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Ian A Sigal, Ning-Jiun Jan, Kira L Lathrop, Andrew P Voorhees; Between a basket and a finger trap: a unified model of posterior pole fiber architecture. Invest. Ophthalmol. Vis. Sci. 2017;58(8):3161. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
The fiber architecture of the posterior pole plays a critical role in eye biomechanics. Models postulated to describe the architecture typically include a ring of fibers thought to protect the neural tissues from mechanical insult from IOP. These models, do not explain other aspects of the architecture, such as radial or intertwined fibers in the sclera, or the observations of IOP-induced contraction of the canal. We propose a new model of posterior pole architecture in which fibers follow near-geodesic curves. We compared the fiber distributions and posterior pole biomechanics arising from our model with previous models and experimental data from ours and other laboratories
We constructed virtual posterior poles with our proposed architecture and of other common models (Fig 1). We simulated how these poles would appear in histological analysis done at high resolution with our own polarized light microscopy (Jan BOE 2015) and at low resolution with SALS (Jones Interace 2015) and WAXS (Pijanka IOVS 2012). We constructed finite element models of the posterior poles and simulated increases in IOP
There was good correspondence between our proposed architecture and experimental observations obtained from SALS, WAXS and PLM (Fig 1c). Our geodesic architecture resulted in much lower mechanical insult than all other models (Fig 2). Small deviations from the geodesics produced various amounts of canal expansion and even canal contraction
The geodesic fiber architecture model we propose is more biomechanically favorable than previous models, reducing insult to the neural tissues. Our model was consistent with experiments, explaining the appearance of a circumferential ring of fibers around the canal in low resolution imaging, as well as the radial and intertwined fibers observed in the more distal sclera at higher resolution. The model architecture is highly adaptable, allowing eye-specific responses, including canal expansion and contraction
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Fig 1. Our proposed fiber architecture is consistent with high resolution fiber orientation measurements. Simulating a low resolution SALS experiment causes the appearance of a ring of highly aligned fibers around the canal, surrounded by a region of low alignment
Fig 2. Five models of fiber architecture and the stretch induced by 50mmHg IOP. Our model of geodesic fibers greatly reduced stretch in both the lamina cribrosa and sclera
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