Glaucoma is the abnormally high pressure in the eye. Inside the normal eye there is constant production and
drainage of a watery fluid called aqueous humor. When there is a problem with the drainage of the fluid, the
pressure within the eye can increase, and high pressure causes damage to the optic nerve, which in turn, causes
vision loss. During this study period only two cases (0.05%) of glaucoma were recorded in old dogs aged above
36 months (Table 1). However, glaucoma may be classified as primary and secondary. Primary glaucoma occurs
without previous trauma or ocular disease and will eventually affect both eyes. Secondary glaucoma is a
consequence of some other disease, such as ocular inflammation, lens dislocation, intraocular tumors or trauma.