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Ian A Sigal, Huong Tran, Ziyi Zhu, Bo Wang, Elizabeth Tyler-Kabara, Hiroshi Ishikawa, Joel S Schuman, Matthew A Smith, Gadi Wollstein; Interplay between intraocular and intracranial pressure effects on the optic nerve head in vivo. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4785.
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© ARVO (1962-2015); The Authors (2016-present)
Intracranial pressure (ICP) may influence the sensitivity to intraocular pressure (IOP) and thus susceptibility to glaucoma. We quantified in vivo the deformations of the anterior lamina cribrosa (ALC) and scleral canal under acute controlled elevation of IOP and/or ICP
Four eyes of three monkeys were imaged with OCT under four pressure conditions: IOP and/or ICP either at baseline or elevated. The scleral canal and the ALC were reconstructed from manual delineations, and canal area, aspect ratio and planarity, and ALC visibility and median depth (Fig 1). Bootstrap sampling of the markings was used to obtain mean estimates and confidence intervals, and to determine the effects of IOP and ICP, independently and in interaction (α=0.05)
Significant deformations were observed in a majority (68%) of the parameters. Interactions between ICP and IOP occurred in half (47%) of the parameters (Fig 2). On average, ICP elevation expanded canal area by 0.17mm2 at baseline IOP, while contracting canal area by -0.02 mm2 at high IOP. ICP elevation decreased ALC depth by 10mm at baseline IOP, but increased depth by 7mm at high IOP. ALC visibility decreased as ICP increased, both at baseline (-10%) and high IOP (-17%). IOP elevation expanded canal area by 0.04 mm2 at baseline ICP, while contracting canal area by -0.09 mm2 at high ICP. ALC displaced 3.3 mm anteriorly and 22 mm posteriorly with IOP elevation at baseline and high ICP, respectively. ALC visibility improved as IOP increased, both at baseline (5%) and high ICP (8%)
Changing IOP or ICP significantly deformed both the scleral canal and the lamina of the monkey, regardless of the other pressure level. There were significant interactions between the effects of IOP and those of ICP on LC depth, canal area, aspect ratio and planarity. On most eyes, elevating both pressures by the same amount did not cancel out the effects, suggesting that translaminar pressure difference, defined as IOP-ICP, misses important information available in IOP and ICP
This is a 2020 ARVO Annual Meeting abstract.
(Left) Example baseline B-scan with markings. (Right) Overlaid markings from all pressure conditions. Note Y-axis stretched 3-fold
a) Interaction plots of five parameters for one eye. b) Summary of statistical results for the same eye. Significant independent effects are indicated by circles and significant interactions by the red boxes
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