap-free approach of the primary procedure, the aspect of pain and a slow visual recovery might render it less attractive as compared with CIRCLE and thin-flap LASIK which offer quick recovery, however at the price of flap creation. Besides, each retreatment method generates specific tissue responses and has a different impact on corneal biomechanics, which is strongly dependent on the previous SMILE parameters, especially the cap thickness. CONCLUSIONS Refractive enhancement after SMILE is currently mostly performed by surface ablation, CIRCLE cap-to-flap conversion or thin-flap LASIK, which all offer safety and efficacy comparable to LASIK retreatments. In this review, a detailed overview over each method, its technical aspects, and specific advantages and disadvantages is given.
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Affiliation(s)
- Jakob Siedlecki
- Department of Ophthalmology, Ludwig-Maximilians-University, Munich, Germany
- SMILE Eyes Linz, Austria
| | - Nikolaus Luft
- Department of Ophthalmology, Ludwig-Maximilians-University, Munich, Germany
- SMILE Eyes Linz, Austria
| | - Siegfried G. Priglinger
- Department of Ophthalmology, Ludwig-Maximilians-University, Munich, Germany
- SMILE Eyes Linz, Austria
| | - Martin Dirisamer
- Department of Ophthalmology, Ludwig-Maximilians-University, Munich, Germany
- SMILE Eyes Linz, Austria
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Siedlecki J, Siedlecki M, Luft N, Kook D, Meyer B, Bechmann M, Wiltfang R, Sekundo W, Priglinger SG, Dirisamer M. Surface Ablation Versus CIRCLE for Myopic Enhancement After SMILE: A Matched Comparative Study. J Refract Surg 2019; 35:294-300. [PMID: 31059578 DOI: 10.3928/1081597x-20190416-02] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 04/15/2019] [Indexed: 11/20/2022]
Abstract
PURPOSE To compare the outcomes of enhancement after small incision lenticule extraction (SMILE) using surface ablation versus the VisuMax CIRCLE option (Carl Zeiss Meditec AG, Jena, Germany), which converts the SMILE cap into a femtosecond laser-assisted laser in situ keratomileusis flap. METHODS The databases of the SMILE Eyes centers in Munich, Marburg, and Cologne, Germany, and Linz, Austria, were screened for eyes that had undergone enhancement using surface ablation with mitomycin C or CIRCLE. Eyes from both enhancement methods suitable for a retrospective matched analysis were identified based on pre-SMILE and pre-enhancement mean refractive spherical equivalent (MRSE), astigmatism, age, and corrected and uncorrected distance visual acuity (CDVA/UDVA). Refractive and functional outcomes were compared after a follow-up of 3 months. RESULTS After the application of the matching criteria on 2,803 SMILE procedures, 24 eyes (12 in each group) with a follow-up of 3 months or longer were available for analysis. Enhancement was performed after a mean 9.7 ± 7.2 (surface ablation) and 11.0 ± 4.4 (CIRCLE) months for a residual MRSE of -0.91 ± 0.55 (surface ablation) and -0.90 ± 0.61 (CIRCLE) diopters. At 3 months, residual MRSE showed comparable accuracy with -0.07 ± 0.19 (surface ablation) and 0.04 ± 0.22 (CIRCLE) diopters (P = .18). UDVA improvement was similar to a final value of 0.02 ± 0.10 (surface ablation) versus 0.03 ± 0.07 (CIRCLE) logMAR (P = .78). Only one eye in the surface ablation group and no eye in the CIRCLE group lost one line of CDVA. At 3 months, the safety (surface ablation: 1.00, CIRCLE: 1.06; P = .36) and efficacy (surface ablation: 0.95, CIRCLE: 1.03; P = .36) indices were equivalent. In terms of speed of visual recovery, at week 1 UDVA and CDVA were significantly better after CIRCLE than surface ablation (P = .008 and .002, respectively). CONCLUSIONS In this first study directly comparing surface ablation versus CIRCLE enhancement after SMILE, both methods yielded comparable results at 3 months. However, CIRCLE re-treated eyes showed a markedly increased speed of recovery concerning UDVA and CDVA compared to surface ablation. [J Refract Surg. 2019;35(5):294-300.].
