Translaminar Pressure Effect on the Lamina Cribrosa of Non-Human Primate Eyes as a Function of Depth

Abstract

Purpose : To analyze how controlled intracranial pressure (ICP) and intraocular pressure (IOP) combinations affect the lamina cribrosa (LC) microstructure of the non-human primate eye through the LC depth in order to understand the effect of these opposing forces in vivo.

Methods : OCT scans of the optic nerve head (ONH) were obtained from adult healthy macaques while IOP and ICP were changed in a controlled environment. Gravity-based perfusion through a needle inserted into the anterior chamber controlled IOP (range 5-50mmHg). Perfusion through the lateral ventricle controlled ICP (range 3-45mmHg). The ONH was scanned at up to 16 pressure combinations. Scans were registered in 3D and LC microstructure measurements (beam thickness, pore diameter) were calculated from shared regions among all scan settings using a previously described segmentation algorithm. Microstructure measurements were analyzed throughout the LC thickness as a function of depth to examine the translaminar pressure (IOP-ICP) effect.

Results : The results of 5 eyes were analyzed. Baseline IOP was considered 15mmHg and baseline ICP ranged between 4-10mmHg between animals. Response to the range of pressure combinations was eye specific, ranging from no effect (Fig.1D,E) to a large effect (Fig.1A,C). Eyes affected by ICP showed increased beam/pore ratio in the posterior LC in scans with low IOP/high ICP, and the amount of deformation increased with more negative translaminar pressure (Fig.1A vs B). In one eye a response was seen for high IOP/low ICP in the anterior LC (Fig.1C).

Conclusions : Our study suggests that the LC deforms in response to changes in the translaminar pressure with large inter-individual variability, and the effect of ICP tends to be greater than IOP. Therefore, comprehensive evaluation of the LC pressure response should include analysis of the entire LC volume.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.

 

Figure 1. Effect of translaminar pressure on the lamina cribrosa (LC). Blue line indicates scans with high intracranial pressure (ICP) and low intraocular pressure (IOP), green indicates baseline ICP/IOP, red indicates low ICP/high IOP. Increased beam/pore ratio reflecting small pores and large beams was observed with negative or positive translaminar pressure (IOP-ICP). Deformation could be due to ICP centripetal forces in the posterior LC of scans with high ICP/low IOP (A,B). Effect in the low ICP/high IOP scan could be due to anterior movement of the LC (C).