Posture‐dependent collapse of the optic nerve subarachnoid space: a combined MRI and modeling study

Purpose Large trans-lamina cribrosa pressure differences (TLCPD) have been suggested to play a role in the development of normal-tension glaucoma. To avoid substantial increases TLCPD upright postures, we hypothesize that collapse optic nerve subarachnoid space (ONSAS) protects eyes from large TLCPDs when stand up, i.e., by preventing low cerebrospinal fluid pressures around nerve. In this study, combined magnetic resonance imaging (MRI) and mathematical modeling investigate ONSAS its effects on TLCPD. Methods First, MRI was performed six healthy volunteers 6° head-down tilt (HDT) 13° head-up (HUT) assess changes volume with posture. The change represents sheath distensibility. Second, used data simulate potential fully posture (90°). Results showed decrease 33% going HDT HUT position (p < 0.001). posture, simulations predicted an orbital section nerve, disrupting communication between intracranial space. reduced simulated postural increase roughly 1 mmHg, although reduction highly sensitive distensibility, varying 0–4.8 mmHg distensibility ±1 SD. Conclusions along is dependent during acute changes. supported hypothesized even small stiffness/distensibility may substantially affect TLCPD, thereby bear relevance for TLCPD-related disorders such as Ref-erence Holmlund, P. et al. Posture-Dependent Collapse Optic Nerve Subarachnoid Space: A Combined Modeling Study. IOVS 62.4 (2021).