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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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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
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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