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Hira S, Klein Heffel K, Mehmood F, Sehgal K, Felix De Farias Santos AC, Steuernagel Del Valle G. Comparison of refractive surgeries (SMILE, LASIK, and PRK) with and without corneal crosslinking: systematic review and meta-analysis. J Cataract Refract Surg 2024; 50:523-533. [PMID: 38288954 DOI: 10.1097/j.jcrs.0000000000001405] [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: 11/15/2023] [Accepted: 01/22/2024] [Indexed: 04/24/2024]
Abstract
Corneal crosslinking (CXL) is used for treating keratoconus and post-laser in situ keratomileusis ectasia. However, refractive surgery is not usually performed with prophylactic CXL. Therefore, we performed a meta-analysis comparing outcomes of refractive surgeries with vs without prophylactic CXL. We systematically searched databases for studies comparing refractive surgeries for myopic correction with vs without prophylactic corneal crosslinking. Review Manager 5.4.1 was used to perform statistical analysis. We included 2820 eyes from 28 studies. Compared with refractive surgery alone, surgery with prophylactic CXL resulted in decreased central corneal thickness, corrected distance visual acuity logMAR, and safety and efficacy indices. There were no significant differences in postoperative uncorrected distance visual acuity of 20/20 or better at ≥12 months and other visual outcomes among both groups. More randomized controlled trials with standard crosslinking protocols are needed to analyze the prophylactic use of crosslinking with refractive surgeries.
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Affiliation(s)
- Sara Hira
- From the FMH College of Medicine & Dentistry, Lahore, Pakistan (Hira); Federal University of Pelotas, Pelotas, Brazil (Klein Heffel); Department of Ophthalmology, Fatima Memorial Hospital, Lahore, Pakistan (Mehmood); Teerthanker Mahaveer University, Moradabad, UP, India (Sehgal); City University of São Paulo, São Paulo, Brazil (Felix De Farias Santos); University of Iowa, Iowa City, Iowa (Steuernagel Del Valle)
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Al-Mahrouqi H, Cheung IMY, Angelo L, Yu TY, Gokul A, Ziaei M. Therapeutic non-ectasia applications of cornea cross-linking. Clin Exp Optom 2023; 106:580-590. [PMID: 36690333 DOI: 10.1080/08164622.2022.2159790] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2022] [Revised: 08/28/2022] [Accepted: 10/10/2022] [Indexed: 01/25/2023] Open
Abstract
Corneal cross-linking is a photopolymerization technique traditionally used to strengthen corneal tissue. Corneal cross-linking utilizes riboflavin (vitamin B2) as a photosensitizer and ultraviolet-A light (UVA) to create strong covalent bonds within the corneal stroma, increasing tissue stiffness. Multiple studies have demonstrated corneal cross-linking's effectiveness in treating corneal ectasia, a progressive, degenerative, and non-inflammatory thinning disorder, as quantified by key tomographic, refractive, and visual parameters. Since its introduction two decades ago, corneal cross-linking has surpassed its original application in halting corneal ectatic disease and its application has expanded into several other areas. Corneal cross-linking also possesses antibacterial, antienzymolytic and antioedematous properties, and has since become a tool in treating microbial keratitis, correcting refractive error, preventing iatrogenic ectasia, stabilising bullous keratopathy and controlling post keratoplasty ametropia. This review provides an overview of the current evidence base for the therapeutic non-ectasia applications of cornea cross-linking and looks at future developments in the field.
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Affiliation(s)
| | | | - Lize Angelo
- Department of Ophthalmology, University of Auckland, Auckland, New Zealand
| | - Tzu-Ying Yu
- Department of Ophthalmology, Greenlane Clinical Centre, Auckland District Health Board, Auckland, New Zealand
| | - Akilesh Gokul
- Department of Ophthalmology, University of Auckland, Auckland, New Zealand
| | - Mohammed Ziaei
- Department of Ophthalmology, University of Auckland, Auckland, New Zealand
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Clinical Outcomes Comparison of Combined Small Incision Lenticule Extraction with Collagen Cross-Linking Versus Small Incision Lenticule Extraction Only. J Ophthalmol 2022; 2022:2625517. [PMID: 36267955 PMCID: PMC9578865 DOI: 10.1155/2022/2625517] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 06/28/2022] [Accepted: 08/25/2022] [Indexed: 12/04/2022] Open
Abstract
