Phosphotungstic Acid Diffusion in Porcine Ocular Tissue for MicroCT Shape Reconstruction

For any ocular research involving finite element analysis, measurement of sample geometry is an important step that determines the accuracy of subsequent results. A shape reconstruction method using diffused Phosphotungstic Acid (PTA) within ocular samples for measurement with a microCT device will be presented here. With all finite element modeling, the material properties of the tissue must be determined using techniques such as digital image correlation (DIC) [1]. With this technique, the limitations for displacement measurement accuracy are the size of non-altering markers and camera resolution. This means that only certain material points can be tracked and the non-tracked material points must be interpolated in finite element models. Along with this interpolation, techniques for thickness measurements across the ocular tissue such as using calipers or a pachymeter [2] typically only give values at a small quantity of points while the thickness changes continuously across the tissue. The PTA staining will provide the advantage of internal geometry as well as external shape to give thickness across the entire sample. While these other techniques provide repeatable results, we believe the PTA method presented here for geometry acquisition provides accurate shape reconstruction of the tissue for finite element applications. The purpose of this study was to quantify the depth of penetration of PTA in porcine scleral samples as a function of PTA concentration and time.