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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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Damgaard IB, Reffat M, Hjortdal J. Review of Corneal Biomechanical Properties Following LASIK and SMILE for Myopia and Myopic Astigmatism. Open Ophthalmol J 2018; 12:164-174. [PMID: 30123381 PMCID: PMC6062908 DOI: 10.2174/1874364101812010164] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 01/08/2018] [Accepted: 01/20/2018] [Indexed: 11/22/2022] Open
Abstract
Worldwide, femtosecond Laser Assisted In-situ Keratomileusis (LASIK) is a well known and commonly used refractive technique, although Small Incision Lenticule Extraction (SMILE) has become increasingly popular since it was introduced in 2011. In LASIK, a corneal flap is cut with a microkeratome or femtosecond laser, followed by thinning of the stromal bed with excimer laser ablation. In SMILE, a minor intrastromal lenticule is cut with a femtosecond laser and subsequently removed through a small incision, leaving the anterior and strongest part of the cornea almost intact. Both LASIK and SMILE require cutting of corneal lamellae that may reduce the biomechanical stability of the cornea, with the potential risk of corneal iatrogenic ectasia as a severe complication. However, SMILE preserves the anterior corneal integrity and may, in theory, better preserve the corneal biomechanical strength than LASIK after surgery. A review aimed to examine the current literature that describes and compares the corneal biomechanical properties after Laser Assisted In-situ Keratomileusis (LASIK) and Small Incision Lenticule Extraction (SMILE). A comprehensive search was performed in Pubmed.gov using the following search queries: Corneal biomechanical properties, corneal biomechanics, ocular response analyser, ocular response analyzer, ORA, ex vivo, in vitro, Corvis, Corvis ST, LASIK, and SMILE.
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Affiliation(s)
- Iben Bach Damgaard
- Department of Ophthalmology, Aarhus University Hospital, Aarhus, Denmark
| | | | - Jesper Hjortdal
- Department of Ophthalmology, Aarhus University Hospital, Aarhus, Denmark
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Inducing fibrogenesis and new interfibrillary bonds in post-laser in situ keratomileusis keratectasia. J Cataract Refract Surg 2018; 44:1062-1065. [PMID: 30055956 DOI: 10.1016/j.jcrs.2018.05.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Revised: 04/28/2018] [Accepted: 05/20/2018] [Indexed: 11/20/2022]
Abstract
Flap creation weakens the cornea and is a risk factor for keratectasia after laser in situ keratomileusis (LASIK). We describe a new technique to halt the progression of keratectasia by mechanically reintegrating the flap into the residual stroma. Deep stromal vertical puncturing is performed in the 4.0 to 9.0 mm paracentral corneal zone at a depth of 350 to 420 μm. The puncturing is applied in circumferential rows using a 25-gauge needle or a diamond blade, with denser puncturing at the level of the cone. In 5 eyes with worsening post-LASIK keratectasia, improved uncorrected and corrected visual acuities, corneal flattening, and a hyperopic shift were observed. There was no progression of keratectasia on serial topographies. New collagen fibrogenesis was documented by optical coherence tomography. The technique seems to be promising to halt the progression of post-LASIK keratectasia. More clinical data and longer follow-up are needed for validation.
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Song YW, He R, Ma JX, Koch DD, Wang L. Long-term safety of laser in situ keratomileusis in eyes with thin corneas: 5-year follow-up. Int J Ophthalmol 2018; 11:1227-1233. [PMID: 30046544 DOI: 10.18240/ijo.2018.07.25] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Accepted: 02/05/2018] [Indexed: 01/01/2023] Open
Abstract
AIM To investigate the long term (≥5y) efficacy, predictability, and safety of laser in situ keratomileusis (LASIK) in eyes with thin corneas [central corneal thickness (CCT) <500 µm]. METHODS A total of 339 patients met the criteria of this study. Finally, 175 eyes of 89 patients who had thin corneas and underwent LASIK≥5y ago returned to our clinic and included in this study. Preoperative parameters recorded included uncorrected visual acuity (UCVA), corrected distance visual acuity (CDVA), manifest refraction, CCT and corneal topography. At returning visits, in addition to visual acuity and manifest refraction, ultrasound CCT and corneal topography were performed. Optical coherence tomography was used to measure the CCT, LASIK flap thickness, and residual stromal bed thickness (RSBT). Safety index, efficacy index, percentage of eyes within ±0.5 D and ±1.0 D of refraction, percent tissue altered (PTA), and percentage stromal bed thickness (PSBT) were calculated. RESULTS The safety index was 1.09 and efficacy index was 0.99. The percentages of eyes within ±0.5 D and ±1.0 D were 71.2% and 87.7%, respectively. The mean PTA was 40%±6% (range 20% to 55%); 76 eyes (43.4%) had PTA <40% and 99 eyes (56.6%) had PTA≥40%. The mean RSBT was 303±27 µm (range 240 to 390 µm), and 2 eyes had RSBT<250 µm. The mean PSBT was 61%±9% (range 51% to 85%). No eyes developed ectasia. CONCLUSION In this cohort with the PSBT of 50% or more, LASIK is safe with follow-up for at least 5y.
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Affiliation(s)
- Yao-Wen Song
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Science Key Laboratory, Beijing 100730, China
| | - Rui He
- Shanxi Eye Hospital, Taiyuan 030002, Shanxi Province, China
| | - Jack X Ma
- McGovern Medical School, University of Texas Health Science Center at Houston, TX 75835, USA
| | - Douglas D Koch
- Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, Houston, TX 75844, USA
| | - Li Wang
- Shanxi Eye Hospital, Taiyuan 030002, Shanxi Province, China.,Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, Houston, TX 75844, USA
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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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Damgaard IB, Ivarsen A, Hjortdal J. Biological Lenticule Implantation for Correction of Hyperopia: An Ex Vivo Study in Human Corneas. J Refract Surg 2018; 34:245-252. [PMID: 29634839 DOI: 10.3928/1081597x-20180206-01] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 01/02/2018] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate changes in corneal tomography after stromal lenticule implantation ex vivo, with respect to the dependency of the lenticule thickness and implantation depth on the corneal curvature and the postoperative biomechanical strength at increased chamber pressure. METHODS Twenty-eight human donor corneas underwent pocket implantation of refractive stromal lenticules. Four groups were created by the combination of two implantation depths (110 and 160 µm) and two lenticule thicknesses (95 µm = 4.00 diopters [D], 150 µm = 8.00 D). Sagittal keratometry and total corneal refractive power (TCRP4mm,apex,zone) were obtained for the front and back curvature with Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany) at chamber pressures of 15 and 40 mm Hg. RESULTS The anterior curvature steepening was comparable between the 4.00 D and 8.00 D groups (P > .141), but more pronounced with 110 µm implantation depth (P < .038). The posterior curvature flattened significantly more after implantation of 8.00 D than 4.00 D lenticules (P < .002), but was similar at 110 and 160 µm implantation depths (P > .071). Average ΔTCRP for the 4.00 D and 8.00 D groups was 3.10 ± 0.60 and 5.30 ± 1.66 diopters (D) at 110-µm depth, respectively (P = .003), but 1.99 ± 0.79 and 3.36 ± 1.45 D at 160-µm depth, respectively (P = .066). The relative correction achieved was 66% to 78% at 110-µm depth and 42% to 50% at 160-µm depth, but similar when using 4.00 D and 8.00 D lenticules. Increased chamber pressure caused significant anterior and posterior curvature steepening after implantation in all four groups (P < .001), but not before implantation (P > .632). CONCLUSIONS The power of the implanted lenticule must be higher than the intended correction, and customized to the chosen implantation depth. Biomechanical strength seems to decrease after lenticule implantation. [J Refract Surg. 2018;34(4):245-252.].
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Seven I, Vahdati A, Pedersen IB, Vestergaard A, Hjortdal J, Roberts CJ, Dupps WJ. Contralateral Eye Comparison of SMILE and Flap-Based Corneal Refractive Surgery: Computational Analysis of Biomechanical Impact. J Refract Surg 2018; 33:444-453. [PMID: 28681903 DOI: 10.3928/1081597x-20170504-01] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Accepted: 03/23/2017] [Indexed: 11/20/2022]
Abstract
PURPOSE Computational analyses were performed to quantify and directly compare the biomechanical impact of flapless and flap-based procedures in a series of patients undergoing small incision lenticule extraction (SMILE) in one eye and flap-based femtosecond lenticule extraction in the other. METHODS Tomographic data from 10 eyes of 5 patients undergoing femtosecond laser refractive lenticule extraction for myopic astigmatism with or without a stromal flap (femtosecond lenticule extraction in one eye, SMILE in the contralateral eye) were used to generate computational models. Inverse finite element analyses were performed at physiologic intraocular pressure followed by forward analyses at elevated intraocular pressure to assess corneal displacement and stress under differential loading. Case-specific treatment settings were incorporated. Preoperative material constants were obtained through inverse finite element analyses, and the surgically induced change in fiber stiffness within each flap was determined by minimization of the error between the simulated and actual 6-month topographic outcomes. RESULTS Flap-based procedures produced a 49% (range: 2% to 87%) greater mean reduction in effective stromal collagen fiber stiffness within the flap region than contralateral SMILE cases. Lower stresses and deformations were observed within the residual stromal bed in SMILE cases than in flap-based cases. Stromal bed displacements and stresses were more affected by a loading increase in flap-based eyes than flapless eyes. CONCLUSIONS Intrastromal flapless procedures had less impact on anterior stromal collagen mechanics and resulted in lower stromal bed displacements and stresses than flap-based procedures in contralateral eyes. However, biomechanical impact varied widely between individuals and this reinforces the need for individualized assessment of ectasia risk. [J Refract Surg. 2017;33(7):444-453].
