Relative Contributions of Intracranial Pressure and Intraocular Pressure on Lamina Cribrosa Behavior.

Junfei Tong,Sachin Kedar,Deepta Ghate,Linxia Gu

doi:10.1155/2019/3064949

Abstract

Purpose To characterize the relative contributions of intraocular pressure (IOP) and intracranial pressure (ICP) on lamina cribrosa (LC) behavior, specifically LC depth (LCD) and LC peak strain. Methods An axially symmetric finite element model of the posterior eye was constructed with an elongated optic nerve and retro-orbital subarachnoid space ensheathed by pia and dura mater. The mechanical environment in LC was evaluated with ICP ranging from 5 to 15 mmHg and IOP from 10 to 45 mmHg. LCD and LC peak strains at various ICP and IOP levels were estimated using full factorial experiments. Multiple linear regression analyses were then applied to estimate LCD and LC peak strain using ICP and IOP as independent variables. Results Both increased ICP and decreased IOP led to a smaller LCD and LC peak strain. The regression correlation coefficient for LCD was −1.047 for ICP and 1.049 for IOP, and the ratio of the two regression coefficients was −1.0. The regression correlation coefficient for LC peak strain was −0.025 for ICP and 0.106 for IOP, and the ratio of the two regression coefficients was −0.24. A stiffer sclera increased LCD but decreased LC peak strain; besides, it increased the relative contribution of ICP on the LCD but decreased that on the LC peak strain. Conclusions ICP and IOP have opposing effects on LCD and LC peak strain. While their effects on LCD are equivalent, the effect of IOP on LC peak strain is 3 times larger than that of ICP. The influences of these pressure are dependent on sclera material properties, which might explain the pathogenesis of ocular hypertension and normal-tension glaucoma.

Highlights

Glaucoma is the second leading cause of blindness worldwide
Full Factorial Computational Experiments. e LC depth (LCD) and lamina cribrosa (LC) peak strains obtained from the 12 simulation scenarios are listed in Tables 1 and 2. e regression equations modeled for LCD and LC peak strain using data listed below show an excellent tting (R2∼1): Table 1: LCD in the trial runs of full factorial simulation experiment with human sclera material property
A 5 mmHg intraocular pressure (IOP) reduction led to an anterior shift of 5.5 μm at the center and 3.7 μm at the quarter-point location. e LC shift in the quarter-point compared to the LC shift in the center was 69.2% in the elevated intracranial pressure (ICP) model and 67.3% in the decreased IOP model, respectively

Summary

Introduction

Elevated intraocular pressure (IOP) is the major risk factor for the development of glaucoma [1, 2]. High IOP causes abnormal displacement and strain in the optic nerve head (ONH), within the load-bearing component lamina cribrosa (LC). Is indicates that other factors besides elevated IOP, such as intracranial pressure (ICP), may contribute to the development of glaucoma. Artificially lowering ICP in monkeys produced an optic neuropathy that resembled glaucoma [13]. Since the optic nerve subarachnoid space is located along the periphery of LC, the loading effect of ICP on LC is likely to be different from that of IOP. E aim of this work was to estimate and compare the relative contributions of ICP and IOP on LCD and LC peak strain using the finite element method LC peak maximum principal strain (hereafter referred to as LC peak strain) differently. e aim of this work was to estimate and compare the relative contributions of ICP and IOP on LCD and LC peak strain using the finite element method

Materials and Methods

Results

Conclusion

Disclosure