1
|
Raiskup F, Herber R, Lenk J, Pillunat LE, Spoerl E. Crosslinking with UV-A and riboflavin in progressive keratoconus: From laboratory to clinical practice - Developments over 25 years. Prog Retin Eye Res 2024; 102:101276. [PMID: 38830532 DOI: 10.1016/j.preteyeres.2024.101276] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 05/30/2024] [Accepted: 05/31/2024] [Indexed: 06/05/2024]
Abstract
Changes in the biomechanical and biochemical properties of the human cornea play an important role in the pathogenesis of ectatic diseases. A number of conditions in primarily acquired (keratoconus or pellucid marginal degeneration) or secondarily induced (iatrogenic keratectasia after refractive laser surgeries) ectatic disorders lead to decreased biomechanical stability. Corneal collagen cross-linking (CXL) represents a technique to slow or even halt the progression of ectatic pathologies. In this procedure, riboflavin is applied in combination with ultraviolet A radiation. This interaction induces the production of reactive oxygen species, which leads to the formation of additional covalent bonds between collagen molecules and subsequent biomechanical corneal strengthening. This procedure is so far the only method that partially interferes etiopathogenetically in the treatment of ectatic diseases that slows or stops the process of corneal destabilization, otherwise leading to the need for corneal transplantation. Besides, CXL process increases markedly resistance of collagenous matrix against digesting enzymes supporting its use in the treatment of corneal ulcers. Since the discovery of this therapeutic procedure and the first laboratory experiments, which confirmed the validity of this method, and the first clinical studies that proved the effectiveness and safety of the technique, it has been spread and adopted worldwide, even with further modifications. Making use of the Bunsen-Roscoe photochemical law it was possible to shorten the duration of this procedure in accelerated CXL and thus improve the clinical workflow and patient compliance while maintaining the efficacy and safety of the procedure. The indication spectrum of CXL can be further expanded by combining it with other vision-enhancing procedures such as individualized topographically-guided excimer ablation. Complementing both techniques will allow a patient with a biomechanically stable cornea to regularize it and improve visual acuity without the need for tissue transplantation, leading to a long-term improvement in quality of life.
Collapse
Affiliation(s)
- Frederik Raiskup
- Department of Ophthalmology, University Hospital Carl Gustav Carus, TU Dresden, Fetscherstrasse 74, 01307, Dresden, Germany.
| | - Robert Herber
- Department of Ophthalmology, University Hospital Carl Gustav Carus, TU Dresden, Fetscherstrasse 74, 01307, Dresden, Germany
| | - Janine Lenk
- Department of Ophthalmology, University Hospital Carl Gustav Carus, TU Dresden, Fetscherstrasse 74, 01307, Dresden, Germany
| | - Lutz E Pillunat
- Department of Ophthalmology, University Hospital Carl Gustav Carus, TU Dresden, Fetscherstrasse 74, 01307, Dresden, Germany
| | - Eberhard Spoerl
- Department of Ophthalmology, University Hospital Carl Gustav Carus, TU Dresden, Fetscherstrasse 74, 01307, Dresden, Germany
| |
Collapse
|
2
|
Identification of Treatment Protocols for Effective Cross-Linking of the Peripheral Cornea: An Experimental Study. Ophthalmol Ther 2022; 11:2057-2066. [PMID: 36066843 DOI: 10.1007/s40123-022-00564-1] [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: 07/15/2022] [Accepted: 08/24/2022] [Indexed: 10/14/2022] Open
Abstract
INTRODUCTION This study aimed to test and evaluate modified corneal cross-linking (CXL) protocols regarding improved treatment effects on the peripheral cornea in terms of tissue stability and cellular response. METHODS Peripheral CXL (pCXL) was performed within a ring of 9-11 mm of 36 human donor corneas with variations in applied energy (5.4, 7.2, and 10 J/cm2) at 9 mW/cm2 irradiance. Each energy level was additionally modulated regarding the oxygen level surrounding the cornea during treatment (21%; 100%). Stress-strain tests with endpoints at 12% strain and collagenase A-assisted digestions to complete digestion were performed to evaluate the rigidity and resistance of treated and control tissue. Further, corneas were processed histologically via TUNEL assay and H&E staining to demonstrate the effects on stromal cells during treatment under varying CXL conditions. RESULTS Increases in energy dosage achieved significant increases in resistance to stress in all variations except when comparing protocols A and B under normoxic conditions. Supplemental oxygen significantly increased rigidity in protocols B (p < 0.01) and C (p = 0.018). Hyperoxic conditions significantly increased resistance to digestion in all protocols. The number of DNA strand breaks in TUNEL assay staining showed significant increases in all increases in energy as well as with oxygen supplementation. CONCLUSIONS Increases in energy and supplemental oxygen improved the effect of CXL, though endothelial safety could not be verified with confidence in high-fluence CXL with supplemental oxygen. Results suggest that CXL protocols using 7.2 J/cm2 with 100% O2 or 10 J/cm2 without supplemental oxygen prove most effective without anticipated risk of endothelial damage.
