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Sinha Roy A, Rocha KM, Randleman JB, Stulting RD, Dupps WJ. Inverse computational analysis of in vivo corneal elastic modulus change after collagen crosslinking for keratoconus. Exp Eye Res 2013; 113:92-104. [PMID: 23664859 PMCID: PMC4104483 DOI: 10.1016/j.exer.2013.04.010] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Revised: 03/14/2013] [Accepted: 04/13/2013] [Indexed: 10/26/2022]
Abstract
Corneal collagen crosslinking with riboflavin photosensitization and ultraviolet irradiation is a novel approach to limiting the progression of keratoconus in patients by increasing the elastic modulus of the degenerate cornea. Beneficial reductions in corneal steepness and aberrations after crosslinking also frequently occur. In a previous study, we described a computational modeling approach to simulating topographic progression in keratoconus and regression of disease with corneal collagen crosslinking. In the current study, this model has been expanded and applied to the inverse problem of estimating longitudinal time-dependent changes in the corneal elastic modulus after crosslinking using in vivo measurements from 16 human eyes. Topography measured before crosslinking was used to construct a patient-specific finite element model with assumed hyperelastic properties. Then the properties of the cornea were altered using an inverse optimization method to minimize the difference between the model-predicted and in vivo corneal shape after crosslinking. Effects of assumptions regarding sclera-to-cornea elastic modulus ratio and spatial attenuation of treatment effect due to ultraviolet beam characteristics on the predicted change in elastic modulus were also investigated. Corneal property changes computed by inverse finite element analysis provided excellent geometric agreement with clinical topography measurements in patient eyes post-crosslinking. Over all post-treatment time points, the estimated increase in corneal elastic modulus was 110.8 ± 48.1%, and slightly less stiffening was required to produce the same amount of corneal topographic regression of disease when the sclera-to-cornea modulus ratio was increased. Including the effect of beam attenuation resulted in greater estimates of stiffening in the anterior cornea. Corneal shape responses to crosslinking varied considerably and emphasize the importance of a patient-specific approach.
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Affiliation(s)
| | | | | | - R. Doyle Stulting
- Department of Ophthalmology, Emory University, Atlanta, GA, USA
- Woolfson Eye Clinic, Atlanta, GA, USA
| | - William J. Dupps
- Cleveland Clinic Cole Eye Institute, Cleveland, OH, USA
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, OH, USA
- Transplant Center, Surgery Institute, Cleveland Clinic, OH, USA
- Department of Biomedical Engineering, Case Western Reserve University, OH, USA
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Bottos KM, Oliveira AG, Bersanetti PA, Nogueira RF, Lima-Filho AAS, Cardillo JA, Schor P, Chamon W. Corneal absorption of a new riboflavin-nanostructured system for transepithelial collagen cross-linking. PLoS One 2013; 8:e66408. [PMID: 23785497 PMCID: PMC3681906 DOI: 10.1371/journal.pone.0066408] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 05/07/2013] [Indexed: 11/18/2022] Open
Abstract
Corneal collagen cross-linking (CXL) has been described as a promising therapy for keratoconus. According to standard CXL protocol, epithelium should be debrided before treatment to allow penetration of riboflavin into the corneal stroma. However, removal of the epithelium can increase procedure risks. In this study we aim to evaluate stromal penetration of a biocompatible riboflavin-based nanoemulsion system (riboflavin-5-phosphate and riboflavin-base) in rabbit corneas with intact epithelium. Two riboflavin nanoemulsions were developed. Transmittance and absorption coefficient were measured on corneas with intact epithelia after 30, 60, 120, 180, and 240 minutes following exposure to either the nanoemulsions or standard 0.1% or 1% riboflavin-dextran solutions. For the nanoemulsions, the epithelium was removed after measurements to assure that the riboflavin had passed through the hydrophobic epithelium and retained within the stroma. Results were compared to de-epithelialized corneas exposed to 0.1% riboflavin solution and to the same riboflavin nanoemulsions for 30 minutes (standard protocol). Mean transmittance and absorption measured in epithelialized corneas receiving the standard 0.1% riboflavin solution did not reach the levels found on the debrided corneas using the standard technique. Neither increasing the time of exposure nor the concentration of the riboflavin solution from 0.1% to 1% improved riboflavin penetration through the epithelium. When using riboflavin-5-phosphate nanoemulsion for 240 minutes, we found no difference between the mean absorption coefficients to the standard cross-linking protocol (p = 0.54). Riboflavin nanoemulsion was able to penetrate the corneal epithelium, achieving, after 240 minutes, greater stromal concentration when compared to debrided corneas with the standard protocol (p = 0.002). The riboflavin-5-phosphate nanoemulsion diffused better into the stroma than the riboflavin-base nanoemulsion.
