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Ioannis G Pallikaris - One of the best experts on this subject based on the ideXlab platform.
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Corneal Stroma demarcation line after standard and high intensity collagen crosslinking determined with anterior segment optical coherence tomography
Journal of Cataract and Refractive Surgery, 2014Co-Authors: George D Kymionis, Konstantinos I Tsoulnaras, Michael A Grentzelos, Argyro D Plaka, Dimitrios G Mikropoulos, Dimitrios A Liakopoulos, Nikolaos G Tsakalis, Ioannis G PallikarisAbstract:PURPOSE: To use anterior segment optical coherence tomography (AS-OCT) to compare Corneal Stroma demarcation line depth after Corneal collagen crosslinking (CXL) with 2 treatment protocols. SETTING: Vardinoyiannion Eye Institute of Crete, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece. DESIGN: Prospective comparative interventional case series. METHODS: Corneal collagen crosslinking was performed in all eyes using the same ultraviolet-A (UVA) irradiation device (CCL-365). Eyes were treated for 30 minutes with 3 mW/cm(2) according to the standard Dresden protocol (Group 1) or for 10 minutes with 9 mW/cm(2) of UVA irradiation intensity (Group 2). One month postoperatively, 2 independent observers measured the Corneal Stroma demarcation line using AS-OCT. RESULTS: Sixteen patients (21 eyes) were enrolled. Group 1 comprised 7 patients (9 eyes) and Group 2, 9 patients (12 eyes). The mean Corneal Stroma demarcation line depth was 350.78 μm ± 49.34 (SD) (range 256.5 to 410 μm) in Group 1 and 288.46 ± 42.37 μm (range 238.5 to 353.5 μm) in Group 2; the Corneal Stroma demarcation line was statistically significantly deeper in Group 1 than in Group 2 (P=.0058, t test for unpaired data). CONCLUSION: The Corneal Stroma demarcation line was significantly deeper after a 30-minute CXL treatment than after a 10-minute CXL procedure with high-intensity UVA irradiation.
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Corneal Stroma demarcation line after standard and high intensity collagen crosslinking determined with anterior segment optical coherence tomography
Journal of Cataract and Refractive Surgery, 2014Co-Authors: George D Kymionis, Konstantinos I Tsoulnaras, Michael A Grentzelos, Argyro D Plaka, Dimitrios G Mikropoulos, Dimitrios A Liakopoulos, Nikolaos G Tsakalis, Ioannis G PallikarisAbstract:Purpose To use anterior segment optical coherence tomography (AS-OCT) to compare Corneal Stroma demarcation line depth after Corneal collagen crosslinking (CXL) with 2 treatment protocols. Setting Vardinoyiannion Eye Institute of Crete, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece. Design Prospective comparative interventional case series. Methods Corneal collagen crosslinking was performed in all eyes using the same ultraviolet-A (UVA) irradiation device (CCL-365). Eyes were treated for 30 minutes with 3 mW/cm 2 according to the standard Dresden protocol (Group 1) or for 10 minutes with 9 mW/cm 2 of UVA irradiation intensity (Group 2). One month postoperatively, 2 independent observers measured the Corneal Stroma demarcation line using AS-OCT. Results Sixteen patients (21 eyes) were enrolled. Group 1 comprised 7 patients (9 eyes) and Group 2, 9 patients (12 eyes). The mean Corneal Stroma demarcation line depth was 350.78 μm ± 49.34 (SD) (range 256.5 to 410 μm) in Group 1 and 288.46 ± 42.37 μm (range 238.5 to 353.5 μm) in Group 2; the Corneal Stroma demarcation line was statistically significantly deeper in Group 1 than in Group 2 ( P =.0058, t test for unpaired data). Conclusion The Corneal Stroma demarcation line was significantly deeper after a 30-minute CXL treatment than after a 10-minute CXL procedure with high-intensity UVA irradiation. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.
George D Kymionis - One of the best experts on this subject based on the ideXlab platform.