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Hatami-Marbini H, Jayaram SM. UVA/riboflavin collagen crosslinking stiffening effects on anterior and posterior corneal flaps. Exp Eye Res 2018; 176:53-58. [PMID: 29777678 DOI: 10.1016/j.exer.2018.05.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 05/04/2018] [Accepted: 05/15/2018] [Indexed: 10/16/2022]
Abstract
The UVA/riboflavin collagen crosslinking (CXL) is one of the treatment procedure for stopping the progression of keratoconus. The inclusion criterion for this procedure is a minimum corneal thickness of 400 μm, which is not often met in patients with advanced keratoconus. Preoperatively swelling thin corneas was shown to stabilize the keratectasia without any postoperative endothelial damage. Recently, we have shown that swelling porcine corneas prior to the CXL treatment had no significant effect on the resulting improvement in their tensile properties. In the present study, we extended this previous study and characterized the stiffening effects of CXL on anterior and posterior flaps as a function of their hydration. A DSAEK system was used to excise 10 mm corneal flaps from 80 porcine corneas. Individual flaps were crosslinked at different initial hydration levels by using riboflavin solutions composed of different dextran concentrations; the thickness was taken as a measure of flap hydration. A DMA machine was used to measure the tensile properties either immediately after the CXL treatment or after the thickness (hydration) of the crosslinked samples was brought down to a specific value. The average thickness of anterior groups was 670 μm, 540 μm, and 410 μm, and the average thickness of posterior groups was 845 μm, 650 μm, and 440 μm. It was found that although CXL significantly increased the tensile properties of all anterior groups, it had an insignificant effect on the stiffness of posterior flaps. Furthermore, except for the posterior flaps in 845 μm and 650 μm thickness groups, decreasing the hydration significantly increased the tensile modulus (p < 0.05). Finally, the anterior flaps that were crosslinked at higher hydration, i.e. swollen before CXL, showed significantly less amount of stiffening in comparison with those crosslinked at lower hydration when the tensile property measurement was done at similar hydration (p < 0.05).
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Affiliation(s)
- Hamed Hatami-Marbini
- Computational Biomechanics Research Laboratory, Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL, USA.
| | - Sandeep M Jayaram
- Computational Biomechanics Research Laboratory, Mechanical and Industrial Engineering Department, University of Illinois at Chicago, Chicago, IL, USA
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Burazovitch J, Ferguene H, Naguszewski D. La prédictibilité du small incision lenticule extraction (SMILE) dans la correction de la myopie sphérocylindrique, étude rétrospective, sur cinq ans, à partir de 616 yeux. J Fr Ophtalmol 2018; 41:433-440. [DOI: 10.1016/j.jfo.2018.01.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2017] [Revised: 12/13/2017] [Accepted: 01/03/2018] [Indexed: 11/26/2022]
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Ganesh S, Brar S, Arra RR. Refractive lenticule extraction small incision lenticule extraction: A new refractive surgery paradigm. Indian J Ophthalmol 2018; 66:10-19. [PMID: 29283117 PMCID: PMC5778540 DOI: 10.4103/ijo.ijo_761_17] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Small incision lenticule extraction (SMILE), a variant of refractive lenticule extraction technology is becoming increasingly popular, as a flapless and minimally invasive form of laser vision correction (LVC) for the treatment of myopia and myopic astigmatism. This review aims at summarizing the principles, surgical technique, and clinical outcomes in terms of visual and refractive results, safety, efficacy, postoperative dry eye, aberrations, and biomechanics of SMILE and its comparison with other conventional techniques of LVC, such as laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). Recent advancements in the laser frequency and energy delivery patterns, instrumentation, and surgical techniques have shown significant improvement in the visual recovery and outcomes after SMILE, compared to the initial results published by Sekundo and Shah et al. Most of the recently published literature on long-term outcomes of SMILE shows excellent stability of the procedure, especially for higher myopia. In terms of the postoperative dry eye, SMILE shows a clear advantage over LASIK as numerous studies have shown significant differences about the Schirmer's, Tear film break up time, corneal sensitivity, and corneal nerve regeneration to be better following SMILE compared to LASIK. There is some evidence that since the Bowman's membrane (BM) and the anterior lamellae remain intact after SMILE, this may be a potential advantage for corneal biomechanics over LASIK and PRK where the BM is either severed or ablated, respectively, however, the data on biomechanics are inconclusive at present. Overall, this procedure has proved to be promising, delivering equivalent, or better visual and refractive results to LASIK and providing clear advantage in terms of being a flapless, minimally invasive procedure with minimal pain and postoperative discomfort thus offering high patient satisfaction.
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Affiliation(s)
- Sri Ganesh
- Department of Phaco-Refractive, Nethradhama Superspeciality Eye Hospital, Bengaluru, Karnataka, India
| | - Sheetal Brar
- Department of Phaco-Refractive, Nethradhama Superspeciality Eye Hospital, Bengaluru, Karnataka, India
| | - Raghavender Reddy Arra
- Department of Phaco-Refractive, Nethradhama Superspeciality Eye Hospital, Bengaluru, Karnataka, India
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Comparison of 2 Different Methods of Transepithelial Corneal Collagen Cross-Linking: Analysis of Corneal Histology and Hysteresis. Cornea 2018; 36:860-865. [PMID: 28486315 DOI: 10.1097/ico.0000000000001229] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To compare the effect of 2 different methods of transepithelial corneal collagen cross-linking (CXL) on corneal histology and hysteresis. METHODS The right eyes of New Zealand white rabbits (n = 50) were treated using one of the 2 transepithelial CXL methods. The eyes were then divided into 2 groups: group 1, transepithelial CXL using continuous ultraviolet A (UVA); group 2, accelerated transepithelial CXL using pulsed UVA. RESULTS Both groups showed a postoperative increase in central corneal thickness. In both groups, an increase in corneal hysteresis was found after CXL, but the changes were not significant when compared with the baseline value. The corneal resistance factor and corneal-compensated intraocular pressure also remained unchanged in both groups after treatment. In both groups, the CXL effect reached the anterior-mid part of the corneal stroma. In group 1, CXL mostly affected the anterior-mid part stroma, whereas group 2 showed stromal keratocyte loss, and an acellular zone, in the deep stroma. More signs of keratocyte apoptosis were observed in group 2 than in group 1. CONCLUSIONS Accelerated transepithelial CXL using pulsed UVA showed considerably deeper effect in the stroma with keratocyte loss than transepithelial CXL using continuous UVA.
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Scheibenberger D, Frings A, Steinberg J, Schüler H, Druchkiv V, Katz T, von Kodolitsch Y, Linke S. Ocular manifestation in Marfan syndrome: corneal biomechanical properties relate to increased systemic score points. Graefes Arch Clin Exp Ophthalmol 2018. [DOI: 10.1007/s00417-018-3946-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Kanellopoulos AJ. Comparison of corneal biomechanics after myopic small-incision lenticule extraction compared to LASIK: an ex vivo study. Clin Ophthalmol 2018; 12:237-245. [PMID: 29416315 PMCID: PMC5790083 DOI: 10.2147/opth.s153509] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Purpose To investigate ex vivo potentially different corneal biomechanical properties after small-incision lenticule extraction (SMILE) versus LASIK for myopic correction. Methods Thirty human donor corneas were subjected to either myopic SMILE or femtosecond laser-assisted LASIK. Donor corneas were assigned to six investigative groups: Group A, −3.00 D (diopters) SMILE; Group B, −8.00 D SMILE; Group C, −3.00 D LASIK; and Group D, −8.00 D LASIK. Additionally, two control groups were formed: Group E, SMILE and Group F, LASIK. All groups consisted of five corneas, randomly allocated. The corneas in the control groups were subjected to the corresponding femtosecond-laser lamellar cuts but not to tissue removal. Evaluation of biomechanical tensile strength was conducted by biaxial force application. Primary outcome measures were stress at 10% and 15% strain, and Young’s modulus at 10% and 15% strain. Results In SMILE, the average relative difference (Δ) of the four outcome measures was −34.46% for −3.00 D correction versus control Group E and −49.34% for −8.00 D correction versus control Group E. In LASIK, average Δ was −24.88% for −3.00 D correction versus control, and −52.73% for −8.00 D correction versus control. All these differences were statistically significant; SMILE compared to LASIK for the same myopic correction appears to result in more biomechanical reduction for −3.00 D corrections by −26%, while a nonstatistically significant difference was noted in −8.00 D corrections. Conclusion Both SMILE and LASIK procedures do substantially alter corneal biomechanical properties, and the degree of tensile strength reduction is statistically significantly correlated to the extent of myopic correction. Additionally, SMILE procedure seems to result in more tensile strength reduction in lower myopic corrections compared to LASIK, and similar tensile strength reduction to LASIK in higher myopic corrections when compared to LASIK.
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Affiliation(s)
- Anastasios John Kanellopoulos
- Department of Ophthalmology, Laservision Clinical and Research Institute, Athens, Greece.,Department of Ophthalmology, New York University Medical School, New York, NY, USA
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Ramirez-Garcia MA, Sloan SR, Nidenberg B, Khalifa YM, Buckley MR. Depth-Dependent Out-of-Plane Young's Modulus of the Human Cornea. Curr Eye Res 2017; 43:595-604. [PMID: 29283675 DOI: 10.1080/02713683.2017.1411951] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Purpose/Aim: Despite their importance in accurate mechanical modeling of the cornea, the depth-dependent material properties of the cornea have only been partially elucidated. In this work, we characterized the depth-dependent out-of-plane Young's modulus of the central and peripheral human cornea with high spatial resolution. MATERIALS AND METHODS Central and peripheral corneal buttons from human donors were subjected to unconfined axial compression followed by stress relaxation for 30 min. Sequences of fluorescent micrographs of full-thickness corneal buttons were acquired throughout the experiment to enable tracking of fluorescently labeled stromal keratocyte nuclei and measurements of depth-dependent infinitesimal strains. The nominal (gross) out-of-plane Young's modulus and drained Poisson's ratio for each whole specimen was computed from the equilibrium stress and overall tissue deformation. The depth-dependent (local) out-of-plane Young's modulus was computed from the equilibrium stress and local tissue strain based on an anisotropic model (transverse isotropy). RESULTS The out-of-plane Young's modulus of the cornea exhibited a strong dependence on in-plane location (peripheral versus central cornea), but not depth. The depth-dependent out-of-plane Young's modulus of central and peripheral specimens ranged between 72.4-102.4 kPa and 38.3-58.9 kPa. The nominal out-of-plane Young's modulus was 87 ± 41.51 kPa and 39.9 ± 15.28 kPa in the central and peripheral cornea, while the drained Poisson's ratio was 0.05 ± 0.02 and 0.07 ± 0.04. CONCLUSIONS The out-of-plane Young's modulus of the cornea is mostly independent of depth, but not in-plane location (i.e. central vs. peripheral). These results may help inform more accurate finite element computer models of the cornea.
