The Impact of Acutely Elevated Intraocular Pressure on the Porcine Optic Nerve Head

Abstract

PURPOSE: To investigate the effects of acute elevations in intraocular pressure (IOP) on the cup, prelaminar, and lamina cribrosa regions of the porcine optic nerve head (ONH). METHODS: Ex vivo imaging of 10 porcine ONHs was performed using spectral-domain optical coherence tomography (OCT). The IOP was manipulated with a pressure head and measured with a pressure transducer. Reference scans were taken at 0 mm Hg, before further scanning was performed at 7-mm Hg steps, up to 49 mm Hg. Morphometric parameters were measured across centrally located OCT B-scans at different IOPs, and the relationship between IOP and changes in these parameters was analyzed. RESULTS: As IOP increased from 0 to 49 mm Hg, mean cross-sectional cup area increased (28% ± 3%, P < 0.001), lamina cribrosa area decreased (18% ± 2%, P < 0.001), and prelaminar tissue area decreased (5.5% ± 0.5%, P < 0.001). Multivariate regression demonstrated that most of the change in cup area is associated with changes in both lamina cribrosa position and thickness (r = 0.89, P < 0.001). CONCLUSIONS: Acute elevations in IOP were shown to result in posterior displacement of ONH, as well as lamina cribrosa and prelaminar tissue deformation in the porcine ONH.