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Corneal Stroma demarcation line after standard and high intensity collagen crosslinking determined with anterior segment optical coherence tomography
Journal of Cataract and Refractive Surgery, 2014Co-Authors: George D Kymionis, Konstantinos I Tsoulnaras, Michael A Grentzelos, Argyro D Plaka, Dimitrios G Mikropoulos, Dimitrios A Liakopoulos, Nikolaos G Tsakalis, Ioannis G PallikarisAbstract:PURPOSE: To use anterior segment optical coherence tomography (AS-OCT) to compare Corneal Stroma demarcation line depth after Corneal collagen crosslinking (CXL) with 2 treatment protocols. SETTING: Vardinoyiannion Eye Institute of Crete, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece. DESIGN: Prospective comparative interventional case series. METHODS: Corneal collagen crosslinking was performed in all eyes using the same ultraviolet-A (UVA) irradiation device (CCL-365). Eyes were treated for 30 minutes with 3 mW/cm(2) according to the standard Dresden protocol (Group 1) or for 10 minutes with 9 mW/cm(2) of UVA irradiation intensity (Group 2). One month postoperatively, 2 independent observers measured the Corneal Stroma demarcation line using AS-OCT. RESULTS: Sixteen patients (21 eyes) were enrolled. Group 1 comprised 7 patients (9 eyes) and Group 2, 9 patients (12 eyes). The mean Corneal Stroma demarcation line depth was 350.78 μm ± 49.34 (SD) (range 256.5 to 410 μm) in Group 1 and 288.46 ± 42.37 μm (range 238.5 to 353.5 μm) in Group 2; the Corneal Stroma demarcation line was statistically significantly deeper in Group 1 than in Group 2 (P=.0058, t test for unpaired data). CONCLUSION: The Corneal Stroma demarcation line was significantly deeper after a 30-minute CXL treatment than after a 10-minute CXL procedure with high-intensity UVA irradiation.
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Corneal Stroma demarcation line after standard and high intensity collagen crosslinking determined with anterior segment optical coherence tomography
Journal of Cataract and Refractive Surgery, 2014Co-Authors: George D Kymionis, Konstantinos I Tsoulnaras, Michael A Grentzelos, Argyro D Plaka, Dimitrios G Mikropoulos, Dimitrios A Liakopoulos, Nikolaos G Tsakalis, Ioannis G PallikarisAbstract:Purpose To use anterior segment optical coherence tomography (AS-OCT) to compare Corneal Stroma demarcation line depth after Corneal collagen crosslinking (CXL) with 2 treatment protocols. Setting Vardinoyiannion Eye Institute of Crete, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece. Design Prospective comparative interventional case series. Methods Corneal collagen crosslinking was performed in all eyes using the same ultraviolet-A (UVA) irradiation device (CCL-365). Eyes were treated for 30 minutes with 3 mW/cm 2 according to the standard Dresden protocol (Group 1) or for 10 minutes with 9 mW/cm 2 of UVA irradiation intensity (Group 2). One month postoperatively, 2 independent observers measured the Corneal Stroma demarcation line using AS-OCT. Results Sixteen patients (21 eyes) were enrolled. Group 1 comprised 7 patients (9 eyes) and Group 2, 9 patients (12 eyes). The mean Corneal Stroma demarcation line depth was 350.78 μm ± 49.34 (SD) (range 256.5 to 410 μm) in Group 1 and 288.46 ± 42.37 μm (range 238.5 to 353.5 μm) in Group 2; the Corneal Stroma demarcation line was statistically significantly deeper in Group 1 than in Group 2 ( P =.0058, t test for unpaired data). Conclusion The Corneal Stroma demarcation line was significantly deeper after a 30-minute CXL treatment than after a 10-minute CXL procedure with high-intensity UVA irradiation. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.
Noel M Ziebarth - One of the best experts on this subject based on the ideXlab platform.