Purpose To evaluate clinical outcome during 24 months follow-up between small incision lenticule extraction combined with cross-linking (SMILE Xtra) and small incision lenticule extraction (SMILE) only. Setting. Ophthalmology Division of San Rossore Medical Center, Pisa, Italy. Design Retrospective comparative case series. Methods The study comprised 70 eyes (35 patients); 40 eyes were corrected using SMILE and 30 eyes were corrected using SMILE Xtra using a low energy protocol. The outcomes were compared at 1, 6, 12, and 24 months postoperatively. Results The mean spherical equivalent (SEQ) reduced from −7.18 ± 1.21 D to −0.01 ± 0.09 D in the SMILE group and from −6.20 ± 2.99 D to −0.04 ± 0.1 D postoperatively in SMILE Xtra (p < 0.05). At 24 months the mean SEQs were −0.01 ± 0.24 D for SMILE and −0.15 ± 0.33 D for SMILE Xtra (p > 0.05). At 1, 6, 12, and 24 months, there were no statistically significant differences between the SMILE and SMILE Xtra groups in logarithm of the minimum angle of resolution (logMAR) uncorrected distance visual acuity (UDVA), safety, and efficacy index (p > 0.05). The mean average keratometry (K-avg) at 1, 6, 12, and 24 months after surgery did not shown any statistically significant difference between SMILE and SMILE Xtra group (p > 0.05). The mean maximum keratometry (K-max) readings at 1, 6, 12, and 24 months were not statistically significant between SMILE and SMILE Xtra group (p > 0.05). The preoperative mean thinnest point pachymetry (TTP) was 543.90 ± 22.85 μm in the SMILE group and 523.40 ± 37.01 μm in the SMILE Xtra group (p < 0.05). At 1, 6, 12, and 24 months the mean TTP was not statistically significant between the SMILE and SMILE Xtra groups (p > 0.05). At 24 months, the TTP was 408.29 ± 38.75 μm for the SMILE group and 402.22 ± 37 μm for the SMILE Xtra group (p > 0.05). In the preoperative period, the mean maximum posterior elevation (MPE) was 8.63 ± 4.35 μm for SMILE and 8.13 ± 2.54 μm for SMILE Xtra (p > 0.05). After the surgical procedure, both groups showed a statistically significant increase of the MPE (p < 0.05). At 24 months, the MPE was 11.00 ± 4.72 μm for SMILE Xtra and 10.14 ± 3.85 μm for the SMILE group (p > 0.05). In the preoperative period, the means of the root mean square (RMS) of high-order aberration (HOA) were 0.08 ± 0.03 μm for the SMILE group and 0.08 ± 0.03 μm for the SMILE Xtra group (p > 0.05). At 24 months, the RMS of HOA was 0.13 ± 0.07 μm for the SMILE group and 0.14 ± 0.07 μm for the SMILE Xtra group (p > 0.05). In the preoperative period, the root mean square of coma aberration (RMS-Coma) aberration was 0.06 ± 0.09 μm for the SMILE group and 0.04 ± 0.03 μm for the SMILE Xtra group (p > 0.05). At 24 months, the coma aberration of SMILE group was 0.12 ± 0.21 μm and 0.16 ± 0.25 μm for SMILE Xtra group (p > 0.05). Conclusions SMILE Xtra procedure is a safe and simple procedure that can be offered to patients with high corneal ectasia risk because there were no differences in the indices of ectasia compared to the group treated only with SMILE which has a low corneal ectatic risk.
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Mo F, Di Y, Li Y. Changes in Corneal Morphology and Biomechanics in Cases of Small Incision Lenticule Extraction with Prophylactic Accelerated Collagen Cross-Linking. J Ophthalmol 2022; 2022:1640249. [PMID: 35859778 PMCID: PMC9293522 DOI: 10.1155/2022/1640249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Accepted: 06/12/2022] [Indexed: 11/18/2022] Open
Abstract
Purpose To study the corneal morphology and biomechanics in cases of small incision lenticule extraction with prophylactic accelerated collagen cross-linking (SMILE Xtra). Methods This study was a retrospective study. 28 eyes of 14 patients with moderate-high risk of postoperative ectasia according to the Randleman scoring system underwent SMILE Xtra procedure. Outcome data were recorded including uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent (MRSE), surface regularity index (SRI), surface asymmetry index (SAI), simulated keratometry (SimK), posterior axial curvature (PAC), anterior and posterior corneal elevations (ACE and PCE), central corneal thickness (CCT), corneal resistance factor (CRF), corneal hysteresis (CH), and cornea-compensated intraocular pressure (IOPcc). The follow-up period was 12 months. Results There were 28, 26, 22, 12, and 10 eyes enrolled at postoperative 1st day and 1st, 3rd, 6th, and 12th months, respectively. The UDVA improved from 1.27 ± 0.18 logMAR preoperatively to -0.06 ± 0.04 logMAR postoperatively (P < 0.05). The MRSE improved from -5.05 ± 1.15 D preoperatively to -0.14 ± 0.30 D postoperatively (P < 0.05). SAI, SimK, PAC, PCE, and CCT all changed significantly at 1st month postoperatively (P < 0.05) and stabilized during the remainder of the follow-up (P > 0.05). There was no significant change in SRI or ACE before and after surgery (P > 0.05). CRF, CH, and IOPcc all decreased significantly at 1st month postoperatively (P < 0.05) and remained stable afterwards (P > 0.05). Conclusions The changes in the corneal morphology and biomechanics remained stable after SMILE Xtra, and there was no sign of postoperative ectasia or refractive regression. Combined with the improvement of visual and refractive results, SMILE Xtra may be a promising method for corneal refractive surgeries in patients at risk.
