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Leandro B C Teixeira, Teresa Linder, Richard R Dubielzig; Spontaneous Post-Trabecular Open Angle Glaucoma in Cats. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3267.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize the clinicopathological features of spontaneous cases of open angle glaucoma in cats.
33 cases of feline open angle glaucoma were identified in the Comparative Ocular Pathology Laboratory of Wisconsin database. Case inclusion was based on clinical history, histological signs of glaucoma (ganglion cells loss and optic nerve atrophy) and presence of normal iridocorneal angle morphology without secondary cause of glaucoma. Patient data, clinical history, and follow-up information were recorded. Enucleated eyes were formalin-fixed-paraffin-embedded, sections were stained with H&E, alcian blue/PAS and Masson’s trichrome and analyzed by light microscopy and histomorphometry.
The median age of affected animals was 10.1 years. Females represented 68% of cases. No breed predisposition was found. Average IOP at the time of enucleation was 47.7mmHg (25-67mmHg). Disease was bilateral in 57% of cases and affect OD only and OS only in 26% and 15% of cases respectively. The average time to glaucoma on the 2nd eye after diagnosis was 399 days (0-1795 days). 54.5% of the bilateral cases developed glaucoma in the other eye in <1 year and 27.2% first presented with bilateral glaucoma. Histologically all cases presented an open iridocorneal angle, normal ciliary cleft and trabecular meshwork and varying degrees of ganglion cells loss and cupping, gliosis and atrophy of the optic nerve. An alcian-blue-positive, trichrome-negative myxomatous matrix expended the stroma surrounding the channels of the angular aqueous plexus (analogous to schlemm’s canal), intrascleral plexus and vortex veins. No other intraocular or scleral/episcleral lesions were found. The average area of myxomatous lesion surrounding the vortex veins was significantly (p<0.01) increased in affected cats (56.2±12mm2) compared to controls (0.61±0.12mm2) and significantly correlated with the area of optic nerve cupping (r=.85, p=<.001).
Open angle glaucoma in cats is an uncommon and insidious disease that affects adult animals and share similarities with human POAG and some forms of post-trabecular glaucoma. The morphologic features suggest a post-trabecular obstruction of aqueous outflow associated with perivascular deposition of myxomatous matrix in the intrascleral veins. Its pathophysiology is poorly understood and further investigations might add to the understanding of human POAG and post-trabecular glaucomas.
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