Why Non-contact Tonometry Tests Cannot Evaluate the Effects of Corneal Collagen Cross-linking

Ortillés, Ángel; Rodríguez-Matas, José F.; Ariza-Gracia, Miguel Ángel; Pascual, Gemma; Calvo, Begoña

doi:10.3928/1081597x-20161206-02

Cited by 9 publications

(8 citation statements)

References 27 publications

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“…Although compressed fibrils may have a very reduced stiffness related to local buckling [36,37], the material model used in this study does not exclude the contribution of compressed fibrils. The actual role of compressed fibrils has initiated an interesting discussion concerning a criterion to switch between tension and compression in fiber reinforced material models [38,39]. Although we believe that this criterion would be fundamental in materials made only by fibers, in our model we do not account for it because the particular structure of the cornea, made of collagen fibrils immersed into a matrix of elastin and proteoglycans, is able to provide some confinement to the compressed fibrils ruling out the possibility to observe local buckling.…”

Section: Methodsmentioning

confidence: 99%

Cornea modelling

Pandolfi

2020

Eye and Vis

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Background: Biomechanics introduces numerous technologies to support clinical practice in ophthalmology, with the goal of improving surgical outcomes and to develop new advanced technologies with minimum impact on clinical training. Unfortunately, a few misconceptions on the way that computational methods should be applied to living tissues contributes to a lack of confidence towards computer-based approaches. Methods: Corneal biomechanics relies on sound theories of mechanics, including concepts of equilibrium, geometrical measurements, and complex material behaviors. The peculiarities of biological tissues require the consideration of multi-physics, typical of the eye environment, and to adopt customized geometrical models constructed on the basis of advanced optical imaging and in-vivo testing. Results: Patient-specific models are able to predict the outcomes of refractive surgery and to exploit the results of in-vivo test to characterize the material properties of the corneal tissue. Conclusions: Corneal biomechanics can become an important support to clinical practice, provided that methods are based on the actual multi-physics and use customized geometrical and mechanical models.

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Section: Methodsmentioning

confidence: 99%

Cornea modelling

Pandolfi

2020

Eye and Vis

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“…Despite evidences suggesting the beneficial effect of riboflavin/UV-A corneal phototherapy, different studies report contrasting outcomes [8,10,[20][21][22][23]. Due to this disagreement in the literature, further experimental data are necessary to understand the mechanical behaviour of corneal tissues and represent a prerequisite for the formulation and validation of constitutive models.…”

Section: Introductionmentioning

confidence: 99%

Mechanical behaviour of healthy versus alkali-lesioned corneas by a porcine organ culture model

et al. 2021

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Background Cornea is a composite tissue exhibiting nonlinear and time-dependent mechanical properties. Corneal ulcers are one of the main pathologies that affect this tissue, disrupting its structural integrity and leading to impaired functions. In this study, uniaxial tensile and stress-relaxation tests are developed to evaluate stress-strain and time-dependent mechanical behaviour of porcine corneas. Results The samples are split in two groups: some corneas are analysed in an unaltered state (healthy samples), while others are injured with alkaline solution to create an experimental ulcer (lesioned samples). Furthermore, within each group, corneas are examined in two conditions: few hours after the enucleation (fresh samples) or after 7 days in a specific culture medium for the tissue (cultured samples). Finally, another condition is added: corneas from all the groups undergo or not a cross-linking treatment. In both stress-strain and stress-relaxation tests, a weakening of the tissue is observed due to the imposed conditions (lesion, culture and treatment), represented by a lower stiffness and increased stress-relaxation. Conclusions Alkali-induced corneal stromal melting determines changes in the mechanical response that can be related to a damage at microstructural level. The results of the present study represent the basis for the investigation of traditional and innovative corneal therapies.

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“…51,52 Our results confirmed that Ki67 is located in stroma adjacent to the epithelium, whereas Ki67 was localized in the basal layer of the epithelium. 53,54 This similar localization can be checked in the reports of Ortilles et al, 55 Wilson et al, 56 and Nagata et al 57 Ortilles et al 55 reported that ki67 also was expressed in stroma and epithelium after 7 days, and then observed only in the basal layer of epithelium after 8 weeks with the decrease of the percentage of positively stained cells with Ki67. Immunofluorescence showed that Ki67 expression was changed depended with the location of rabbit corneal epithelium after two weeks (Supplementary Fig.…”

Section: Discussionmentioning

confidence: 52%

Human Conjunctival Epithelial Sheets Grown on Poly(Lactic-Co-Glycolic) Acid Membranes and Cocultured With Human Tenon's Fibroblasts for Corneal Repair

Hong

Yun

Kim

et al. 2018

Invest. Ophthalmol. Vis. Sci.

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Citation: Hong S, Yun JH, Kim E-S, Kim JS, Tchah H, Hwang C. Human conjunctival epithelial sheets grown on poly(lactic-co-glycolic) acid membranes and cocultured with human Tenon's fibroblasts for corneal repair. Invest Ophthalmol Vis Sci. 2018;59:1475-1485. https://doi.org/ 10.1167/iovs.17-22719 PURPOSE. We determine the feasibility of human conjunctival epithelial cells (hCjECs) on poly(lactic-co-glycolic) acid (PLGA) membranes for corneal epithelium regeneration. hCjECs on PLGA or polyester (PET) membranes with or without coculture of human Tenon's fibroblasts (hTFs) were compared in vitro, and to determine whether epithelial sheets grown on PLGA membranes can repair injured rabbit corneal epithelium by transplantation for 2 weeks in vivo.METHODS. Primary hCjECs were cultured on PLGA or the original PET membrane-based transwell inserts with or without coculture of hTFs on the floor of the culture plate. Cell behaviors, such as proliferation and differentiation, were compared. For in vivo assessment, the corneas of rabbits were burned, and PLGA-based epithelial sheets then were transplanted for 2 weeks before histologic staining was conducted and analyzed to determine the effectiveness of the repair. RESULTS.Primary human epithelial cells on the PLGA membrane showed an increased proliferation when cocultured with fibroblasts, which was confirmed by CCK-8 analysis, and upregulation of Ki67, with the expression of the epithelial marker CK19. The stratified squamous cell marker MUC1 and conjunctival cell marker MUC5AC also were expressed in the epithelial sheet. The epithelial defect in the burned corneas was decreased in the PLGAbased epithelial sheet treatment group (6.1% 6 1.6% of the area) compared to that in the notreatment group (30.5% 6 6.3%) 2 weeks postoperatively.CONCLUSIONS. We developed a coculture system using a human feeder cell layer and PLGA membrane-based transwell inserts to create human conjunctival epithelial sheets. This system represents a promising strategy to regenerate corneal epithelium by transplantation.

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Why Non-contact Tonometry Tests Cannot Evaluate the Effects of Corneal Collagen Cross-linking

Abstract: Indentation tests cannot characterize the changes in the corneal collagen scaffold caused by the CXL, but the uniaxial test can. However, indentation tests can assess the recovery of keratocyte density after CXL. [J Refract Surg. 2017;33(3):184-192.].

Cited by 9 publications

References 27 publications

Cornea modelling

Cornea modelling

Mechanical behaviour of healthy versus alkali-lesioned corneas by a porcine organ culture model

Human Conjunctival Epithelial Sheets Grown on Poly(Lactic-Co-Glycolic) Acid Membranes and Cocultured With Human Tenon's Fibroblasts for Corneal Repair

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