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Affiliation(s)
- Katia M. Bottos
- Department of Ophthalmology, Paulista School of Medicine, Federal University of Sao Paulo - UNIFESP, Sao Paulo, SP, Brazil
| | - Anselmo G. Oliveira
- Department of Pharmaceutics, School of Pharmaceutical Sciences, Sao Paulo State University, UNESP, Araraquara, SP, Brazil
| | - Patrícia A. Bersanetti
- Department of Informatics in Health, Paulista School of Medicine, Federal University of Sao Paulo - UNIFESP, Sao Paulo, SP, Brazil
- * E-mail:
| | - Regina F. Nogueira
- Department of Informatics in Health, Paulista School of Medicine, Federal University of Sao Paulo - UNIFESP, Sao Paulo, SP, Brazil
| | - Acácio A. S. Lima-Filho
- Department of Ophthalmology, Paulista School of Medicine, Federal University of Sao Paulo - UNIFESP, Sao Paulo, SP, Brazil
| | - José A. Cardillo
- Department of Ophthalmology, Paulista School of Medicine, Federal University of Sao Paulo - UNIFESP, Sao Paulo, SP, Brazil
| | - Paulo Schor
- Department of Ophthalmology, Paulista School of Medicine, Federal University of Sao Paulo - UNIFESP, Sao Paulo, SP, Brazil
| | - Wallace Chamon
- Department of Ophthalmology, Paulista School of Medicine, Federal University of Sao Paulo - UNIFESP, Sao Paulo, SP, Brazil
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103
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Meek KM, Hayes S. Corneal cross-linking - a review. Ophthalmic Physiol Opt 2013; 33:78-93. [DOI: 10.1111/opo.12032] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Accepted: 01/10/2013] [Indexed: 11/26/2022]
Affiliation(s)
- Keith M Meek
- Structural Biophysics Group; School of Optometry and Vision Sciences; Cardiff University; Cardiff; UK
| | - Sally Hayes
- Structural Biophysics Group; School of Optometry and Vision Sciences; Cardiff University; Cardiff; UK
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Raiskup F, Spoerl E. Corneal crosslinking with riboflavin and ultraviolet A. I. Principles. Ocul Surf 2013; 11:65-74. [PMID: 23583042 DOI: 10.1016/j.jtos.2013.01.002] [Citation(s) in RCA: 175] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/01/2012] [Indexed: 01/20/2023]
Abstract
Changes in the biomechanical properties of the human cornea play an important role in the pathogenesis of corneal ectatic diseases. Biomechanical investigation shows significant differences between human ectatic corneas and normal corneas, including decreased stiffness and reduction of collagen crosslinks in the ectatic cornea. Induction of crosslinks is a well-established procedure in polymer chemistry to increase the elastic modulus of materials. Crosslinking (CXL) in connective tissue can occur during aging and as a side effect of diabetes mellitus. CXL has been used medically to increase stability and reduce the biodegradation of collagen-based biomaterials for bioprostheses. CXL of the cornea using riboflavin and UVA light with a wavelength of 370 nm and a dosage of 5.4 J/cm² is a new approach that increases the mechanical and biochemical stability of stromal tissue. This technique combines the principles of CXL (chemical and nonenzymatic) and the biochemical mechanisms of photo-oxidative CXL with riboflavin as a photosensitizer. In this review, the enrichment of riboflavin in the stroma by standard (epi-off) and transepithelial (epi-on) CXL is discussed. The theoretical and experimental measurements of the absorption of UV light explain the stronger CXL effect in the anterior stroma and its importance for the prevention of damage to the endothelial cells. UV devices are described. Changes of the physical properties after CXL, as well as the cellular changes, are discussed. From these basic investigations, treatment parameters for effective and safe CXL are identified.
