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Keskin Perk FFN, Tanriverdi C, Karaca ZY, Tran KD, Kilic A. Long-Term Results of Sterile Corneal Allograft Ring Segments Implantation in Keratoconus Treatment. Cornea 2024:00003226-990000000-00581. [PMID: 38900741 DOI: 10.1097/ico.0000000000003592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Accepted: 05/05/2024] [Indexed: 06/22/2024]
Abstract
PURPOSE To evaluate the efficacy and safety of sterile corneal allograft ring segments implantation for the treatment of keratoconus by analyzing long-term visual, refractive, and tomographic clinical outcomes. METHODS This prospective study included 62 eyes of 49 patients with keratoconus who underwent corneal allograft ring segments implantation at Istanbul Medipol University Faculty of Medicine between February 2020 and August 2022. Surgical outcomes using the Istanbul nomogram were evaluated in patients preoperatively and postoperatively at 1 month, 6 months, 1 year, and 3 years. Outcomes measured were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SE), spherical refraction (SR), cylindrical refraction (CR), topographic keratometric values, and corneal thickness at the thinnest point. RESULTS Preoperative mean UDVA and CDVA (LogMAR) were 0.96 ± 0.50 and 0.72 ± 0.47, respectively, and increased to 0.41 ± 0.34 and 0.22 ± 0.19 at the last visit (P < 0.001). There was a significant decrease in SE, SR, and keratometric values postoperatively (P < 0.001). There was no difference in CR and thinnest corneal thickness values (P = 0.333 and 0.154, respectively). The stromal and epithelial thicknesses measured by anterior segment optical coherence tomography were stabilized at 6 months and 1 year, respectively. No major complications or side effects were observed intraoperatively or postoperatively. CONCLUSIONS This study demonstrated that sterile corneal allograft ring segments implantation is a safe and feasible treatment for keratoconus, yielding notable long-term visual outcomes with minimal implant-related complications.
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Affiliation(s)
| | - Cafer Tanriverdi
- Department of Ophthalmology, Istanbul Medipol University, Faculty of Medicine, Istanbul, Turkey
| | - Zeki Yigit Karaca
- Department of Ophthalmology, Istanbul Medipol University, Faculty of Medicine, Istanbul, Turkey
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2
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Mittal V, Jain N, Pandya Y, Chatterjee D. Customized Bowman-Stromal Inlay: An Attempt to Change the Topography of the Keratoconus Cornea. Cornea 2023; 42:739-743. [PMID: 36977127 DOI: 10.1097/ico.0000000000003257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
PURPOSE The objective of this report is to describe a modification of a previously reported technique with an aim of improving the corneal topography and visual outcomes in progressive keratoconus along with stabilization of ectasia. METHOD In a 26-year-old man with progressive keratoconus, corneal collagen cross-linking was performed in one eye. The other eye had a keratometry of 69.6 D and thinnest pachymetry of 397 µm for which a customized Bowman-stromal inlay surgery was performed. The technique involved the harvesting of Bowman-stromal inlay (anterior 180-μm human donor cornea having the Bowman's layer and anterior stroma) using the femtosecond laser and central ablation of this inlay was done on the stromal side using an excimer laser. This customized inlay was placed in the anterior stromal pocket of the patient's cornea using a regular intraocular lens injector. RESULTS Stabilization of keratoconus could be achieved in the present case along with improvement in the corrected distance visual acuity and pachymetry. Maximum keratometry decreased from 69.6 D to 57.3 D. CONCLUSIONS Customized Bowman-stromal inlay technique appears to be a step towards creating an ideal inlay for the keratoconus cornea.
