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Gillian J McLellan, Kevin C Snyder, Kazuya Oikawa, Julie A Kiland, Shaile Gehrke, Alex Huang; Imaging distal aqueous outflow pathways in a Spontaneous Model of Primary Congenital Glaucoma (PCG). Invest. Ophthalmol. Vis. Sci. 2018;59(9):5908. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
PCG severity and response to treatment can be highly variable, even within families.This study aims to determine if morphological abnormalities in post-trabecular aqueous outflow pathways contribute to this variability in a feline model of PCG.
Ex-vivo aqueous angiography (AA) and optical coherence tomography (OCT; Spectralis HRA+OCT) were performed immediately post-enucleation in 9 adult cat eyes (5 PCG and 4 normal controls), following intracameral infusion of 2.5% fluorescein and 0.4% indocyanine green (ICG) at physiologic intraocular pressure (IOP;10-20mmHg). Scleral OCT line scans were acquired in areas of high and low angiographic signal around the limbus. Infusion of fixable fluorescent dextrans facilitated direct histologic validation of AA and OCT findings. Eyes were perfusion fixed at physiologic IOP before dissection of regions of high and low AA signal, cryosectioned and either stained with H&E or immunolabeled (IF) for pericyte and vascular endothelial markers prior to microscopy.
Aqueous angiography yielded circumferential, high quality images of distal aqueous outflow pathways in both normal and PCG eyes. No AA signal was appreciated in a buphthalmic PCG eye with pronounced IOP elevation for several months, though collapsed vascular profiles were identified on IF. In contrast, the remaining 8/9 eyes showed similar, segmental regions of AA signal distinguished by differences in time of signal onset but not by differences in ultimate signal intensity. AA signal correlated with lumens seen on OCT (Fig), in turn validated by histology. Number of intrascleral vessels on AA, OCT, and on histology was not significantly different between groups, but collector channels and scleral vessels appeared to be posteriorly displaced relative to the limbus in eyes with PCG.
This first report of AA in eyes with spontaneous glaucoma confirmed distal aqueous humor outflow in feline PCG ex vivo. Distal outflow channels were identified and patent in all but the most severely affected eyes, but appeared posteriorly displaced relative to the limbus in PCG eyes. Studies are ongoing to verify these findings and examine the relationship between anterior segment morphology and IOP history in an expanded population.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
Aqueous angiograms (A,C) and corresponding OCT images (B,D) of the perilimbal region of the inferiornasal quadrant in 1yr-old FCG (A,B) and normal (C,D) cat eyes
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