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Stanislava Fialova, Marco Augustin, Corinna Knopf, Michael Pircher, Leopold Schmetterer, Christoph K Hitzenberger, Bernhard Baumann; Acute Intraocular Pressure Elevation Rat Model Studied Using High Resolution Multifunctional Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2198.
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© 2017 Association for Research in Vision and Ophthalmology.
Intraocular pressure (IOP) plays an important role in glaucoma. In this study, we investigated the effect of changes in intraocular pressure on the morphology and polarization properties of retinal layers and sclera in a rat model of acute IOP elevation.
IOP was elevated by cannulation of the anterior chamber of the right eye in 5 male Sprague Dawley rats using a needle connected to a reservoir filled with 0.9% NaCl solution. A pressure transducer was connected between needle and the reservoir. In order to elevate IOP, the reservoir was placed at different heights with increments of 5 or 10 mmHg (determined by transducer) starting at ~14 mmHg and ended when ocular blood flow was stopped. The time interval between measurements at different IOP levels was approximately 4 minutes. Three-dimensional data were recorded using a polarization sensitive optical coherence tomography (PS-OCT) prototype with a central wavelength 840 nm and high axial resolution of 3.8 µm in tissue. Multi-functional OCT images including reflectivity contrast, motion contrast, and polarization contrast were computed.
Changes in the reflectivity (increase) of inner plexiform layer (IPL) and outer plexiform layer (OPL) were observed during the experiments. Vessels diameters decreased as IOP increased during the experiments. On OCT angiography images, a decrease of blood flow was observed. Due to this effect, the optic nerve head, which is usually shadowed by vessels at regular IOP, became visible in the OCT images. Retinal nerve fiber layer (RNFL) phase retardation was investigated in an annulus around optic nerve head and did not show a correlation with increased pressure. In contrast, reversible changes in the retardation of the sclera were detected in PS-OCT images.
Multi-functional OCT provides threefold contrast channels for the investigation of rat eyes. Acute elevation of IOP up to 100 mmHg produced changes in the retina that were observable on reflectivity images as increase in the reflectivity of IPL and OPL. Circumpapillary RNFL phase retardation did not change during the experiments. This suggests that such acute IOP elevation did not produce instant changes in the RNFL that would manifest as change of retardation. Retardation changes in the sclera suggest that its structure (and therefore its biomechanical properties) could be influenced by the IOP.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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