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Torres-Netto EA, Kling S, Hafezi N, Vinciguerra P, Randleman JB, Hafezi F. Oxygen Diffusion May Limit the Biomechanical Effectiveness of Iontophoresis-Assisted Transepithelial Corneal Cross-linking. J Refract Surg 2018; 34:768-774. [DOI: 10.3928/1081597x-20180830-01] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Accepted: 08/30/2018] [Indexed: 11/20/2022]
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Garcia-Gonzalez M, Teus MA. Comments on "Biomechanical Properties of Human Cornea Tested by Two-Dimensional Extensiometry Ex Vivo in Fellow Eyes". J Refract Surg 2018; 34:783. [PMID: 30428100 DOI: 10.3928/1081597x-20180904-01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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17
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Spiru B, Kling S, Hafezi F, Sekundo W. Biomechanical Properties of Human Cornea Tested by Two-Dimensional Extensiometry Ex Vivo in Fellow Eyes: Femtosecond Laser-Assisted LASIK Versus SMILE. J Refract Surg 2018; 34:419-423. [PMID: 29889296 DOI: 10.3928/1081597x-20180402-05] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 04/02/2018] [Indexed: 11/20/2022]
Abstract
PURPOSE To investigate the biomechanical properties of the ex vivo human cornea after flap-based versus cap-based laser refractive surgery in the same donor. METHODS In this experimental study, 11 pairs of human corneas unsuitable for transplantation were equally divided into two groups. Corneas from the right eye were treated with femtosecond laser-assisted LASIK (FSLASIK) and corneas from the left eye with small incision lenticule extraction (SMILE). Pachymetry was measured in each eye directly before laser refractive surgery. All corneas were subjected to a refractive correction of -10.00 diopters (D) sphere and -0.75 D cylinder at 0° with a 7-mm zone, using either a 110-μm flap (FS-LASIK) or 130-μm cap (SMILE). For two-dimensional biomechanical measurements, corneoscleral buttons underwent two testing cycles (preconditioning stress-strain curve from 0.03 to 9.0 N and stress-relaxation at 9.0 N during 120 sec) to analyze the elastic and viscoelastic material properties. The effective elastic modulus was calculated. Statistical analysis was performed with a confidence interval of 95%. RESULTS In stress-strain measurements, the effective elastic modulus was 1.47 times higher (P = .003) after SMILE (median = 8.22 [interquartile range = 4.76] MPa) compared to FS-LASIK (median = 5.59 [inter-quartile range = 2.77] MPa). The effect size was large (r = 0.83). No significant differences (P = .658) were observed among stress-relaxation measurements, with a mean remaining stress of 181 ± 31 kPa after SMILE and 177 ± 26 kPa after FS-LASIK after relaxation. CONCLUSIONS Compared to a flap-based procedure such as FS-LASIK, the SMILE technique can be considered superior in terms of biomechanical stability, when measured experimentally in ex vivo human fellow eye corneas. [J Refract Surg. 2018;34(6):419-423.].
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Chiche A, Trinh L, Baudouin C, Denoyer A. [SMILE (Small Incision Lenticule Extraction) among the corneal refractive surgeries in 2018 (French translation of the article)]. J Fr Ophtalmol 2018; 41:650-658. [PMID: 30170707 DOI: 10.1016/j.jfo.2018.03.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 03/05/2018] [Accepted: 03/13/2018] [Indexed: 11/24/2022]
Abstract
Refractive surgery is a field in constant evolution. In recent years, a new procedure has appeared under the name SMILE (Small Incision Lenticule Extraction). This technique, carried out solely with a femtosecond laser, should make it possible to better preserve corneal innervation and biomechanics. After a detailed review of the technique itself, we then focus on the scientific evidence for the safety and efficacy of SMILE and its current indications. Advantages of SMILE will be discussed in comparison to disadvantages of the conventional techniques, particularly concerning dry eye and the risk of corneal ectasia with LASIK. Lastly, the current limitations of SMILE (indications, retreatment) are discussed, and future applications are considered regarding improvements in the technique.
