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Jonathan Vande Geest, Jeff Pyne, Katia Genovese, Luciana Casaletto; A Sequential Digital Image Correlation Technique for Improved Strain Mapping in Pressure Inflation Tests of Posterior Sclera. Invest. Ophthalmol. Vis. Sci. 2013;54(15):66. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Recent research has demonstrated the importance of understanding and quantifying the deformational behavior of human posterior scleral tissues. The peripapillary sclera and surrounding scleral tissue in large part control scleral canal expansion and as such may play an important role in nerve fiber damage in glaucoma. The purpose of this abstract was to demonstrate a new technique for pressure inflation of posterior scleral tissues using a sequential digital image correlation (DIC). The results are reported and compared to those generated using standard stereo DIC. In particular, we seek to address the current challenges of standard DIC by improving both shape reconstruction and axial displacement resolution.
Differences between the standard stereo technique and the sequential procedure were quantified by analyzing a phantom object with vertical edges (a cylinder extended hemisphere). For investigating differences in displacement calculation, a DIC test was also performed on a flexible polymeric membrane at pressures of 30 and 40 mmHg. All samples were prepared for DIC by applying a speckle pattern using black and white ink. For each configuration of interest (e.g., at a given pressure), a manually controlled bi-rotational gimbal system was utilized to sequentially rotate the object through +/-15 degrees in two orthogonal directions. During rotation, images were acquired at 10 frames per second using a Falcon2 monochrome camera equipped with a 28-105 mm NIKKOR lens approximately 40 cm directly above the pressure inflation device. For each object tested at each configuration, standard 3D-DIC reconstruction was performed using a stereo angle of 10° degrees. Serial reconstruction was then performed using 10 images approximately 30° angles apart. Marker location was compared between the standard and serial approach, with results being reported in the mean percent difference between the two techniques.
The qualitative differences between the two techniques in shape reconstruction and axial displacement are observed in the attached figure. The mean percent difference in the axial displacement between the standard and stereo DIC techniques was 27% for the polymeric membrane.
These results suggest that our sequential DIC approach may provide better shape reconstruction and axial displacement accuracy than a standard stereo DIC technique.
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