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multiscale investigation of the depth dependent mechanical anisotropy of the human Corneal Stroma
Investigative Ophthalmology & Visual Science, 2015Co-Authors: Cristina Labate, Marco Lombardo, Maria Penelope De Santo, Janice Dias, Noel M Ziebarth, Giuseppe LombardoAbstract:The histology and, accordingly, biomechanics of the human Corneal Stroma are highly heterogeneous. There is extensive knowledge on the existence of regional differences in the collagen fibril bundles' packing arrangement and lamellar orientation across and throughout the thickness of the human Corneal Stroma.1–5 The anterior Stroma consists of short bundles of collagen fibrils that show dense intertwining and also insert vertically into Bowman's layer, thus contributing to maintain Corneal shape. The deeper Stroma contains collagen fibril bundles that are arranged in wide lamellae oriented predominantly along the superior/inferior and nasal/temporal meridians and with reduced connections between adjacent layers. Several laboratory techniques have been used to elucidate the depth-dependent mechanical properties of the human Corneal Stroma.6–17 All of these studies have shown that the elastic modulus within the Stroma decreases from anterior to posterior, regardless of the mechanical testing used. It is therefore well accepted that the depth-dependent changes of Stromal mechanical elasticity are linked to the depth-dependent change of Stromal microstructure. Atomic force microscopy (AFM) enables localized mechanical sample testing and has been used to investigate the local elastic modulus of the human Corneal Stroma at different depths. Although the results from previous studies6–11 could not be directly compared, because of the use of AFM tips with variable geometry and dimension as well as different study protocols, the elastic modulus is shown to decrease 40% to 80% with depth from the anterior Stroma to the posterior part of the Stroma. The aim of this study was to provide information on the depth-dependent compressive elastic modulus of the human Corneal Stroma both at the tissue (Stroma) and molecular (collagen) level by using AFM. In addition, we correlated the depth-dependent anisotropy of Stromal elasticity with images of the human Corneal Stroma acquired by second harmonic generation (SHG) microscopy.
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anterior and posterior Corneal Stroma elasticity after Corneal collagen crosslinking treatment
Experimental Eye Research, 2013Co-Authors: Janice Dias, Vasilios F Diakonis, Vardhaman P Kankariya, Sonia H Yoo, Noel M ZiebarthAbstract:Abstract The purpose of this project was to assess anterior and posterior Corneal Stromal elasticity after Corneal collagen cross linking (CXL) treatment in human cadaver eyes using Atomic Force Microscopy (AFM) through indentation. Twenty four human cadaver eyes (12 pairs) were included in this study and divided into 2 groups (6 pairs per group). In both groups, the left eye (OS) served as a control (no riboflavin or CXL treatment was performed) and the right eye (OD) underwent CXL treatment (30 min of riboflavin pretreatment followed by 30 min of exposure to 3 mW/cm 2 of ultraviolet light). In group 1, the anterior Stroma was exposed by manual delamination of approximately 50 μm of the Corneal Stroma including Bowman's membrane. In group 2, the posterior Stroma was exposed by delamination of the anterior 50% of the Corneal Stroma including Bowman's membrane. Delamination was performed after crosslinking treatment in the case of the treated eyes. In all eyes, the Stromal elasticity was quantified using AFM through indentation. Young's modulus of elasticity for the anterior cornea (group 1) was 245.9 ± 209.1 kPa (range: 82.3–530.8 kPa) for the untreated control eyes, and 467.8 ± 373.2 kPa (range: 157.4–1126 kPa) for the CXL treated eyes. Young's modulus for the posterior cornea (group 2) was 100.2 ± 61.9 kPa (range: 28.1–162.6 kPa) for the untreated control eyes and 66.0 ± 31.8 kPa (range: 31.3–101.7 kPa) for the CXL treated eyes. Young's modulus of the anterior Stroma significantly increased after CXL treatment ( p = 0.024), whereas the posterior Stroma did not demonstrate a significant difference in Young's modulus after CXL treatment ( p = 0.170). The anterior Stroma was stiffer than the posterior Stroma for both the control and CXL treatment groups ( p = 0.077 and p = 0.023, respectively). Our findings demonstrate that stiffness of the anterior Corneal Stroma after CXL treatment seems to increase significantly, while the posterior Stroma does not seem to be affected by CXL.
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anterior and posterior Corneal Stroma elasticity assessed using nanoindentation
Experimental Eye Research, 2013Co-Authors: Janice Dias, Noel M ZiebarthAbstract:Abstract Corneal biomechanics is an essential parameter for developing diagnostic and treatment methods of Corneal-related diseases. It is widely accepted that Corneal mechanical strength stems from the Stroma's collagenous composition. However, more comprehensive insight into the mechanical properties within the Stroma is needed to improve current Corneal diagnostic and treatment techniques. The purpose of this study was to perform elasticity characterization of anterior and posterior Stromal regions of human corneas using atomic force microscopy (AFM). Nine pairs of human whole globes were placed in 20% Dextran solution, cornea side down, to restore the Corneal thickness to physiological levels (400–600 μm). The epithelium and Bowman's membrane were removed from all eyes. Anterior Stromal AFM elasticity testing was then performed on left (OS) eyes. Additional Stroma was removed from right (OD) eyes to allow posterior Stromal measurements at a depth of 50% of the original thickness. All experiments were performed with corneas submerged in 15% Dextran to maintain Corneal hydration. The results of the study showed that the Young's modulus of elasticity of the anterior Stroma (average: 281 ± 214 kPa; range: 59–764 kPa) was significantly higher than that of the posterior Stroma (average: 89.5 ± 46.1 kPa; range: 29–179 kPa) (p = 0.014). In addition, a linear relationship was found between the posterior Stromal elasticity and anterior Stromal elasticity (p = 0.0428). On average, the elasticity of the posterior Stroma is 39.3% of the anterior Stroma. In summary, there appears to be an elasticity gradient within the Corneal Stroma, which should be considered in the design and development of Corneal diagnostic and treatment methods to enhance efficacy.