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Affiliation(s)
- Vikas Mittal
- Cornea and Anterior Segment Services, L J Eye Institute, 251, Model Town, Ambala, Haryana 134002, India
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3
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Moshirfar M, Milner DC, Martheswaran T, McCabe SE, Ronquillo YC, Hoopes PC. Delayed Perforation of an Intrastromal Corneal Ring Segment into the Anterior Chamber: A Case Report and Review of the Literature. Case Rep Ophthalmol 2021; 12:740-748. [PMID: 34720972 PMCID: PMC8460883 DOI: 10.1159/000518012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 06/20/2021] [Indexed: 11/19/2022] Open
Abstract
Intrastromal corneal ring segments (ICRSs) are an effective treatment for stabilizing and normalizing corneal shape in patients with keratoconus and other corneal ectasias. Intraoperative segment perforation through the corneal endothelium into the anterior chamber (AC) is an uncommon but known complication. However, perforation into the AC postoperatively is an exceedingly rare complication with only 3 reported cases in the literature. One case was due to Descemet membrane detachment and another due to ocular trauma. In the third case, the mechanism for perforation was unclear. We present the fourth case of delayed ICRS perforation due to silent migration through the endothelium into the AC. We also present all reported cases in the literature of intraoperative and postoperative perforation into the AC.
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Affiliation(s)
- Majid Moshirfar
- Hoopes Vision Research Center, Hoopes Vision, Draper, Utah, USA.,John A. Moran Eye Center, University of Utah School of Medicine, Salt Lake City, Utah, USA.,Utah Lions Eye Bank, Murray, Utah, USA
| | - Dallin C Milner
- University of Colorado School of Medicine, Aurora, Colorado, USA
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Ariza-Gracia MÁ, Flecha-Lescún J, Büchler P, Calvo B. Corneal Biomechanics After Intrastromal Ring Surgery: Optomechanical In Silico Assessment. Transl Vis Sci Technol 2020; 9:26. [PMID: 33150051 PMCID: PMC7585389 DOI: 10.1167/tvst.9.11.26] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 09/10/2020] [Indexed: 11/24/2022] Open
Abstract
Purpose To provide a biomechanical framework to better understand the postsurgical optomechanical behavior of the cornea after ring implantation. Methods Calibrated in silico models were used to determine the corneal shape and stresses after ring implantation. After mechanical simulations, geometric ray-tracing was used to determine the change in spherical equivalent. The effect of the surgical procedure, circadian variation of intraocular pressure, or the biomechanical weakening introduced by keratoconus (KC) were evaluated for each intrastromal ring. Results Models predicted the postsurgical optomechanical response of the cornea at a population level. The localized mechanical effect of the additional intrastromal volume introduced by the implants (size and diameter) drives the postsurgical corneal response. However, central corneal stresses did not increase more than 50%, and thus implants did not strengthen the cornea globally. Because of the biomechanical weakening introduced by laser pocketing, continuous implants in a pocket resulted in higher refractive corrections and in the relaxation of the anterior stroma, which could slow down KC progression. Implants can move within the stroma, acting as a dynamic pivot point that modifies corneal kinematics and flattens the corneal center. Changes in stromal mechanical properties did not impact on refraction for normal or pathological corneas. Conclusions Implants do not stiffen the cornea but create a local bulkening effect that regularizes the corneal shape by modifying corneal kinematics without canceling corneal motion. Translational Relevance In silico models can help to understand corneal biomechanics, to plan patient-specific interventions, or to create biomechanically driven nomograms.