Collapse
|
3
|
Lenk J, Herber R, Raiskup F, Pillunat LE, Spörl E. [Principles of corneal cross-linking : Presentation based on the development of the various treatment protocols]. Ophthalmologe 2021; 119:332-341. [PMID: 34882268 DOI: 10.1007/s00347-021-01538-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/08/2021] [Indexed: 11/28/2022]
Abstract
BACKGROUND Corneal cross-linking (CXL) is used to treat corneal ectatic diseases. The aim is to improve the reduced consolidation of the cornea in order to halt further corneal protrusion and therefore subsequent deterioration of the optical imaging proportions. MATERIAL AND METHODS In this article the principles of corneal cross-linking based on riboflavin and UV light are presented including recent research results. Furthermore, the most important treatment protocols including standard CXL (S-CXL), accelerated CXL (A-CXL), transepithelial CXL (TE-CXL) and the approach of the CXL procedure for thin corneas are explained. RESULTS The CXL method depends on four major components, the riboflavin solution, oxygen, UV light and the availability of cross-linking sites on the collagen tissue. According to the present state of knowledge, the photochemical process of the CXL method induces covalent bonds between the fibrils and proteoglycans and thus stabilizes the collagen fibers, resulting in corneal consolidation. In addition to the S‑CXL, which has proven its effectiveness and safety in a large number of studies, there are other treatment protocols that have been developed based on the Bunsen-Roscoe law of reciprocity. The A‑CXL protocol has the advantage of having a shorter irradiation time but it seems to be less effective than the S‑CXL protocol concerning the increase in corneal stiffness. The use of TE-CXL has so far not yet gained acceptance in the clinical practice. CONCLUSION The CXL procedures primarily aim to stabilize the cornea. In the future, in addition to stabilization of the cornea, simultaneous improvement of visual acuity will be the main focus.
Collapse
Affiliation(s)
- Janine Lenk
- Augenklinik, Universitätsklinikum Carl Gustav Carus, TU Dresden, Fetscherstr. 74, 01307, Dresden, Deutschland.
| | - Robert Herber
- Augenklinik, Universitätsklinikum Carl Gustav Carus, TU Dresden, Fetscherstr. 74, 01307, Dresden, Deutschland
| | - Frederik Raiskup
- Augenklinik, Universitätsklinikum Carl Gustav Carus, TU Dresden, Fetscherstr. 74, 01307, Dresden, Deutschland
| | - Lutz E Pillunat
- Augenklinik, Universitätsklinikum Carl Gustav Carus, TU Dresden, Fetscherstr. 74, 01307, Dresden, Deutschland
| | - Eberhard Spörl
- Augenklinik, Universitätsklinikum Carl Gustav Carus, TU Dresden, Fetscherstr. 74, 01307, Dresden, Deutschland
| |
Collapse
|
4
|
Kubaloglu A, Sari ES, Koytak A. Deep anterior lamellar keratoplasty in eyes previously treated with collagen crosslinking for keratoconus: 3-year results. Graefes Arch Clin Exp Ophthalmol 2020; 258:821-827. [PMID: 31915972 DOI: 10.1007/s00417-019-04587-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 11/29/2019] [Accepted: 12/19/2019] [Indexed: 01/09/2023] Open
Abstract
