The Effects of Negative Periocular Pressure on Biomechanics of the Optic Nerve Head and Cornea: A Computational Modeling Study

Abstract

PurposeTo evaluate the effects of negative periocular pressure (NPP), and concomitant intraocular pressure (IOP) lowering, on the biomechanics of the optic nerve head (ONH) and cornea.MethodsWe developed a validated finite element (FE) model of the eye to compute tissue biomechanical strains induced in response to NPP delivered using the Multi-Pressure Dial (MPD) system. The model was informed by clinical measurements of IOP lowering and was based on published tissue properties. We also conducted sensitivity analyses by changing pressure loads and tissue properties.ResultsApplication of -7.9 mmHg NPP decreased strain magnitudes in the ONH by c. 50% while increasing corneal strain magnitudes by c. 25%. Comparatively, a similar increase in corneal strain was predicted to occur due to an increase in IOP of 4 mmHg. Sensitivity studies indicated that NPP lowers strain in the ONH by reducing IOP and that these effects persisted over a range of tissue stiffnesses and spatial distributions of NPP.ConclusionsNPP is predicted to considerably decrease ONH strain magnitudes. It also increases corneal strain but to an extent expected to be clinically insignificant. Thus, using NPP to lower IOP and hence decrease ONH mechanical strain is likely biomechanically beneficial for glaucoma patients.Translational RelevanceThis study provides the first description of how NPP affects ONH biomechanics and explains the underlying mechanism of ONH strain reduction. It complements current empirical knowledge about the MPD system and guides future studies of NPP as a treatment for glaucoma.

The Effect of Negative Pressure on IOP in the Living Human Eye

“…Application of the negative pressure goggles has been proposed as a novel non-medical and non-invasive treatment for glaucoma and recent computational modeling has predicted that IOP will reduce with the application of negative pressure goggles initially due to scleral expansion and longer term with increasing episcleral outflow. 16 Another recent computational study reported a reduction in IOP with exposure to negative pressure 24 , which is consistent with the expected mechanical response of a generic closed vessel under pressure expose to reduce external pressure. Results of numerical models based on simplified and generic ocular morphology and mechanical properties would of course omit all the eye-specific and orbital characteristics that may mediate the response of IOP to varying extra orbital pressure, as observed by our study.…”

A Histomorphometric and Computational Investigation of the Stabilizing Role of Pectinate Ligaments in the Aqueous Outflow Pathway

“…We used the average first principal Lagrangian strain (Ξ I ) and SCLA estimates for the most compliant case from each age model and ensured that the error relative to an exhaustively refined mesh was less than 1% for Ξ I and SCLA (relative to the baseline SCLA of the corresponding age model). The meshes were generated using the Frontal algorithm, and ten steps of smoothing and optimization were conducted to enhance mesh quality [30].…”

“…Specifically, we decreased the elemental characteristic edge length in the TM by a factor of 4 and in the PL region by a factor of 8. The meshes were generated using the Frontal algorithm, and ten steps of smoothing and optimization were conducted to enhance mesh quality (Safa et al, 2022b).…”