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Affiliation(s)
| | - Stephen R Sloan
- a Department of Biomedical Engineering , University of Rochester , Rochester , NY , USA
| | - Bennett Nidenberg
- a Department of Biomedical Engineering , University of Rochester , Rochester , NY , USA
| | - Yousuf M Khalifa
- b Department of Ophthalmology , Emory University , Atlanta , GA , USA
| | - Mark R Buckley
- a Department of Biomedical Engineering , University of Rochester , Rochester , NY , USA
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Goussous IA, El-Agha MS, Awadein A, Hosny MH, Ghaith AA, Khattab AL. The effect of flap thickness on corneal biomechanics after myopic laser in situ keratomileusis using the M-2 microkeratome. Clin Ophthalmol 2017; 11:2065-2071. [PMID: 29200820 PMCID: PMC5701557 DOI: 10.2147/opth.s148216] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Purpose The purpose of this study was to determine the effect of flap thickness on corneal biomechanics after myopic laser in situ keratomileusis (LASIK). Methods This is a prospective controlled non-randomized, institutional study. Patients underwent either epi-LASIK with mitomycin (advanced surface ablation [ASA]), thin-flap LASIK (90 µm head), or thick-flap LASIK (130 µm head). In ASA, the Moria Epi-K hydroseparator was used. LASIK flaps were created using the Moria M-2 mechanical microkeratome. The corneal hysteresis (CH) and corneal resistance factor (CRF) were measured preoperatively and 3 months after surgery, using the Ocular Response Analyzer®. Results Ten patients (19 eyes) underwent ASA, 11 patients (16 eyes) underwent thin-flap LASIK, and 11 patients (16 eyes) underwent thick-flap LASIK. The mean preoperative CH was 10.47±0.88, 10.52±1.4, and 11.28±1.4 mmHg (p=0.043), respectively, decreasing after surgery by 1.75±1.02, 1.66±1.00, and 2.62±1.03 mmHg (p=0.017). The mean reduction of CH per micron of central corneal ablation was 0.031, 0.023, and 0.049 mmHg/µm (p=0.005). Mean preoperative CRF was 10.11±1.28, 10.34±1.87, and 10.62±1.76 mmHg (p=0.66), decreasing after surgery by 2.33±1.35, 2.77±1.03, and 2.92±1.10 mmHg (p=0.308). The mean reduction of CRF per micron of central corneal ablation was 0.039, 0.040, and 0.051 mmHg/µm (p=0.112). Conclusion Thick-flap LASIK caused a greater reduction of CH and CRF than thin-flap LASIK and ASA, although this was statistically significant only for CH. ASA and thin-flap LASIK were found to be biomechanically similar.
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Affiliation(s)
- Iyad A Goussous
- Department of Ophthalmology, Faculty of Medicine, Cairo University, Cairo
| | | | - Ahmed Awadein
- Department of Ophthalmology, Faculty of Medicine, Cairo University, Cairo
| | - Mohamed H Hosny
- Department of Ophthalmology, Faculty of Medicine, Cairo University, Cairo
| | - Alaa A Ghaith
- Faculty of Medicine, Alexandria University, Alexandria, Egypt
| | - Ahmed L Khattab
- Faculty of Medicine, Alexandria University, Alexandria, Egypt
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Nemeth G, Hassan J, Modis L, Hassan Z. Long-Term Changes in Backscattered Light Measurements in Keratoconus Corneas Treated with Collagen Cross-Linking. Curr Eye Res 2017; 43:18-26. [PMID: 29111836 DOI: 10.1080/02713683.2017.1377260] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
PURPOSE Our aim was to compare densitometry data between keratoconus and normal corneas and to assess the long-term changes in corneal backscattered light values after corneal collagen cross-linking (CXL) treatment. MATERIAL AND METHODS Retrospective analysis was performed on 26 eyes of normal patients (age: 32.71 ± 12.68 years) and 39 eyes of keratoconus patients (28.93 ± 7.59 years) using the Pentacam HR corneal densitometry module before CXL and during the postoperative period, which lasted a mean of 2.53 years (range: 1-4 years). Corneal backscattered light values in grey scale unit (GSU) were recorded for the anterior 120 µm, the center layer, and the posterior 60 µm of the cornea in four concentric, central rings. An additional calculation was performed with converting GSU values to GSU/cubic millimeters (mm3) with surface area calculations and using corneal thickness data. RESULTS Statistically significant differences were observed between normal and keratoconus group densitometry values (in GSU/mm3) in all annuli of the center layer; all, but anterior layer of the 10-12 annuli; all annuli of the total thickness and in all values of the total diameter. In all these cases, the normal cornea showed higher GSU/mm3 values compared to keratoconus corneas (p < 0.05). One month after the CXL treatment, the GSU/mm3 data increased significantly in the anterior, the center, and the posterior zone (p < 0.05), followed by its slow decrease. At the end of the follow-up period, the GSU/mm3 values were significantly higher in all three zones compared to those before the CXL treatment (p < 0.01). CONCLUSION Densitometry measurements can reflect the changes of optical quality of the cornea. These measurements may play a valuable role in assessing keratoconus and optical changes of the corneas after CXL treatment.
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Affiliation(s)
- Gabor Nemeth
- a Department of Ophthalmology , Borsod-Abaúj-Zemplén County Central Hospital and University Teaching Hospital , Miskolc , Hungary
| | - Jasmin Hassan
- b Orbi-Dent Refractive Surgery and Medical Center , Debrecen , Hungary
| | - Laszlo Modis
- c Department of Ophthalmology , University of Debrecen , Debrecen , Hungary
| | - Ziad Hassan
- b Orbi-Dent Refractive Surgery and Medical Center , Debrecen , Hungary
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Moshirfar M, Albarracin JC, Desautels JD, Birdsong OC, Linn SH, Hoopes PC. Ectasia following small-incision lenticule extraction (SMILE): a review of the literature. Clin Ophthalmol 2017; 11:1683-1688. [PMID: 28979096 PMCID: PMC5608083 DOI: 10.2147/opth.s147011] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Purpose Four cases of corneal ectasia after small-incision lenticule extraction (SMILE) have been reported. In this review, we provide an overview of the published literature on corneal ectasia after SMILE and risk factors associated with this complication. Methods Case reports were identified by a search of seven electronic databases for pertinent heading terms between 2011 and July 2017. We identified patient characteristics and surgical details including preoperative topography, central corneal thickness, and anterior keratometry (Km). Residual stromal bed (RSB) values not reported were computed using VisuMax ReLEx SMILE software Version 2.10.10. Preoperative ectasia risk was measured using the Randleman Ectasia Risk Score System (ERSS). Percent tissue alteration was calculated for each patient as described by Santhiago et al. Results Seven eyes of four patients developed corneal ectasia post SMILE. Two patients had abnormal topography in both eyes. One patient had abnormal topography in one eye. Only one patient was noted to have normal topography in both eyes and later developed ectasia in one eye in the absence of any known risk factors. The mean Randleman ectasia risk score was 4±3 (range: 1–8). The mean calculated percent tissue altered (PTA) was 38%±6% (range: 30%–47%). Conclusion A majority of reported ectasia cases occurred in patients with subclinical keratoconus. These conditions may be exacerbated by SMILE and should be considered absolute contraindications to the procedure. Three patients were identified to have high risk based on the ERSS, and one patient exhibited a PTA ≥40%. We formulated a modification to the current calculation of PTA that takes into account the differences in tissue altered between SMILE and laser in situ keratomileusis (LASIK). More studies are needed to fully quantify the risk of ectasia. For now, we propose adopting the same exclusion criteria used for LASIK in the SMILE procedure until more specific metrics have been validated.
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Affiliation(s)
- Majid Moshirfar
- HDR Research Center, Hoopes Vision, Draper.,John A Moran Eye Center, Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, UT
| | - Julio C Albarracin
- Department of Ophthalmology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, TX
| | - Jordan D Desautels
- HDR Research Center, Hoopes Vision, Draper.,Department of Ophthalmology, Warren Alpert Medical School of Brown University, Providence, RI, USA
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Randleman JB, Su JP, Scarcelli G. Biomechanical Changes After LASIK Flap Creation Combined With Rapid Cross-Linking Measured With Brillouin Microscopy. J Refract Surg 2017; 33:408-414. [DOI: 10.3928/1081597x-20170421-01] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Accepted: 03/23/2017] [Indexed: 01/20/2023]
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Keraring Intrastromal Segment Depth Measured by Spectral-Domain Optical Coherence Tomography in Eyes with Keratoconus. J Ophthalmol 2017; 2017:4313784. [PMID: 28261495 PMCID: PMC5312050 DOI: 10.1155/2017/4313784] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 12/13/2016] [Accepted: 12/29/2016] [Indexed: 11/21/2022] Open
Abstract
Purpose. To evaluate agreement between measured and intended distance of Keraring (Mediphacos, Belo Horizonte, Brazil) intracorneal ring segments from the anterior and posterior corneal surfaces. Methods. Twenty-six Keraring ICRS implanted in 24 keratoconic eyes were examined. The distance from the Keraring apex to the anterior corneal surface and the distance from the inner and the outer corners to the posterior corneal surface were measured 3 months postoperatively using spectral-domain optical coherence tomography. Agreement between measured distance and intended distance was assessed by calculating the absolute differences and 95% limits of agreement (95% LoA). Results. The mean absolute difference was significantly lower (p < 0.001) for the measurements taken at the inner corner (23.54 ± 15.90 μm) than that for those taken at the apex (108.92 ± 62.72 μm) and the outer corner (108.35 ± 56.99 μm). The measurements taken at the inner corner were within ±25 and ±50 μm of the intended distance in 15/26 (57.7%) and 24/26 (92.3%) cases, respectively, and showed the narrowest 95% LoA with the intended distance (−57.61 to 55.15 μm). Conclusions. The distance of the inner corner from the posterior corneal surface showed the best agreement with the intended distance. This measurement is suitable for determining whether the actual Keraring depth matches the intended depth.