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Affiliation(s)
- Miguel Ángel Ariza-Gracia
- ARTORG Center for Biomedical Engineering Research, Faculty of Medicine, University of Bern, Bern, Switzerland
| | - Julio Flecha-Lescún
- Aragón Institute for Engineering Research (i3A), University of Zaragoza, Zaragoza, Spain
| | - Philippe Büchler
- ARTORG Center for Biomedical Engineering Research, Faculty of Medicine, University of Bern, Bern, Switzerland
| | - Begoña Calvo
- Aragón Institute for Engineering Research (i3A), University of Zaragoza, Zaragoza, Spain.,CIBER in Bioengineering, Biomaterials & Nanomedicine (CIBER-BBN), Madrid, Spain
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5
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Atalay E, Yu DJ, Nongpiur ME. When to use anterior segment optical coherence tomography. EXPERT REVIEW OF OPHTHALMOLOGY 2020. [DOI: 10.1080/17469899.2020.1767596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Eray Atalay
- Department of Ophthalmology, Eskisehir Osmangazi University Faculty of Medicine, Turkey
| | - Daryle Jason Yu
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
| | - Monisha Esther Nongpiur
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore
- Duke-NUS Medical School, Singapore, Singapore
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Eliaçık M, Kırgız A, Tülü Aygün B. Evaluation of corneal thickness with spectral-domain optical coherence tomography following keraring implantation for keratoconus: five year follow-up. Curr Eye Res 2020; 45:1359-1363. [PMID: 32228114 DOI: 10.1080/02713683.2020.1749667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
To evaluate the change in the position of intrastromal corneal ring segments (ICRS) implanted in keratoconus patients within five years of implantation. Participants in this study included keratoconus patients who received Keraring 10 ICRS implantation and had a follow-up time of at least 5 years. The distances from apex to anterior corneal surface (AA), from outer basal corner to posterior corneal surface (BP), and from inner basal corner to posterior corneal surface (CP) were measured at every postoperative visit (6 months, 1 year, 3 years, and 5 years) and compared to each other. Thirty eyes of 22 patients were included. The CP showed a statistically significant decrease at all 15 time points (p < .001); however, no statistically significant difference was found at 5 years regarding AA or BP (p > .05 for all). Triangular ICRS implanted in keratoconus patients remained stable for five years without any complications, which is an extremely important aspect of ICRS surgery. The only difference was a slight posterior movement of the inner basal corner, although without anterior chamber perforation.
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Affiliation(s)
- Mustafa Eliaçık
- School of Medicine, Department of Ophthalmology, Medipol University , Istanbul, Turkey
| | - Ahmet Kırgız
- Ophthalmology Department, Beyoglu Eye Training and Research Hospital, University of Health Sciences , Istanbul, Turkey
| | - Beril Tülü Aygün
- Ophthalmology Department, Beyoglu Eye Training and Research Hospital, University of Health Sciences , Istanbul, Turkey
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Abstract
PURPOSE OF REVIEW To review the efficacy of intrastromal corneal ring segments (ICRS) for keratoconus and with other interventions such as contacts lens, keratoplasty, and corneal collagen cross-linking. RECENT FINDINGS Changes in ICRS thickness and size, combination of procedures, and the adaptation of a more sophisticated classification system have broadened our application of ICRS. Recent studies have shown the long-term efficacy of ICRS in visual acuity, keratometry, and astigmatism. SUMMARY Studies have demonstrated the short-term and long-term efficacy of ICRS implantation in patients with keratoconus.
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Peris-Martínez C, Dualde-Beltrán C, Fernández-López E, Roig-Revert MJ, Hernández-Díaz M, Piñero DP. Effect of the variability in implantation depth of intracorneal ring segments using the femtosecond laser technology in corneal ectasia. Eur J Ophthalmol 2019; 30:668-675. [DOI: 10.1177/1120672119852026] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Purpose: To analyze the impact of the depth of implantation of intracorneal ring segments on morphological, biomechanical, and clinical outcomes in ectatic corneas. Methods: This prospective longitudinal study enrolled 40 eyes of 29 patients (age 20–51 years) with corneal ectasia that underwent intracorneal ring segments implantation (KeraRing, Mediphacos). Changes in visual acuity, refraction, corneal tomography, and corneal biomechanics (Ocular Response Analyzer, Reichert) were evaluated during a 6 month follow-up. Likewise, changes in ring segment implantation depth measured by optical coherence tomography (Visante OCT, Carl Zeiss Meditec) were also evaluated. Results: Mean relative depth of implantation was 71.6 ± 5.8%, 71.5 ± 6.5%, and 71.9 ± 6.3% at 1, 3, and 6 months after surgery, respectively (p = 0.827). The difference between the real relative depth of implantation and the theoretical attempted value of 70% was not statistically significant (p = 0.072). Differences in spherical equivalent during the follow-up changed significantly depending on the level of relative depth of implantation (p = 0.036), with an increase of 0.114 D per each 1% increase in relative depth of implantation. Likewise, a decrease of –0.194 D in the steepest keratometric reading was found per each decrease of 1% in relative depth of implantation (p = 0.026). Changes in corneal thickness (p = 0.092) and biomechanics (p = 0.080) were not related to relative depth of implantation. Conclusion: The effect on visual acuity and refraction of intracorneal ring segments when implanted in corneal ectasia is less clinically relevant when the implantation is done at a very deep plane. The variability of the depth of intracorneal ring segments implantation when using femtosecond laser technology is minimal and with no clinically significant effect on clinical outcomes.