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Affiliation(s)
- Fei Mo
- Department of Ophthalmology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Yu Di
- Department of Ophthalmology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Ying Li
- Department of Ophthalmology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China
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Comparison of the Clinical Outcomes between Combined Femtosecond Laser-Assisted In Situ Keratomileusis and Corneal Cross Linking versus Combined Small-Incision Lenticule Extraction and Corneal Cross Linking. J Ophthalmol 2022; 2022:6994355. [PMID: 35140987 PMCID: PMC8820861 DOI: 10.1155/2022/6994355] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2021] [Accepted: 12/27/2021] [Indexed: 11/22/2022] Open
Abstract
Purpose The purpose of this study was to compare femtosecond laser-assisted in situ keratomileusis with prophylactic cross linking (FS-LASIK Xtra) and small-incision lenticule extraction with prophylactic cross linking (SMILE Xtra) in terms of their postoperative clinical outcomes. Methods In this retrospective study, 24 patients (48 eyes) with myopia and myopia astigmatism were recruited from 2017 to 2018. All patients underwent comprehensive ophthalmic examinations preoperatively and follow-up visits at one and three months. Four patients (eight eyes) in each group were followed up for 12 months. The following were assessed at each visit: uncorrected distance visual acuity (UDVA), manifest refractive spherical equivalent (MRSE), keratometry values, biomechanical properties, anterior and posterior curvature, and corneal pachymetry. Results The FS-LASIK Xtra and SMILE Xtra groups both included 24 eyes of 12 patients. At 1, 3, and 12 months after surgery, a UDVA of 20/20 or better was achieved for 91.7%, 91.7%, and 87.5% of individuals, respectively, in the FS-LASIK group and 95.8%, 100%, and 100% in the SMILE group, respectively. For 75% of eyes in the FS-LASIK Xtra group and 100% of eyes in the SMILE Xtra group, the achieved MRSE was within ±1.00D of attempted correction. The LASIK Xtra group had a significantly higher mean MRSE than the SMILE Xtra group at 3 and 12 months after surgery (P=0.006, 0.01), and the SMILE Xtra group had significantly higher K1 and K2 values than the FS-LASIK group at one month after surgery (P=0.024, 0.023). Corneal thickness decreased significantly at one month postoperatively and started to increase over the next 12 months in both groups (P=0.001). The biomechanical properties showed no significant intergroup differences at the 12-month follow-up. Conclusions FS-LASIK Xtra and SMILE Xtra are safe and effective in the correction of myopia and myopia astigmatism, and both procedures have the same effect on postoperative corneal morphology and biomechanics.
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Nicula CA, Nicula D, Bolboacă SD, Bulboacă AE. One year outcomes after small incision lenticule extraction ReLEX in the correction of myopia and myopic astigmatism. BMC Ophthalmol 2021; 21:423. [PMID: 34879853 PMCID: PMC8656009 DOI: 10.1186/s12886-021-02195-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Accepted: 11/29/2021] [Indexed: 12/02/2022] Open
Abstract
Purpose To report the visual and refractive outcomes of small incision lenticule extraction ReLEX (SMILE) technique using VisuMax femtosecond laser in myopia and myopic astigmatism patients. Material and methods A non-randomized clinical study has been conducted on patients with myopia and myopic astigmatism who underwent ReLEX SMILE technique, using the Zeiss VisuMax Laser system (Carl Zeiss Meditec AG, Jena, Germany) at Oculens Clinic, Cluj-Napoca, Romania. Patients older than 18 years, with ocular astigmatism up to -5 diopters (D), spherical equivalent up to -10.00 D, corrected distance visual acuity (CDVA) of 0.3 or better before the surgery, stable refraction for one year, and with a minimum calculated post operator residual stromal bed of 250μ were included in the study. Results The study involved a total of 25 myopic eyes (median of sphere diopters equal with -4D) and 67 myopic astigmatic eyes (median of cylinder diopters equal with -1.5 D). The mean refractive spherical equivalent (MRSE) on patients with myopic eyes reduced from -4.25D (median) to -0.5D at one month follow-up, -0.25 D at 6 and 12 months. The mean refractive spherical equivalent (MRSE) on patients with astigmatic myopic eyes reduced from-6.25 D to -0.67 D at one month, -0.62 D at six and twelve months. The value of sphere decreased postoperatively on myopic eyes with a median of -0.25D at one, six and twelve months. The value of cylinder decreased postoperatively on myopic astigmatic eyes with a median of -0.50 D at one month, -0.25 D at six months and -0.50 D at 12 months. At 6 and 12 months, 20 (80.0%) of myopic eyes were maintained within ±0.5 D and 22 (88.0%) with ±1D. On both groups (myopic eyes and myopic astigmatic eyes), statistically significant differences were observed when the keratometric baseline values were compared to each follow-up (P-values < 0.0001), without any significant differences between follow-ups (P-values>0.15). At 1-month follow-up, uncorrected distance visual acuity (UDVA) was better than or equal to 0.5 in 88.0% of myopic eyes and 82.1% of myopic astigmatic eyes. UDVA remained stable in all cases of myopic eyes at six months and the percentage increased at 92.0% in myopic eyes. UDVA slightly increased at 6-months (85.1%) and remained at the same value at 12-months in myopic astigmatism eyes. Conclusions SMILE proved an effective and safe refractive corneal procedure and provided a predictable and stable correction of myopia and myopic astigmatism. SMILE technique demonstrated very good outcomes in terms of keratometric, cylinder, spherical measurements.