Michael A Grentzelos - One of the best experts on this subject based on the ideXlab platform.
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Corneal Stroma demarcation line after standard and high intensity collagen crosslinking determined with anterior segment optical coherence tomography
Journal of Cataract and Refractive Surgery, 2014Co-Authors: George D Kymionis, Konstantinos I Tsoulnaras, Michael A Grentzelos, Argyro D Plaka, Dimitrios G Mikropoulos, Dimitrios A Liakopoulos, Nikolaos G Tsakalis, Ioannis G PallikarisAbstract:PURPOSE: To use anterior segment optical coherence tomography (AS-OCT) to compare Corneal Stroma demarcation line depth after Corneal collagen crosslinking (CXL) with 2 treatment protocols. SETTING: Vardinoyiannion Eye Institute of Crete, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece. DESIGN: Prospective comparative interventional case series. METHODS: Corneal collagen crosslinking was performed in all eyes using the same ultraviolet-A (UVA) irradiation device (CCL-365). Eyes were treated for 30 minutes with 3 mW/cm(2) according to the standard Dresden protocol (Group 1) or for 10 minutes with 9 mW/cm(2) of UVA irradiation intensity (Group 2). One month postoperatively, 2 independent observers measured the Corneal Stroma demarcation line using AS-OCT. RESULTS: Sixteen patients (21 eyes) were enrolled. Group 1 comprised 7 patients (9 eyes) and Group 2, 9 patients (12 eyes). The mean Corneal Stroma demarcation line depth was 350.78 μm ± 49.34 (SD) (range 256.5 to 410 μm) in Group 1 and 288.46 ± 42.37 μm (range 238.5 to 353.5 μm) in Group 2; the Corneal Stroma demarcation line was statistically significantly deeper in Group 1 than in Group 2 (P=.0058, t test for unpaired data). CONCLUSION: The Corneal Stroma demarcation line was significantly deeper after a 30-minute CXL treatment than after a 10-minute CXL procedure with high-intensity UVA irradiation.
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Corneal Stroma demarcation line after standard and high intensity collagen crosslinking determined with anterior segment optical coherence tomography
Journal of Cataract and Refractive Surgery, 2014Co-Authors: George D Kymionis, Konstantinos I Tsoulnaras, Michael A Grentzelos, Argyro D Plaka, Dimitrios G Mikropoulos, Dimitrios A Liakopoulos, Nikolaos G Tsakalis, Ioannis G PallikarisAbstract:Purpose To use anterior segment optical coherence tomography (AS-OCT) to compare Corneal Stroma demarcation line depth after Corneal collagen crosslinking (CXL) with 2 treatment protocols. Setting Vardinoyiannion Eye Institute of Crete, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece. Design Prospective comparative interventional case series. Methods Corneal collagen crosslinking was performed in all eyes using the same ultraviolet-A (UVA) irradiation device (CCL-365). Eyes were treated for 30 minutes with 3 mW/cm 2 according to the standard Dresden protocol (Group 1) or for 10 minutes with 9 mW/cm 2 of UVA irradiation intensity (Group 2). One month postoperatively, 2 independent observers measured the Corneal Stroma demarcation line using AS-OCT. Results Sixteen patients (21 eyes) were enrolled. Group 1 comprised 7 patients (9 eyes) and Group 2, 9 patients (12 eyes). The mean Corneal Stroma demarcation line depth was 350.78 μm ± 49.34 (SD) (range 256.5 to 410 μm) in Group 1 and 288.46 ± 42.37 μm (range 238.5 to 353.5 μm) in Group 2; the Corneal Stroma demarcation line was statistically significantly deeper in Group 1 than in Group 2 ( P =.0058, t test for unpaired data). Conclusion The Corneal Stroma demarcation line was significantly deeper after a 30-minute CXL treatment than after a 10-minute CXL procedure with high-intensity UVA irradiation. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.