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Affiliation(s)
- Cristina Peris-Martínez
- Cornea and External Diseases Unit, FISABIO-Oftalmología Médica (FOM), Valencia, Spain
- Clínica Oftalmológica Aviñó&Peris, Valencia, Spain
| | | | - Ester Fernández-López
- Cornea and External Diseases Unit, FISABIO-Oftalmología Médica (FOM), Valencia, Spain
| | | | - Mikhail Hernández-Díaz
- Cornea and External Diseases Unit, FISABIO-Oftalmología Médica (FOM), Valencia, Spain
- Clínica Oftalmológica Aviñó&Peris, Valencia, Spain
| | - David P Piñero
- Department of Optics, Pharmacology and Anatomy, University of Alicante, Alicante, Spain
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Wang SB, Cornish EE, Grigg JR, McCluskey PJ. Anterior segment optical coherence tomography and its clinical applications. Clin Exp Optom 2019; 102:195-207. [PMID: 30635934 DOI: 10.1111/cxo.12869] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 11/05/2018] [Accepted: 11/29/2018] [Indexed: 11/29/2022] Open
Abstract
Anterior segment optical coherence tomography (AS-OCT) has become one of the cornerstones of non-contact imaging modalities for assessing such structures as the cornea, anterior chamber angle, aqueous outflow pathway, sclera, and ocular surface structures. As such, it has a broad range of clinical applications, which have been independently reported in the literature. This paper aims to present a review of extant literature on the utility of AS-OCT and its efficacy in clinical applications, and to evaluate the quality of available evidence. The following databases were searched from inception to 24 June 2018: Medline via Ovid, Cochrane Central Register of Controlled Trials, PubMed, World Health Organization International Clinical Trials Registry Platform, EMBASE, and CINAHL. Bibliographies of identified papers were hand searched. Inclusion criteria: articles describing or assessing the use of OCT for visualising the AS. The authors excluded studies without an identified primary outcome variable. One author independently selected studies, extracted data, and assessed for risk of bias using PRISMA guidelines. This review included 82 studies, of which there were 11 cohort studies, 37 case series, 10 case studies, 21 comparative observational studies, and three non-systematic review articles. Primary outcome variables included anterior chamber angle, angle opening distance, angle recess area, trabecular iris angle, trabecula-iris space area, corneal thickness, tear meniscus height, tear meniscus area, tear meniscus volume, and the morphology of AS structures, including the ocular surface, blebs, flaps, and graft sites. This review attempts to encompass the breadth and depth of evidence for AS-OCT in the arena of diagnostics, therapeutics, and prognostics. At the same time, it brings to light the dearth of high-level evidence on this topic, suggesting the important role of randomised controlled trials and meta-analyses for the future validation of this technology.
