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Appropriate Sequence of Combined Intracorneal Ring Implantation and Corneal Collagen Cross-Linking in Keratoconus
摘要： To compare surgical sequences of combined intracorneal ring segment (ICRS) implantation and corneal collagen cross-linking (CXL) in keratoconus and corneal ectasia in terms of visual, refractive, and keratometric outcomes.
关键词： corneal ectasia,corneal collagen cross-linking,keratoconus,intracorneal ring
更新于2025-09-10 09:29:36
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Second Harmonic Generation Imaging Analysis of Collagen Arrangement in Human Cornea
摘要： PURPOSE. To describe the horizontal arrangement of human corneal collagen bundles by using second harmonic generation (SHG) imaging. METHODS. Human corneas were imaged with an inverted two photon excitation ?uorescence microscope. The excitation laser (Ti:Sapphire) was tuned to 850 nm. Backscatter signals of SHG were collected through a 425/30-nm bandpass emission ?lter. Multiple, consecutive, and overlapping image stacks (z-stacks) were acquired to generate three dimensional data sets. ImageJ software was used to analyze the arrangement pattern (irregularity) of collagen bundles at each image plane. RESULTS. Collagen bundles in the corneal lamellae demonstrated a complex layout merging and splitting within a single lamellar plane. The patterns were signi?cantly different in the super?cial and limbal cornea when compared with deep and central regions. Collagen bundles were smaller in the super?cial layer and larger in deep lamellae. CONCLUSIONS. By using SHG imaging, the horizontal arrangement of corneal collagen bundles was elucidated at different depths and focal regions of the human cornea.
关键词： collagen,corneal stroma,second harmonic generation,cornea
更新于2025-09-09 09:28:46
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Raman Spectroscopic Analysis to Detect Reduced Bone Quality after Sciatic Neurectomy in Mice
摘要： Bone mineral density (BMD) is a commonly used diagnostic indicator for bone fracture risk in osteoporosis. Along with low BMD, bone fragility accounts for reduced bone quality in addition to low BMD, but there is no diagnostic method to directly assess the bone quality. In this study, we investigated changes in bone quality using the Raman spectroscopic technique. Sciatic neurectomy (NX) was performed in male C57/BL6J mice (NX group) as a model of disuse osteoporosis, and sham surgery was used as an experimental control (Sham group). Eight months after surgery, we acquired Raman spectral data from the anterior cortical surface of the proximal tibia. We also performed a BMD measurement and micro-CT measurement to investigate the pathogenesis of osteoporosis. Quantitative analysis based on the Raman peak intensities showed that the carbonate/phosphate ratio and the mineral/matrix ratio were significantly higher in the NX group than in the Sham group. There was direct evidence of alterations in the mineral content associated with mechanical properties of bone. To fully understand the spectral changes, we performed principal component analysis of the spectral dataset, focusing on the matrix content. In conclusion, Raman spectroscopy provides reliable information on chemical changes in both mineral and matrix contents, and it also identifies possible mechanisms of disuse osteoporosis.
关键词： bone quality,sciatic neurectomy,hydroxyapatite,Raman spectroscopy,collagen crosslink,mineral maturity,osteoporosis,bone matrix
更新于2025-09-09 09:28:46
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A Comparative Study of Vertebrate Corneal Structure: The Evolution of a Refractive Lens
摘要： PURPOSE. Although corneal curvature plays an important role in determining the refractive power of the vertebrate eye, the mechanisms controlling corneal shape remain largely unknown. To address this question, we performed a comparative study of vertebrate corneal structure to identify potential evolutionarily based changes that correlate with the development of a corneal refractive lens. METHODS. Nonlinear optical (NLO) imaging of second-harmonic–generated (SHG) signals was used to image collagen and three-dimensionally reconstruct the lamellar organization in corneas from different vertebrate clades. RESULTS. Second-harmonic–generated images taken normal to the corneal surface showed that corneal collagen in all nonmammalian vertebrates was organized into sheets (?sh and amphibians) or ribbons (reptiles and birds) extending from limbus to limbus that were oriented nearly orthogonal (ranging from 77.78–88.28) to their neighbors. The slight angular offset (28–138) created a rotational pattern that continued throughout the full thickness in ?sh and amphibians and to the very posterior layers in reptiles and birds. Interactions between lamellae were limited to "sutural" ?bers in cartilaginous ?sh, and occasional lamellar branching in ?sh and amphibians. There was a marked increase in lamellar branching in higher vertebrates, such that birds (cid:2) reptiles > amphibians > ?sh. By contrast, mammalian corneas showed a nearly random collagen ?ber organization with no orthogonal, chiral pattern. CONCLUSIONS. Our data indicate that nonmammalian vertebrate corneas share a common orthogonal collagen structural organization that shows increased lamellar branching in higher vertebrate species. Importantly, mammalian corneas showed a different structural organization, suggesting a divergent evolutionary background.