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Affiliation(s)
- Frederik Raiskup
- Department of Ophthalmology, Carl Gustav Carus University Hospital, Dresden, Germany.
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106
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Agrawal V. Outcomes of Corneal Collagen Cross-linking for Keratoconus the Effect of Cone Location. ACTA ACUST UNITED AC 2013. [DOI: 10.5005/jp-journals-10025-1042] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
ABSTRACT
Aim
One-year outcome of corneal collagen cross-linking (CXL) for keratoconus with reference to topographic cone location.
Materials and methods
Clinical audit of the results of CXL were used. Three hundred and seventy-eight eyes of 225 patients with preoperative and 12-month completed follow-up were included. Cone location was defined by cone location magnitude index (CLMI) using the Keratron scout topography system. The eyes were divided into two groups–central with cone location within 3 mm zone of the topography map and paracentral with cone location between the 3 and 5 mm zones.
Results
The overall group showed a mean flattening of the CLMI of 1.67 D [preoperative 53.35 ± 5.63 D, 12 months 51.69 ± 4.67 (p = 0.095)]. The flattening in central cone group was 2.67 D [preoperative 54.01 ± 5.3819, at 12 months to 51.341 ± 4.588 (p = 0.016)]. In paracentral cone group the flattening was lesser at 1.73 D [preoperative apex K 52.805 ± 6.382, at 12 months 51.03 ± 4.82 (p = 0.006)]. The difference between groups was statistically significant (p < 0.001). The central cone group showed no significant shift in cone position [preoperative 1.0059 ± 0.24, at 12 months 0.986 ± 0.206 (p = 0.45)]. The paracentral cone group showed a significant mean shift of 1.05 mm in cone location [preoperative 2.224 ± 0.440, at 12 months 1.196 ± 0.529 (p = 0.001)].
Conclusion
Cone location has an impact on the results of corneal cross-linking. The paracentral cones show a significant shift toward the center of the cornea and the central cones show a larger flattening.
How to cite this article
Agrawal V. Outcomes of Corneal Collagen Cross-linking for Keratoconus the Effect of Cone Location. Int J Kerat Ect Cor Dis 2013;2(1):16-19.
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Fawzy AS, Nitisusanta LI, Iqbal K, Daood U, Neo J. Riboflavin as a dentin crosslinking agent: Ultraviolet A versus blue light. Dent Mater 2012; 28:1284-91. [DOI: 10.1016/j.dental.2012.09.009] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Revised: 08/26/2012] [Accepted: 09/11/2012] [Indexed: 11/15/2022]
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Chen S, Li Y, Stojanovic A, Zhang J, Wang Y, Wang Q, Seiler T. Evaluation of the efficacy of excimer laser ablation of cross-linked porcine cornea. PLoS One 2012; 7:e46232. [PMID: 23056269 PMCID: PMC3463596 DOI: 10.1371/journal.pone.0046232] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 08/28/2012] [Indexed: 12/04/2022] Open
Abstract
Background Combination of riboflavin/UVA cross-linking (CXL) and excimer laser ablation is a promising therapy for treating corneal ectasia. The cornea is strengthened by cross-linking, while the irregular astigmatism is reduced by laser ablation. This study aims to compare the efficacy of excimer laser ablation on porcine corneas with and without cross-linking. Methods and Findings The porcine cornea was de-epithelialized and treated with 0.1% riboflavin solution for 30 minutes. A half of the cornea was exposed to UVA-radiation for another 30 minutes while the controlled half of the cornea was protected from the UVA using a metal shield. Photo therapeutic keratectomy (PTK) was then performed on the central cornea. Corneal thickness of 5 paired locations on the horizontal line, ±0.5, ±1.0, ±1.5, ±2.0, and ±2.5 mm from the central spot, were measured using optical coherence tomography prior to and after PTK. The ablation depth was then determined by the corneal thickness. There was a 9% difference (P<0.001) in the overall ablation depth between the CXL-half corneas (158±22 µm) and the control-half corneas (174±26 µm). The ablation depths of all 5 correspondent locations on the CXL-half were significantly smaller (P<0.001). Conclusion The efficacy of the laser ablation seems to be lower in cross-linked cornea. Current ablation algorithms may need to be modified for cross-linked corneas.