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Affiliation(s)
- Cristina Ariadna Nicula
- Department of Ophthalmology, "Iuliu Hațieganu" University of Medicine and Pharmacy, Victor Babeș Str., no. 8, 400012, Cluj-Napoca, Romania.,Oculens Clinic, Calea Turzii, No. 134-136, 400501, Cluj-Napoca, Romania
| | - Dorin Nicula
- Oculens Clinic, Calea Turzii, No. 134-136, 400501, Cluj-Napoca, Romania
| | - Sorana D Bolboacă
- Department of Medical Informatics and Biostatistics, "Iuliu Hațieganu" University of Medicine and Pharmacy, Louis Pasteur Str., no. 6, 400349, Cluj-Napoca, Romania.
| | - Adriana Elena Bulboacă
- Department of Pathophysiology, "Iuliu Hațieganu" University of Medicine and Pharmacy, Victor Babeș Str., no. 8, 400012, Cluj-Napoca, Romania
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Liang C, Zhang Y, He Y, Wang S. Research Progress on Morphological Changes and Surgery-related Parameters of Corneal Cap in Small Incision Lenticule Extraction. Ophthalmic Res 2021; 65:4-13. [PMID: 34670218 DOI: 10.1159/000520241] [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: 06/11/2021] [Accepted: 10/10/2021] [Indexed: 11/19/2022]
Abstract
Small incision lenticule extraction (SMILE) is an "all-in-one" surgical method for refractive correction. An advantage of the SMILE over traditional surgery is that it depends on the corneal cap's design. This review discusses the morphological evaluation of the corneal cap, selection of the corneal cap with different thickness and diameters, influence of the corneal cap design on retreatment, and management of corneal cap-related complications. The following points should be recognized to define the correct morphology and design of the operation-related parameters of the corneal cap during SMILE: (1) the thickness and diameter of the corneal cap are predictable and influence postoperative visual quality, (2) the change in anterior surface curvature of the corneal cap should be considered in the design of nomogram value, (3) for patients with moderate myopic correction, early visual quality is better with a 6.9-mm than with a 7.5-mm diameter corneal cap, (4) there is no significant difference in visual quality or biomechanics among corneal caps with different thickness; (5) primary corneal cap thickness plays an important role in the SMILE retreatment, (6) a 7.78-mm diameter corneal cap has a greater risk of suction loss than a 7.60-mm diameter corneal cap, (6) if suction loss occurs when lenticular scanning exceeds 10%, then SMILE can be continued by changing corneal cap thickness, (7) preventive collagen cross-linking with SMILE caps are 90-120 μm thick and 7-7.8 mm in diameter, and (8) properly treating SMILE-related complications ensures better postoperative results. The data presented herein shall deepen the understanding of the importance of the corneal cap during SMILE and provide diversified analysis for personalized operational design of corneal cap parameters.
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Affiliation(s)
- Chen Liang
- Corneal Refraction Department, The Second Hospital of Jilin University, Changchun, China,
| | - Yan Zhang
- Corneal Refraction Department, The Second Hospital of Jilin University, Changchun, China
| | - Yuxi He
- Corneal Refraction Department, The Second Hospital of Jilin University, Changchun, China
| | - Shurong Wang
- Corneal Refraction Department, The Second Hospital of Jilin University, Changchun, China
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Comparative study of small-incision lenticule extraction with and without prophylactic corneal crosslinking: 1-year outcomes. J Cataract Refract Surg 2021; 47:1196-1204. [PMID: 34468458 DOI: 10.1097/j.jcrs.0000000000000594] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 01/18/2021] [Indexed: 11/26/2022]
Abstract
PURPOSE To compare myopia and astigmatic correction after small-incision lenticule extraction (SMILE) with or without prophylactic crosslinking (SMILE Xtra). SETTING Shenyang Aier Eye Hospital, Central South University, China. DESIGN Retrospective study. METHODS Patients with comparable manifest sphere and cylinder undergoing SMILE Xtra or SMILE were enrolled. The crosslinking (CXL) energy was 2.7 J/cm2. Only right eyes were selected. Visual and refractive changes were evaluated for 1 year. Astigmatic correction was analyzed using Alpins method. RESULTS Thirty-six eyes undergoing SMILE Xtra and 40 eyes undergoing SMILE were enrolled. The uncorrected distance visual acuity at 1-day visit was lower after SMILE Xtra than that after SMILE (P = .01). At 12 months, the mean manifest refraction spherical equivalent (MRSE) and manifest cylinder were 0.08 ± 0.32 diopters (D) and -0.29 ± 0.23 D in SMILE Xtra group, whereas -0.25 ± 0.29 D and -0.22 ± 0.19 D in SMILE group (P < .01 and P = .135), respectively. Thirty-four eyes (94%) and 32 eyes (89%) in SMILE Xtra group and 36 eyes (91%) and 39 eyes (98%) in SMILE group exhibited target MRSE and manifest cylinder within ±0.50 D (P = .771 and P = .294), respectively. Compared with SMILE group, spherical correction index (SCI), correction index (CI), and difference vector were higher in SMILE Xtra group since 1-week follow-up (all P < .05). SCI and CI were slightly more than 1.0 after SMILE Xtra even at postoperative 12-month follow-up. CONCLUSIONS With CXL protocol of 30 mW/cm2 for 90 seconds, SMILE Xtra exhibited comparable astigmatic correction with SMILE up to 1-year follow-up, although slight spherical equivalent and astigmatic overcorrection were evident after SMILE Xtra.