关键词： stroma,nonlinear optical,collagen,cornea,second-harmonic generation
更新于2025-09-04 15:30:14
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Corneal changes after collagen crosslinking for keratoconus using dual scheimpflug imaging
摘要： Purpose: To evaluate corneal changes after collagen crosslinking (CXL) therapy for keratoconus (KCN) using the Galilei dual Scheimpflug analyzer. Methods: This prospective, nonrandomized clinical study included 35 eyes of 32 keratoconus patients who had undergone CXL. The eyes were saturated with riboflavin solution and were subjected for 30 minutes to ultraviolet-A (UV-A) light with irradiance of 3 mW/cm2. Effectiveness of the treatment was assessed by measuring uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), manifest cylinder/sphere, keratometry, pachymetry, posterior and anterior elevations by the Galilei dual Scheimpflug analyzer. Prior to treatment and 8 months after therapy, Scheimpflug analysis was performed using the Galilei system. The four sets of data including keratometry values, pachymetry, elevation parameters and surface indices were statistically analyzed and compared. Results: Mean patient age was 22.3 ± 3.8 years and mean postoperative follow-up was 8.1 ± 3.2 months. There was a significant increase in UCVA (0.54 ± 0.35 Log MAR preoperatively to 0.49 ± 0.34 LogMAR postoperatively, P = 0.01) and BCVA (0.21 ± 0.19 Log MAR preoperatively to 0.16 ± 0.17 LogMAR postoperatively, P = 0.01). Mean cycloplegic spherical equivalent refractive error was ?4.13 ± 2.65 Diopter (D) preoperatively and ? 4.67 ± 2.96 D postoperatively (P < 0.001). During the follow-up period, no significant difference was observed in pachymetric and elevation data postoperatively. Conclusion: Corneal stabilization could be achieved by collagen crosslinking therapy for keratoconus in terms of corneal thickness, keratometry values, elevation parameters and surface indices.
关键词： Keratoconus,Galilei Dual Scheimpflug Analyzer,Collagen Crosslinking
更新于2025-09-04 15:30:14
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Correlation Between Multimodal Microscopy, Tissue Morphology, and Enzymatic Resistance in Riboflavin-UVA Cross-Linked Human Corneas
摘要： PURPOSE. To explore the utility of multimodal microscopy as a noninvasive tool to assess corneal collagen cross-linking (CXL) efficacy, we investigated the correlation between riboflavin (RF) axial profile, second harmonic generation (SHG) imaging, and histological/biochemical changes of human corneas after RF-ultraviolet A (UVA)–catalyzed CXL. METHODS. De-epithelialized human corneoscleral tissues were imaged by confocal and multiphoton microscopy to study RF tissue diffusion profile and SHG-based roughness index (Rq) after CXL. We installed 0.1% RF for 5, 10, and 20 minutes, respectively, followed by UVA irradiation, while dextran drug vehicle–treated corneas served as controls. Masson’s trichrome staining and collagenase digestion assay were employed to assess ultrastructural modifications of collagen lamellae and bioenzymatic strength following RF-UVA CXL. RESULTS. Stromal absorption of RF was significantly higher in 20 minutes compared with 5- and 10-minute drug instillations. The roughness index of SHG images was reduced after RF-UVA CXL at all RF instillation time points compared with dextran controls. Interestingly, correlation between axial profiles of RF dosage and Rq index was only observed in 10- and 20-minute RF instillations (R2 ? 0.13 and 0.28, respectively, all P < 0.05), but not in the 5-minute group. Masson’s trichrome staining revealed collagen fibril compaction in cross-linked corneas in an RF dose-dependent manner. Collagenase digestion assay showed significantly increased biochemical strength by higher RF doses in cross-linked corneas. CONCLUSIONS. Intrastromal RF distribution profiles correlated with histological and functional property changes in RF-UVA cross-linked corneas. A riboflavin-defined threshold further determined the sensitivity of SHG imaging as a noninvasive imaging modality to assess the efficacy of RF-UVA CXL.
关键词： collagenase digestion,collagen cross-linking,second harmonic generation,Masson’s trichrome staining,riboflavin
更新于2025-09-04 15:30:14
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Assessment of UVA-Riboflavin Corneal Cross-Linking Using Small Amplitude Oscillatory Shear Measurements
摘要： The effect of ultraviolet (UV)–riboflavin cross-linking (CXL) has been measured primarily using the strip extensometry technique. We propose a simple and reliable methodology for the assessment of CXL treatment by using an established rheologic protocol based on small amplitude oscillatory shear (SAOS) measurements. It provides information on the average cross-link density and the elastic modulus of treated cornea samples. METHODS. Three fresh postmortem porcine corneas were used to study the feasibility of the technique, one serving as control and two receiving corneal collagen cross-linking treatment. Subsequently, five pairs of fresh postmortem porcine corneas received corneal collagen cross-linking treatment with riboflavin and UVA-irradiation (370 nm; irradiance of 3 mW/cm2) for 30 minutes (Dresden protocol); the contralateral porcine corneas were used as control samples. After the treatment, the linear viscoelastic moduli of the corneal samples were measured using SAOS measurements and the average cross-linking densities extracted. RESULTS. For all cases investigated, the dynamic moduli of the cross-linked corneas were higher compared to those of the corresponding control samples. The increase of the elastic modulus of the treated samples was between 122% and 1750%. The difference was statistically significant for all tested samples (P ? 0.018, 2-tailed t-test). CONCLUSIONS. We report a simple and accurate methodology for quantifying the effects of cross-linking on porcine corneas treated with the Dresden protocol by means of SAOS measurements in the linear regime. The measured dynamic moduli, elastic and viscous modulus, represent the energy storage and energy dissipation, respectively. Hence, they provide a means to assess the changing physical properties of the cross-linked collagen networks after CXL treatment.
关键词： small amplitude oscillatory shear measurements,linear viscoelasticity,elastic modulus,rheology,cross-link density,corneal collagen cross-linking
更新于2025-09-04 15:30:14