Goals of Treating Glaucoma
Treating options for glaucoma in dogs vary based upon the underlying cause of the condition. Treatment normally involves application of topical eye medications, administration of systemic medication and eventually surgery. This progressive condition may occur in one or both eyes, and immediate treatment is necessary to prevent permanent eye damage, pain and blindness. The goals of glaucoma therapy are to lower intraocular pressure of affected eyes in order to maintain the dog’s vision as long as possible, and also to eliminate ocular pain.
Regardless of the cause, most cases of canine glaucoma are initially treated with some combination of topical and systemic medications designed to decrease intraocular pressure. A number of prescription drugs are available to dehydrate the aqueous humor (the fluid inside of the eye), reduce the production of aqueous humor and/or increase the drainage of aqueous humor from the eye. Topical corticosteroids also may be used, provided that corneal ulcers are not present (because in addition to their anti-inflammatory effects, steroids tend to delay tissue healing).
If only one eye is affected by glaucoma, the other eye (called the “fellow eye”) can be treated prophylactically; this seems to delay the onset of glaucoma in the fellow eye for several months, or even longer. New medications are always in development, and only a veterinarian can determine which of the available drugs to use in any given situation. In all cases, dogs with glaucoma should be reevaluated regularly in order to track intraocular pressure and make necessary adjustments in medication. Medical treatment is usually life-long and can be quite expensive. Unfortunately, with drug therapy alone, most dogs with primary glaucoma will eventually go blind.
A number of surgical procedures are available to help manage glaucoma if medical management is unsuccessful. The goals of glaucoma surgery are to increase the outflow of aqueous humor, decrease its production, maintain vision as long as possible and resolve ocular pain. Surgical options include placement of small implants (called shunts) into the eye and/or using laser therapy (called cyclophotocoagulation) to promote fluid drainage, reduce fluid production, prolong vision and reduce pain. Another procedure involves the injection of certain drugs into the eye or using cryosurgery (freezing) to damage or destroy the cells that produce aqueous humor. Surgical removal of the lens in affected eyes is also possible.
Unfortunately, in most cases, these surgical procedures only slow the progression of glaucoma rather than curing it. Affected eyes often develop irreversible scarring and vision loss, despite surgery performed by a skilled veterinarian. Once glaucoma progresses to blindness, or if medical pain management is unsuccessful, there are several surgical salvage options. The globe (eyeball) can be surgically removed, which is called enucleation. It can also be surgically eviscerated, which involves removing the contents of the eyeball while leaving the tough, usually white outer part of the globe, called the sclera, intact. These procedures will remove the source of the severe and chronic pain that typically accompanies end-stage glaucoma, although they of course will not restore vision. Prosthetic implants are available as well, for a result that is cosmetically acceptable to owners.
The success of any glaucoma treatment depends heavily upon how early the condition is diagnosed, and whether it is primary or secondary to another problem. The prognosis for the first eye affected by glaucoma is normally poor, regardless of the cause or treatment protocol, because by the time the disease is diagnosed, it usually is advanced and unresponsive to medical therapy. Preventative (prophylactic) medical treatment of the fellow eye can help delay the onset of glaucoma for many months.