Abstract
Abstract: :
Purpose: Aqueous humor levels of endothelin-1 (ET-1) are elevated in canine and human glaucoma. In humans with chronic open angle glaucoma, the ganglion cell and nerve fiber layers are the most common retinal layers affected. Studies on canine acute primary angle closure glaucoma, with high elevations of intraocular pressure, have shown cell death of all retinal layers. The purpose of this study was to investigate the correlation between retinal degeneration and ET-1 levels in aqueous humor and vitreous in canine hypertensive glaucoma. Methods: Samples of aqueous humor, vitreous and retina were obtained from enucleated eyes (n=7) of seven glaucomatous dogs. Measurements of ET-1 levels were made by enzyme immunoassay (ELISA). The retinas were embedded in LR White and evaluated by light microscopy. Retinal damage was graded from severe atrophy (1) to minor degeneration (5) by two observers (MEK and AEE). Results: The ranges for aqueous humor and vitreal ET-1 levels were 1.91 - 9.67 and 1.13 - 5.2 pg/ml respectively. Retinal changes varied from minor disorganization to complete necrosis of all retinal layers with the most marked changes in the ganglion cell layer. The peripheral retina was most affected in all eyes with panretinal necrosis in 4 cases. No apparent difference in the degree of changes was seen between the tapetal and nontapetal retina. There was a strong correlation between the degree of retinal degeneration and aqueous humor and vitreal ET-1 levels in dogs at hypertensive stages of glaucoma (Spearman corr. coeff. 0.94, p = 0.0019). Conclusion: Endothelin-1 levels in aqueous humor and vitreous are correlated to the degree of retinal degeneration in dogs with spontaneous hypertensive glaucoma.
Keywords: 316 animal model • 324 aqueous • 385 degenerations/dystrophies