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Wang X, Li X, Chen W, He R, Gao Z, Feng P. Effects of ablation depth and repair time on the corneal elastic modulus after laser in situ keratomileusis. Biomed Eng Online 2017; 16:20. [PMID: 28095867 PMCID: PMC5240448 DOI: 10.1186/s12938-017-0311-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 01/02/2017] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND The biomechanical properties of the cornea should be taken into account in the refractive procedure in order to perform refractive surgery more accurately. The effects of the ablation depth and repair time on the elastic modulus of the rabbit cornea after laser in situ keratomileusis (LASIK) are still unclear. METHODS In this study, LASIK was performed on New Zealand rabbits with different ablation depth (only typical LASIK flaps were created; residual stroma bed was 50 or 30% of the whole cornea thickness respectively). The animals without any treatment were served as normal controls. The corneal thickness was measured by ultrasonic pachymetry before animals were humanly killed after 7 or 28 days post-operatively. The corneal elastic modulus was measured by uniaxial tensile testing. A mathematical procedure considering the actual geometrics of the cornea was created to analyze the corneal elastic modulus. RESULTS There were no obvious differences among all groups in the elastic modulus on after 7 days post-operatively. However, after 28th days post-operatively, there was a significant increase in the elastic modulus with 50 and 30% residual stroma bed; only the elastic modulus of the cornea with 30% residual stroma bed was significantly higher than that of 7 days. CONCLUSIONS Changes in elastic modulus after LASIK suggest that this biomechanical effect may correlate with the ablation depth and repair time.
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Affiliation(s)
- Xiaojun Wang
- Collage of Mechanics, Taiyuan University of Technology, Yingze west street 79, Taiyuan, 030024, People's Republic of China
| | - Xiaona Li
- Collage of Mechanics, Taiyuan University of Technology, Yingze west street 79, Taiyuan, 030024, People's Republic of China.
| | - Weiyi Chen
- Collage of Mechanics, Taiyuan University of Technology, Yingze west street 79, Taiyuan, 030024, People's Republic of China.
| | - Rui He
- Department of Excimer Laser, Shanxi Eye Hospital, Fudong street 100, Taiyuan, 030002, People's Republic of China
| | - Zhipeng Gao
- Collage of Mechanics, Taiyuan University of Technology, Yingze west street 79, Taiyuan, 030024, People's Republic of China
| | - Pengfei Feng
- Collage of Mechanics, Taiyuan University of Technology, Yingze west street 79, Taiyuan, 030024, People's Republic of China
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Affiliation(s)
- Davin Johnson
- Department of Ophthalmology, CHUM-Notre Dame Hospital, Montreal, Canada
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Abstract
PURPOSE OF REVIEW This article reviews the association of a novel metric, percentage tissue altered (PTA), with the occurrence of ectasia after laser in-situ keratomileusis in eyes with normal corneal topography, and analyses the influence of the variables that comprise it, and its role on eyes with suspicious topography. RECENT FINDINGS PTA is derived from [PTA = (FT + AD)/CCT] where FT = flap thickness, AD = ablation depth, and CCT = preoperative central corneal thickness. Our studies revealed that there is a robust relationship between high PTA and ectasia risk in eyes with normal preoperative topography. PTA higher or equal to 40% presented the highest odds ratio and highest predictive capabilities for ectasia risk than each of the variables that comprise it, residual stromal bed or age. Average thicker flaps alone were insufficient to create ectasia unless coupled with greater ablation depths, meaning a high PTA. In eyes with suspicious topography, even low PTA value is sufficient to induce ectasia. SUMMARY This new metric, PTA, should be taken into account when screening patients for refractive surgery. Patients with normal topography or tomography, presenting a PTA higher or equal to 40% should be considered at higher risk for post laser in-situ keratomileusis ectasia.
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Influence of the flap on outcomes in corneal refractive surgery with femtosecond laser: SMILE vs. FLEx. ACTA ACUST UNITED AC 2016; 92:218-224. [PMID: 27916313 DOI: 10.1016/j.oftal.2016.10.007] [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: 06/09/2016] [Revised: 10/04/2016] [Accepted: 10/08/2016] [Indexed: 11/23/2022]
Abstract
OBJECTIVE To investigate the influence of creating a flap on the postoperative optical quality of the cornea in terms of predicted corneal curvature and Seidel aberrations after 2 modalities of femtosecond assisted corneal lenticule extraction laser for the correction of myopia and myopic astigmatism: The flapless procedure small incision lenticular extraction (SMILE) and the flap-based femtosecond lenticular extraction (FLEx). METHODS The study is a prospective consecutive non-randomised comparative interventional case series including 64 eyes with myopic or myopic astigmatism refractive errors. Patients were divided into 2 groups matched for age, sex and myopia. One group underwent SMILE treatment and the other underwent FLEx treatment. Seidel aberrations root-mean-square values were obtained with a 10mm aperture using the ATLAS 9000 topographer before surgery and 3 months after surgery. The relationship between the post-surgical corneal radius and the predicted sculpted radius were analysed in each group. RESULTS The mean percentage change in the curvature radius was -2.03% in the FLEx group and -1.77% in the SMILE group (P=.655). The higher correlation for the SMILE group demonstrates a better predictability after the surgery. As regards corneal aberrations, the FLEx treatment showed a greater increase of higher order aberrations than SMILE treatment (P=.04). CONCLUSION The mean refractive change in corneal curvature, which is indirectly related to the biomechanical response of the corneal surface after the lenticule cut and extraction, was similar after both treatments. However, the flap based FLEx procedure showed a greater degradation of the corneal optical quality in terms of induction of higher order aberrations.
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Seven I, Vahdati A, De Stefano VS, Krueger RR, Dupps WJ. Comparison of Patient-Specific Computational Modeling Predictions and Clinical Outcomes of LASIK for Myopia. Invest Ophthalmol Vis Sci 2016; 57:6287-6297. [PMID: 27893094 PMCID: PMC5119490 DOI: 10.1167/iovs.16-19948] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Accepted: 09/10/2016] [Indexed: 11/24/2022] Open
Abstract
Purpose To assess the predictive accuracy of simulation-based LASIK outcomes. Methods Preoperative and 3-month post-LASIK tomographic data from 20 eyes of 12 patients who underwent wavefront-optimized LASIK for myopia were obtained retrospectively. Patient-specific finite element models were created and case-specific treatment settings were simulated. Simulated keratometry (SimK) values and the mean tangential curvature of the central 3 mm (Kmean) were obtained from the anterior surfaces of the clinical tomographies, and computational models were compared. Correlations between Kmean prediction error and patient age, preoperative corneal hysteresis (CH), and corneal resistance factor (CRF) were assessed. Results The mean difference for Kmean between simulated and actual post-LASIK cases was not statistically significant (-0.13 ± 0.36 diopters [D], P = 0.1). The mean difference between the surgically induced clinical change in Kmean and the model-predicted change was -0.11 ± 0.34 D (P = 0.2). Kmean prediction error was correlated to CH, CRF, and patient age (r = 0.63, 0.53, and 0.5, respectively, P < 0.02), and incorporation of CH values into predictions as a linear offset increased their accuracy. Simulated changes in Kmean accounted for 97% of the variance in actual spherical equivalent refractive change. Conclusions Clinically feasible computational simulations predicted corneal curvature and manifest refraction outcomes with a level of accuracy in myopic LASIK cases that approached the limits of measurement error. Readily available preoperative biomechanical measures enhanced simulation accuracy. Patient-specific simulation may be a useful tool for clinical guidance in de novo LASIK cases.
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Affiliation(s)
- Ibrahim Seven
- Ocular Biomechanics and Imaging Lab, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - Ali Vahdati
- Ocular Biomechanics and Imaging Lab, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | | | - Ronald R. Krueger
- Refractive Surgery Service, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
| | - William J. Dupps
- Ocular Biomechanics and Imaging Lab, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
- Refractive Surgery Service, Cole Eye Institute, Cleveland Clinic, Cleveland, Ohio, United States
- Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States
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Chen M, Yu M, Dai J. Comparison of biomechanical effects of small incision lenticule extraction and laser-assisted subepithelial keratomileusis. Acta Ophthalmol 2016; 94:e586-e591. [PMID: 27130377 DOI: 10.1111/aos.13035] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2015] [Accepted: 01/22/2016] [Indexed: 11/30/2022]
Abstract
PURPOSE To compare the corneal biomechanical properties after small incision lenticule extraction (SMILE) group and laser-assisted subepithelial keratomileusis (LASEK) group. METHODS The SMILE group comprised 39 patients (75 eyes) while it was 38 patients (76 eyes) in the LASEK group. Corneal hysteresis (CH) and the corneal resistance factor (CRF) parameters were determined using the Ocular Response Analyzer preoperatively and at 1 and 3 months postoperatively. RESULTS There were significant differences in the preoperative manifest refraction spherical equivalent (MRSE), central corneal thickness (CCT), the planned ablation depth (AD) or CRF values between the two groups, except for the CH value (p = 0.07). The CH and CRF values at 1 and 3 months postoperatively were significantly lower than the preoperative values in both groups (p < 0.01). The postoperative CH values were significantly lower in the LASEK group than in the SMILE group at both follow-up visits after adjusting for age, sex, preoperative CCT, preoperative SE, planned AD and the use of both eyes in the same subject (p < 0.01). However, no significant differences were observed in postoperative CRF between groups (p = 0.22 at 1 month and p = 0.41 at 3 months). No significant correlation was found between the planned AD and the changes in CH or CRF at any follow-up visit in the SMILE group. The preoperative magnitude of CH and CRF may be predictors of postoperative changes in CH and CRF in the both groups. CONCLUSIONS CH and CRF decreased after SMILE and LASEK. However, the changes in the CH values were less after SMILE than after LASEK.
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Affiliation(s)
- Minjie Chen
- Department of Ophthalmology; EENT Hospital; Fudan University; Shanghai China
- Key Laboratory of Myopia; Ministry of Health; Shanghai China
| | - Manrong Yu
- Department of Ophthalmology; EENT Hospital; Fudan University; Shanghai China
- Key Laboratory of Myopia; Ministry of Health; Shanghai China
| | - Jinhui Dai
- Department of Ophthalmology; EENT Hospital; Fudan University; Shanghai China
- Key Laboratory of Myopia; Ministry of Health; Shanghai China
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Osman IM, Helaly HA, Abdalla M, Shousha MA. Corneal biomechanical changes in eyes with small incision lenticule extraction and laser assisted in situ keratomileusis. BMC Ophthalmol 2016; 16:123. [PMID: 27457241 PMCID: PMC4960872 DOI: 10.1186/s12886-016-0304-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 07/17/2016] [Indexed: 11/28/2022] Open
Abstract
Background Evaluating the corneal biomechanical changes using the Ocular Response Analyzer and the Corvis ST in eyes with incision lenticule extraction (SMILE) and laser assisted in situ keratomileusis (LASIK). Methods This is a retrospective study that included 50 eyes equally divided into two groups. The first group included eyes that underwent SMILE procedure using VisuMax® 500 kHz laser system (Carl Zeiss Meditec, Jena, Germany) and the second group included eyes that underwent LASIK procedure using the EX500 Allegretto excimer laser platform (Wavelight GmbH, Erlangen, Germany). The Ocular Response Analyzer (ORA) and the Corvis ST (CST) measured the corneal biomechanical changes before and after the procedures. Results The ORA showed significant decrease of corneal hysteresis (CH) and corneal resistance factor (CRF) in both groups postoperatively. The percentage of change of CH and CRF were found to be significantly higher in group II. There was no significant difference in the IOP with the ORA and the CST pre and postoperatively in either group. Using CST, the deformation amplitude and HC peak distances increased significantly in both groups. It was also noted that the mean percentage of change of the deformation amplitude was nearly five times higher in group II than group I. Conclusion Both LASIK and SMILE substantially decreased the corneal biomechanical properties with greater reduction in the LASIK group.