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Comparison of 1-Year Outcomes Between Small Incision Lenticule Extraction With Prophylactic Cross-Linking and Femtosecond Laser-Assisted In Situ Keratomileusis With Prophylactic Cross-Linking. Cornea 2021; 40:12-18. [PMID: 33214416 DOI: 10.1097/ico.0000000000002547] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To compare small incision lenticule extraction with prophylactic cross-linking (SMILE Xtra) and femtosecond laser-assisted in situ keratomileusis with prophylactic cross-linking (FS-LASIK Xtra) in their safety, efficacy, predictability, and stability. METHODS This is a prospective cohort study. Forty-eight eyes subjected to SMILE Xtra and 90 eyes subjected to FS-LASIK Xtra were enrolled. The enrolled eyes exhibited either borderline corneal topography or high myopia with thin cornea. The following parameters were evaluated before surgery and at 1 day; 1 week; and 1, 3, 6, and 12 months after surgery: corrected distance visual acuity, uncorrected distance visual acuity, manifest refractive spherical equivalent (MRSE), keratometry values, and thinnest corneal thickness. RESULTS After 1 month, no eye showed loss of 1 or more lines of corrected distance visual acuity. At 12 months, uncorrected distance visual acuity was 20/20 or better for 98% and 99% eyes in the SMILE Xtra and FS-LASIK Xtra groups, respectively (P = 0.657). For 93.8% eyes in the SMILE Xtra group and 90% eyes in the FS-LASIK Xtra group, the achieved MRSE was within ±0.50 diopter of the intended MRSE (P = 0.669). The correlation coefficients for predictability of MRSE correction by SMILE Xtra and FS-LASIK Xtra were 0.987 and 0.983, respectively. The mean MRSE values, keratometry values, and thinnest corneal thickness measured at the different time points showed no significant intra- or intergroup differences. CONCLUSIONS Our evaluations of 1-year outcomes suggest that the safety, efficacy, predictability, and stability of SMILE Xtra are comparable with those of FS-LASIK Xtra.
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Kankariya VP, Dube AB, Grentzelos MA, Kontadakis GA, Diakonis VF, Petrelli M, Kymionis GD. Corneal cross-linking (CXL) combined with refractive surgery for the comprehensive management of keratoconus: CXL plus. Indian J Ophthalmol 2020; 68:2757-2772. [PMID: 33229651 PMCID: PMC7856931 DOI: 10.4103/ijo.ijo_1841_20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The past two decades have witnessed an unprecedented evolution in the management of keratoconus that demands a holistic approach comprising of inhibiting the ectatic progression as well as visual rehabilitation. The advent of corneal cross-linking (CXL) in the late 1990s resulted in long-term stabilization of the ectatic cornea along with limited reduction in corneal steepening and regularization of corneal curvature. However, CXL as a standalone procedure does not suffice in rehabilitating the functional vision especially in patients who are unwilling or intolerant towards contact lenses. The concept of “CXL plus” was proposed which incorporates adjunctive use of refractive procedures with CXL in order to overcome the optical inefficiency due to corneal irregularity, decrease the irregular astigmatism, correct the residual refractive error and improve functional visual outcome in keratoconus. Several refractive procedures such as conductive keratoplasty (CK), photorefractive keratectomy (PRK), transepithelial phototherapeutic keratectomy (t-PTK), intrastromal corneal ring segments (ICRS) implantation, phakic intraocular lens (PIOL) implantation and multiple other techniques have been combined with CXL to optimize and enhance the CXL outcome. This review aimed to summarize the different protocols of CXL plus, provide guidelines for selection of the optimum CXL plus technique and aid in decision-making for the comprehensive management of cases with primary keratoconus in addition to discussing the future and scope for innovations in the existing treatment protocols.