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Affiliation(s)
- Sarah B Wang
- Faculty of Medicine and Health, Save Sight Institute, The University of Sydney, Sydney Eye Hospital, Sydney, New South Wales, Australia
| | - Elisa E Cornish
- Faculty of Medicine and Health, Save Sight Institute, The University of Sydney, Sydney Eye Hospital, Sydney, New South Wales, Australia.,Sydney Eye Hospital Foundation, Sydney Eye Hospital, Sydney, New South Wales, Australia.,Sydney Eye Hospital, Sydney, New South Wales, Australia
| | - John R Grigg
- Faculty of Medicine and Health, Save Sight Institute, The University of Sydney, Sydney Eye Hospital, Sydney, New South Wales, Australia
| | - Peter J McCluskey
- Faculty of Medicine and Health, Save Sight Institute, The University of Sydney, Sydney Eye Hospital, Sydney, New South Wales, Australia
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Anterior Segment Changes After Femtosecond Laser-Assisted Implantation of a 355-Degree Intrastromal Corneal Ring Segment in Advanced Keratoconus. Cornea 2018; 37:1438-1443. [DOI: 10.1097/ico.0000000000001702] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Venkateswaran N, Galor A, Wang J, Karp CL. Optical coherence tomography for ocular surface and corneal diseases: a review. EYE AND VISION 2018; 5:13. [PMID: 29942817 PMCID: PMC5996489 DOI: 10.1186/s40662-018-0107-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Accepted: 05/27/2018] [Indexed: 01/31/2023]
Abstract
The advent of optical coherence tomography (OCT) imaging has changed the way ophthalmologists image the ocular surface and anterior segment of the eye. Its ability to obtain dynamic, high and ultra-high resolution, cross-sectional images of the ocular surface and anterior segment in a noninvasive and rapid manner allows for ease of use. In this review, we focus on the use of anterior segment OCT, which provides an “optical biopsy” or in vivo imaging of various ocular surface and corneal pathologies, allowing the clinician to diagnose diseases otherwise not visualized by traditional methods. The utility of anterior segment OCT for various anterior segment pathologies is reviewed.
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Affiliation(s)
- Nandini Venkateswaran
- 1Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, McKnight Building Room 202A, 1638 NW 10th Avenue, 900 NW 17th Street, Miami, FL 33136 USA
| | - Anat Galor
- 1Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, McKnight Building Room 202A, 1638 NW 10th Avenue, 900 NW 17th Street, Miami, FL 33136 USA.,2Department of Ophthalmology, Miami Veterans Administration Medical Center, 1201 NW 16th Street, Miami, FL 33125 USA
| | - Jianhua Wang
- 1Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, McKnight Building Room 202A, 1638 NW 10th Avenue, 900 NW 17th Street, Miami, FL 33136 USA
| | - Carol L Karp
- 1Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, McKnight Building Room 202A, 1638 NW 10th Avenue, 900 NW 17th Street, Miami, FL 33136 USA
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Pirhadi S, Mohammadi N, Mosavi SA, Daryabari H, Aghamollaei H, Jadidi K. Comparison of the MyoRing implantation depth by mechanical dissection using PocketMaker microkeratome versus Melles hook via AS-OCT. BMC Ophthalmol 2018; 18:137. [PMID: 29879937 PMCID: PMC5992749 DOI: 10.1186/s12886-018-0806-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 05/30/2018] [Indexed: 11/30/2022] Open
Abstract
Background This paper seeks to evaluate the depth and outcomes of MyoRing implantation using two mechanical dissection procedures including: PocketMaker microkeratome in opposition to the Melles hook method. Methods This retrospective study was carried out on 39 eyes of 38 keratoconus patients (28 male and 10 female) with the mean age of \documentclass[12pt]{minimal}
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\begin{document}$$ 28.97\frac{+}{.}10.37 $$\end{document}28.97+.10.37 years and had undergone MyoRing implantation by the two mentioned methods. The MyoRing was inserted into the corneal pocket which was made manually in 18 eyes (Melles hook group) or with PocketMaker microkeratome in 21 eyes (PocketMaker group). The mean follow up time was \documentclass[12pt]{minimal}
