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Glaucoma is a relatively common disease in which the pathological death of retinal ganglion cells causes progressive losses of sight, often leading to blindness. The diagnosis of glaucoma and the assessment of progression are based on a clinical quantification of the ocular characteristics of cupping of the optic nerve head, a loss of retinal nerve fiber layer thickness, and associated functional vision defects. Consequently, clinical tests are based on the quantification of these clinical characteristics of glaucomatous optic neuropathy. However, the basic neural and cellular pathophysiology that cause the characteristic signs of glaucoma cannot be studied in clinical patients and, therefore, animal models must be employed for basic research on glaucomatous optic neuropathy. For basic research that is directly applicable to the clinical disease, the primate model of experimental glaucoma is especially appropriate because the visual systems of macaque monkeys and humans are essentially identical, in terms of visual sensitivity, the anatomy and physiology of aqueous humor circulation, and the structure and neurology of the eye and visual pathway. This chapter attempts to illustrate the scope of basic research on glaucoma, using the primate model to study fundamental aspects of the disease process relating to: (1) the relationship between intraocular pressure and visual field defects, (2) the correlation of visual sensitivity and retinal ganglion cell density, (3) the association between reduced visual sensitivity and retinal nerve fiber layer thinning, (4) the use on noninvasive electrophysiology to objectively assess functional integrity of the retina, and (5) the alterations of the tissue properties and biomechanics of the connective tissue of the optic nerve head that lead to clinical cupping and axonal injury in early glaucoma. In many cases, the results and models developed from data on experimental glaucoma have been applied to clinical patients to illustrate that the primate model offers an approach to clinical research that provides essential data that should be applicable to improving methods for assessing glaucomatous optic neuropathy in patients.
R. S. Harwerth. College of Optometry, University of Houston, Houston, TX, United States. rharwerth@uh.edu
5.2 Primates (Part of: 5 Experimental glaucoma; animal models)