Assessing UVA and Laser-Induced Crosslinking via Brillouin Microscopy

Keratoconus and other corneal ectatic disorders involve the degradation of collagen fibers, which compromises the corneal biomechanical properties. UVA crosslinking has emerged as the primary treatment to slow down collagen degradation. This treatment is limited in both penetration depth and spatial precision, potentially leading to unwanted side effects. This work compares the changes in stiffness of corneas crosslinked with UVA irradiation and a near infrared femtosecond laser, using Brillouin microscopy. The stiffness of the crosslinked regions was mapped in terms of Brillouin frequency shift in three dimensions. UVA crosslinking showed an average increase in Brillouin shift of ~ 100 MHz. We demonstrate targeted spatial and axial corneal femtosecond crosslinking, with similar Brillouin shift values to UVA in crosslinked regions.