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Jafar Arash Arash Mehr, Heather E Moss, Hamed Hatami-Marbini; Mechanical Factors contributing to ocular globe flattening in states of elevated intracranial pressure: A Finite Element Analysis. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2192.
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© ARVO (1962-2015); The Authors (2016-present)
Idiopathic intracranial hypertension (IIH) is characterized by raised intracranial pressure (ICP) in the absence of other identifiable causes. In this study, we used the finite element analysis (FEA) to explore likely mechanical causes contributing to the flattening of the ophthalmic globe, which is a finding of high ICP on clinical exam and magnetic resonance (MR) images of patients with IIH.
A finite element model of the ocular globe using axisymmetric plane elements and linear elastic material properties was created. A comprehensive parametric study was done in order to simulate globe flattening (GF) in which the ICP, intraocular pressure (IOP), material properties as well as the geometry of different domains were changed systematically. The Angle-Distance graph was plotted for the peripheral points. Angle-Distance analysis was also performed for a patient with high ICP’s MR image. Figure.1 clarifies the parameters used for the analysis:
It was found that GF is likely to happen by increasing the ICP up to 80-90 mm-Hg and decreasing the IOP within the range of 5-10 mm-Hg. Moreover, decreasing the elastic modulus of the pia mater, optic nerve, lamina cribrosa and retina in parallel with increasing the elastic modulus of the dura mater had considerable effects on the level of GF. In addition, the degree of GF was found less sensitive to alteration of the elastic modulus of sclera, peripapillary sclera and central vessel. The numerical results were compared well with the data captured from the MR image (Figure.2):
In this numerical analysis, potential contributing factors to ocular changes in IIH, in addition to elevated ICP, were identified. Differences in the material properties of certain components along with the IOP and geometry may also be involved in globe flattening in states of high ICP. Our investigation could open new research directions to the diagnosis and monitoring of diseases associated with high ICP like IIH.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Figure.1 an MR image of the eye globe with NP (left). 2D model used for the FEA (Right).
Figure.2 Comparison between experimental data (MR image) and FEA.
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