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Affiliation(s)
- Shihao Chen
- The Affiliated Eye Hospital of Wenzhou Medical College, Lucheng District, Wenzhou, Zhejiang, People's Republic of China
| | - Yini Li
- The Affiliated Eye Hospital of Wenzhou Medical College, Lucheng District, Wenzhou, Zhejiang, People's Republic of China
| | - Aleksander Stojanovic
- Eye Department, University Hospital of North Norway and Synslaser Kirurgi AS, Tromsø, Norway
| | - Jia Zhang
- The Affiliated Eye Hospital of Wenzhou Medical College, Lucheng District, Wenzhou, Zhejiang, People's Republic of China
| | - Yibo Wang
- The Affiliated Eye Hospital of Wenzhou Medical College, Lucheng District, Wenzhou, Zhejiang, People's Republic of China
| | - Qinmei Wang
- The Affiliated Eye Hospital of Wenzhou Medical College, Lucheng District, Wenzhou, Zhejiang, People's Republic of China
- * E-mail:
| | - Theo Seiler
- Institute for Refractive and Ophthalmic Surgery, Zurich, Switzerland
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109
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Efficacy and safety of transepithelial corneal collagen crosslinking. J Cataract Refract Surg 2012; 38:1304; author reply 1304-5. [PMID: 22727312 DOI: 10.1016/j.jcrs.2012.05.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Indexed: 01/11/2023]
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Safety and efficacy of epithelium-on corneal collagen cross-linking using a multifactorial approach to achieve proper stromal riboflavin saturation. J Ophthalmol 2012; 2012:498435. [PMID: 22900147 PMCID: PMC3413959 DOI: 10.1155/2012/498435] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Accepted: 06/10/2012] [Indexed: 11/18/2022] Open
Abstract
Purpose. To evaluate the efficacy and safety of epithelium-on corneal collagen cross-linking (CXL) using a multifactorial approach to achieve proper stromal riboflavin saturation. Methods. This non-randomized retrospective study comprised 61 eyes with progressive keratoconus treated with epithelium-on CXL. Chemical epithelial penetration enhancement (benzalkonium chloride-containing local medication and hypotonic riboflavin solution), mechanical disruption of the superficial epithelium, and prolongation of the riboflavin-induction time until verification of stromal saturation were used before the UVA irradiation. Uncorrected and corrected distance visual acuity (UDVA, CDVA), refraction, corneal topography, and aberrometry were evaluated at baseline and at 1, 3, 6, and 12 months postoperative. Results. At 12-month, UDVA and CDVA improved significantly. None of the eyes lost lines of CDVA, while 27.4% of the eyes gained 2 or more lines. Mean spherical equivalent decreased by 0.74 D, and mean cylindrical reduction was 1.15 D. Irregularity index and asymmetry from Scheimpflug-based topography and Max-K at the location of cone from Placido-based topography showed a significant decrease. Higher-order-aberration data demonstrated a slight reduction in odd-order aberrations S 3, 5,7 (P = 0.04). Postoperative pain without other complications was recorded. Conclusion. Epithelium-on CXL with our novel protocol appeared to be safe and effective in the treatment of progressive keratoconus.
