Canine glaucoma collapsed filtration angle, or closed angle glaucoma. Glaucoma often goes unnoticed in dogs until it is in a more severe state. There are rarely any symptoms in the early stages of the disease so regular eye checks by qualified veterinary professionals are important. Dogs will sometimes rub the eye if it is painful. An eye affected with glaucoma may be red, swollen, sore, or become clouded in appearance. There are three broad categories of causes of glaucoma: congenital, primary and secondary. Congenital glaucomas are present at birth, although they may not become apparent until the animal is a few months
Normal tension glaucoma of cases that have been reported in medical literature in the 1980s and 1990s who had the typical signs of glaucomatous damage, like optic nerve head excavation and thinning of the retinal nerve fiber layer, while these patients had an IOP that would generally have been regarded as "normal". It is now widely estimated that a larger percentage of patients with primary open-angle glaucoma (POAG) are suffering from normal tension glaucoma: probably half of all POAG patients in Europe and the majority of POAG patients in East Asia. Among Americans of Japanese descent, for instance, the prevalence of NTG is