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Affiliation(s)
| | - Ankita B Dube
- Asian Eye Hospital and Laser Institute, Pune, Maharashtra, India
| | - Michael A Grentzelos
- Asian Eye Hospital and Laser Institute, Pune, Maharashtra, India; Department of Ophthalmology, University of Lausanne, Jules-Gonin Eye Hospital, Fondation Asile des Aveugles, Lausanne, Switzerland
| | - George A Kontadakis
- Laboratory of Vision and Optics, Medical School, University of Crete, Heraklion, Greece
| | | | - Myrsini Petrelli
- Department of Ophthalmology, University of Lausanne, Jules-Gonin Eye Hospital, Fondation Asile des Aveugles, Lausanne, Switzerland
| | - George D Kymionis
- Department of Ophthalmology, University of Lausanne, Jules-Gonin Eye Hospital, Fondation Asile des Aveugles, Lausanne, Switzerland
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Brar S, Gautam M, Sute SS, Ganesh S. Refractive surgery with simultaneous collagen cross-linking for borderline corneas - A review of different techniques, their protocols and clinical outcomes. Indian J Ophthalmol 2020; 68:2744-2756. [PMID: 33229650 PMCID: PMC7856924 DOI: 10.4103/ijo.ijo_1709_20] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Simultaneous corneal cross-linking (CXL) has been proposed as an adjunct therapy to corneal refractive procedures to prevent future ectasia, especially when performed in borderline corneas. This review analyses the currently available literature (minimum follow-up 6 months) on corneal refractive surgery and simultaneous CXL (PRK Xtra, LASIK Xtra, and SMILE Xtra) to evaluate the overall results including the safety, efficacy, and potential complications associated with these procedures. A comprehensive literature search of various electronic databases (PubMed, PubMed Central, Cochrane database, and MEDLINE) was performed up to 20th May 2020. Four relevant studies were found for PRK Xtra, 12 for LASIK Xtra, and 3 for SMILE Xtra. The total number of eyes included in this review was 1,512: 294 for PRK Xtra, 221 for PRK-only, 446 eyes for LASIK Xtra, 398 eyes for LASIK-only, 91 for SMILE Xtra and 62 for SMILE-only. Current literature suggests that refractive surgery and simultaneous CXL is generally safe and delivers comparable results in terms of visual and refractive outcomes than refractive surgery alone. However, there is no consensus on a standard cross-linking protocol, and complications such as diffuse lamellar keratitis, central toxic keratopathy, and corneal ectasia following Xtra procedures have been reported. It is therefore suggested that surgeons exercise caution in case-selection and counsel their patients regarding the potential risks and benefits with Xtra procedures. Also, further studies are required to standardize the UV-A irradiation protocols and to evaluate the long-term effect on safety, refractive predictability, and stability of these procedures.
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Affiliation(s)
- Sheetal Brar
- Nethradhama Superspeciality Eye Hospital, Bengaluru, Karnataka, India
| | - Megha Gautam
- Nethradhama Superspeciality Eye Hospital, Bengaluru, Karnataka, India
| | - Smith Snehal Sute
- Nethradhama Superspeciality Eye Hospital, Bengaluru, Karnataka, India
| | - Sri Ganesh
- Nethradhama Superspeciality Eye Hospital, Bengaluru, Karnataka, India
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Liu T, Shen M, Li H, Zhang Y, Mu B, Zhao X, Wang Y. Changes and quantitative characterization of hyper-viscoelastic biomechanical properties for young corneal stroma after standard corneal cross-linking treatment with different ultraviolet-A energies. Acta Biomater 2020; 113:438-451. [PMID: 32525050 DOI: 10.1016/j.actbio.2020.06.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 05/30/2020] [Accepted: 06/02/2020] [Indexed: 12/27/2022]
Abstract
Corneal collagen cross-linking (CXL) treatment can restore vision in patients suffering from keratoconus and corneal injury, by improving the mechanical properties of the cornea. The correlation between ultraviolet-A (UVA) irradiant energies of standard CXL (SCXL) and corneal visco-hyperelastic mechanical behavior remains unknown. In this study, SCXL with four different UVA irradiant energy doses (0-5.4 J/cm2) were administered as part of quantitative treatments of corneal stromal lenticules extracted from young myopic patients via small incision lenticule extraction (SMILE) corneal refractive surgery. Double-strip samples with symmetric geometries were cut simultaneously for SCXL treatment and non-treated control. First, 40 pairs of strips were loaded to failure to assess the mechanical parameters of the material. Then, another 40 pairs were tested using a special uniaxial tensile test including quasi-static loading-unloading, instantaneous loading, and stress relaxation, to determine the visco-hyperelastic mechanical behavior. Upon combining the collagen fibril crimping constitutive model with the quasi-linear viscoelastic model, it was observed that with increasing UVA energy dose, the corneal strength and hyperelastic stiffness were significantly enhanced, while the maximum stretch and viscosity of the cornea were significantly reduced. Considering the quantitative analysis of SCXL and the rehabilitation prediction of keratoconus treatment, the results clarify the biomechanical behavior of human corneal stroma in SCXL clinical surgery. STATEMENT OF SIGNIFICANCE: This study quantitatively analyzes the improvement in the biomechanical properties of young central corneal stroma, due to SCXL treatment with different energies. Furthermore, the correlation between the hyper-viscoelastic mechanical parameters and UVA irradiant energy doses of SCXL are clarified. The contribution of this study fills the knowledge gap of the CXL on corneal biomechanics. It can not only clarify this mechanism better but also assist with guiding SCXL surgery for individualized patient corneas.
