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Animal models of glaucoma are important to better understand the molecular mechanisms of glaucomatous optic neuropathy and to test potential new neuroprotective therapies. Several different rat glaucoma models have been developed in which the outflow pathway is destroyed (with hypertonic sa
line or laser) or ocular surface veins are cauterized. Glycosaminoglycans (GAG) are proposed to play an important role in aqueous humor outflow resistance, and glaucomatous eyes have changes in their trabecular meshwork GAG profile. Moreno et al. (457) report a new rat model of glaucoma in which IOP is elevated by weekly intracameral injections of hyaluronic acid (HA). The elevated IOP (from 12 to ~22 mmHg) was associated with glaucomatous structure and functional changes. After ten weeks of elevated IOP, there was a significant loss of cells from the retinal ganglion cell layer as well as axonal degeneration and gliosis in the optic nerve. Rats with elevated IOPs had decreased scotopic ERG oscillatory potentials, which were apparent at three weeks. IOP and ERG readings were recorded by readers masked to the treatment status. Although the authors injected a relatively large volume (25uL) into the anterior segment of the rat eye, the control eyes received comparable volumes of saline, with little or no damage to the eye. Other labs using similar approaches have been discouraged by the marked anterior chamber inflammation induced by HA injections, which the current authors have apparently avoided. We eagerly await independent conformation of this potentially important new rat model of glaucoma.