Biomechanical parameters of the cornea after collagen crosslinking measured by waveform analysis

Sedaghat, Mohamad-Reza; Naderi, Mostafa; Zarei-Ghanavati, Mehran

doi:10.1016/j.jcrs.2010.06.056

Cited by 66 publications

(50 citation statements)

References 19 publications

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“…Ultrasound measurements on in vitro human corneas provided a value of 5.3 MPa, 21 and an in vivo approach based on the deformation with applanation tonometry 0.29 MPa in humans. 22 The large differences across reports of Young's modulus likely arise from the different working principles of the techniques, and the hydration condition in which corneal tissue is measured.…”

Section: Discussionmentioning

confidence: 99%

Corneal Biomechanical Properties from Two-Dimensional Corneal Flap Extensiometry: Application to UV-Riboflavin Cross-Linking

Kling

Ginis

Marcos

2012

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. Corneal biomechanical properties are usually measured by strip extensiometry or inflation methods. We developed a two-dimensional (2D) flap extensiometry technique, combining the advantages of both methods, and applied it to measure the effect of UV-Riboflavin cross-linking (CXL).METHODS. Corneal flaps (13 pig/8 rabbit) from the deepithelialized anterior stroma (96 lm) were mounted on a custom chamber, consisting of a BK7 lens, a reflective retina, and two reservoirs (filled with Riboflavin and silicone oil). Stretching the corneal flap during five pressure increase/ decrease cycles (0-30 mm Hg) changed the refractive power of the system, whose Zernike aberrations were monitored with a ray-tracing aberrometer. Porcine flaps were used to test the system. Rabbits were treated with CXL unilaterally in vivo following standard clinical procedures. Flaps were measured 1 month postoperatively. An analytical model allowed estimating Young's modulus from the change in surface (strain) and pressure (stress). Confocal microscopy examination was performed before, and at different times after CXL. CONCLUSIONS. 2D flap extensiometry allows estimating corneal elasticity in vitro. The measurements are spatially resolved in depth, minimize the effects of corneal hydration, and preserve the integrity of the cornea. The method proved the efficacy of CXL in increasing corneal rigidity after 1 month in rabbits. (Invest Ophthalmol Vis Sci. 2012;53:5010-5015)

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Section: Discussionmentioning

confidence: 99%

Corneal Biomechanical Properties from Two-Dimensional Corneal Flap Extensiometry: Application to UV-Riboflavin Cross-Linking

Kling

Ginis

Marcos

2012

Invest. Ophthalmol. Vis. Sci.

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“…There were no significant differences in corneal biomechanical properties as measured with the parameters CH and CRF. 15 In another study, Sedaghat et al 16 compared CH and CRF before and after CXL for KC and concluded that although previous in vitro studies found a change in corneal rigidity, their study found no significant change in CH or CHF measured by biomechanical waveform analysis. These results were echoed in a study by Gkika et al, in which no significant change in the CRF parameters were found in keratoconic eyes before and after riboflavin/ UVA corneal CXL.…”

Section: Clinical Evaluation Of the Biomechanical Changes Occurring Imentioning

confidence: 98%

Reevaluating the Effectiveness of Corneal Collagen Cross-linking and Its True Biomechanical Effect in Human Eyes

Gatinel¹

2017

International Journal of Keratoconus and Ectatic Corneal Diseases

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The induction of cross-links in corneal tissue appears to be a promising technique to increase its stiffness and this has been the basis of treatment of keratoconus (KC) and corneal ectatic disease. However, there exists a striking discrepancy between the reported biomechanical effects of corneal collagen cross-linking (CXL) in vitro compared to in vivo, and this has not received much attention in the literature. Despite the documentation of an increase in corneal stiffness in vitro by many investigators, reports that provide evidence of measurable and consistent biomechanical changes in corneal rigidity in vivo after CXL are lacking. Indeed, the absence of documented in vivo biomechanical improvement in CXL-treated corneas is a conundrum, which needs to be further explored. To explain this discrepancy, it has been postulated that biomechanical changes induced by CXL are too subtle to be measured by currently available diagnostic tools or have characteristics not discernible by these technologies. However, the dynamic bidirectional applanation device (Ocular Response Analyzer) and dynamic Scheimpflug analyzer instruments (Corvis ST) have demonstrated the ability to quantify even subtle biomechanical differences in untreated KC corneas of different ectatic degree, and document the reduction in corneal hysteresis (CH) and corneal resistance factor (CRF) in situations where the corneal stiffness is reduced, such as after laser in situ keratomileusis and surface ablation procedures. It has also been possible to demonstrate an altered CH and CRF in patients with diabetes, smoking habit, glaucoma, Fuchs’ dystrophy, and corneal edema. It is puzzling that these diagnostic tools could document subtle biomechanical changes in these situations, yet fail to measure the purported changes induced by CXL on corneas with progressive KC. This failure to document significant and consistent biomechanical changes in corneal rigidity could suggest that CXL does not induce a simple reversal of the particular biomechanical deficits that characterize KC, or make the cornea significantly more resistant to bending forces as has been widely postulated. The absence of measurable biomechanical change in living KC corneas after CXL could be a consequence of biomechanical strengthening which is insignificant compared to the marked weakening caused by preexisting alteration of the collagen structure, disorganization of collagen fiber intertwining, and compromised structural–mechanical homogeneity that are hallmarks of keratoconic disease, especially in corneas with progressive KC. The changes in the cornea induced by CXL that have been described in vivo may instead be driven by a wound healing process in response to the removal of the corneal epithelial layer and subsequent exposure to riboflavin and ultraviolet-A (UVA). This paper will present evidence that sustains this hypothesis. How to cite this article Gatinel D. Reevaluating the Effectiveness of Corneal Collagen Cross-linking and Its True Biomechanical Effect in Human Eyes. Int J Kerat Ect Cor Dis 2017;6(1):34-41.