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Affiliation(s)
- Taiwei Liu
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin 300350 China; Department of Engineering Mechanics, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Min Shen
- Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin 300350 China.
| | - Hongxun Li
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin 300020 China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070 China
| | - Yan Zhang
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin 300020 China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070 China
| | - Bokun Mu
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin 300020 China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070 China
| | - Xinheng Zhao
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin 300020 China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070 China
| | - Yan Wang
- Tianjin Key Lab of Ophthalmology and Visual Science, Tianjin Eye Hospital, Tianjin 300020 China; Clinical College of Ophthalmology, Tianjin Medical University, Tianjin 300070 China
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Gamidov GA, Mushkova IA, Kostenev SV, Gamidov AA. [SMILE keratorefractive surgery technique]. Vestn Oftalmol 2019; 135:99-106. [PMID: 31714520 DOI: 10.17116/oftalma201913505199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Small incision lenticule extraction (SMILE) keratorefractive surgery technique is a laser surgery alternative to common methods that doesn't require laser ablation of the cornea. Despite its novelty, SMILE technique has already demonstrated positive clinical results comparable to Photorefractive Keratectomy (PRK) and Laser-Assisted in Situ Keratomileusis (LASIK), which led to its widespread application in clinical practice. Compared with other keratorefractive techniques, SMILE has a number of distinct advantage including high biomechanical stability of the cornea, low risk of dry eye syndrome, absence of a corneal flap and associated complications, preservation of corneal epithelium. The article describes the most common SMILE modifications, its weak points and possible complications, as well as methods of additional correction of remaining ametropy.
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Affiliation(s)
- G A Gamidov
- S.N. Fyodorov National Medical Research Center 'MNTK 'Eye Microsurgery', 59A Beskudnikovsky Blvd., Moscow, Russian Federation, 127486
| | - I A Mushkova
- S.N. Fyodorov National Medical Research Center 'MNTK 'Eye Microsurgery', 59A Beskudnikovsky Blvd., Moscow, Russian Federation, 127486
| | - S V Kostenev
- S.N. Fyodorov National Medical Research Center 'MNTK 'Eye Microsurgery', 59A Beskudnikovsky Blvd., Moscow, Russian Federation, 127486
| | - A A Gamidov
- Research Institute of Eye Diseases, 11A Rossolimo St., Moscow, Russian Federation, 119021
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Konstantopoulos A, Liu YC, Teo EP, Nyein CL, Yam GH, Mehta JS. Corneal Stability of LASIK and SMILE When Combined With Collagen Cross-Linking. Transl Vis Sci Technol 2019; 8:21. [PMID: 31143527 PMCID: PMC6526961 DOI: 10.1167/tvst.8.3.21] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Accepted: 04/03/2019] [Indexed: 11/24/2022] Open
Abstract
Purpose We investigate whether small incision lenticule extraction (SMILE) is associated with less ectasia than laser-assisted in-situ keratomileusis (LASIK) and whether concomitant collagen cross-linking (CXL) is protective in SMILE Xtra and LASIK Xtra. Methods Using an established LASIK rabbit ectasia model, we performed −5 diopter (D) LASIK on six eyes and −5 D SMILE on six eyes; five eyes had −5 D LASIK Xtra, five eyes −5 D SMILE Xtra. Anterior segment optical coherence tomography and corneal topography were performed preoperatively and 2, 4, and 6 weeks postoperatively. Mean (standard deviation [SD]) values of postoperative keratometry (K), maximum posterior elevation (MPE) and minimum corneal thickness (CT) were compared to preoperatively and among the surgical groups (paired t-test, analysis of variance). Results Mean (SD) K values decreased significantly following SMILE, SMILE Xtra, LASIK, and LASIK Xtra. The MPE increased significantly (P < 0.05) following LASIK, SMILE, and SMILE Xtra, but not following LASIK Xtra (P = 0.12). The MPE was less following SMILE than LASIK, but not statistically significant (week 2, 17.73 [5.77] vs. 22.75 [5.05] μm; P = 0.13); post-LASIK Xtra MPE was less than that following LASIK (week 2. 13.39 [3.05] vs. 22.75 [5.05] μm; P < 0.001). CT decreased significantly in all surgical groups; no differences were detected among the groups. Conclusions SMILE may have less potential than LASIK to induce ectasia. LASIK Xtra and SMILE Xtra showed the smallest increase in MPE. Translational Relevance Concomitant CXL may be protective following keratorefractive surgery and may reduce further the risk of ectasia.
