Abstract
Purpose :
Atomic force microscopy (AFM) cantilevers have been used to measure the biomechanical properties of the full-thickness cornea ex vivo. In this study we examine the effect of repetitive cantilever indentations on corneal epithelial integrity to assess the utility of cantilevers for in vivo applications.
Methods :
Human cadaveric corneas prepared for research purposes were obtained from the Miracles in Sight Eye Bank (Winston-Salem, NC) without apparent epithelial or stromal defect and mounted in a custom-designed holder, which enabled complete submersion of the corneas in Optisol GS (Bausch + Lomb, Rochester, NY) at room temperature. The corneal bath was placed in the Puima nanoindenter (Optics 11 Life, Amsterdam, Netherlands). Standard AFM cantilevers (4.59 N/m, 45.5 µm diameter, Optics 11 Life) were used to complete 1000 indentations in the same location with a 5µm indentation depth over 4 hours. The cornea was sectioned for histology and expression of apoptotic/stress markers. Hematoxylin and eosin staining was used to compare epithelial integrity in indented and adjacent non-indented areas of the cornea. Expression of apoptotic/stress markers, including cleaved Caspase-3 (Asp175), phospho-HSP27 (Ser82), phospho-c-Jun (Ser73), and phospho-SAPK/JNK (Thr183/Tyr185), were compared between indented and adjacent non-indented areas.
Results :
Young’s modulus of elasticity was 14.6kPa with drift towards lower values over the duration of the trial. Hematoxylin and eosin staining of the indented cornea demonstrated epithelial deformation and partial stromal edema without epithelial denuding. There was no expression of the four apoptotic/stress markers observed in the indented area, which was comparable to the adjacent non-indented area from the same cornea.
Conclusions :
AFM cantilevers can accurately assess Young’s modulus of elasticity without significant damage to the corneal epithelium. This suggests that cantilevers can be used in in vivo applications to assess biomechanical properties.
This is a 2021 ARVO Annual Meeting abstract.