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Affiliation(s)
- Ihab Mohamed Osman
- Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt.,Roayah Vision Correction Center, Alexandria, Egypt
| | - Hany Ahmed Helaly
- Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt.
| | | | - Mohsen Abou Shousha
- Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt
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Sharifipour F, Panahi-Bazaz M, Bidar R, Idani A, Cheraghian B. Age-related variations in corneal biomechanical properties. J Curr Ophthalmol 2016; 28:117-22. [PMID: 27579455 PMCID: PMC4992116 DOI: 10.1016/j.joco.2016.05.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Revised: 05/15/2016] [Accepted: 05/15/2016] [Indexed: 11/26/2022] Open
Abstract
Purpose To determine age-related changes in corneal viscoelastic properties in healthy individuals. Methods This observational cross-sectional study was performed at the Department of Ophthalmology, Imam Khomeini Hospital, Ahvaz, Iran and included 302 healthy individuals in 6 age decades (range: 10–69 years). After complete ocular examination, corneal viscoelastic properties were measured by ocular response analyzer and central corneal thickness (CCT) by an ultrasonic pachymeter. Our main outcome measures were corneal viscoelastic properties in different age groups. Results Corneal hysteresis (CH) and corneal resistance factor (CRF) showed a significant negative correlation with age (P < 0.001 for both, r = −0.353 and r = −0.246, respectively). Female gender had significantly higher CH (P = 0.017) and CRF (P = 0.019). CH and CRF were significantly correlated (P < 0.001, r = 0.821). CCT showed a biphasic pattern with significantly higher thicknesses before 20 and after 50 years of age. CH and CRF were significantly correlated with CCT (P < 0.001 for both, r = 0.21 and r = 0.26, respectively) and intraocular pressure (IOP) (P < 0.001 for both, r = −0.474 and r = 0.598, respectively). Corneal-compensated IOP (IOPcc) was significantly higher after age 40 compared to age group <20 (p < 0.045). Goldmann-correlated IOP (IOPg) was significantly correlated with CCT (P = 0.001, r = 0.193), while IOPcc showed no correlation with CCT (P = 0.265, r = 0.062). CH was significantly higher in hyperopic eyes compared to emmetropic eyes (P = 0.009) and myopic eye (P < 0.001). Conclusions In this study, there was a decrease in CH and CRF with an increase in age. Hyperopia and female gender are associated with higher CH and CRF. CCT is higher toward the extremes of life and is significantly correlated with CH and CRF.
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Affiliation(s)
- Farideh Sharifipour
- Department of Ophthalmology, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | | | - Roghayeh Bidar
- Department of Ophthalmology, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
| | - Aida Idani
- Iran University of Medical Sciences, Tehran, Iran
| | - Bahman Cheraghian
- Department of Biostatics and Epidemiology, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
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Abstract
OBJECTIVES To determine the effect of hydration media on ex vivo corneal elasticity. METHODS Experiments were conducted on 40 porcine eyes retrieved from an abattoir (10 eyes each for phosphate-buffered saline (PBS), balanced salt solution, Optisol, 15% dextran). The epithelium was removed, and the cornea was excised with an intact scleral rim and placed in 20% dextran overnight to restore its physiological thickness. For each hydration media, corneas were evenly divided into two groups: one with an intact scleral rim and the other without. Corneas were mounted onto a custom chamber and immersed in a hydration medium for elasticity testing. Although in each medium, corneal elasticity measurements were performed for 2 hr: at 5-min intervals for the first 30 min and then 15-min intervals for the remaining 90 min. Elasticity testing was performed using nanoindentation with spherical indenters, and Young modulus was calculated using the Hertz model. Thickness measurements were taken before and after elasticity testing. RESULTS The percentage change in corneal thickness and elasticity was calculated for each hydration media group. Balanced salt solution, PBS, and Optisol showed an increase in thickness and Young moduli for corneas with and without an intact scleral rim. Fifteen percent dextran exhibited a dehydrating effect on corneal thickness and provided stable maintenance of corneal elasticity for both groups. CONCLUSIONS Hydration media affects the stability of corneal thickness and elasticity measurements over time. Fifteen percent dextran was most effective in maintaining corneal hydration and elasticity, followed by Optisol.
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Chan C, Lawless M, Sutton G, Versace P, Hodge C. Small incision lenticule extraction (SMILE) in 2015. Clin Exp Optom 2016; 99:204-12. [PMID: 27156103 DOI: 10.1111/cxo.12380] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Revised: 11/11/2015] [Accepted: 11/19/2015] [Indexed: 11/30/2022] Open
Abstract
Small incision lenticule extraction (SMILE) represents a recent addition to the refractive surgeon's range of procedures. Although there remains a number of similarities to existing techniques in terms of patient selection and treatment parameters, consideration is required to optimise patient outcomes and satisfaction. Here, we review the selection criteria, contraindications, indications and existing published safety and efficacy outcomes.
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Affiliation(s)
- Colin Chan
- Vision Eye Institute, Chatswood, New South Wales, Australia
| | - Michael Lawless
- Vision Eye Institute, Chatswood, New South Wales, Australia.,Save Sight Institute, Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | - Gerard Sutton
- Vision Eye Institute, Chatswood, New South Wales, Australia.,Save Sight Institute, Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia
| | | | - Chris Hodge
- Vision Eye Institute, Chatswood, New South Wales, Australia.,University of New South Wales, Kensington, New South Wales, Australia
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Santhiago MR, Giacomin NT, Smadja D, Bechara SJ. Ectasia risk factors in refractive surgery. Clin Ophthalmol 2016; 10:713-20. [PMID: 27143849 PMCID: PMC4844427 DOI: 10.2147/opth.s51313] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
This review outlines risk factors of post-laser in situ keratomileusis (LASIK) ectasia that can be detected preoperatively and presents a new metric to be considered in the detection of ectasia risk. Relevant factors in refractive surgery screening include the analysis of intrinsic biomechanical properties (information obtained from corneal topography/tomography and patient’s age), as well as the analysis of alterable biomechanical properties (information obtained from the amount of tissue altered by surgery and the remaining load-bearing tissue). Corneal topography patterns of placido disk seem to play a pivotal role as a surrogate of corneal strength, and abnormal corneal topography remains to be the most important identifiable risk factor for ectasia. Information derived from tomography, such as pachymetric and epithelial maps as well as computational strategies, to help in the detection of keratoconus is additional and relevant. High percentage of tissue altered (PTA) is the most robust risk factor for ectasia after LASIK in patients with normal preoperative corneal topography. Compared to specific residual stromal bed (RSB) or central corneal thickness values, percentage of tissue altered likely provides a more individualized measure of biomechanical alteration because it considers the relationship between thickness, tissue altered through ablation and flap creation, and ultimate RSB thickness. Other recognized risk factors include low RSB, thin cornea, and high myopia. Age is also a very important risk factor and still remains as one of the most overlooked ones. A comprehensive screening approach with the Ectasia Risk Score System, which evaluates multiple risk factors simultaneously, is also a helpful tool in the screening strategy.
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Affiliation(s)
- Marcony R Santhiago
- Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil
| | - Natalia T Giacomin
- Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil
| | - David Smadja
- Ophthalmology Department, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
| | - Samir J Bechara
- Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil
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83
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Kocamış Sİ, Çakmak HB, Gerçeker S, Çağıl N. Long-Term Clinical Outcomes of Myopic Patients Having Thin Residual Corneal Thickness after Excimer Laser Surface Ablation. Semin Ophthalmol 2016; 32:474-481. [PMID: 27078188 DOI: 10.3109/08820538.2015.1120755] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE To investigate and compare the long-term safety, efficacy, and accuracy of PRK (photorefractive keratectomy) and LASEK (laser epithelial keratomileusis) in myopic corneas having residual corneal thickness less than 400 micron meters (µm). METHODS The medical reports of the patients who had undergone excimer laser surface ablation between 2007-2011 and had a residual corneal thickness less than 400 µm were retrospectively reviewed. RESULTS Forty-two eyes of 42 patients with a mean age of 28.79±7.76 years were enrolled into the study. Twenty-two PRK and 20 LASEK procedures were performed. The mean follow-up time was 45.00±11.80 months. At the end of follow-up, no ectasia was detected. Nineteen percent of eyes had trace haze. No eyes lost any lines in corrected distance visual acuity. Eighty-one percent of the patients had an uncorrected distance visual acuity better than 20/40. The regression rate was 16.7%. Sixty-two percent of eyes were within ±1.00 D. The safety and efficacy indexes were 1.19±0.42 and 1.00±0.40, respectively. There was not any difference between LASEK and PRK regarding achieved spherical equivalent refraction, haze ratio, visual acuity, safety, efficacy, and regression. CONCLUSIONS Both PRK and LASEK are safe and effective in myopic corneas having thin residual thickness.
