Glaucoma is characterized as a progressive optic neuropathy with characteristic optic disc changes and progressive visual field deficits.1 Elevated intraocular pressure (IOP) is considered a primary risk factor for the initiation and progression of glaucomatous neuropathy.1,2 However, in many patients, despite adequate control of the IOP, the loss of vision continues to progress, which necessitates further identification of molecular mechanisms responsible for the glaucomatous neurodegeneration and development of novel therapeutic modalities that directly target disease-affected retinal ganglion cells (RGCs).2–4 Despite new discoveries, the underlying genetic abnormalities and environmental factors that may contribute to the development and progression of glaucoma have not been clearly defined.5,6 Glaucoma in humans is typically a chronic and slowly progressive disease that may cause significant damage to the optic nerve before any symptoms of the disease are recognized. The gradual and often silent progression of the disease creates difficulties in early diagnosis and understanding of early changes in glaucomatous eyes. To better understand early glaucomatous changes and to develop effective diagnostic and therapeutic modalities, it is essential to create animal models that recapitulate the silent and slow development of the disease characterized by a progressive loss of RGC function. Numerous inducible animal models of glaucoma have been used successfully to test different therapeutic strategies and to evaluate molecular mechanisms of RGC damage resulting from chronic elevation of IOP.2,7,8 However, the major obstacles in many of these models is a very high elevation of IOP immediately after glaucoma induction surgery,9–11 the inability to sustain elevated IOP longer than a period of a several months,12–17 and the size of the eye, which is dramatically smaller than the human eye, posing a problem for effective translation of therapeutic options to the human patients.18,19 Spontaneously occurring animal models of glaucoma in mice and dogs have also been described and have provided important information about the structural and molecular events occurring during the development of glaucomatous optic neuropathy.20–26 Spontaneously occurring large animal models of glaucoma offer a unique opportunity to collect data by using instrumentation identical to that used in human patients with glaucoma. They are an excellent tool for the rapid development and translation of novel medical and surgical therapies from animals to human patients, and they provide interesting data correlating morphologic or biochemical findings to functional parameters. The principal purpose of this manuscript was to describe the morphologic and functional changes in a canine model of hereditary primary angle-closure glaucoma (PACG). We hope this model will further advance our understanding of early functional, structural, and molecular changes in glaucomatous eyes.