PURPOSE To evaluate the 3-year results of deep anterior lamellar keratoplasty (DALK) using the big-bubble technique in keratoconus patients with previous corneal collagen crosslinking (CXL) treatment. METHODS Twenty eyes of 20 keratoconus patients who underwent DALK surgery using the big-bubble technique after CXL treatment between January 2011 and September 2015 were retrospectively reviewed. All patients completed 3 years follow-up. Intraoperative and postoperative complications were recorded. Uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), maximum keratometry, keratometric astigmatism and endothelial cell density (ECD) were analysed. RESULTS The mean interval between CXL and DALK surgery was 47.5 ± 24.0 months (mean ± SD). DALK was completed in all eyes. Big-bubble was successfully achieved in 16 eyes (80%), and manual dissection was performed in four eyes (20%). Microperforation occurred in three eyes (15%). Postoperatively, persistent epithelial defect occurred in three eyes (15%). The mean UCVA and mean BSCVA values were significantly improved preoperatively to all postoperative visits (p < 0.001). UCVA was 20/100 or lower in all eyes preoperatively and 20/100 or better in 18 eyes (80%) at 3 years; BSCVA was 20/40 or better in all eyes (100%) and 20/20 or better in three eyes (15%), and keratometric astigmatism was lower than 4 dioptres in 14 eyes (70%) at 3 years. The mean ECD loss was 6.3 ± 4.4% at 1 year, 9.0 ± 6.3% at 2 years and 11.2 ± 7.4% at 3 years. CONCLUSION Previous CXL treatment in keratoconus patients did not cause a negative impact on the visual, refractive and surgical outcomes of DALK surgery using the big-bubble technique. DALK surgery seems to be a safe and effective surgical approach in these patients.
Collapse
Affiliation(s)
- Anıl Kubaloglu
- Ophthalmology Department, Yeni Yuzyıl University Faculty of Medicine and Dunya Eye Hospital, Istanbul, Turkey
| | - Esin Sogutlu Sari
- Ophthalmology Department, Faculty of Medicine, Bursa Uludag University, Görükle - Bursa, Turkey.
| | - Arif Koytak
- Ophthalmology Department, Faculty of Medicine, Bezmialem Vakıf University, Istanbul, Turkey
| |
Collapse
|
5
|
Hong H, Huh MI, Park SM, Lee KP, Kim HK, Kim DS. Decellularized corneal lenticule embedded compressed collagen: toward a suturable collagenous construct for limbal reconstruction. Biofabrication 2018; 10:045001. [PMID: 29978836 DOI: 10.1088/1758-5090/aad1a4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Recently, compressed collagen has attracted much attention as a potential alternative for a limbal epithelial stem cell (LESC) carrier to treat limbal stem cell deficiency (LSCD), in that it can provide mechanically improved collagen fibrillar structures compared to conventional collagen hydrogel. However, its clinical efficacy as an LESC carrier has not yet been studied through in vivo transplantation due to limited mechanical strength that cannot withstand a force induced by surgical suturing and low resistance to enzymatic degradation. This study firstly presents a suturable LESC carrier based on compressed collagen in the form of a biocomposite. The biocomposite was achieved by integrating a decellularized corneal lenticule, which is a decellularized stromal tissue obtained from corneal refractive surgery, inside a compressed collagen to form a sandwich structure. A suture retention test verified that the biocomposite has a much higher suture retention strength (0.56 ± 0.12 N) compared to the compressed collagen (0.02 ± 0.01 N). The biocomposite also exhibited more than 3 times higher resistance to enzymatic degradation, indicating long-term stability after transplantation. In vitro cell culture results revealed that the biocomposite effectively supported the expansion and stratification of the LESCs with expressions of putative stem cell and differentiated corneal epithelial cell markers. Finally, the biocomposite verified its clinical efficacy by stably delivering the LESCs onto an eye of a rabbit model of LSCD and effectively reconstructing the ocular surface.