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Affiliation(s)
| | | | | | - Nurullah Çağıl
- d Department of Ophthalmology , Yıldırım Beyazıt University , Ankara , Turkey
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84
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Yıldırım Y, Ölçücü O, Başcı A, Ağca A, Özgürhan EB, Alagöz C, Demircan A, Demirok A. Comparison of Changes in Corneal Biomechanical Properties after Photorefractive Keratectomy and Small Incision Lenticule Extraction. Turk J Ophthalmol 2016; 46:47-51. [PMID: 27800259 PMCID: PMC5082248 DOI: 10.4274/tjo.49260] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2015] [Accepted: 04/27/2015] [Indexed: 12/02/2022] Open
Abstract
Objectives: To compare the postoperative biomechanical properties of the cornea after photorefractive keratectomy (PRK) and small incision lenticule extraction (SMILE) in eyes with low and moderate myopia. Materials and Methods: We retrospectively examined 42 eyes of 23 patients undergoing PRK and 42 eyes of 22 patients undergoing SMILE for the correction of low and moderate myopia. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured with an Ocular Response Analyzer before and 6 months after surgery. We also investigated the relationship between these biomechanical changes and the amount of myopic correction. Results: In the PRK group, CH was 10.4±1.3 mmHg preoperatively and significantly decreased to 8.5±1.3 mmHg postoperatively. In the SMILE group, CH was 10.9±1.7 mmHg preoperatively and decreased to 8.4±1.5 mmHg postoperatively. CRF was significantly decreased from 10.8±1.1 mmHg to 7.4±1.5 mmHg in the PRK group whereas it was decreased from 11.1±1.5 mmHg to 7.9±1.6 mmHg in the SMILE group postoperatively. There was a significant correlation between the amount of myopic correction and changes in biomechanical properties after PRK (r=-0.29, p=0.045 for CH; r=-0.07, p=0.05 for CRF) and SMILE (r=-0.25, p=0.048 for CH; r=-0.37, p=0.011 for CRF). Conclusion: Both PRK and SMILE can affect the biomechanical strength of the cornea. SMILE resulted in larger biomechanical changes than PRK.
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Affiliation(s)
- Yusuf Yıldırım
- Beyoğlu Eye Training and Research Hospital, Ophthalmology Clinic, İstanbul, Turkey
| | - Onur Ölçücü
- Beyoğlu Eye Training and Research Hospital, Ophthalmology Clinic, İstanbul, Turkey
| | - Abdurrahman Başcı
- Beyoğlu Eye Training and Research Hospital, Ophthalmology Clinic, İstanbul, Turkey
| | - Alper Ağca
- Beyoğlu Eye Training and Research Hospital, Ophthalmology Clinic, İstanbul, Turkey
| | - Engin Bilge Özgürhan
- Beyoğlu Eye Training and Research Hospital, Ophthalmology Clinic, İstanbul, Turkey
| | - Cengiz Alagöz
- Beyoğlu Eye Training and Research Hospital, Ophthalmology Clinic, İstanbul, Turkey
| | - Ali Demircan
- Rize State Hospital, Ophthalmology Clinic, Rize, Turkey
| | - Ahmet Demirok
- Beyoğlu Eye Training and Research Hospital, Ophthalmology Clinic, İstanbul, Turkey
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85
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Contralateral Eye Comparison Between Femtosecond Small Incision Intrastromal Lenticule Extraction at Depths of 100 and 160 μm. Cornea 2016; 34:1272-5. [PMID: 26266430 DOI: 10.1097/ico.0000000000000571] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To compare the visual results, higher-order aberrations, and corneal biomechanical properties of femtosecond small incision lenticule extraction (SMILE) at depths of 100 and 160 μm. METHODS A prospective comparative interventional clinical trial of a series of patients who underwent SMILE. In the right eye, a refractive lenticule was created at a depth of 100 μm, and in the left eye, a depth of 160 μm was used. Manifest refraction, uncorrected visual acuity, total high-order aberrations (THOA), and corneal biomechanical properties of both eyes were evaluated 1 month postoperatively. RESULTS Thirty patients with bilaterally stable refractive errors were included in this study. One month postoperatively, mean corneal hysteresis was 9.71 ± 0.68 in the right eyes and 9.97 ± 0.77 in the left eyes, whereas the mean corneal resistant factor was 9.13 ± 1.04 and 9.31 ± 0.92 in the right and left eyes, respectively. Both corneal hysteresis and corneal resistant factor showed statistically significantly higher values in the left eyes (lenticule at a depth of 160 μm). No statistically significant differences were found between the right and the left eyes regarding manifest refraction, uncorrected visual acuity, and THOA. CONCLUSIONS Creating the refractive lenticule at a depth of 160 μm in SMILE had less effect on the corneal biomechanics than did creating a lenticule at a depth of 100 μm with no statistically significant differences in the refractive outcome and THOA between both groups.
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86
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Changes in ocular biomechanics after femtosecond laser creation of a laser in situ keratomileusis flap. J Cataract Refract Surg 2016; 42:127-31. [PMID: 26948787 DOI: 10.1016/j.jcrs.2015.07.047] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2015] [Revised: 07/29/2015] [Accepted: 07/31/2015] [Indexed: 11/21/2022]
Abstract
PURPOSE To evaluate ocular biomechanical parameters with the Corvis ST, a noncontact tonometer combined with an ultra-high-speed Scheimpflug camera, before and after creation of a femtosecond laser-created laser in situ keratomileusis (LASIK) flap. SETTING Private practice, Siena, Italy. DESIGN Prospective consecutive study. METHODS Right eyes of patients having LASIK were assessed with the dynamic Scheimpflug camera before and after femtosecond laser (LDV Z4) flap creation but before mechanical flap lifting. RESULTS Twenty-eight eyes of 28 patients were evaluated. Before flap creation, the mean values on the dynamic Scheimpflug camera were intraocular pressure (IOP), 15.04 mm Hg ± 3.99 (SD); central pachymetry, 550.8 ± 101.0 μm; applanation 1 length, 1.721 ± 0.134 mm; applanation 2 length, 1.674 ± 0.287 mm; applanation 1 velocity, 0.126 ± 0.031 m/s; and deflection amplitude, 1.039 ± 0.141 mm. After flap creation, the mean values were IOP, 16.10 ± 3.11 mm Hg (95% confidence interval [CI], 0.44-1.78; P < .05); central pachymetry, 561.8 ± 35.9 μm (95% CI, -28.9 to 50.9; P = .21); applanation 1 length, 1.789 ± 0.1492 mm (95% CI, 0.003-0.134; P < .05); applanation 2 length, 1.759 ± 0.259 mm (95% CI, -0.005 to 0.173; P = .08); applanation 1 velocity, 0.136 ± 0.022 m/s (95% CI, 0.001-0.017; P < .05); and deflection amplitude, 1.029 ± 0.151 mm (95% CI: -0.043 to 0.025; P = .34). CONCLUSION The dynamic Scheimpflug camera showed changes in biomechanical properties after femtosecond creation of a LASIK flap as indicated by an increased applanation 1 length and applanation 1 velocity. FINANCIAL DISCLOSURE No author has a financial or proprietary interest in any material or method mentioned.
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87
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Can Riboflavin Penetrate Stroma Without Disrupting Integrity of Corneal Epithelium in Rabbits? Iontophoresis and Ultraperformance Liquid Chromatography With Electrospray Ionization Tandem Mass Spectrometry. Cornea 2016; 34:932-6. [PMID: 26075452 DOI: 10.1097/ico.0000000000000438] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
PURPOSE To examine riboflavin concentrations in corneas and aqueous humor from rabbits with standard and transepithelial methods and iontophoresis without disrupting the integrity of the corneal epithelium before corneal collagen cross-linking. METHODS Twenty-four eyes of 12 adult New Zealand rabbits were used. They were assigned to 4 groups, each including 6 eyes. Group 1 was exposed to the standard method and given riboflavin 0.1% after epithelial debridement. Group 2 was exposed to the transepithelial method and given benzalkonium chloride (BAC), ethylenediaminetetraacetic acid (EDTA), trometamol (TRIS), hydroxypropylmethylcellulose (HPMC), and riboflavin 0.2% 3 times at 1.5-minute intervals followed by riboflavin 0.2%. Group 3 was given riboflavin 0.1% by using 1-mA electric current for 10 minutes with the help of iontophoresis without using substances disrupting the integrity of the corneal epithelium. Group 4 received the same treatment as did group 3, except that it was given riboflavin 0.2%. Following these treatments, riboflavin concentrations in aqueous humor and corneas were measured with ultraperformance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS). RESULTS Riboflavin concentrations in the cornea and aqueous humor were higher in group 1 (42.4 ± 5.4 μg/g) than in the other groups. They were significantly higher in group 4 (34.2 ± 6.6 μg/g) than in group 2 (24.4 ± 1.2 μg/g) (P = 0.009) and group 3 (23.6 ± 6.1 μg/g) (P = 0.026). There was not a significant difference in corneal riboflavin concentrations between group 2 and group 3 (P = 0.937). CONCLUSIONS Intrastromal and aqueous riboflavin concentrations after administration of riboflavin 0.2% through iontophoresis without disrupting the integrity of the corneal epithelium were lower than those after the standard method, but higher than those after the transepithelial method. In this study, in which riboflavin concentrations were measured with a very sensitive method, iontophoresis was observed to increase the transmission of riboflavin molecules into the cornea without using substances disrupting epithelial integrity.
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Wolle MA, Randleman JB, Woodward MA. Complications of Refractive Surgery: Ectasia After Refractive Surgery. Int Ophthalmol Clin 2016; 56:127-139. [PMID: 26938343 PMCID: PMC4780337 DOI: 10.1097/iio.0000000000000102] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Affiliation(s)
- Meraf A. Wolle
- Department of Ophthalmology, University of Michigan, Ann Arbor, MI, USA
| | - J. Bradley Randleman
- Department of Ophthalmology, Emory University, Atlanta, GA, USA
- Emory Vision, Emory Eye Center, Atlanta, GA
| | - Maria A. Woodward
- Department of Ophthalmology, University of Michigan, Ann Arbor, MI, USA
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Graue-Hernandez EO, Pagano GL, Garcia-De la Rosa G, Ramirez-Miranda A, Cabral-Macias J, Lichtinger A, Abdala-Figuerola A, Navas A. Combined small-incision lenticule extraction and intrastromal corneal collagen crosslinking to treat mild keratoconus: Long-term follow-up. J Cataract Refract Surg 2015; 41:2524-32. [PMID: 26703503 DOI: 10.1016/j.jcrs.2015.06.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 06/01/2015] [Accepted: 06/03/2015] [Indexed: 10/22/2022]
Abstract
PURPOSE To report visual, refractive, and topographic outcomes of sequential, same-day small-incision lenticule extraction and intrastromal corneal collagen crosslinking (CXL) in eyes with mild keratoconus. SETTING Institute of Ophthalmology Conde de Valenciana, Mexico City, Mexico. DESIGN Prospective interventional case series. METHODS Fifteen eyes with forme fruste keratoconus and/or irregular corneas, corrected distance visual acuity 20/40 or better, stable refraction of at least 1 year, age 18 years or older, and residual corneal thickness of greater tan 400 μm before performing collagen crosslinking were studied. Patients were treated with small-incision lenticule extraction followed by intrastromal injection of riboflavin inside the pocket. Ultraviolet A light with a wavelength of 370 nm to 3 mW/cm(2) was applied for 30 minutes. Follow-up was done at 1 day, at 1 week, and at 1, 3, 6, 12, 18, and 24 months. RESULTS Eight patients were included in the study. The mean age was 29.5 years ± 5.5 (SD) (range 20 to 36 years). Twenty-four months of follow-up were completed in 13 eyes, and 12 months were completed in 2 eyes. Preoperative uncorrected distance visual acuity improved from 1.6 ± 0.3 LogMAR (Snellen 20/796) to postoperative 0.12 ± 0.20 LogMAR (Snellen 20/26) and was statistically significant (P < .001). Best-corrected distance visual acuity did not change significantly (P = .186), from 0.006 ± 0.02 LogMAR (Snellen 20/20) preoperatively to 0.04 ± 0.05 LogMAR (Snellen 20/21) postoperatively, and spherical equivalent improved from -4.3 ± 1.02 preoperatively to 0.2 ± 0.66 (P < .001). CONCLUSION Although further follow-up and larger samples are needed to fully confirm these findings, the results suggest that combined small-incision lenticule extraction and intrastromal corneal collagen crosslinking are a promising treatment option for patients for whom conventional laser refractive surgery is contraindicated. FINANCIAL DISCLOSURE Drs. Ramirez-Miranda and Navas are consultants to Carl Zeiss Meditec. No other author has a financial or proprietary interest in any material or method mentioned.