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Affiliation(s)
- A Chiche
- Service d'ophtalmologie 3, centre hospitalier national d'ophtalmologie des Quinze-Vingts, université de Versailles-Saint-Quentin-en-Yvelines, 28, rue de Charenton, 75012 Paris, France
| | - L Trinh
- Service d'ophtalmologie 3, centre hospitalier national d'ophtalmologie des Quinze-Vingts, université de Versailles-Saint-Quentin-en-Yvelines, 28, rue de Charenton, 75012 Paris, France; Espace Nouvelle Vision, 6, rue de la Grande Chaumière, 75006 Paris, France
| | - C Baudouin
- Service d'ophtalmologie 3, centre hospitalier national d'ophtalmologie des Quinze-Vingts, université de Versailles-Saint-Quentin-en-Yvelines, 28, rue de Charenton, 75012 Paris, France; Inserm U968, université UPMC Paris VI, UMR S 968, CNRS, UMR 7210, 75012 Paris, France
| | - A Denoyer
- Inserm U968, université UPMC Paris VI, UMR S 968, CNRS, UMR 7210, 75012 Paris, France; Hôpital Robert-Debré, CHU de Reims, rue du Général Koenig, 51100 Reims, France; URCA, université de Reims-Champagne-Ardenne, Reims, France.
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19
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Vanathi M. Advances in Cornea. Open Ophthalmol J 2018; 12:130-133. [PMID: 30123377 PMCID: PMC6062899 DOI: 10.2174/1874364101812010130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Chiche A, Trinh L, Baudouin C, Denoyer A. SMILE (Small Incision Lenticule Extraction) among the corneal refractive surgeries in 2018. J Fr Ophtalmol 2018; 41:e245-e252. [PMID: 29914764 DOI: 10.1016/j.jfo.2018.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 04/27/2018] [Accepted: 05/15/2018] [Indexed: 11/27/2022]
Abstract
Refractive surgery is a field in constant evolution. In recent years, a new procedure has appeared under the name SMILE (SMall Incision Lenticule Extraction). This technique, carried out solely with a femtosecond laser, should make it possible to better preserve corneal innervation and biomechanics. After a detailed review of the technique itself, we then focus on the scientific evidence for the safety and efficacy of SMILE and its current indications. Advantages of SMILE will be discussed in comparison to the conventional techniques, particularly concerning dry eye and the risk of corneal ectasia related to LASIK. Lastly, the current limitations of SMILE (indications, retreatment) are discussed, and future applications are considered regarding new improvements in the technique.
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Affiliation(s)
- A Chiche
- Ophthalmology Service 3, Quinze-Vingts National Ophthalmology Hospital, University of Versailles Saint-Quentin-en-Yvelines, 78000 Versailles, France
| | - L Trinh
- Ophthalmology Service 3, Quinze-Vingts National Ophthalmology Hospital, University of Versailles Saint-Quentin-en-Yvelines, 78000 Versailles, France; Espace Nouvelle Vision, 75012 Paris, France
| | - C Baudouin
- Ophthalmology Service 3, Quinze-Vingts National Ophthalmology Hospital, University of Versailles Saint-Quentin-en-Yvelines, 78000 Versailles, France; INSERM, U968, 75012 Paris, France; UMR S 968, Institut de la Vision, University UPMC Paris VI, 75012 Paris, France; CNRS, UMR 7210, 75012 Paris, France
| | - A Denoyer
- INSERM, U968, 75012 Paris, France; UMR S 968, Institut de la Vision, University UPMC Paris VI, 75012 Paris, France; CNRS, UMR 7210, 75012 Paris, France; University Hospital Robert-Debré, rue du Général-Koenig, 51100 Reims, France; URCA, University of Reims Champagne-Ardenne, 51100 Reims, France.
