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

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.

Intracranial pressure modulates aqueous humour dynamics of the eye

“…; Tong et al . ). The feedback mechanism does not operate in reverse given that ICP was unaffected by IOP elevation, and it appears inactive under normal operating conditions because TTX application had no effect on outflow facility at resting ICP.…”

“…One might expect a complete restoration of baseline TLP based on the CSFP hypothesis (Berdahl & Allingham, 2010), but this was not observed and might not be necessary for a protective effect. Computational models indicate that IOP has a much greater influence on optic nerve head biomechanics than ICP and that TLP alone is insufficient to capture their complex interaction with material properties (Hua et al 2018;Tong et al 2019). The feedback mechanism does not operate in reverse given that ICP was unaffected by IOP elevation, and it appears inactive under normal operating conditions because TTX application had no effect on outflow facility at resting ICP.…”

Problems in CSF and Ophthalmic Disease Research

“…The difference between these two compartments is termed the translaminar pressure difference (TLPD). An increased TLPD (IOP>CSFP) is postulated to precipitate glaucomatous nerve damage, perhaps contributing to posterior bowing of the lamina cribrosa (4)(5)(6). Elevations in IOP can certainly cause this imbalance, but low ICP in the presence of a "normal" IOP has also been linked with glaucomatous nerve damage.…”

Prospective Clinical Study of Non-Invasive Intracranial Pressure Measurements in Open-Angle Glaucoma Patients and Healthy Subjects

“…The lamina cribrosa (LC), located deep within the optic nerve head [1], is a sieve-like structure in the posterior portion of the sclera that allows optic nerve fibres to exit from the eye [2,3]. The LC plays an important role as a barrier between intraocular pressure (IOP) and intracranial pressure (ICP) [4,5]. Elevated IOP was formerly considered to be the main risk factor in the development of glaucoma, however, elevated IOP is not always present in all forms of glaucoma [5,6].…”