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Affiliation(s)
- Enrique O Graue-Hernandez
- From the Department of Cornea and Refractive Surgery, Instituto de Oftalmologia "Conde de Valenciana", Mexico City, Mexico.
| | - Gabriela L Pagano
- From the Department of Cornea and Refractive Surgery, Instituto de Oftalmologia "Conde de Valenciana", Mexico City, Mexico
| | - Guillermo Garcia-De la Rosa
- From the Department of Cornea and Refractive Surgery, Instituto de Oftalmologia "Conde de Valenciana", Mexico City, Mexico
| | - Arturo Ramirez-Miranda
- From the Department of Cornea and Refractive Surgery, Instituto de Oftalmologia "Conde de Valenciana", Mexico City, Mexico
| | - Jesus Cabral-Macias
- From the Department of Cornea and Refractive Surgery, Instituto de Oftalmologia "Conde de Valenciana", Mexico City, Mexico
| | - Alejandro Lichtinger
- From the Department of Cornea and Refractive Surgery, Instituto de Oftalmologia "Conde de Valenciana", Mexico City, Mexico
| | - Alexandra Abdala-Figuerola
- From the Department of Cornea and Refractive Surgery, Instituto de Oftalmologia "Conde de Valenciana", Mexico City, Mexico
| | - Alejandro Navas
- From the Department of Cornea and Refractive Surgery, Instituto de Oftalmologia "Conde de Valenciana", Mexico City, Mexico
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90
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Brenner LF. Corneal higher-order aberrations and higher-order Strehl ratio after aberration-free ablation profile to treat compound myopic astigmatism. J Cataract Refract Surg 2015; 41:2672-82. [DOI: 10.1016/j.jcrs.2015.06.035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 06/24/2015] [Accepted: 06/26/2015] [Indexed: 10/22/2022]
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91
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Mathew JH, Goosey JD, Söderberg PG, Bergmanson JPG. Lamellar changes in the keratoconic cornea. Acta Ophthalmol 2015; 93:767-73. [PMID: 26278201 DOI: 10.1111/aos.12811] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 06/23/2015] [Indexed: 11/28/2022]
Abstract
PURPOSE The purpose of this study was to identify ultrastructural changes associated with ectasia and to determine the association between lamellar count and corneal thinning. METHODS Five surgically removed keratoconic corneal buttons and four, non-keratoconic, normal eye bank control corneas were processed for transmission electron microscopy using an established protocol, ensuring minimal tissue distortion. A sequence of overlapping digital images, spanning the full apical cone corneal thickness, was assembled. A seamless digital montage was printed at 5000× magnification. Lamellae were counted in the anterior-posterior orientation, along a linear line, using established criteria for identification of individual lamellae. RESULTS The stromal thickness estimated as a 95% confidence interval for the mean, CI (0.95), in the keratoconic corneas was 372 ± 62 μm, while in the normal cornea, it was 446 ± 89 μm. All keratoconic corneas showed ultrastructural evidence of lamellar splitting and a loss of interweaving anterior lamellae. In the keratoconic corneas, the median total linear stromal lamellar absolute count tangential to the corneal surface was 362, (25th percentile; 75th percentile) = (355; 365) lamellae and in the normal cornea, 246, (25th percentile; 75th percentile) = (239; 251). The linear lamellar density in the keratoconic corneas was estimated as CI (0.95) 117 ± 22 and 86 ±19 lamellae per 100 μm in the anterior and posterior portion of the stroma, respectively. In normal cornea, the linear lamellar density was estimated as CI (0.95) 51 ± 8 and 80 ± 20 lamellae per 100 μm. The mean difference of linear lamellar count between the anterior and the posterior portion of the cornea was estimated as CI (0.95) 31 ± 23 for keratoconic corneas and -29 ± 28 for the normal corneas. CONCLUSIONS The current morphometric analysis of ultrastructural changes suggests that ectasia and thinning in keratoconus is associated with lamellar splitting into multiple bundles of collagen fibrils and loss of anterior lamellae. These structural changes, possibly in addition to lateral shifting of lamellae due to the pressure gradient over the cornea, are a potential explanation to the central loss of mass.
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Affiliation(s)
- Jessica H. Mathew
- Texas Eye Research and Technology Center; University of Houston College of Optometry; Houston Texas USA
| | - John D. Goosey
- Texas Eye Research and Technology Center; University of Houston College of Optometry; Houston Texas USA
- Houston Eye Associates; Houston Texas USA
| | - Per G. Söderberg
- Department of Neuroscience; Gullstrand Lab, Ophthalmology; Uppsala University; Uppsala Sweden
| | - Jan P. G. Bergmanson
- Texas Eye Research and Technology Center; University of Houston College of Optometry; Houston Texas USA
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92
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Santhiago MR, Smajda D, Wilson SE, Randleman JB. Relative contribution of flap thickness and ablation depth to the percentage of tissue altered in ectasia after laser in situ keratomileusis. J Cataract Refract Surg 2015; 41:2493-500. [PMID: 26452432 DOI: 10.1016/j.jcrs.2015.05.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 03/24/2015] [Accepted: 05/07/2015] [Indexed: 10/23/2022]
Abstract
PURPOSE To evaluate the contribution of flap thickness and ablation depth to the percentage of tissue altered (PTA) (flap thickness plus ablation depth divided by central corneal thickness) in determining the risk for ectasia after laser in situ keratomileusis (LASIK). SETTING University of São Paulo, São Paulo, Brazil; Cleveland Clinic, Cleveland, Ohio, and Emory Vision at Emory University, Atlanta, Georgia, USA. DESIGN Retrospective comparative study. METHODS The study included 1 group of eyes with bilateral normal preoperative topography that developed ectasia after LASIK (ectasia group) and 2 control groups of eyes that did not develop ectasia after LASIK, 1 with 40% or more of tissue altered (high-PTA group) and 1 with flaps 120 μm or thicker (thick-flap group). RESULTS The 29 eyes (16 patients) in the ectasia group had thicker flaps (146 μm) than the 24 eyes (20 patients) in the high-PTA group (118 μm) and derived a higher portion of PTA from flap thickness. The ectasia group had a higher PTA (45%) than the 100 eyes (50 patients) in the thick-flap group (34%) and greater ablation depths (94 μm versus 43 μm) and derived a higher portion of the PTA from ablation depth. CONCLUSIONS Flap thickness had more impact than ablation depth; however, thicker flaps were insufficient to create ectasia unless coupled with greater ablation depths and thus a high PTA. This percentage was a more significant factor than the variables it comprised. FINANCIAL DISCLOSURE Drs. Santhiago and Smadja are consultants to Ziemer Ophthalmic Systems AG. No other author has a financial or proprietary interest in any material or method mentioned.
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Affiliation(s)
- Marcony R Santhiago
- From the Departments of Ophthalmology, University of São Paulo (Santhiago), and Federal University of Rio de Janeiro (Santhiago), São Paulo, Brazil; University Center Hospital of Bordeaux (Smajda), Bordeaux, France; Cole Eye Institute (Wilson), Cleveland Clinic, Cleveland, Ohio, and Department of Ophthalmology (Randleman), Emory University School of Medicine, and Emory Vision (Randleman), Emory Eye Center, Atlanta, Georgia, USA.
| | - David Smajda
- From the Departments of Ophthalmology, University of São Paulo (Santhiago), and Federal University of Rio de Janeiro (Santhiago), São Paulo, Brazil; University Center Hospital of Bordeaux (Smajda), Bordeaux, France; Cole Eye Institute (Wilson), Cleveland Clinic, Cleveland, Ohio, and Department of Ophthalmology (Randleman), Emory University School of Medicine, and Emory Vision (Randleman), Emory Eye Center, Atlanta, Georgia, USA
| | - Steven E Wilson
- From the Departments of Ophthalmology, University of São Paulo (Santhiago), and Federal University of Rio de Janeiro (Santhiago), São Paulo, Brazil; University Center Hospital of Bordeaux (Smajda), Bordeaux, France; Cole Eye Institute (Wilson), Cleveland Clinic, Cleveland, Ohio, and Department of Ophthalmology (Randleman), Emory University School of Medicine, and Emory Vision (Randleman), Emory Eye Center, Atlanta, Georgia, USA
| | - J Bradley Randleman
- From the Departments of Ophthalmology, University of São Paulo (Santhiago), and Federal University of Rio de Janeiro (Santhiago), São Paulo, Brazil; University Center Hospital of Bordeaux (Smajda), Bordeaux, France; Cole Eye Institute (Wilson), Cleveland Clinic, Cleveland, Ohio, and Department of Ophthalmology (Randleman), Emory University School of Medicine, and Emory Vision (Randleman), Emory Eye Center, Atlanta, Georgia, USA
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Hayes S, Lewis P, Islam MM, Doutch J, Sorensen T, White T, Griffith M, Meek KM. The structural and optical properties of type III human collagen biosynthetic corneal substitutes. Acta Biomater 2015; 25:121-130. [PMID: 26159106 PMCID: PMC4570929 DOI: 10.1016/j.actbio.2015.07.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2015] [Revised: 06/03/2015] [Accepted: 07/06/2015] [Indexed: 11/30/2022]
Abstract
The structural and optical properties of clinically biocompatible, cell-free hydrogels comprised of synthetically cross-linked and moulded recombinant human collagen type III (RHCIII) with and without the incorporation of 2-methacryloyloxyethyl phosphorylcholine (MPC) were assessed using transmission electron microscopy (TEM), X-ray scattering, spectroscopy and refractometry. These findings were examined alongside similarly obtained data from 21 human donor corneas. TEM demonstrated the presence of loosely bundled aggregates of fine collagen filaments within both RHCIII and RHCIII-MPC implants, which X-ray scattering showed to lack D-banding and be preferentially aligned in a uniaxial orientation throughout. This arrangement differs from the predominantly biaxial alignment of collagen fibrils that exists in the human cornea. By virtue of their high water content (90%), very fine collagen filaments (2–9 nm) and lack of cells, the collagen hydrogels were found to transmit almost all incident light in the visible spectrum. They also transmitted a large proportion of UV light compared to the cornea which acts as an effective UV filter. Patients implanted with these hydrogels should be cautious about UV exposure prior to regrowth of the epithelium and in-growth of corneal cells into the implants.
