Changes in Corneal Biomechanical Properties With Different Corneal Cross-linking Irradiances

Bao, Fangjun; Zheng, Yaru; Liu, Chang; Zheng, Xiang; Zhao, Yiping; Wang, Yuan; Li, LinNa; Wang, Qinmei; Chen, ShiHao; Elsheikh, Ahmed

doi:10.3928/1081597x-20171025-01

Cited by 46 publications

(43 citation statements)

References 39 publications

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“…So far, the most reliable approach to the estimate of the biomechanical effects of CXL must be based on numerical analysis using realistic geometrical and material models of the cornea, e.g., the finite element analysis (FEA) 84,103,104 , that accounts for the exact geometry, the complex microstructure of the stroma, and furthermore for the presence of the fluids filling the anterior chamber 105,106,107 . Numerical approaches must be combined with experimental testing conducted with advanced devices conceived to provide accurate information on the variability of the material parameters of the stroma, such as the ones based on Bruilloin microscopy 27 .…”

Section: Discussionmentioning

confidence: 99%

The meaning of the demarcation line after riboflavin-UVA corneal collagen crosslinking

Mazzotta

Wollensak

Raiskup³

et al. 2019

Expert Review of Ophthalmology

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Since at least two decades, corneal cross-linking by riboflavin and UV-A irradiation stands as an established treatment option of progressive corneal ectasia. More than ten years ago, the histological evaluation of animal corneas and later of human corneas by means of in vivo biomicroscopy and scanning laser confocal microscopy demonstrated in corneas treated with cross-linking procedure the occurrence of a demarcation line running almost parallel to the corneal surface. The feature is a direct consequence of the cross-linking-induced photooxidative modification of the stromal tissue due to riboflavin stromal concentration, light distribution within the corneal stroma, riboflavin activation, oxygen availability and diffusion in the corneal stroma, radicals release, and UV-A exposure time. In this study, the general role of the demarcation line observed after a corneal cross-linking process, in particular its mechanical relevance, clinical consequences, and other various findings in the numerous nowadays available modalities of this treatment, are reviewed objectively.

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Section: Discussionmentioning

confidence: 99%

The meaning of the demarcation line after riboflavin-UVA corneal collagen crosslinking

Mazzotta

Wollensak

Raiskup³

et al. 2019

Expert Review of Ophthalmology

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“…Moreover, the Bunsen‐Roscoe law of reciprocity may not be fully applicable for corneal tissue cross‐linking (Bao et al. ).…”

Section: Discussionmentioning

confidence: 99%

“…This would suggest that standard CXL is more powerful than accelerated CXL in inducing corneal stiffening. Moreover, the Bunsen-Roscoe law of reciprocity may not be fully applicable for corneal tissue crosslinking (Bao et al 2018).…”

Section: Discussionmentioning

confidence: 99%

Standard cross‐linking versus photorefractive keratectomy combined with accelerated cross‐linking for keratoconus management: a comparative study

Iqbal

Elmassry

Tawfik

et al. 2018

Acta Ophthalmologica

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Purpose To compare the safety and efficacy of standard 30 min epithelium‐off cross‐linking ( CXL ) versus photorefractive keratectomy ( PRK ) combined with accelerated epithelium‐off cross‐linking ( AXL ) for the treatment of progressive keratoconus ( CXL ‐Plus). Methods This study was a prospective multicentre comparative clinical study. A total of 125 eyes of 75 patients with grade 1 keratoconus and documented progression were divided into two groups. Group A included 58 eyes treated with standard CXL . Group B included 67 eyes treated with combined PRK and AXL . The recorded data included UDVA , CDVA , subjective and objective refraction, keratometry and pachymetry using corneal topographies preoperatively and postoperatively at 3, 6, 12 and 24 months of follow‐up. Results In group A, at 24 months of UDVA and CDVA were improved from 1.12 ± 0.38 and 0.58 ± 0.42 to 0.66 ± 0.20 and 0.20 ± 0.12 (Log MAR ± SD ). The spherical equivalent was reduced from 4.03 ± 1.18 to 1.78 ± 1.04 D. The cylinder reduction was 0.32 ± 0.19 D. In group B, at 24 months of UDVA and CDVA were improved from 1.26 ± 0.52 and 0.68 ± 0.36 to 0.58 ± 0.28 and 0.20 ± 0.16 (Log MAR ± SD ). The spherical equivalent was reduced from 4.23 ± 0.95 to 1.92 ± 0.74 D. The cylinder reduction was ±1.76 D. Conclusion Surprisingly, standard CXL showed close results to CXL ‐Plus at the 24th follow‐up month. Standard CXL acted as a stabilizing procedure associated with a late myopic component reduction. CXL ‐Plus acted as a refractive and stabilizing procedure with an early effect on both the myopic and the astigmatic component but no later improvements. Standard CXL seems to be more powerful than AXL in its long‐term effect. Therefore, in the future, we want to test the combination of PRK with standard CXL .

