Biomechanical Analysis of Symmetric And Antisymmetric Modes In Corneal Deformation Profiles

Po Jen Shih

National Taiwan University, Taiwan

Biography :

Po-Jen Shih completed his PhD in the Civil Engineering Department at National Taiwan University (NTU), focus­ing on computational mechanical analysis. He then pursued postdoctoral studies in Mechanical Engineering at NTU, specializing in the fabrication of MEMs. Currently, he serves as an associate professor in the Biomedical Engineering Department at NTU. He applies mechanical analysis technology to address interdisciplinary chal­lenges in the field of biomechanics, particularly focusing on dynamic analysis of corneal biomechanics. He has authored 51 papers in reputable journals.

Abstract :

The recorded deformation profiles of the cornea under new non-contact tonometry with a high-speed camera provide valuable insights into identifying corneal diseases through bio­mechanical alterations. Previous researches, driven by the importance of distinguishing kera­toconus through the integration of corneal apex deformation and tomographic severity, have proposed several indices for diagnosis. However, prior studies have overlooked character­istics of the entire corneal profiles during deformation, leading to a gap in understanding the mechanical properties and their application. To analyze these corneal profiles, we used mathematical decomposition techniques to break down the geometric shapes of corneas into several modes with modal coefficients. Then we recorded these modal coefficients as time-sequential curves. By analyzing these time-sequential curves from 500 normal, 200 keratoconus, 250 post-reflective surgery, and 100 glaucoma subjects, we identified several features from these modal coefficients, which could be categorized into symmetric and an­tisymmetric categories. These findings suggest that features in the symmetric category are associated with major deformations, such as intraocular pressure measurements and eyeball movement. High-order modes in the symmetric category are linked to characteristics fol­lowing reflective surgeries (PRK, LASIK, and SMILE) and the bowtie patterns of keratoconus (AB/IS and AB/SS). Conversely, features in the antisymmetric category are associated with misalignment during testing, primary angle closure glaucoma, and lateral behaviors of forme fruste keratoconus. In conclusion, our method emphasizes the importance of considering the entire corneal profiles, as their categories reveal distinct behaviors. These insights offer po­tential for improved diagnosis by providing greater details on corneal biomechanics.