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Association Between Corneal Deformation and Ease of Lenticule Separation From Residual Stroma in Small Incision Lenticule Extraction. Cornea 2015; 34:1067-71. [DOI: 10.1097/ico.0000000000000463] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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95
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Aristeidou A, Taniguchi EV, Tsatsos M, Muller R, McAlinden C, Pineda R, Paschalis EI. The evolution of corneal and refractive surgery with the femtosecond laser. EYE AND VISION 2015; 2:12. [PMID: 26605365 PMCID: PMC4655461 DOI: 10.1186/s40662-015-0022-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 06/20/2015] [Indexed: 01/12/2023]
Abstract
The use of femtosecond lasers has created an evolution in modern corneal and refractive surgery. With accuracy, safety, and repeatability, eye surgeons can utilize the femtosecond laser in almost all anterior refractive procedures; laser in situ keratomileusis (LASIK), small incision lenticule extraction (SMILE), penetrating keratoplasty (PKP), insertion of intracorneal ring segments, anterior and posterior lamellar keratoplasty (Deep anterior lamellar keratoplasty (DALK) and Descemet's stripping endothelial keratoplasty (DSEK)), insertion of corneal inlays and cataract surgery. As the technology matures, it will push surgical limits and open new avenues for ophthalmic intervention in areas not yet explored. As we witness the transition from femto-LASIK to femto-cataract surgery it becomes obvious that this innovation is here to stay. This article presents some of the most relevant advances of femtosecond lasers to modern corneal and refractive surgery.
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Affiliation(s)
| | - Elise V Taniguchi
- Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA USA ; Massachusetts Eye and Ear Infirmary/Schepens Eye Research Institute, Boston Keratoprosthesis Laboratory, Harvard Medical School, Boston, 02114 MA USA
| | | | - Rodrigo Muller
- Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA USA
| | - Colm McAlinden
- Flinders University, Adelaide, South Australia Australia ; Wenzhou Medical University, Wenzhou, Zhejiang China
| | - Roberto Pineda
- Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA USA
| | - Eleftherios I Paschalis
- Massachusetts Eye and Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA USA ; Massachusetts Eye and Ear Infirmary/Schepens Eye Research Institute, Boston Keratoprosthesis Laboratory, Harvard Medical School, Boston, 02114 MA USA
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Scarcelli G, Besner S, Pineda R, Kalout P, Yun SH. In vivo biomechanical mapping of normal and keratoconus corneas. JAMA Ophthalmol 2015; 133:480-2. [PMID: 25611213 DOI: 10.1001/jamaophthalmol.2014.5641] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Giuliano Scarcelli
- Wellman Center for Photomedicine, Massachusetts General Hospital, Cambridge2Department of Dermatology, Harvard Medical School, Boston, Massachusetts
| | - Sebastien Besner
- Wellman Center for Photomedicine, Massachusetts General Hospital, Cambridge2Department of Dermatology, Harvard Medical School, Boston, Massachusetts
| | - Roberto Pineda
- Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Boston
| | - Patricia Kalout
- Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Boston
| | - Seok Hyun Yun
- Wellman Center for Photomedicine, Massachusetts General Hospital, Cambridge2Department of Dermatology, Harvard Medical School, Boston, Massachusetts
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Randleman JB, Khandelwal SS, Hafezi F. Corneal cross-linking. Surv Ophthalmol 2015; 60:509-23. [PMID: 25980780 DOI: 10.1016/j.survophthal.2015.04.002] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2014] [Revised: 04/28/2015] [Accepted: 04/30/2015] [Indexed: 12/26/2022]
Abstract
Since its inception in the late 1990s, corneal cross-linking has grown from an interesting concept to a primary treatment for corneal ectatic disease worldwide. Using a combination of ultraviolet-A light and a chromophore (vitamin B2, riboflavin), the cornea can be stiffened, usually with a single application, and progressive thinning diseases such as keratoconus arrested. Despite being in clinical use for many years, some of the underlying processes, such as the role of oxygen and the optimal treatment times, are still being worked out. More than a treatment technique, corneal cross-links represent a physiological principle of connective tissue, which may explain the enormous versatility of the method. We highlight the history of corneal cross-linking, the scientific underpinnings of current techniques, evolving clinical treatment parameters, and the use of cross-linking in combination with refractive surgery and for the treatment of infectious keratitis.
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Affiliation(s)
- J Bradley Randleman
- Department of Ophthalmology, Emory University, Atlanta, Georgia, USA; Emory Vision, Emory Eye Center, Atlanta, Georgia, USA.
| | | | - Farhad Hafezi
- ELZA Institute, Zurich, Switzerland; Laboratory for Ocular Cell Biology, University of Geneva, Geneva, Switzerland; Department of Ophthalmology, Keck School of Medicine, University of Southern California, Los Angeles, California, USA; Center for Applied Biotechnology and Molecular Medicine (CABMM), University of Zurich, Zurich, Switzerland
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Xu Z, Shen M, Hu L, Zhuang X, Peng M, Hu D, Liu J, Wang J, Qu J, Lu F. The Impact of Flap Creation Methods for Sub-Bowman's Keratomileusis (SBK) on the Central Thickness of Bowman's Layer. PLoS One 2015; 10:e0124996. [PMID: 25938492 PMCID: PMC4418749 DOI: 10.1371/journal.pone.0124996] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 03/19/2015] [Indexed: 11/20/2022] Open
Abstract
Purpose To determine the impact of flap creation methods for sub-Bowman’s keratomileusis (SBK) on central Bowman’s layer thickness. Methods SBK flaps were made by Moria microkeratome for 20 subjects and by femtosecond (FEMTO) laser for 21 subjects. Corneal sublayer thicknesses were measured by ultra-high resolution optical coherence tomography before SBK and at 1 day, 1 week, 2 weeks, and 1 month afterwards. Each subject was imaged twice on each visit. Thicknesses of central epithelium, Bowman’s layer, flap, and total cornea were calculated using a custom-made automated image processing algorithm. The repeatability of sublayer thickness measurements was tested by the intraclass correlation coefficient (ICC) and by the coefficient of repeatability (CoR) at 1 week post-SBK. Results ICCs of the Moria and FEMTO groups were ≥0.959 and ≥0.961 respectively for all sublayer measurements. The segmentation CoRs were less than 6.78% and 5.63% respectively. For both groups, microdistortions were present in the epithelium and Bowman’s layer after SKB. The flap thickness of the Moria group was 9.8 μm (95% confidence interval: 4.8 – 14.8μm) thinner than the FEMTO group one day after SBK (independent samples t-test, P < 0.05). Bowman’s layer became thicker by 1.6 ± 1.1 μm and 1.7 ± 1.6 μm one day post-SBK for the Moria and FEMTO groups (repeated ANOVA, P < 0.05) and then remained stable. Corneal and sublayer thickness were similar between the two groups. Conclusions Central Bowman’s layer thickness increased 1 day post-SBK. Flap creation by Moria microkeratome and femtosecond laser did not have significantly different impacts on Bowman’s layer thickness following SBK. Trial Registration Chinese Clinical Trial Registry (ChiCTR) NO: ChiCTR-OCH-14004525
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Affiliation(s)
- Zhe Xu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Meixiao Shen
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Liang Hu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Xiran Zhuang
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Mei Peng
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Di Hu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Jing Liu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Jianhua Wang
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami, Miami, FL, United States of America
| | - Jia Qu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
| | - Fan Lu
- School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
- * E-mail:
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Abstract
PURPOSE The aim of this study was to evaluate exclusion criteria in screening patients for refractive surgery. METHODS Patients screened for initial refractive surgery by a single surgeon at the Cole Eye Institute (Cleveland Clinic) between 2007 and 2012 were reviewed. Exclusion criteria for patients who were not offered refractive surgery based on history and/or examination parameters were analyzed. RESULTS A total of 1067 refractive candidates were enrolled in the study. Five hundred nineteen (48.6%) were male and 548 (51.4%) were female with a mean age of 39 ± 12 (range, 17-78) years. Refractive surgery was performed in 657 (61.6%) patients, and photorefractive keratectomy was considered the best option for 106 (9.9%) patients. Four hundred ten (38.4%) of all screened patients did not have refractive surgery, and 134 of these patients (12.6%) were considered to have contraindications for laser in situ keratomileusis and photorefractive keratectomy. Among the excluded patients, 69 (51.5%) were male and 65 (48.5%) were female with a mean age of 40 ± 14 (range, 18-78) years. Abnormal corneal topography (34.3%) and low or insufficient corneal thickness (23.1%) were the most common reasons for exclusion. High myopia (10.5%) and (insipient or definite) cataract (9.7%) were also common reasons for exclusion. Other common factors for exclusion were high hyperopia (3.7%), need to wear reading glasses after surgery (3.7%), and severe dry eye unresponsive to treatment (3.7%). CONCLUSIONS Abnormal corneal topography and low, or insufficient, corneal thickness remain the most common exclusion factors for corneal refractive surgery. Factors such as cataract, too high of correction, and severe dry eye are also common reasons for exclusion of patients.
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