Dimitrios A Liakopoulos - One of the best experts on this subject based on the ideXlab platform.
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Corneal Stroma demarcation line after standard and high intensity collagen crosslinking determined with anterior segment optical coherence tomography
Journal of Cataract and Refractive Surgery, 2014Co-Authors: George D Kymionis, Konstantinos I Tsoulnaras, Michael A Grentzelos, Argyro D Plaka, Dimitrios G Mikropoulos, Dimitrios A Liakopoulos, Nikolaos G Tsakalis, Ioannis G PallikarisAbstract:PURPOSE: To use anterior segment optical coherence tomography (AS-OCT) to compare Corneal Stroma demarcation line depth after Corneal collagen crosslinking (CXL) with 2 treatment protocols. SETTING: Vardinoyiannion Eye Institute of Crete, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece. DESIGN: Prospective comparative interventional case series. METHODS: Corneal collagen crosslinking was performed in all eyes using the same ultraviolet-A (UVA) irradiation device (CCL-365). Eyes were treated for 30 minutes with 3 mW/cm(2) according to the standard Dresden protocol (Group 1) or for 10 minutes with 9 mW/cm(2) of UVA irradiation intensity (Group 2). One month postoperatively, 2 independent observers measured the Corneal Stroma demarcation line using AS-OCT. RESULTS: Sixteen patients (21 eyes) were enrolled. Group 1 comprised 7 patients (9 eyes) and Group 2, 9 patients (12 eyes). The mean Corneal Stroma demarcation line depth was 350.78 μm ± 49.34 (SD) (range 256.5 to 410 μm) in Group 1 and 288.46 ± 42.37 μm (range 238.5 to 353.5 μm) in Group 2; the Corneal Stroma demarcation line was statistically significantly deeper in Group 1 than in Group 2 (P=.0058, t test for unpaired data). CONCLUSION: The Corneal Stroma demarcation line was significantly deeper after a 30-minute CXL treatment than after a 10-minute CXL procedure with high-intensity UVA irradiation.
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Corneal Stroma demarcation line after standard and high intensity collagen crosslinking determined with anterior segment optical coherence tomography
Journal of Cataract and Refractive Surgery, 2014Co-Authors: George D Kymionis, Konstantinos I Tsoulnaras, Michael A Grentzelos, Argyro D Plaka, Dimitrios G Mikropoulos, Dimitrios A Liakopoulos, Nikolaos G Tsakalis, Ioannis G PallikarisAbstract:Purpose To use anterior segment optical coherence tomography (AS-OCT) to compare Corneal Stroma demarcation line depth after Corneal collagen crosslinking (CXL) with 2 treatment protocols. Setting Vardinoyiannion Eye Institute of Crete, Faculty of Medicine, University of Crete, Heraklion, Crete, Greece. Design Prospective comparative interventional case series. Methods Corneal collagen crosslinking was performed in all eyes using the same ultraviolet-A (UVA) irradiation device (CCL-365). Eyes were treated for 30 minutes with 3 mW/cm 2 according to the standard Dresden protocol (Group 1) or for 10 minutes with 9 mW/cm 2 of UVA irradiation intensity (Group 2). One month postoperatively, 2 independent observers measured the Corneal Stroma demarcation line using AS-OCT. Results Sixteen patients (21 eyes) were enrolled. Group 1 comprised 7 patients (9 eyes) and Group 2, 9 patients (12 eyes). The mean Corneal Stroma demarcation line depth was 350.78 μm ± 49.34 (SD) (range 256.5 to 410 μm) in Group 1 and 288.46 ± 42.37 μm (range 238.5 to 353.5 μm) in Group 2; the Corneal Stroma demarcation line was statistically significantly deeper in Group 1 than in Group 2 ( P =.0058, t test for unpaired data). Conclusion The Corneal Stroma demarcation line was significantly deeper after a 30-minute CXL treatment than after a 10-minute CXL procedure with high-intensity UVA irradiation. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.