Scanning Acoustic Microscopy for Mapping the Microelastic Properties of Human Corneal Tissue

Purpose: To assess the feasibility of applying scanning acoustic microscopy (SAM) on UV cross-linked corneal tissue for mapping and analyzing its biomechanical properties. Materials and Methods: Five corneal pairs (10 corneas) were used. In each pair, one cornea was cross-linked (epithelium removed, riboflavin application for 45 min and UVA irradiation for 30 min) and the contralateral control cornea was epithelial debrided and treated only with riboflavin for 45 min. Histological sections were prepared and their mechanical properties were examined using SAM. A line profile technique and 2D analysis was used to analyze the mechanical properties of the corneas. Then the corneal paraformaldehyde and unfixed sections were examined histologically using hematoxylin and eosin (H&E) staining. Results: In the frozen fresh corneal tissue, the speed of sound of the treated corneas was 1672.5 +/- 36.9 ms(-1), while it was 1584.2 +/- 25.9 ms(-1) in the untreated corneas. In the paraformaldehyde fixed corneal tissue, the speed of sound of the treated corneas was 1863.0 +- 12.7 ms(-1), while it was 1739.5 +/- 30.4 ms(-1) in the untreated corneas. The images obtained from the SAM technique corresponded well with the histological images obtained with H& E staining. Conclusion: SAM is a novel tool for examining corneal tissue with a high spatial resolution, providing both histological and mechanical data.