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. (Invest Ophthalmol Vis Sci. 2011; 52: 6192-6198) DOI:10.1167/iovs.107137