Collapse
Affiliation(s)
- Hyeonjun Hong
- Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-ro, Pohang, Gyeongbuk, 37673, Republic of Korea
| | | | | | | | | | | |
Collapse
|
6
|
Lim L, Lim EWL. A Review of Corneal Collagen Cross-linking - Current Trends in Practice Applications. Open Ophthalmol J 2018; 12:181-213. [PMID: 30123383 PMCID: PMC6062907 DOI: 10.2174/1874364101812010181] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 12/05/2017] [Accepted: 01/22/2018] [Indexed: 01/02/2023] Open
Abstract
Objective: To review the literature on current applications of corneal Collagen Cross-Linking (CXL). Methods: A review of publications on corneal cross-linking was conducted. This included systemic reviews, randomized controlled clinical trials, cohort studies, case-controlled studies and case series. A summary of the publications is tabulated. Results: The original indication of riboflavin – Ultraviolet-A (UVA) induced corneal collagen cross-linking is to arrest the progression of keratoconus. Studies show that it is effective in arresting the progression of keratoconus and post-LASIK ectasia with the standard Dresden protocol (epithelium-off). There are also improvements in visual, keratometric and topographic measurements over time. Severe complications of cross-linking are rare. The epithelium-on techniques have less efficacy than the Dresden protocol. Accelerated protocols have variable results, with some studies reporting comparable outcomes to the Dresden protocol while other studies reporting less efficacious outcomes. Cross-linking combined with refractive procedures provide better visual outcome but long term studies are warranted. Cross-linking for the treatment of infective keratitis is a promising new treatment modality. Initial studies show that it is more effective for superficial rather than deep infections and for bacterial rather than fungal infections. Conclusions: Corneal cross-linking is a procedure with an expanding list of indications from the treatment of corneal ectasias to infective keratitis. While the standard Dresden protocol is established as the gold standard treatment for progressive keratoconus, the more recent protocols may require further refinements, investigative and long-term studies.
Collapse
Affiliation(s)
- Li Lim
- MBBS (Singapore), MMed (Ophth), FRCS(Ed), FAMS (S'pore) Senior Consultant, Corneal and External Eye Disease Service, Singapore National Eye Centre, Singapore, Singapore
| | - Elizabeth Wen Ling Lim
- Undergraduate medical student, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
| |
Collapse
|
7
|
Protection of Corneal Limbus from Riboflavin Prevents Epithelial Stem Cell Loss after Collagen Cross-Linking. J Ophthalmol 2018; 2018:6854298. [PMID: 29967694 PMCID: PMC6008863 DOI: 10.1155/2018/6854298] [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: 02/19/2018] [Accepted: 04/29/2018] [Indexed: 11/18/2022] Open
Abstract
Purpose To investigate whether the protection of corneal limbus from riboflavin exposure during collagen cross-linking (CXL) prevents limbal epithelial stem cell (LESC) loss. Methods Ten New Zealand white rabbits received an epithelium-off CXL using an accelerated protocol. Seven days before procedure, 5-bromo-2-deoxyuridine (BrdU) was intraperitoneally injected. During procedure, riboflavin was applied to the corneal surface within a 9 mm diameter retention ring in 5 rabbits, thereby preventing the limbus from riboflavin exposure. In other 5 rabbits, riboflavin was instilled every 2 min, allowing the spillover to the limbus. One day after UVA irradiation, corneas were subjected to histological and molecular assays. Results There were no differences in corneal thickness and epithelial healing between the groups. The numbers of BrdU-labelled and p63+ limbal epithelial cells were markedly reduced in the group without a ring, but significantly increased when a ring was used. Robust expression of CK3/12 was observed in the limbal epithelium in the group with a ring. The mRNA levels of ABCG2, FGF2, IL-1β, and IL-6 were significantly increased in the corneas with a ring. Conclusions Protection of limbus from riboflavin during CXL was effective in preserving LESCs. However, inflammation was increased in the cornea treated with riboflavin using a ring.
