Biomechanische Zustand der Hornhaut als neuer Indikator für pathologische und strukturelle Veränderungen

Spörl, E.; Terai, Naim; Haustein, Michael; Böhm, A.; Raiskup-Wolf, F; Pillunat, Lutz E

doi:10.1007/s00347-008-1910-0

Cited by 50 publications

(38 citation statements)

References 38 publications

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“…The CH as measured by the ORA in the human eye as an entity is not only dependent on the absolute properties of cornea (and sclera) but also on IOP. For the first time, we could show a direct dependency of CH on IOP that was shown indirectly by Spo¨rl et al (Sporl et al 2009). The formula of Spo¨rl is a recommendation not yet generally accepted.…”

Section: Discussionmentioning

confidence: 48%

“…In healthy eyes, viscous and elastic properties are balanced and the difference between CH and CRF (CH-CRF) is close to zero (Sporl et al 2009). It is suspected that IOP is underestimated in patients with normal tension glaucoma, as IOP CC in those patients reveals higher values than GAT or digital contour tonometry (Morita et al 2009).…”

Section: Discussionmentioning

confidence: 99%

“…Calculations of IOP-corrected CH and CRF was conducted according to Spo¨rl et al (Sporl et al 2009) with references of IOP = 18 mmHg and CCT = 540 lm :…”

Section: Calculation Of Iop-corrected Biomechanicsmentioning

confidence: 99%

“…While the CH characterizes the viscosity as a measure of absorption and energy conversion of the cornea and the whole eye, the CRF is more likely to display the elastic properties. There is a well-described relationship between CH and intraocular pressure (IOP) (Kamiya et al 2008;Touboul et al 2008;Sporl et al 2009), but this has been shown only indirectly to date.…”

Section: Introductionmentioning

confidence: 99%

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Corneal biomechanics measured with the ocular response analyser in patients with unilateral open-angle glaucoma

Hirneiß

Neubauer

et al. 2011

Acta Ophthalmologica

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. Purpose: To evaluate the relationship between biomechanical properties of the cornea and intraocular pressure (IOP) and the role of biomechanical properties in eyes of patients with unilateral primary open‐angle glaucoma (POAG). Methods: The biomechanical properties of corneal hysteresis (CH) and the corneal resistance factor (CRF) were measured with the ocular response analyser (ORA). In an experimental setting, three human donor eyes with Schiotz‐tonometry‐controlled IOP were investigated. In addition, a series of patients with unilateral POAG were evaluated. Main outcome measures were CH, CRF, corneal‐compensated IOP (IOPcc), standard automated perimetry parameters mean defect (MD) and pattern standard deviation, central corneal thickness, Goldmann applanation tonometry (GAT), and cup‐to‐disc ratio. Results: A highly significant linear correlation between CH and the corneal‐compensated IOP (IOPcc, r = −0.926; p < 0.001) was found. The correlation between IOPCC and CRF was not significant (r = 0.335; p = 0.08). In total, 36 eyes of 18 patients with unilateral POAG were examined. Regarding uncorrected CH (mean 7.73 ± 1.46 mmHg glaucomatous eye and 9.28 ± 1.42 mmHg fellow eye), there was a highly significant difference between both eyes. This difference disappears, when CH was corrected for IOP (9.44 ± 3.78 mmHg and 9.97 ± 3.22 mmHg, respectively). Conclusions: Corneal hysteresis but not corneal resistance factor is dependent on IOP. In patients with unilateral POAG, IOP is higher in the affected eye. When CH is corrected for IOP, corneal biomechanical properties do not differ in both eyes of patients with unilateral POAG.

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Section: Discussionmentioning

confidence: 48%

Section: Discussionmentioning

confidence: 99%

“…Calculations of IOP-corrected CH and CRF was conducted according to Spo¨rl et al (Sporl et al 2009) with references of IOP = 18 mmHg and CCT = 540 lm :…”

Section: Calculation Of Iop-corrected Biomechanicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Corneal biomechanics measured with the ocular response analyser in patients with unilateral open-angle glaucoma

Hirneiß

Neubauer

et al. 2011

Acta Ophthalmologica

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“…[6][7][8] The CH and CRF have been shown to be altered in patients with diabetes (correlated with HbA1c levels), 25 in smokers, 26,27 Marfan syndrome, 12 and in other instances where altered corneal biomechanics consistent with modified collagen properties would be expected. 28 The observation of the reduction in CH and CRF values after LASIK and surface ablation procedures have also been demonstrated. [29][30][31][32] The same authors who concluded that the Corvis ST may not be reliable to quantify the effect of CXL in KC eyes have published another study where they showed that it was possible to evaluate the corneal biomechanical properties after LASIK, ReLEx flex, and ReLEx smile.…”

Section: How Then Can We Explain the Lack Of Clearly Documented Biomementioning

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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Numerical analysis of corneal curvature dynamics based on Corvis tonometer images

Kasprzak

Boszczyk

2016

Journal of Biophotonics

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The paper presents numerical analysis of corneal curvature distribution, based on Corvis ST images. It was shown that a new approach to analysis of corneal curvature from tonometer images enables a better description and understanding of processes during fast corneal deformation. Ten healthy volunteers participated in nine repeated measurements on one eye. 90 sequences of images were processed with software written in Matlab, with the use of the Image Processing Toolbox. Time-spatial distribution of the local curvature distribution of the corneal profile was obtained for each and every measurement. Some new curvature parameters were proposed and analyzed. A high repeatability for individual subjects was obtained for the proposed parameters. For four of these new parameters, the ICC coefficients were higher than 0.85. The ICC value for the calculated curvature of the cornea before deformation reaches 0.989. Such high repeatability of the proposed new parameters can be useful in examination and differentiation of corneas due to their geometrical and biomechanical properties.

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Biomechanische Zustand der Hornhaut als neuer Indikator für pathologische und strukturelle Veränderungen

Abstract: CRF and CH changes may reflect structural changes of the cornea. Thus, the ORA provides valuable information for a better understanding and characterization of the biomechanical condition of the cornea, especially with regard to diseases such as keratoconus and glaucoma.

Cited by 50 publications

References 38 publications

Corneal biomechanics measured with the ocular response analyser in patients with unilateral open-angle glaucoma

Corneal biomechanics measured with the ocular response analyser in patients with unilateral open-angle glaucoma

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

Numerical analysis of corneal curvature dynamics based on Corvis tonometer images

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