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111
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Raiskup F, Pinelli R, Spoerl E. Riboflavin osmolar modification for transepithelial corneal cross-linking. Curr Eye Res 2012; 37:234-8. [PMID: 22335811 DOI: 10.3109/02713683.2011.637656] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE To investigate the influence of osmolarity on the transepithelial permeability of riboflavin solutions in a cross-linking procedure. METHODS Several riboflavin 0.1% solutions that contained different NaCl and benzalkonium chloride (BAC) concentrations were applied to 36 rabbit eyes for 30 min. To serve as a control, the epithelium was removed in group A (standard protocol). The groups then received the following solutions: (A) riboflavin 0.1% in NaCl 0.9% solution; (B) riboflavin 0.1% in NaCl 0.44% solution with BAC 0.02%; (C) riboflavin 0.1% in NaCl 0.44% solution with BAC 0.01%; (D) riboflavin 0.1% in NaCl 0.44% solution without BAC; (E) riboflavin 0.1% in NaCl 0.9% solution with BAC 0.02%; and (F) riboflavin 0.1% in NaCl 0.9% solution without BAC. Six eyes in each group were treated. The absorption coefficients of the corneas were measured to characterize the riboflavin penetration into the cornea. RESULTS There is a large difference in the transepithelial riboflavin penetration of riboflavin 0.1% + BAC 0.02% solutions that contain different NaCl concentrations (NaCl 0.9% versus NaCl 0.44%). The absorption coefficients differed by more than a factor of two (P = 0.004). No statistically significant difference was found between riboflavin 0.1% in NaCl 0.44% solution containing BAC 0.02% and BAC 0.01%. Compared to the standard protocol, these solutions resulted in an absorption coefficient of 37% (BAC 0.02%) and 33% (BAC 0.01%) of the standard epithelium-off procedure. CONCLUSION The transepithelial riboflavin solution should contain no dextran, but it should include 0.01% BAC and 0.44% NaCl to promote the permeability of riboflavin through the epithelium, resulting in a sufficient concentration of riboflavin in the corneal stroma.
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Affiliation(s)
- Frederik Raiskup
- Department of Ophthalmology, Carl Gustav Carus University Hospital, Fetscherstrasse 74, Dresden, Germany.
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112
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Satyam A, Subramanian GS, Raghunath M, Pandit A, Zeugolis DI. In vitroevaluation of Ficoll-enriched and genipin-stabilised collagen scaffolds. J Tissue Eng Regen Med 2012; 8:233-41. [DOI: 10.1002/term.1522] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2011] [Revised: 02/14/2012] [Accepted: 03/08/2012] [Indexed: 01/08/2023]
Affiliation(s)
- A. Satyam
- Network of Excellence for Functional Biomaterials; National University of Ireland Galway; Galway Ireland
- Department of Mechanical & Biomedical Engineering; National University of Ireland Galway; Galway Ireland
| | - G. S. Subramanian
- Tissue Modulation Laboratory; National University of Singapore; Singapore
- Division of Bioengineering, Faculty of Engineering; National University of Singapore; Singapore
| | - M. Raghunath
- Tissue Modulation Laboratory; National University of Singapore; Singapore
- Division of Bioengineering, Faculty of Engineering; National University of Singapore; Singapore
| | - A. Pandit
- Network of Excellence for Functional Biomaterials; National University of Ireland Galway; Galway Ireland
| | - D. I. Zeugolis
- Network of Excellence for Functional Biomaterials; National University of Ireland Galway; Galway Ireland
- Department of Mechanical & Biomedical Engineering; National University of Ireland Galway; Galway Ireland
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Intraoperative Corneal Thickness Measurements During Corneal Collagen Cross-Linking With Hypoosmolar Riboflavin Solution in Thin Corneas. Cornea 2012; 31:486-90. [DOI: 10.1097/ico.0b013e31821e4286] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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114
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Schumacher S, Mrochen M, Spoerl E. Absorption of UV-light by riboflavin solutions with different concentration. J Refract Surg 2012; 28:91-2. [PMID: 22313434 DOI: 10.3928/1081597x-20120117-01] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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115
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Vetter JM, Brueckner S, Tubic-Grozdanis M, Voßmerbäumer U, Pfeiffer N, Kurz S. Modulation of central corneal thickness by various riboflavin eyedrop compositions in porcine corneas. J Cataract Refract Surg 2012; 38:525-32. [DOI: 10.1016/j.jcrs.2011.09.045] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Revised: 09/02/2011] [Accepted: 09/05/2011] [Indexed: 10/14/2022]