Collapse
|
8
|
Shetty R, Vunnava KP, Dhamodaran K, Matalia H, Murali S, Jayadev C, Murugeswari P, Ghosh A, Das D. Characterization of Corneal Epithelial Cells in Keratoconus. Transl Vis Sci Technol 2018; 8:2. [PMID: 30627477 PMCID: PMC6322712 DOI: 10.1167/tvst.8.1.2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 11/09/2018] [Indexed: 01/08/2023] Open
Abstract
Purpose We studied the cellular characteristics of epithelial cells in the cone and extraconal periphery of corneas in keratoconus eyes. Methods This prospective observational study was conducted at Narayana Nethralaya Eye Institute. A total of 83 and 42 eyes with keratoconus and normal topography, respectively, were included in the study. Corneal epithelial cells were collected and analyzed for apoptosis, proliferation, epithelial-mesenchymal transition, and differentiation status using molecular and biochemical tools. Statistical analysis was performed using the Student's t-test. Results Corneal epithelial cells from the cone showed significantly higher expression of proapoptotic marker BAX (P < 0.005) compared to controls. Significantly elevated expression of cell cycle markers CYCLIN D1 (P < 0.005) and Ki67 (P < 0.005) were noted in the extraconal region compared to controls. Cells of the cone showed significantly higher ZO-1 (P < 0.005) and lower vimentin (P < 0.005) compared to controls. Significantly lower expression of the differentiation marker CK3/12 (P < 0.05) was observed in cones compared to controls. Conclusions Cones of keratoconic corneas show enhanced cell death, poor differentiation, proliferation and epithelial-mesenchymal transition. The cellular changes of the corneal epithelial cells in the cone and extraconal region differ significantly in a keratoconus corneas. Translational Relevance Characterization of patient-specific corneal epithelial cellular status in keratoconus has the potential to determine the optimal treatment and therapeutic outcomes paving the way towards personalized treatment in the future.
Collapse
Affiliation(s)
- Rohit Shetty
- Department of Cornea and Refractive Surgery, Narayana Nethralaya Eye Institute, Bangalore, Karnataka, India
| | - Krishna Poojita Vunnava
- Department of Cornea and Refractive Surgery, Narayana Nethralaya Eye Institute, Bangalore, Karnataka, India
| | - Kamesh Dhamodaran
- Stem Cell Research Laboratory, GROW Laboratory, Narayana Nethralaya Foundation, Bangalore, Karnataka, India.,Current address: Department of Basic Sciences, The Ocular Surface Institute, College of Optometry, University of Houston, Houston, TX, USA
| | - Himanshu Matalia
- Department of Cornea and Refractive Surgery, Narayana Nethralaya Eye Institute, Bangalore, Karnataka, India
| | - Subramani Murali
- Stem Cell Research Laboratory, GROW Laboratory, Narayana Nethralaya Foundation, Bangalore, Karnataka, India
| | - Chaitra Jayadev
- Department of Vitreo-Retinal Services, Narayana Nethralaya Eye Institute, Bangalore, Karnataka, India
| | - Ponnulagu Murugeswari
- Stem Cell Research Laboratory, GROW Laboratory, Narayana Nethralaya Foundation, Bangalore, Karnataka, India
| | - Arkasubhra Ghosh
- GROW Laboratory, Narayana Nethralaya Foundation, Bangalore, Karnataka, India
| | - Debashish Das
- Stem Cell Research Laboratory, GROW Laboratory, Narayana Nethralaya Foundation, Bangalore, Karnataka, India
| |
Collapse
|
9
|
Morphology of the Corneal Limbus Following Standard and Accelerated Corneal Collagen Cross-Linking (9 mW/cm2) for Keratoconus. Cornea 2017; 36:78-84. [PMID: 27749450 DOI: 10.1097/ico.0000000000001029] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To evaluate the morphological features of the corneal limbus as measured by in vivo confocal microscopy (IVCM) following standard and accelerated corneal collagen cross-linking (CXL) for keratoconus. METHODS Patients with progressive keratoconus scheduled to undergo standard CXL (group 1; 31 patients, 3 mW/cm, 370 nm, 30 minutes), or accelerated CXL (group 2; 20 patients, 9 mW/cm, 370 nm, 10 minutes) in the worse eye were included in this prospective study. Thirty eyes of 30 age-matched patients served as controls (group 3). All patient eyes underwent IVCM scanning of the central cornea and the inferior limbal area at baseline and 1, 3, and 6 months after CXL. RESULTS After CXL, epithelial regrowth was complete by day 4 in both groups 1 and 2. There were no statistically significant differences between the baseline mean central corneal wing or basal cell density, limbus-palisade middle or basal cell densities of groups 1, 2, or 3. At postoperative months 1, 3, and 6, there were no statistically significant differences in either central or limbus-palisade epithelial cell densities or diameters in keratoconic eyes that underwent standard or accelerated CXL (P > 0.05). The morphology of the limbal cells was preserved as well. CONCLUSIONS The morphology of limbus structures seems to be preserved following standard and accelerated CXL in short-term follow-up, as measured using IVCM.