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“…После УФ-сшивания величина эластичности роговицы становится еще меньше [46]. Тогда как, по сведениям M. Sedaghat и соавт., повышенная после кросслинкинга жесткость ро-говиц не влияет на данные корнеального коэффициента резистентности и гистерезиса у пациентов до и через 6 мес после процедуры [47].…”

Section: биомеханика роговицы при уф-кросслинкингеunclassified

Ultraviolet Corneal Crosslinking

Бикбов¹,

Khalimov²,

Usubov³

2016

Annals RAMS

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Во всем мире ежегодно отмечается значительный рост заболеваний роговицы, сопровождающихся деструктив-ными изменениями коллагена в ее составе, что связывают с ухудшением экологии, интенсификацией глазной хи-рургии, травмами глаза, а также с увеличившимся числом офтальмоинфекций [1]. В Российской Федерации на больных с заболеваниями роговицы приходится до 18% общего числа слепых и слабовидящих [2].В основе кератоэктазий, в частности кератоконуса, лежит прогрессирующая деградация коллагеновой струк-туры роговицы и, соответственно, снижение ее прочност-но-механических свойств, приводящие к помутнению, нередко рубцеванию и значительному снижению остроты зрения. Как правило, это билатеральный патологический процесс, чаще наблюдаемый у лиц молодого трудоспо-собного возраста. Качественные и количественные из-менения состава коллагена органа зрения, отрицательно сказываясь на его структуре, проявляются в различных сочетаниях симптоматики болезни.Этиология кератоконуса считается многофакторной и наряду с вышеуказанными причинами включает также наследственную, эндокринную, аллергическую, имму-нологическую и другие теории, среди которых наиболее признанной у специалистов считается генетическая ги-потеза [3]. Несомненно, в пользу этого свидетельствуют семейные случаи заболевания, а также их сочетание с некоторыми наследственными синдромами. Так, по дан-ным мультицентрового проспективного исследования CLERK (США), генетические формы кератоконуса были выявлены в 13,5% случаев [4].В последнее десятилетие так называемый инжини-ринг тканей, базирующийся на процессах фотополи-меризации, стали использовать для лечения широкого спектра заболеваний. В частности, с целью укрепления роговой оболочки глаза при хронических дегенеративных процессах успешно применяется ультрафиолетовый (УФ) кросслинкинг роговицы (UV Corneal Crosslinking, CXL), основанный на ее облучении при длине волны 370 нм с использованием светочувствительного рибофлавина [5].Кросслинкинг (перекрестное связывание, или сши-вание) способствует стабилизации биомеханических свойств роговицы за счет увеличения количества свя-зей между фибриллами стромального коллагена, кера-тоцитами и белками межклеточной адгезии посредством рибофлавин-УФ-индуцируемых фотохимических реак-ций [5−8]

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Biomechanical parameters of the cornea after collagen crosslinking measured by waveform analysis

Abstract: Although previous in vitro studies found a change in corneal rigidity, this study found no significant change in CH or CHF measured by biomechanical waveform analysis.

Cited by 66 publications

References 19 publications

Corneal Biomechanical Properties from Two-Dimensional Corneal Flap Extensiometry: Application to UV-Riboflavin Cross-Linking

Corneal Biomechanical Properties from Two-Dimensional Corneal Flap Extensiometry: Application to UV-Riboflavin Cross-Linking

Reevaluating the Effectiveness of Corneal Collagen Cross-linking and Its True Biomechanical Effect in Human Eyes

Ultraviolet Corneal Crosslinking

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