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Sinha Roy A, Dupps WJ. Patient-specific computational modeling of keratoconus progression and differential responses to collagen cross-linking. Invest Ophthalmol Vis Sci 2011; 52:9174-87. [PMID: 22039252 PMCID: PMC3253542 DOI: 10.1167/iovs.11-7395] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2011] [Revised: 08/12/2011] [Accepted: 10/22/2011] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To model keratoconus (KC) progression and investigate the differential responses of central and eccentric cones to standard and alternative collagen cross-linking (CXL) patterns. METHODS Three-dimensional finite element models (FEMs) were generated with clinical tomography and IOP measurements. Graded reductions in regional corneal hyperelastic properties and thickness were imposed separately in the less affected eye of a KC patient. Topographic results, including maximum curvature and first-surface, higher-order aberrations (HOAs), were compared to those of the more affected contralateral eye. In two eyes with central and eccentric cones, a standard broad-beam CXL protocol was simulated with 200- and 300-μm treatment depths and compared to spatially graded broad-beam and cone-centered CXL simulations. RESULTS In a model of KC progression, maximum curvature and HOA increased as regional corneal hyperelastic properties were decreased. A topographic cone could be generated without a reduction in corneal thickness. Simulation of standard 9-mm-diameter CXL produced decreases in corneal curvature comparable to clinical reports and affected cone location. A 100-μm increase in CXL depth enhanced flattening by 24% to 34% and decreased HOA by 22% to 31%. Topographic effects were greatest with cone-centered CXL simulations. CONCLUSIONS Progressive hyperelastic weakening of a cornea with subclinical KC produced topographic features of manifest KC. The clinical phenomenon of topographic flattening after CXL was replicated. The magnitude and higher-order optics of this response depended on IOP and the spatial distribution of stiffening relative to the cone location. Smaller diameter simulated treatments centered on the cone provided greater reductions in curvature and HOA than a standard broad-beam CXL pattern.
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Affiliation(s)
- Abhijit Sinha Roy
- Cleveland Clinic Cole Eye Institute, 9500 Euclid Avenue, Cleveland, OH 44120, USA
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118
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Beckman Rehnman J, Janbaz CC, Behndig A, Lindén C. Spatial distribution of corneal light scattering after corneal collagen crosslinking. J Cataract Refract Surg 2011; 37:1939-44. [PMID: 21873026 DOI: 10.1016/j.jcrs.2011.05.028] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2011] [Revised: 04/12/2011] [Accepted: 05/04/2011] [Indexed: 10/17/2022]
Abstract
PURPOSE To assess the spatial distribution and time course of increased corneal light scattering after corneal collagen crosslinking (CXL) with riboflavin and ultraviolet-A irradiation. SETTING Umeå University Hospital Eye Clinic, Umeå, Sweden. DESIGN Case series. METHODS Eyes with keratoconus were examined with Scheimpflug photography before and 1 and 6 months after CXL. Corneal light scattering was quantified throughout the corneal thickness at 8 measurement points 0.0 to 3.0 mm from the central cornea. RESULTS The study comprised 11 eyes of 11 patients. Central corneal light scattering increased significantly 1 month after CXL (P<.001). At 6 months, it decreased (P = .002); however, it was still higher than pretreatment values (P<.001). Light scattering at 1 month was more pronounced in the superficial stroma, gradually diminishing to zero at 240 μm depth. It was greater at the corneal center than 1.0 to 3.0 mm from the center. At 6 months, a second peak of light scattering occurred between 240 μm and 340 μm depth. No increased light scattering deeper than 340 μm was seen at either time point. CONCLUSIONS Corneal light scattering after CXL showed distinctive spatial and temporal profiles. Analysis of corneal light scattering may give an impression of tissue changes, the depth of the CXL treatment effect, and the corneal response to the treatment. Scheimpflug photography appears to be useful for this purpose. FINANCIAL DISCLOSURE No author has a financial or proprietary interest in any material or method mentioned.
