Three-dimensional ocular surface displacement and strain measurement using fringe projection profilometry and digital image correlation.

SIGNIFICANCE: Accurate measurement of ocular surface deformation under intraocular pressure (IOP) is essential for understanding eye biomechanics and the progression of pressure-related diseases such as glaucoma. However, existing imaging techniques often involve trade-offs among spatial resolution, system complexity, and the ability to capture full-field three-dimensional (3D) deformation on highly curved, compliant tissues.

AIM: We investigate the feasibility of a noncontact measurement framework that combines fringe projection profilometry (FPP) and two-dimensional digital image correlation (2D DIC) to recover full-field 3D displacement and strain on the ocular surface during pressurization.

APPROACH: An ex vivo porcine eye was subjected to controlled hydrostatic pressurization to simulate IOP variation. FPP was used to reconstruct dense 3D surface geometry across successive loading states, whereas 2D DIC was applied to corresponding texture images to estimate in-plane displacements. These measurements were fused through pixel-wise mapping to recover full-field 3D displacement vectors, from which Green-Lagrange strain components were computed and expressed in a spherical coordinate framework.

RESULTS

The proposed framework was able to capture the evolving deformation of the ocular surface, revealing spatially heterogeneous displacement and strain patterns. Localized regions of elevated strain were consistently observed, whereas the deformation fields exhibited smooth temporal progression across loading stages. The recovered strain distributions aligned with expected biomechanical behavior of the ocular structure, suggesting the capability of the method to resolve meaningful deformation features on a curved, compliant surface.

CONCLUSIONS

The combined FPP-DIC framework indicates potential as a viable approach for measuring dense 3D displacement and strain on the ocular surface. This feasibility study establishes the potential of structured-light-based methods for ocular biomechanics and lays the foundation for future quantitative validation and in vivo applications.