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Glaucoma is a group of diseases with optic nerve degeneration and blindness as a final outcome.
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In primary glaucoma the main risk factors are age, breed, gender, and goniodysgenesis.
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Classification is based on clinical evaluation and assessment of the iridocorneal angle and ciliary cleft with gonioscopy and ultrasound biomicroscopy.
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Cellular and extracellular progressive changes occur at the level of the lamina cribrosa and in the trabecular meshwork and are responsible for retinal ganglion cell
Veterinary Clinics of North America: Small Animal Practice
Definition, Classification, and Pathophysiology of Canine Glaucoma
Section snippets
Key points
Definition
Glaucoma is a heterogeneous group of progressive disorders characterized by retinal ganglion cell (RGC) apoptosis and a specific optic neuropathy (glaucomatous optic neuropathy [GON]) associated with cupping of the optic disc. In human patients, peripheral visual field loss and tunnel vision are common initial clinical signs, which may eventually progress to irreversible blindness.1, 2 Primary glaucoma is considered a bilateral disease, although both eyes may not be affected simultaneously.
This
Classification of glaucomas
A clear, comprehensive classification of the canine glaucomas is impossible. Glaucoma is considered a multifactorial disease in which numerous genes with varying numbers of alleles and related protein products are involved. Epigenetics may also cause the same genes and proteins to undergo differential regulation and expression. Just as an example, if 100 genes are estimated to be involved in a process and each of them have 5 alleles, then
Pathogenesis and pathophysiology of primary glaucoma
A current view of the pathogenesis of glaucoma must account for multiple factors (Fig. 6). Numerous genetic/epigenetic, age-related, immunologic, and vascular factors interact to activate a series of cascades with optic nerve degeneration as a common final outcome.
Ocular damage in the course of glaucoma, primarily GON, follows from mechanisms that lead to outflow obstruction (and subsequent increased IOP) and RGC apoptosis. Although not mutually exclusive, the two factors are not necessarily
Theories and mechanisms
The main end point in all forms of glaucoma is GON, the characteristic features of which are interlinked: RGC death, activation of glial cells, tissue remodeling, and changes in blood flow (Fig. 8).83
The cascades that cause RGC apoptosis are extremely complex. The RGCs are the innermost neurons of the retina and their axons form the optic nerve. All the photic information collected by photoreceptors is eventually carried to the brain by the RGC axons, which travel in the nerve fiber layer of
Summary
Comprehension of the mechanisms that may cause glaucoma is difficult and extremely complex (see Figs. 7 and 8). Structural changes in the anterior and posterior segments occur normally with age and the modulation of subsequent tissue remodeling can be an important event in the pathogenesis of glaucoma in predisposed individuals. The quality of tissue remodeling may be influenced by anatomic, immunologic, and genetic factors. Mechanical and vascular changes are primary triggers for cellular
Acknowledgments
The author would like to acknowledge the terrific help from Dr Stephanie Pumphrey for the editing of the article.
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Cited by (23)
Biomechanical aspects of axonal damage in glaucoma: A brief review
2017, Experimental Eye ResearchCitation Excerpt :Pig, cat and dog eyes have a well-developed LC (Coudrillier et al., 2016a, 2016b; Fatehee et al., 2011; Grozdanic et al., 2010; Radius and Bade, 1982a, b), but their ONH vascular anatomy is considerably different to that of the human (De Schaepdrijver et al., 1989; May, 2008). Glaucoma commonly caused by anterior segment dysgenesis and high IOP is a frequent condition seen in cats and dogs (McLellan and Miller, 2011; Pizzirani, 2015). Colonies of cats and dogs with hereditary glaucoma are available (Grozdanic et al., 2010; Kuchtey et al., 2011; Narfstrom et al., 2013).
Medical Treatment of Primary Canine Glaucoma
2015, Veterinary Clinics of North America - Small Animal PracticeCitation Excerpt :Immune-mediated mechanisms are commonly reported in medical literature and the association of an anti-inflammatory for the treatment/prevention of canine glaucoma is surely justified, especially considering the role that intraocular mononuclear cells may assume in the species.71,72 Because glaucoma is primarily a progressive, irreversible degenerative disease of the optic nerve, the ideal therapy should address the several mechanisms that lead to RGC death and nerve degeneration.73 Currently, however, lowering IOP is the only established medical therapy that may delay the onset and slow the progression of blindness.
Glycine supplementation can partially restore oxidative stress associated glutathione deficiency in ageing cats
2024, British Journal of NutritionPrimary Angle-Closure Glaucoma in a Maltipoo Dog
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Disclosure: The author has nothing to disclose.