Collapse
|
10
|
Abstract
PURPOSE To report the long-term outcome of corneal collagen cross-linking (CXL) for progressive keratoconus in pediatric patients. METHODS "Epithelium-off" CXL was performed in pediatric eyes with progressive keratoconus. Spectacle-corrected distance visual acuity (CDVA), retinoscopy, topography, and tomography were documented preoperatively and postoperatively at 3 months, 6 months, 1 year, and annually thereafter. RESULTS A total of 377 eyes of 336 pediatric patients aged 8 to 18 years with progressive keratoconus underwent CXL. Of these, 194 eyes had a follow-up beyond 2 years and up to 6.7 years. At last follow-up, there was significant improvement in mean CDVA from 0.33 ± 0.22 to 0.27 ± 0.19 logMAR (P ≤ 0.0001), reduction in mean topographic astigmatism from 7.22 ± 3.55 to 6.13 ± 3.28 D (P = 0.0001), mean flattening of 1.20 ± 3.55 diopters in maximum keratometry (Kmax) (P = 0.0002), and mean corneal thinning of 31.1 ± 36.0 μm (P < 0.0001) after CXL. The mean change in Kmax was most significant in moderately advanced keratoconus (average keratometry 48-53 diopters). Central cones showed more corneal flattening than peripheral cones. Stabilization or flattening of Kmax was seen in 85% of eyes at 2 years and in 76% after 4 years. Stabilization or improvement of CDVA was seen in 80.1% of eyes at 2 years and in 69.1% after 4 years. CONCLUSIONS CXL remains effective in stabilizing keratoconus for longer than 2 years in a majority of pediatric eyes. Flattening of Kmax was greater in moderately advanced keratoconus and central cones. Long-term follow-up beyond 4 years, however, revealed that a few eyes showed features suggestive of reversal of the effect of CXL.
Collapse
|
11
|
|
12
|
Corneal collagen crosslinking for corneal ectasias: a review. Eur J Ophthalmol 2016; 27:253-269. [PMID: 28009397 DOI: 10.5301/ejo.5000916] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/15/2016] [Indexed: 11/20/2022]
Abstract
PURPOSE To review the published literature on corneal collagen crosslinking (CXL). METHODS Importance has been placed on seminal publications, systemic reviews, meta-analyses, and randomized controlled clinical trials. Where such evidence was not available, cohort studies, case-controlled studies, and case series with follow-up greater than 12 months were examined. RESULTS Corneal collagen crosslinking with riboflavin and ultraviolet A (UVA) 370 nm radiation appears to be capable of arresting the progression of ectatic corneal disorders, with most studies reporting significant improvements in visual, keratometric, and topographic measurements. Its mode of action at the molecular level is undetermined. Follow-up is limited to 5-10 years but suggests sustained stability and enhancement in corneal shape with time. Nearly all published long-term data and comparative studies are with epithelium-off techniques. Epithelium-on investigations suggest some efficacy but less than with epithelium-off treatments and long-term data are unavailable. Accelerated techniques with higher UVA fluencies and shorter treatments times, delivering the same UVA energy dosage, are the subject of recent investigation, with some laboratory and clinical studies suggesting reduced efficacy compared to the standard 3 mW/cm2 for 30 minutes irradiation procedure. Combined methodologies of CXL with techniques such as photorefractive keratectomy and intrastromal rings show promise but long-term follow-up is indicated. Sight-threatening complications of CXL are rare. CONCLUSIONS Studies of epithelium-off CXL with irradiation at 3 mW/cm2 for 30 minutes support its efficacy. Refinement in techniques may allow for safer and more rapid procedures with less patient discomfort but require further investigation.
