  The cornea, as the outer element of the human eye, plays a pivotal role in
vision. Any defects in its shape can result in visual impairments. Mechanical
defect manifest as shape defects, as the cornea is under to pressure. Our study
presents the first comprehensive observation of human corneal deformation
throughout its entire thickness during an inflation test, through Optical
Coherence Tomography (OCT). Horizontal deformation reveals depth-dependent
heterogeneity, suggesting that the cornea's posterior part is softer than the
anterior part. Vertical deformation was observed at levels significantly higher
than expected and exhibited depth-dependent heterogeneity, delineating three
distinct regions. The central region of the cornea initially experienced rapid
swelling, possibly due to osmotic effects, followed by increasing compressions
as pressure rose. Conversely, the anterior and posterior regions showed no sign
of swelling, and a difference in the compressive response, possibly due to
difference in stiffness. Our study shows the complexity of human corneal
mechanics, highlighting strong anisotropy and depth-dependent behavior, and
implicating osmotic and poroelastic properties.