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\begin{document}$$ 9.81\frac{+}{.}3.7 $$\end{document}9.81+.3.7 months with pre-operative and post-operative ophthalmic examination including uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), keratometry readings and central corneal thickness measurement. AS-OCT (Casia, SS-1000, Tomey, Nagoya, Japan) imaging was used to measure MyoRing insertion depth, exactly. Results Pre-operative and post-operative UCVA (LogMAR) mean change for the PocketMaker and Melles hook groups were recorded at 0.75 ± 0.32 and 0.78 ± 0.33, respectively. Similarly, BCVA (LogMAR) mean change were 0.27 ± 0.22 and 0.23 ± 0.22. Mean keratometry (Kmean) change were 6.06 ± 4.18 and 6.56 ± 3.55 respectively. UCVA change (P = 0.767), BCVA change (P = 0.77) and Kmean change (P = 0.693) showed that there was no statistically significant difference between both groups for any parameter. Depth measurements achieved from AS-OCT images showed that there was no statistically significant difference in pocket depth between two methods of MyoRing implantation (P = 0.413). Conclusions The results of Myoring implantation outcomes using mechanical dissection via PocketMaker microkeratome as against Melles hook are comparable.
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Affiliation(s)
- Shiva Pirhadi
- Department of Biomedical Engineering, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran
| | - Neda Mohammadi
- Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | | | - Hashem Daryabari
- Department of Ophthalmology, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Hossein Aghamollaei
- Vision Health Research Center, Semnan University of Medical Sciences, Semnan, Iran
| | - Khosrow Jadidi
- Department of Ophthalmology, Baqiyatallah University of Medical Sciences, Tehran, Iran.
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Almodin EM, Ferrara P, Camin FMA, Colallilo JMA. Femtosecond laser–assisted intrastromal corneal lenticule implantation for treatment of advanced keratoconus in a child’s eye. ACTA ACUST UNITED AC 2018. [DOI: 10.1016/j.jcro.2018.01.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Template-based methodology for the simulation of intracorneal segment ring implantation in human corneas. Biomech Model Mechanobiol 2018; 17:923-938. [PMID: 29564655 DOI: 10.1007/s10237-018-1013-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 03/12/2018] [Indexed: 10/17/2022]
Abstract
Keratoconus is an idiopathic, non-inflammatory and degenerative corneal disease characterised by a loss of the organisation in the corneal collagen fibrils. As a result, keratoconic corneas present a localised thinning and conical protrusion with irregular astigmatism and high myopia that worsen visual acuity. Intracorneal ring segments (ICRSs) are used in clinic to regularise the corneal surface and to prevent the disease from progressing. Unfortunately, the post-surgical effect of the ICRS is not explicitly accounted beforehand. Traditional treatments rely on population-based nomograms and the experience of the surgeon. In this vein, in silico models could be a clinical aid tool for clinicians to plan the intervention, or to test the post-surgical impact of different clinical scenarios. A semi-automatic computational methodology is presented in order to simulate the ICRS surgical operation and to predict the post-surgical optical outcomes. For the sake of simplicity, circular cross section rings, average corneas and an isotropic hyperelastic material are used. To determine whether the model behaves physiologically and to carry out a sensitivity analysis, a [Formula: see text] full-factorial analysis is carried out. In particular, how the stromal depth insertion, horizontal distance of ring insertion (hDRI) and diameter of the ring's cross section ([Formula: see text]) are impacting in the spherical and cylindrical power of the cornea is analysed. Afterwards, the kinematics, mechanics and optics of keratoconic corneas after the ICRS insertion are analysed. Based on the parametric study, we can conclude that our model follows clinical trends previously reported. In particular and although there is an improvement in defocus, all corneas presented a change in their optical aberrations. The stromal depth insertion is the parameter that affects the corneal optics the most, whereas hDRI and [Formula: see text] are less important. Not only that, but it is almost impossible to achieve an optimal trade-off between spherical and cylindrical correction. Regarding the mechanical behaviour, inserting the rings at 65% depth or above will cause the cornea to slightly bend. This abnormal stress distribution greatly distorts the corneal optics and, more importantly, could be the cause of clinical problems such as corneal extrusion. Not only that, but our model also supports that rings are acting as restraint elements which relax the stresses of the corneal stroma in the cone of the disease. However, depending on the exact spatial location of the keratoconus, the insertion of rings could promote its evolution instead of preventing it. ICRS inserted deeper will prevent keratoconus in the posterior stroma from growing (relaxation of posterior surface), but will promote its growing if they are located in the anterior surface (increment of stress). In conclusion, the methodology proposed is suitable for simulating long-term mechanical and optical effects of ICRS insertion.