Collapse
|
13
|
Potential Effects of Corneal Cross-Linking upon the Limbus. BIOMED RESEARCH INTERNATIONAL 2016; 2016:5062064. [PMID: 27689081 PMCID: PMC5027324 DOI: 10.1155/2016/5062064] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Accepted: 07/10/2016] [Indexed: 12/13/2022]
Abstract
Corneal cross-linking is nowadays the most used strategy for the treatment of keratoconus and recently it has been exploited for an increasing number of different corneal pathologies, from other ectatic disorders to keratitis. The safety of this technique has been widely assessed, but clinical complications still occur. The potential effects of cross-linking treatment upon the limbus are incompletely understood; it is important therefore to investigate the effect of UV exposure upon the limbal niche, particularly as UV is known to be mutagenic to cellular DNA and the limbus is where ocular surface tumors can develop. The risk of early induction of ocular surface cancer is undoubtedly rare and has to date not been published other than in one case after cross-linking. Nevertheless it is important to further assess, understand, and reduce where possible any potential risk. The aim of this review is to summarize all the reported cases of a pathological consequence for the limbal cells, possibly induced by cross-linking UV exposure, the studies done in vitro or ex vivo, the theoretical bases for the risks due to UV exposure, and which aspects of the clinical treatment may produce higher risk, along with what possible mechanisms could be utilized to protect the limbus and the delicate stem cells present within it.
Collapse
|
14
|
Szigiato AA, Bujak M. Focal cross-linking: description of a novel technique for localizing collagen cross-linking. Can J Ophthalmol 2016; 51:e19-21. [PMID: 26874165 DOI: 10.1016/j.jcjo.2015.09.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2015] [Revised: 08/09/2015] [Accepted: 09/23/2015] [Indexed: 11/28/2022]
|
15
|
Sorkin N, Varssano D. Corneal Collagen Crosslinking: A Systematic Review. Ophthalmologica 2014; 232:10-27. [DOI: 10.1159/000357979] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Accepted: 12/10/2013] [Indexed: 11/19/2022]
|
16
|
Abstract
Keratoconus is a progressive, ectatic disease of the cornea leading to thinning and highly irregular astigmatism. Until recently all treatment options, such as prescription of glasses or contact lenses were symptomatic and neither keratoplasty nor the implantation of intracorneal rings can heal the disease. Riboflavin ultraviolet A (UVA) collagen cross-linking (CXL) cannot heal keratoconus either but promises to halt the progression. The therapeutic principle is a photochemical reaction of riboflavin and UVA light leading to free oxygen radicals in the corneal stroma that induce covalent linking of the collagen fibrils. This stiffening effect should stop the progression. After the first reports at the end of the 1990s the treatment was widely used and many case series show that CXL can be effective in stopping disease progression in some patients. However, randomized, controlled multicenter trials showing high evidence of the treatment effectiveness are rare. This report includes a review of the literature regarding treatment effectiveness, indications and new developments.
Collapse
Affiliation(s)
- P Maier
- Universitäts-Augenklinik Freiburg, Killianstr. 5, 79106, Freiburg, Deutschland.
| | | |
Collapse
|
17
|
Seiler TG, Schmidinger G, Fischinger I, Koller T, Seiler T. [Complications of corneal cross-linking]. Ophthalmologe 2014; 110:639-44. [PMID: 23760422 DOI: 10.1007/s00347-012-2682-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND More than 10 years after the clinical introduction of corneal cross-linking (CXL) the indications and contraindications are still not yet defined. Fundamental for such a list is the incidence of complications. METHODS A PubMed search for complications of corneal crosslinking published up to March 2013 was carried out. RESULTS The published complication rates ranged from 1 % to 10 % depending on the stage of keratoconus. Early postoperative complications were transient stromal haze, sterile infiltrates, endothelium decompensation, delayed epithelial healing and infectious keratitis. Stromal opacity can be a delayed postoperative event. CONCLUSIONS Complications after corneal cross-linking treatment for keratoconus are rare but the management of these complications may need keratoplasty.
Collapse
Affiliation(s)
- T G Seiler
- Institut für Refraktive und Ophthalmo-Chirurgie, Stockerstr. 37, 8002, Zürich, Schweiz.