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Affiliation(s)
- Aris Konstantopoulos
- Singapore Eye Research Institute, Singapore.,University Hospital Southampton NHS Foundation Trust, Southampton, UK
| | - Yu-Chi Liu
- Singapore Eye Research Institute, Singapore.,Singapore National Eye Centre, Singapore.,Department of Clinical Sciences, Duke-NUS Graduate Medical School, Singapore
| | | | | | - Gary H Yam
- Singapore Eye Research Institute, Singapore
| | - Jodhbir S Mehta
- Singapore Eye Research Institute, Singapore.,Singapore National Eye Centre, Singapore.,Department of Clinical Sciences, Duke-NUS Graduate Medical School, Singapore.,Nanyang Technological University, Singapore
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Corneal Safety and Stability in Cases of Small Incision Lenticule Extraction with Collagen Cross-Linking (SMILE Xtra). J Ophthalmol 2019; 2019:6808062. [PMID: 31098325 PMCID: PMC6487093 DOI: 10.1155/2019/6808062] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 03/14/2019] [Indexed: 01/01/2023] Open
Abstract
Purpose To assess the safety and stability in cases of small incision lenticule extraction with collagen cross-linking (SMILE Xtra). Methods This study was a retrospective interventional comparative study that included 60 eyes of 30 patients divided equally into two groups: SMILE Xtra and SMILE alone. The inclusion criteria were patients >18 years of age, myopic error >6 D, thinner cornea <520 microns, and abnormal corneal topography. Outcome data were recorded including uncorrected distance visual acuity and corrected distance visual acuity (UDVA and CDVA), manifest refraction spherical equivalent (MRSE), central corneal thickness, average keratometry, endothelial cell density, corneal resistance factor (CRF), and corneal densitometry. The follow-up period was 24 months. Results There was a significant difference between the 2 groups regarding UDVA, CDVA, and MRSE at 1 month. In the SMILE Xtra group, 90% of eyes had postoperative UDVA of 20/20 and 97% had UDVA of 20/30 at 24 months. At 24 months, 26 eyes (87%) vs. 25 eyes (84%) were within ±0.50 D of attempted correction in SMILE Xtra and SMILE groups, respectively. Regarding stability, both groups showed improvement of MRSE at 1st month postoperatively and remained stable along the 24 months of follow-up. CRF and corneal densitometry were higher in the SMILE Xtra group along the whole follow-up period (p=0.001). Conclusion Combining corneal cross-linking with SMILE procedure (SMILE Xtra) is a promising tool to prevent ectasia in high-risk patients. It is a safe and simple procedure that can be offered to patients undergoing SMILE with risk for ectasia. Trial registration no: PACTR201810577524718.
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Ng ALK, Cheng GPM, Woo VCP, Jhanji V, Chan TCY. Comparing a new hydroexpression technique with conventional forceps method for SMILE lenticule removal. Br J Ophthalmol 2017; 102:1122-1126. [PMID: 29122820 DOI: 10.1136/bjophthalmol-2017-310993] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 10/22/2017] [Accepted: 10/24/2017] [Indexed: 12/30/2022]
Abstract
BACKGROUND We described a modified 'hydroexpression' technique for the lenticule removal during small-incision lenticule extraction (SMILE) surgery and compared the results with conventional forceps method. METHODS This was a retrospective, comparative study of 50 patients who underwent SMILE surgery by the same surgeon. We compared the 1-week and 3-months postoperative results after SMILE using the hydroexpression technique with the conventional forceps technique. Main outcome measures included uncorrected distance visual acuity, corrected distance visual acuity, refractive accuracy, safety index and efficacy index. RESULTS The baseline characteristics were comparable between both groups. At postoperative 1 week, the safety index in forceps and hydroexpression group was 0.93±0.11 and 0.97±0.10, respectively (P=0.246). At 3 months, they were 1.00±0.06 and 0.99±0.09 (P=0.850). For efficacy indices, at 1 week they were 0.84±0.17 and 0.91±0.17 (P=0.158). At 3 months, they were 0.92±0.13 and 0.94±0.19 (P=0.624). All eyes aimed for a plano target. 96% in forceps group and 90% in hydroexpression group were within ±0.50 dioptre (D) in spherical equivalent refraction (SEQ) correction at postoperative 3 months (P=0.567). The mean errors of SEQ correction were -0.10±0.21 D in forceps group and -0.08±0.30 D in hydroexpression group (P=0.705). CONCLUSION Hydroexpression was simple and safe and had early results comparable to the conventional forceps technique. This technique was particularly useful for cases with more adhesions between lenticule and anterior cap, thin lenticule cases and for the inexperienced SMILE surgeons.
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Affiliation(s)
- Alex L K Ng
- Department of Ophthalmology, The University of Hong Kong, Cyberport, Hong Kong
| | | | | | - Vishal Jhanji
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Philadelphia, USA.,Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Kowloon, Hong Kong
| | - Tommy C Y Chan
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Kowloon, Hong Kong
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Affiliation(s)
- Davin Johnson
- Department of Ophthalmology, CHUM-Notre Dame Hospital, Montreal, Canada
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Kim B, Mun S, Choi H, Yang Y, Chung Y. Comparison of the Early Clinical Outcomes between Combined SMILE and Collagen Cross-linking versus SMILE. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2017. [DOI: 10.3341/jkos.2017.58.10.1122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Buki Kim
- Onnuri Smile Eye Clinic, Seoul, Korea
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Visual Outcomes After SMILE, LASEK, and LASEK Combined With Corneal Collagen Cross-Linking for High Myopic Correction. Cornea 2016; 36:399-405. [DOI: 10.1097/ico.0000000000001089] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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