June 2023
Volume 64, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2023
Stiffening and dehydration of corneal tissue after crosslinking procedure
Author Affiliations & Notes
  • Raymundo Rodriguez Lopez
    Fischell Department of Bioengineering, University of Maryland at College Park, College Park, Maryland, United States
  • Metecan Erdi
    Chemical and Biomolecular Engineering, University of Maryland at College Park, College Park, Maryland, United States
  • Joshua Norman Webb
    Fischell Department of Bioengineering, University of Maryland at College Park, College Park, Maryland, United States
  • Peter Kofinas
    Chemical and Biomolecular Engineering, University of Maryland at College Park, College Park, Maryland, United States
  • Hongyuan Zhang
    Cleveland Clinic Cole Eye Institute, Cleveland, Ohio, United States
  • James Bradley Randleman
    Cleveland Clinic Cole Eye Institute, Cleveland, Ohio, United States
  • Franco Walfre
    Biomedical Engineering, University of Massachusetts Lowell, Lowell, Massachusetts, United States
  • Edidiong Etim
    Biomedical Engineering, University of Massachusetts Lowell, Lowell, Massachusetts, United States
  • Giuliano Scarcelli
    Fischell Department of Bioengineering, University of Maryland at College Park, College Park, Maryland, United States
  • Footnotes
    Commercial Relationships   Raymundo Rodriguez Lopez None; Metecan Erdi None; Joshua Webb None; Peter Kofinas None; Hongyuan Zhang None; James Randleman None; Franco Walfre None; Edidiong Etim None; Giuliano Scarcelli None
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science June 2023, Vol.64, 4387. doi:
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      Raymundo Rodriguez Lopez, Metecan Erdi, Joshua Norman Webb, Peter Kofinas, Hongyuan Zhang, James Bradley Randleman, Franco Walfre, Edidiong Etim, Giuliano Scarcelli; Stiffening and dehydration of corneal tissue after crosslinking procedure. Invest. Ophthalmol. Vis. Sci. 2023;64(8):4387.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : The purpose of this study is to quantify how the hydration level (H) affects the mechanical properties of the cornea after crosslinking procedure (CXL). A correlation between mechanical properties and H in tissue is expected but often overlooked. For corneal CXL, it is especially important to quantify such connection because the process affects tissue hydration differently ex vivo vs in vivo.

Methods : Corneal buttons (5mm diameter) were cut from freshly enucleated porcine eyes. Corneal CXL was carried on using the Dresden protocol and an accelerated CXL protocol. Compression test by DMA was used to measure Young’s Modulus (E’ ) in a 1-5% strain, force ramp of 1N/min, of 3 different groups: Dresden CXL; accelerated CXL (AccCXL); and a control group. Buttons were left to dehydrate in open air or immersed in DI water to hydrate to change H before compression. H was defined by weight before compression and after total dehydration. To extract the shear modulus (G’) of the solid tissue network, the cornea was modeled as a biphasic material after measuring E’ at different H. Corneal H was also correlated with depth-dependence thickness of the tissue, characterized by confocal reflectance microscopy (CRM).

Results : When H of the tissue is not monitored, the CXL procedure increases E’ 4-fold (0.72±0.1MPa) vs control group (0.17±0.045MPa). However, H decreases from 4.07±0.35 in the control condition to 2.06±0.2 after CXL. accCXL shows a 3-fold increase of E’ (0.53±0.12MPa) when compared to the control, while H decreases to 2.79±0.12. After modulation of H and application of biphasic mechanical modeling, G’ of the solid tissue network showed a much reduced increase (1.6-fold) between the CXL (0.84MPa) and the control condition (0.50MPa); same for the accCXL condition (1.3-fold, 0.66MPa). With CRM, the overall thickness of the corneal tissue was found to linearly correlate to H: Thickness[µm]=368.32+188.67*H; R2=0.9064, as expected; however, we observed no depth dependence of hydration-induced thickness changes throughout the cornea.

Conclusions : The hydration of the corneal tissue plays an important role in affecting stiffness after CXL. Not considering hydration level when measuring mechanical properties leads to an overestimation of the stiffening effect of the CXL procedure. The often assumed difference in hydration induced thickness changes between anterior and posterior corneal stroma may need to be carefully revisited.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

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