| | | | | | | | | |
Collapse
|
18
|
Chew ACY, Mehta JS, Tan DTH. One Year of Cornea Research in Review-2012. Asia Pac J Ophthalmol (Phila) 2013; 2:401-13. [PMID: 26107152 DOI: 10.1097/apo.0000000000000022] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE The purpose of this study was to provide an update of significant cornea literature published in the past 1 year. DESIGN This was a literature review. METHODS The authors conducted a 1-year English-language literature search on PubMed, from January 1, 2012, to December 31, 2012, using the following terms: corneal transplantation, anterior lamellar keratoplasty, penetrating keratoplasty, endothelial keratoplasty, Descemet stripping automated endothelial keratoplasty, Descemet membrane endothelial keratoplasty, Descemet membrane endothelial transfer, ocular surface epithelial transplantation, limbal epithelial transplantation, cultivated oral mucosal epithelial transplantation, keratoprosthesis, infectious keratitis, cross-linking, keratoconus, corneal neovascularization, corneal imaging, optical coherence tomography, Pentacam Scheimpflug imaging, and in vivo confocal microscopy. RESULTS This review includes original articles and review articles that contain significant updates and novel aspects in the field of cornea from the following journals: American Journal of Ophthalmology, British Journal of Ophthalmology, Ophthalmology, Investigative Ophthalmology and Visual Science, and Cornea. Letters to the editor, unpublished work, manuscripts not in English, and abstracts were not included. CONCLUSIONS This review highlights significant literature that is applicable to the practicing ophthalmologist.
Collapse
Affiliation(s)
- Annabel C Y Chew
- From the *Singapore National Eye Centre, †Singapore Eye Research Institute, ‡Duke-NUS Graduate Medical School, and §Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | | | | |
Collapse
|
19
|
Pot SA, Gallhöfer NS, Matheis FL, Voelter-Ratson K, Hafezi F, Spiess BM. Corneal collagen cross-linking as treatment for infectious and noninfectious corneal melting in cats and dogs: results of a prospective, nonrandomized, controlled trial. Vet Ophthalmol 2013; 17:250-60. [DOI: 10.1111/vop.12090] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Simon A. Pot
- Equine Department; Vetsuisse Faculty; University of Zurich; Winterthurerstrasse 260 CH-8057 Zurich Switzerland
| | - Nicolin S. Gallhöfer
- Equine Department; Vetsuisse Faculty; University of Zurich; Winterthurerstrasse 260 CH-8057 Zurich Switzerland
| | - Franziska L. Matheis
- Equine Department; Vetsuisse Faculty; University of Zurich; Winterthurerstrasse 260 CH-8057 Zurich Switzerland
| | - Katrin Voelter-Ratson
- Equine Department; Vetsuisse Faculty; University of Zurich; Winterthurerstrasse 260 CH-8057 Zurich Switzerland
| | - Farhad Hafezi
- Division of Ophthalmology; Department of Clinical Neurosciences; Geneva University Hospitals; Geneva Switzerland
| | - Bernhard M. Spiess
- Equine Department; Vetsuisse Faculty; University of Zurich; Winterthurerstrasse 260 CH-8057 Zurich Switzerland
| |
Collapse
|
20
|
Jeyalatha V, Jambulingam M, Gupta N, Padmanabhan P, Madhavan HN. Study on polymethylmethacrylate ring in protecting limbal stem cells during collagen cross-linking. Ophthalmic Res 2013; 50:113-6. [PMID: 23867297 DOI: 10.1159/000351644] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Accepted: 04/04/2013] [Indexed: 11/19/2022]
Abstract
OBJECTIVE The UV rays used in the collagen cross-linking (CXL) procedure seem to cause potential damage to the limbal stem cells. This study was designed to evaluate the ability of polymethylmethacrylate (PMMA) hemiannulus as an alternative to protect corneal limbal stem cells during CXL. METHODS Ten freshly enucleated human cadaveric eyeballs were subjected to the corneal CXL procedure. The cadaveric eye ball was divided into 2 sectors: A and B. Sector A was left unprotected, while sector B was covered by a PMMA shield. Limbal biopsies from both sectors before and after the procedure were analyzed. Each limbal tissue was placed on human amniotic membrane (HAM) to check the cultivability and was subjected to marker studies using reverse transcriptase PCR. RESULTS Before CXL, biopsies from both sectors showed growth on HAM. After CXL, biopsies from sector A showed no growth on HAM while 2 out of the 10 from sector B covered with the PMMA ring did show growth on HAM. The putative stem-cell marker ABCG2 was negative in all the samples from sector A after CXL and was positive in 2 out of the 10 samples from sector B. CONCLUSION Covering the limbal region with PMMA offers partial protection of the limbus from the UV rays during the CXL procedure.
Collapse
Affiliation(s)
- Vimalin Jeyalatha
- L&T Microbiology Research Centre, Vision Research Foundation, Chennai, India
| | | | | | | | | |
Collapse
|