|  | 
Category: Canine and Feline
Glaucoma is an abnormal increase in the internal pressure of the eye. Normally fluids continually enter and exit various parts of the eye at a balanced rate so that the intraocular pressure varies only slightly within a normal range. Several diseases can disrupt this balance; a net increase of fluid builds up in the eye because the fluid is unable to drain correctly. This causes the rise in intraocular pressure. Measurement of intraocular pressure is a fairly simple procedure, but it requires special instruments.
If the pressure gets high enough, irreversible damage to the retina and optic nerve may result. This can impair vision and may cause blindness. Substantial, acute increases in intraocular pressure may warrant hospitalization for intravenous treatments to lower the pressure. Chronic treatments are directed toward correcting the underlying causes and reducing the intraocular pressure, maintaining vision for as long as possible and delaying or preventing occurrence in the opposite eye.
The signs a given dog or cat with glaucoma will have depends on the underlying cause of the increased intraocular pressure. Signs of glaucoma may include pain, squinting, spasm of the eyelid, redness of the eye, sensitivity around the head and ocular discharge. In certain cases of advanced glaucoma the pupil may be dilated or the eyeball may be enlarged.
Glaucoma is classified as primary or secondary. There is also a congenital form that manifests perinatally, but occurs infrequently. Dogs may develop either primary or secondary forms; cats may develop the secondary form, but primary glaucoma is an infrequent finding in cats. Overall, cats are less likely than dogs to have glaucoma. Primary glaucoma is most likely to affect both eyes, but the changes in intraocular pressure may occur several months apart. Secondary glaucoma may be unilateral or bilateral.
Primary glaucoma may result from a genetic mechanism that produces certain structural anomalies in the eye that are responsible for the faulty fluid drainage and the elevated intraocular pressure. Most cases of primary glaucoma are breed-related. Cocker spaniels, springer spaniels, poodles, beagles, basset hounds, Siberian huskies, elkhounds, Samoyeds, Alaskan malamutes, Chows, Chinese shar peis and Afghans are predisposed to develop this disease. Patients with primary glaucoma may be candidates for surgical improvement of the causative anatomic deformity after they are medically stabilized, but these procedures are rarely completely successful or successful for long periods of time.
Secondary glaucoma develops as a consequence of some other disease process or event. Trauma, masses, inflammation, luxation of the lens and ocular bleeding are potential causes of secondary glaucoma. If an underlying cause can be identified then it must be treated in addition to the glaucoma. Glaucoma itself can be treated with topical and oral medications, including timolol and levobunolol (topical drugs), and methazolamide and dichlorphenamide, among other oral drugs.
If vision is lost, there are various salvage procedures available to make the eye less painful, including removal of the eye. If the eye is removed, a prosthetic implant ("glass eye") can be placed in the eye socket for cosmetic purposes if desired. Alternative procedures to removing the eye involve intraocular surgery or pharmacological destruction of the fluid-producing tissues in the eye. These procedures are usually performed by a veterinary ophthalmologist. You may want to talk to your veterinarian about a consultation with a veterinary ophthalmologist for management of your dog's problem.
|