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Gkika M, Labiris G, Kozobolis V. Corneal collagen cross-linking using riboflavin and ultraviolet-A irradiation: a review of clinical and experimental studies. Int Ophthalmol 2011; 31:309-19. [PMID: 21847678 DOI: 10.1007/s10792-011-9460-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Accepted: 07/08/2011] [Indexed: 11/28/2022]
Abstract
Corneal collagen cross-linking (CXL) using riboflavin and ultraviolet-A irradiation is a common method of tissue stabilization and has been developed primarily to address the need of treating keratoconus. CXL's promising results on keratoconus indicated that it might be effective in other corneal diseases as well. This new treatment promises a slowing effect on the progression of these diseases and its initial results show that it is safe and reasonably curative. The purpose of this review is to critically evaluate this treatment, to explore its benefits, to highlight its limitations in terms of efficacy and long-term safety and finally to identify areas for future research in this topic with a significant potential to change the way we treat our patients. In addition, in this unbiased review we try to bring together all the scientific information from both laboratory and clinical trials that have been conducted during recent years and to review the most recent publications regarding the therapeutic indications of CXL.
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Affiliation(s)
- Maria Gkika
- Eye Institute of Thrace and Department of Ophthalmology, Medical School of Democritus University of Thrace, Dragana, 68100, Alexandroupolis, Greece.
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Hayes S, Boote C, Kamma-Lorger CS, Rajan MS, Harris J, Dooley E, Hawksworth N, Hiller J, Terill NJ, Hafezi F, Brahma AK, Quantock AJ, Meek KM. Riboflavin/UVA collagen cross-linking-induced changes in normal and keratoconus corneal stroma. PLoS One 2011; 6:e22405. [PMID: 21850225 PMCID: PMC3151245 DOI: 10.1371/journal.pone.0022405] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2011] [Accepted: 06/21/2011] [Indexed: 11/18/2022] Open
Abstract
Purpose To determine the effect of Ultraviolet-A collagen cross-linking with hypo-osmolar and iso-osmolar riboflavin solutions on stromal collagen ultrastructure in normal and keratoconus ex vivo human corneas. Methods Using small-angle X-ray scattering, measurements of collagen D-periodicity, fibril diameter and interfibrillar spacing were made at 1 mm intervals across six normal post-mortem corneas (two above physiological hydration (swollen) and four below (unswollen)) and two post-transplant keratoconus corneal buttons (one swollen; one unswollen), before and after hypo-osmolar cross-linking. The same parameters were measured in three other unswollen normal corneas before and after iso-osmolar cross-linking and in three pairs of swollen normal corneas, in which only the left was cross-linked (with iso-osmolar riboflavin). Results Hypo-osmolar cross-linking resulted in an increase in corneal hydration in all corneas. In the keratoconus corneas and unswollen normal corneas, this was accompanied by an increase in collagen interfibrillar spacing (p<0.001); an increase in fibril diameter was also seen in two out of four unswollen normal corneas and one unswollen keratoconus cornea (p<0.001). Iso-osmolar cross-linking resulted in a decrease in tissue hydration in the swollen normal corneas only. Although there was no consistent treatment-induced change in hydration in the unswollen normal samples, iso-osmolar cross-linking of these corneas did result in a compaction of collagen fibrils and a reduced fibril diameter (p<0.001); these changes were not seen in the swollen normal corneas. Collagen D-periodicity was not affected by either treatment. Conclusion The observed structural changes following Ultraviolet-A cross-linking with hypo-osmolar or iso-osmolar riboflavin solutions are more likely a consequence of treatment-induced changes in tissue hydration rather than cross-linking.
