Spatially-resolved Brillouin spectroscopy reveals biomechanical changes in early ectatic corneal disease and post-crosslinking in vivo

Mounting evidence connects the biomechanical properties of tissues to the development of eye diseases such as keratoconus, a common disease in which the cornea thins and bulges into a conical shape. However, measuring biomechanical changes in vivo with sufficient sensitivity for disease detection has proved challenging. Here, we present a first largescale study (~200 subjects, including normal and keratoconus patients) using Brillouin lightscattering microscopy to measure longitudinal modulus in corneal tissues with high sensitivity and spatial resolution. Our results in vivo provide evidence of biomechanical inhomogeneity at the onset of keratoconus and suggest that biomechanical asymmetry between the left and right eyes may presage disease development. We additionally measure the stiffening effect of corneal crosslinking treatment in vivo for the first time. Our results demonstrate the promise of Brillouin microscopy for diagnosis and treatment of keratoconus, and potentially other diseases.