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“…In the future, additional biomechanical studies using whole globe inflation tests instead of the uniaxial stress–strain measurements might allow a more complete and clinically relevant evaluation of the biomechanical efficacy of CACXL (Bao et al. ).…”

Section: Discussionmentioning

confidence: 99%

“…In recent years, CXL has become the standard treatment to halt the progression of keratoconus with favourable and stable long‐term results of up to ten years including paediatric cases (Raiskup et al. ; Caporossi et al. , 2012).…”

Section: Introductionmentioning

confidence: 99%

Biomechanical efficacy of contact lens‐assisted collagen cross‐linking in porcine eyes

Wollensak

Spörl

Herbst

2018

Acta Ophthalmologica

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Purpose: Contact lens-assisted corneal cross-linking (CACXL) has been proposed for the cross-linking treatment in thin corneas. The aim of this study was to assess the biomechanical efficacy of this treatment. Methods: Post-mortem porcine eyes were treated with standard cross-linking and with cross-linking placing a contact lens soaked with isoosmolar riboflavin solution on the debrided cornea with or without an adherent precorneal riboflavin film of up to 100 lm thickness. Three soft contact lenses (Air Optix Aqua, SofLens and Galifa) with different degrees of hydrophilic properties were tested. After cross-linking with a surface UVA irradiance of 3 mW/cm² for 30 min (fluence 5.4 J/cm²), a 400 lm deep anterior corneal flap was created using a lamellar rotating microkeratome. Biomechanical stress-strain measurements and thermal shrinkage tests were performed. Results: In the Air Optix Aqua group (30% hydration) without riboflavin film, Young 0 s modulus and stress at 8% strain were increased significantly versus untreated controls and the effect was 92.4% respectively 86.35% of the standard CXL value. In the SofLens group (59% hydration) without riboflavin film, Young 0 s modulus and stress at 8% strain were increased significantly versus untreated controls and the effect was 67.04% respectively 65.28% of the standard CXL value. In the Galifa group (72% hydration) without riboflavin film, Young 0 s modulus and stress at 8% strain were increased significantly versus untreated controls and the effect was about 68.48% respectively 75.52% of the standard CXL value. In all samples with a precorneal riboflavin film under the contact lens, there was no significant biomechanical effect compared to the untreated controls. Similarly, in the hydrothermal experiments at 70°C, there was a typical mushroom pattern with increased resistance to thermal shrinkage in the anterior stroma after standard CXL, a markedly reduced mushroom effect using a riboflavin-soaked contact lens only and no effect with the use of a riboflavin-soaked contact lens plus a precorneal riboflavin film. Conclusion: The biomechanical effect of CACXL in porcine corneas is about one-third less than after standard CXL. The efficacy of CACXL might be improved by reducing or omitting the riboflavin film on the contact lens. Further risk assessment studies are necessary.

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Changes in Corneal Biomechanical Properties With Different Corneal Cross-linking Irradiances

Abstract: Because the effect of CXL in stiffening the tissue and reducing the interfibrillar spacing consistently decreased with reducing the irradiance duration, the Bunsen-Roscoe law may not be readily applicable in the CXL of corneal tissue. [J Refract Surg. 2018;34(1):51-58.].

Cited by 46 publications

References 39 publications

The meaning of the demarcation line after riboflavin-UVA corneal collagen crosslinking

The meaning of the demarcation line after riboflavin-UVA corneal collagen crosslinking

Standard cross‐linking versus photorefractive keratectomy combined with accelerated cross‐linking for keratoconus management: a comparative study

Biomechanical efficacy of contact lens‐assisted collagen cross‐linking in porcine eyes

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