Factors Influencing Lamina Cribrosa Microcapillary Hemodynamics and Oxygen Concentrations

Abstract

Purpose : To identify and rank the factors that influence lamina cribrosa (LC) microcapillary hemodynamics and oxygen concentrations using computational fluid dynamics (CFD).

Methods : We generated 12,000 ‘artificial’ LC microcapillary networks and predicted blood flow velocities and oxygen concentrations within the microcapillaries using CFD (COMSOL Inc., Burlington, MA). Oxygen consumption was assumed to occur along the capillaries. Across models, we varied the pore size of the LC (5500±2400 µm²), the microcapillary arrangement (radial, isotropic or circumferential), the LC diameter (1.9±0.3 mm), the LC inferior-superior (340±116 m^-1) and nasal-temporal (-78±130 m^-1) curvatures. We assumed that blood flow originated from the Circle of Zinn-Haller, fed the LC uniformly at its periphery, and was drained into the central retinal vein. Arterial (50±6.8 mmHg) and venous (17±6.4 mmHg) pressures were applied as boundary conditions and were also varied. Finally, we performed linear regressions to rank the influence of factors on LC hemodynamics and oxygen concentrations.

Results : The factors influencing the most LC hemodynamics and oxygen concentrations were (in order of importance): LC diameter, arterial pressure, venous pressure, microcapillary arrangement (anisotropy), and nasal-temporal curvature (Figure 1a). LC pore size and superior-inferior curvature had almost no impact. Specifically, we found that LCs with a small diameter, a radial arrangement of the microcapillaries, and an elevated arterial pressure had higher oxygen concentrations across their networks. Examples of oxygen concentration distributions in 2 structurally different LCs are shown in Figure 1b-c.

Conclusions : This study is the first to describe LC hemodynamics using a computational modeling approach. Our study may provide clinically-relevant information for the management and understanding of ischemia-induced neuronal cell death in optic neuropathies.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Figure 1: (a) Ranking of factors influencing LC hemodynamics and oxygen concentrations (red: negative effect on oxygen concentration; green: positive effect). (b-c) Oxygen distribution in two LC microcapillary networks with (b) having smaller pores (mean area: 3400 µm²) and an isotropic arrangement of its microcapillaries and (c) having larger pores (5500 µm²) and a radial arrangement. Red circles indicate the arterial supply and the blue circle (V) the venous drainage.