The optic nerve head (ONH) is located at the interface of intracranial and intraocular compartments. It is comprised of lamina cribrosa (LC), a fenestrated connective tissue tethered to the posterior sclera across the scleral canal. Since LC is exposed to intraocular pressure (IOP) anteriorly and intracranial pressure (ICP) posteriorly, it is an ideal site for noninvasively detecting intracranial pressure (ICP) fluctuation. We hypothesized that the pressure differential between IOP and ICP across LC, will determine LC position and meridional diameter of scleral canal (also called Bruch’s membrane opening- BMOD). We tested our hypothesis in 19 human subjects undergoing medically necessary lumbar puncture (LP) to lower ICP and 6 anesthetized pigs, whose ICP were increased in 5mm Hg increments using lumbar drain. We imaged the ONH using Optical Coherence Tomography (OCT) and measured IOP and ICP at baseline and after each intervention. We measured the following ONH morphological parameters: BMOD, anterior LC depth (ALCD) and retinal thickness from the OCT images. We modeled the effects of acute ICP changes on ONH morphological parameters using AVOVA for human study and generalized linear model with fixed intercepts for the pig study. We found that there was no significant effect of acute ICP changes on ONH morphological parameters in both humans and pigs. We conclude that the LC is resistant to displacement across large changes of ICP. Proposed mechanisms include compensatory change in IOP, and non-linear or non-monotonic effects of IOP and ICP across the LC
