High-resolution mapping of in-vivo stretch and compression of the lamina cribrosa in response to acute changes in intraocular and/or intracranial pressures

Abstract

Purpose : To map with high level of detail the in-vivo stretch and compression of the lamina cribrosa (LC) in response to acute changes in intraocular and/or intracranial pressures (IOP and ICP).

Methods : Three eyes of 3 macaque monkeys were imaged in-vivo with SD-OCT (Bioptigen, Durham, NC) while IOP and ICP were controlled through cannulas in the anterior chamber and the lateral ventricle, respectively. IOP and ICP were set to all combinations of IOPs (15 - baseline, 5, 30 and 50mmHg) and ICPs (10 – baseline, 5, 25 and 40mmHg), and allowed to equilibrate for 10min. A recently developed tracking algorithm based on image registration was adapted to OCT and used to extract the pressure-induced tissue displacements, stretch and compression.

Results : Pressure variations from the baseline caused substantial LC stretch and compression, sometimes exceeding 30%. Effects differed between LC regions and animals, and depended on whether the pressures were increased or decreased (Figure). There were strong interactions between the two pressures.

Conclusions : The effects of IOP and ICP on the LC are detectable in-vivo. These effects are highly nonlinear and interact strongly. Translaminar pressure difference (IOP-ICP) is too simplistic to describe LC mechanics. Alterations in IOP and ICP affected different regions of the LC differentially. Our methods open a new way to investigate the interplay between IOP and ICP.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

C-mode views through the LC of Monkey 1 color coded by stretch and compression resulting from pressure changes from the baseline (B). Increases in IOP caused LC stretch, larger at elevated ICP. Increases in ICP caused LC compression, larger at baseline IOP. Decreases in IOP or ICP caused smaller LC stretch and compression. Simultaneous changes in IOP and ICP that maintained the translaminar pressure difference, also produced small but significant stretch and compression.