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Yi Hua, Haiden McDonald, Jason Walker, Pedro Pallares, Bryn Brazile, Ian A. Sigal; Local decreases in lamina cribrosa oxygen concentration under elevated IOP are not correlated with the degree of IOP-induced compression. Invest. Ophthalmol. Vis. Sci. 2020;61(7):3532.
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© ARVO (1962-2015); The Authors (2016-present)
IOP-induced deformations of the optic nerve head entail blood vessel distortion. This may, in turn, affect blood flow and oxygen perfusion to lamina cribrosa (LC) astrocytes and axons, contributing to neural tissue distress and eventually retinal ganglion cell axon death. We studied how elevated IOP affects LC oxygen concentration.
We reconstructed the LC vessel network based on serial histological sections (thickness: 16 µm) from a monkey optic nerve head, in which the vessels had been labeled with a fluorescent dye. An arterial inlet pressure of 50 mmHg was set at the periphery of the vessel network to simulate blood inflow from the circle of Zinn-Haller. A venous outlet pressure of 18 mmHg was set at the central retinal vein for drainage. Vessel lumen diameter was assumed as 8 µm. The vessel network was virtually embedded in the LC tissue of a finite element model of the eye under simulated IOP loads. The IOP-induced compressive strains in the LC were then used to estimate local vessel lumen diameter reduction. We then used hemodynamics modeling and the Green’s function method to quantify the oxygen concentration in the LC.
IOP elevations of 15, 30, and 45 mmHg reduced the average vessel lumen diameter by 0.32, 0.54, and 0.66 µm, and the average oxygen concentration by 0.80, 1.44, and 1.84 mmHg, respectively. Vessel compression and oxygen decreases did not colocalize and were not correlated.
Our realistic model predicted that elevated IOP compressed the LC blood vessels, resulting in decreased oxygen concentration in the LC, consistent with the predictions from generic models (Chuangsuwanich et al., 2016). Interestingly, regions of large reduction in oxygen concentration did not colocalize with those of large compression. This suggests that clinical measurements of local IOP-induced compression may not adequately predict regions of ischemia. Current efforts aim to understand how the predictions differ between individual eyes and in 3D.
This is a 2020 ARVO Annual Meeting abstract.
IOP-induced reduction in (a) vessel lumen diameter and (b) oxygen concentration. (c) Scatter plots of the reduction in oxygen concentration with respect to the IOP-induced compression. Vessel compression and oxygen decreases did not colocalize and were not correlated.
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