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Ian A Sigal, PoYi Lee, Bryn Brazile, Po Lam, Ziyi Zhu, Yi Hua, Bin Yang; Real-time measurement of lamina cribrosa and sclera collagen architecture and mechanics at sub-micron resolution. Invest. Ophthalmol. Vis. Sci. 2019;60(11):011. doi: https://doi.org/.
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The tools available to visualize and measure eye tissue architecture and mechanics, such as polarized light microscopy, optical coherence tomography and second harmonic imaging, often lack the necessary temporal and/or spatial resolution to study crucial dynamic events. We demonstrate a new technique, snapshot polarized light microscopy (sPLM), for imaging ocular connective tissue microarchitecture and mechanics in real-time
Fresh sheep optic nerve heads were trephined and cut into 16-µm thick sections. The sections were mounted on a custom biaxial-stretching device for dynamic testing while imaged at 30 frames per second using sPLM. Spectral analysis at each pixel revealed the local collagen fiber orientation, which was then used to quantify tissue architecture and load-induced changes in anisotropy. Image tracking techniques were used to determine collagen fiber displacements and deformations
The high spatial and temporal resolution of sPLM revealed load-induced pore deformations and beam thinning in the lamina cribrosa (Fig. 1a). Load straightened the crimped collagen fibers in the sclera (Fig. 2c), such that their fiber orientations changed from bimodal to unimodal (Fig. 2d). Tracking revealed complex deformation patterns in the sclera when under load, including significant shear, stretch, and compression (Fig. 2b), with local tissue deformations reaching 60% (Fig. 2c)
We demonstrated that sPLM allows visualization and quantification of eye tissue architecture. The high temporal and spatial resolution of sPLM revealed sub-bundle details of tissue mechanics previously unreported. These imaging and analysis techniques can be applied in other parts of the eye and other collagenous tissue
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.
Example sPLM images. Pixel color represents local collagen fiber orientation, whereas brightness is proportional to collagen density or presence of pigment. a) Optic nerve head. b) Lamina cribrosa deformations. c) Effect of load in the sclera. d) fiber uncrimping
Sclera a) before and b) after loading. Example of complex resultant c) displacements and d) stretch
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