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Affiliation(s)
- Sally Hayes
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - Craig Boote
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - Christina S. Kamma-Lorger
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - Madhavan S. Rajan
- Vision and Eye Research Unit, Anglia Ruskin University, Cambridge, United Kingdom
| | - Jonathan Harris
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - Erin Dooley
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | | | | | - Nick J. Terill
- Diamond Light Source, Didcot, Oxfordshire, United Kingdom
| | - Farhad Hafezi
- Division of Ophthalmology, Geneva University Hospitals, Geneva, Switzerland
| | - Arun K. Brahma
- Manchester Royal Eye Hospital, Manchester, United Kingdom
| | - Andrew J. Quantock
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
| | - Keith M. Meek
- Structural Biophysics Research Group, School of Optometry and Vision Sciences, Cardiff University, Cardiff, United Kingdom
- * E-mail:
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Cui L, Huxlin KR, Xu L, MacRae S, Knox WH. High-resolution, noninvasive, two-photon fluorescence measurement of molecular concentrations in corneal tissue. Invest Ophthalmol Vis Sci 2011; 52:2556-64. [PMID: 21228379 DOI: 10.1167/iovs.10-6620] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To perform high-resolution, noninvasive, calibrated measurements of the concentrations and diffusion profiles of fluorescent molecules in the live cornea after topical application to the ocular surface. METHODS An 800-nm femtosecond laser was used to perform two-photon fluorescence (TPF) axial scanning measurements. Calibration solutions consisting of sodium fluorescein (Na-Fl; concentration range, 0.01%-2.5%) and riboflavin (concentration range, 0.0125%-0.1%) were tested in well slides, and TPF signals were assessed. Excised feline eyeballs preserved in corneal storage medium and with either intact or removed corneal epithelia were then treated with Na-Fl, riboflavin, or fluorescein dextran (Fl-d) of different molecular weight (MW) for 30 minutes. Calibrated TPF was then used immediately to measure the concentration of these molecules across the central corneal depth. RESULTS The axial resolution of our TPF system was 6 μm, and a linear relationship was observed between TPF signal and low concentrations of most fluorophores. Intact corneas treated with Na-Fl or riboflavin exhibited a detectable penetration depth of only approximately 20 μm, compared with approximately 400 to 600 μm when the epithelium was removed before fluorophore application. Peak concentrations for intact corneas were half those attained with epithelial removal. Debrided corneas treated with 2,000,000 MW Fl-d showed a half-maximum penetration depth of 156.7 μm compared with 384 μm for the 3,000 MW dextran. The peak concentration of the high MW dextran was one quarter that of the lower MW dextran. CONCLUSIONS TPF is an effective, high-resolution, noninvasive method of quantifying the diffusion and concentration of fluorescent molecules across the cornea.
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Affiliation(s)
- Liping Cui
- Institute of Optics, University of Roichester, Rochester, NY, USA
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Spoerl E, Raiskup F, Kampik D, Geerling G. Correlation between UV absorption and riboflavin concentration in different depths of the cornea in CXL. Curr Eye Res 2011; 35:1040-1; author reply 1042-3. [PMID: 20958193 DOI: 10.3109/02713683.2010.506969] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Søndergaard AP, Hjortdal J, Breitenbach T, Ivarsen A. Response to “Correlation Between UV Absorption and Riboflavin Concentration in Different Depths of the Cornea in CXL” by Spoerl et al. Curr Eye Res 2010. [DOI: 10.3109/02713683.2010.506971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
| | - Jesper Hjortdal
- Department of Ophthalmology, Aarhus University Hospital, Aarhus, Denmark
| | - Thomas Breitenbach
- Department of Chemistry, Center for Oxygen Microscopy and Imaging, University of Aarhus, Aarhus, Denmark
| | - Anders Ivarsen
- Department of Ophthalmology, Aarhus University Hospital, Aarhus, Denmark
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Kolli S, Aslanides IM. Safety and efficacy of collagen crosslinking for the treatment of keratoconus. Expert Opin Drug Saf 2010; 9:949-57. [DOI: 10.1517/14740338.2010.495117] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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