Glaucoma is defined as an elevation in intraocular pressure beyond which is not compatible with continued ocular health. Glaucoma can be primary (inherited) or secondary (due to intraocular inflammation, lens luxation, intraocular tumor). Dog breeds predisposed to primary glaucoma include the Cocker Spaniel, Basset Hound, Beagle, Chow, Shar Pei, Arctic breeds, and many others. Unlike humans who are more affected with open angle glaucoma, dogs are affected with closed angle glaucoma. As the intraocular drain closes, the eye builds pressure as the "faucet" part of the eye continues to produce fluid. This increase in pressure can happen extremely quickly in dogs (in a matter of hours) and can be very painful. Failure to lower the pressure rapidly can have vision ending consequences. Therefore, emergency treatment is indicated with acute cases of glaucoma.
Both medical and surgical therapy are available for the treatment of glaucoma. Medical therapy is aimed at turning off the faucet and opening up the drain. This is accomplished using several types of drops several times daily. Some dogs respond well to this therapy and can be controlled long-term. However, in most cases medical therapy is only effective short-term and surgery is usually necessary.
There are two surgical approaches for glaucoma: surgery for vision and surgery for comfort. Surgery for vision is completed only in those eyes that have the potential for vision. Surgery for comfort is completed in those eyes in which the pressure remains elevated despite medical therapy and vision is permanently lost.
Glaucoma in cats is usually secondary to previous intraocular inflammation, called anterior uveitis. Treatment is not only aimed at lowering the pressure, but discovering the primary cause. Cats do not respond as well as dogs to medical therapy and surgery is frequently necessary. The most common surgery performed in cats with chronic glaucoma is enucleation.