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Fernández J, Rodríguez-Vallejo M, Martínez J, Tauste A, Piñero DP. Corneal biomechanics after laser refractive surgery: Unmasking differences between techniques. J Cataract Refract Surg 2018; 44:390-398. [PMID: 29615281 DOI: 10.1016/j.jcrs.2017.10.054] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Revised: 10/02/2017] [Accepted: 10/03/2017] [Indexed: 10/17/2022]
Abstract
The hypothesis that small-incision lenticule extraction provides better preservation of corneal biomechanics than previous laser refractive techniques has led to a growth in the interest in clinical and experimental research in this field. This hypothesis is based on the fact that corneal layers with greater stiffness are preserved with this new technique. However, this hypothesis is controversial because clinical research has shown a great disparity in the outcomes. In this review, we performed an in-depth analysis of the factors that might affect corneal biomechanics in laser refractive surgery procedures from a macrostructural to a microstructural viewpoint. New advances in algorithms with current devices or the introduction of new devices might help unmask the possible advantages of small-incision lenticule extraction in corneal biomechanics.
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Affiliation(s)
- Joaquín Fernández
- From the Department of Ophthalmology (Qvision) (Fernández, Rodríguez-Vallejo, Martínez, Tauste), Vithas Virgen del Mar Hospital and the Department of Ophthalmology (Fernández, Piñero), Torrecárdenas Hospital Complex, Almería, and the Department of Optics, Pharmacology and Anatomy (Piñero), University of Alicante, and the Department of Ophthalmology (Piñero), Vithas Medimar International Hospital, Alicante, Spain
| | - Manuel Rodríguez-Vallejo
- From the Department of Ophthalmology (Qvision) (Fernández, Rodríguez-Vallejo, Martínez, Tauste), Vithas Virgen del Mar Hospital and the Department of Ophthalmology (Fernández, Piñero), Torrecárdenas Hospital Complex, Almería, and the Department of Optics, Pharmacology and Anatomy (Piñero), University of Alicante, and the Department of Ophthalmology (Piñero), Vithas Medimar International Hospital, Alicante, Spain.
| | - Javier Martínez
- From the Department of Ophthalmology (Qvision) (Fernández, Rodríguez-Vallejo, Martínez, Tauste), Vithas Virgen del Mar Hospital and the Department of Ophthalmology (Fernández, Piñero), Torrecárdenas Hospital Complex, Almería, and the Department of Optics, Pharmacology and Anatomy (Piñero), University of Alicante, and the Department of Ophthalmology (Piñero), Vithas Medimar International Hospital, Alicante, Spain
| | - Ana Tauste
- From the Department of Ophthalmology (Qvision) (Fernández, Rodríguez-Vallejo, Martínez, Tauste), Vithas Virgen del Mar Hospital and the Department of Ophthalmology (Fernández, Piñero), Torrecárdenas Hospital Complex, Almería, and the Department of Optics, Pharmacology and Anatomy (Piñero), University of Alicante, and the Department of Ophthalmology (Piñero), Vithas Medimar International Hospital, Alicante, Spain
| | - David P Piñero
- From the Department of Ophthalmology (Qvision) (Fernández, Rodríguez-Vallejo, Martínez, Tauste), Vithas Virgen del Mar Hospital and the Department of Ophthalmology (Fernández, Piñero), Torrecárdenas Hospital Complex, Almería, and the Department of Optics, Pharmacology and Anatomy (Piñero), University of Alicante, and the Department of Ophthalmology (Piñero), Vithas Medimar International Hospital, Alicante, Spain
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