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Monteiro T, Alfonso JF, Franqueira N, Faria-Correia F, Ambrósio R, Madrid-Costa D. Predictability of Tunnel Depth for Intrastromal Corneal Ring Segments Implantation Between Manual and Femtosecond Laser Techniques. J Refract Surg 2018. [DOI: 10.3928/1081597x-20180108-01] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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16
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Corneal Hydrops Secondary to Intrastromal Corneal Ring Intrusion into the Anterior Chamber 7 Years after Implantation: A Case Report. Ophthalmol Ther 2017; 6:373-379. [PMID: 28849554 PMCID: PMC5693822 DOI: 10.1007/s40123-017-0105-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Indexed: 10/25/2022] Open
Abstract
INTRODUCTION This report describes the first known case of late-onset intrusion of an intrastromal ring segment into the anterior chamber due to posterior migration of a ring segment. To our knowledge, intrastromal ring segment penetration has only been shown to occur in the intraoperative or immediate postoperative period. We postulate that the perforation in this case is due to progressive thinning of the cornea, possibly in combination with habitual eye rubbing. CASE REPORT A 44-year-old man presented with acute corneal hydrops related to penetration of Descemet's membrane and endothelium by an intrastromal ring segment implanted 7 years prior. Removal of the ring segment resulted in an anterior chamber fistula that directed fluid through the ring segment tunnel to the ocular surface. Leakage of aqueous humor was successfully controlled, and corneal edema gradually resolved. CONCLUSION This case indicates the need for long term monitoring of ring segment proximity to the posterior corneal surface, especially in patients with ectatic ocular conditions and/or habitual eye rubbing behavior.
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Intracorneal ring segment depth in keratoconus patients: a long-term follow-up study. Int Ophthalmol 2017; 38:1379-1383. [PMID: 28608030 DOI: 10.1007/s10792-017-0595-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2017] [Accepted: 06/05/2017] [Indexed: 10/19/2022]
Abstract
PURPOSE To compare the actual depth of the tunnel created with femtosecond laser for intracorneal ring segment (ICRS) implantation with the target depth in keratoconus patients. METHODS In this mix design study, eligible keratoconus patients were identified through chart review. The inclusion criterion was a history of ICRS implantation with femtosecond laser more than 6 months prior to enrollment. Participants underwent anterior segment optical coherence tomography using Spectralis (Heidelberg Engineering GmbH, Heidelberg, Germany) for depth measurement defined as the distance from the anterior corneal surface to anterior rim of the ring. RESULTS The mean age of the 30 participants was 31.4 ± 7.9 years, and 58.6% were male. Mean follow-up time after ring implantation was 25.8 ± 10.0 (range 7-41) months. Mean actual depth was 59.9% (42.4-86.8%), and the target depth was 85.0% (74.8-90.0%) (P < 0.001). The ring was at a depth of less than 70% in 25 eyes of the 30 (83.3%) studied eyes. CONCLUSION The mean 26 months after implantation, ring segments are placed at a shallower depth than originally intended. Therefore, although femtosecond laser technology is an acceptable method for the surgeon, it is necessary to revisit the depth calculator of the device.
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