Unlike glaucoma in humans, canine glaucoma is extremely difficult to manage and frequently results in both blindness and a procedure to remove the eyes called enucleation which is done to relieve the pain of high ocular pressure. While medical treatments such as eye drops may help moderate pressures for a period of time, the disease which is sometimes called the “silent thief of sight” is relentless in dogs.
There are a variety of causes of glaucoma (high interocular pressure) in dogs, from inherited genetic mutations to injury. Prognosis and treatment are very much dependent on the cause of the glaucoma and how advanced it is upon diagnosis. The goals of treatment also vary, ranging from saving vision to alleviating the chronic and often acute pain associated with the disease.
Primary (Inherited) Glaucoma
Glaucoma that is inherited from parent dogs is called “primary” and is most often broken down into either “Primary Open Angle Glaucoma” (POAG) and “Primary Angle Closure Glaucoma” (PACG). Primary glaucoma usually impacts both eyes (bilateral) and increases with age. POAG usually increases slowly over time and primarily impacts a few breeds including Norwegian Elkhounds, Beagles, and Petit Basset Griffon Vendéens. On the other hand, PACG often occurs rapidly in one eye and requires immediate emergency attention. Unfortunately, both are incurably and progress even when treated with with medications or surgical interventions. It is not unusual for doctors to recommend removal of the eye (enucleation) or both eyes once vision is lost and interocular pressure (IOP) becomes uncontrollable.
Secondary Glaucoma
In secondary glaucoma, the increase in eye pressure is usually caused by another condition, such as inflammation within the eye, trauma, lens displacement, or tumor growth within the eye. This condition can affect any breed of dog, but some breeds such as Cocker Spaniels, Basset Hounds, and Siberian Huskies are more prone to developing secondary glaucoma.
The symptoms of secondary glaucoma in dogs can include redness of the eye, cloudiness or bluish coloration of the cornea, pain, decreased vision, and ultimately, blindness if left untreated. Treatment options may include medications to reduce the pressure in the eye, surgery to correct the underlying condition, or a combination of both. Early detection and treatment are important in managing secondary glaucoma in dogs to prevent irreversible damage to the optic nerve and preserve vision. Unlike Primary Glaucoma, early intervention to resolve the underlying cause of the interocular pressure can halt the progression of the disease and retain vision.
Initial Treatments to Control Pressure
Initial interventions for dogs with glaucoma often involve treatment with eyedrops that lower the pressure by either decreasing the production of fluid within the eye (aqueous humor) by the ciliary body or increasing the drainage through the trabecular meshwork (TM).
- Prostaglandin Analogs: These medications work by increasing the outflow of fluid from the eye. They are commonly used as the first line of treatment in dogs with glaucoma. Examples include latanoprost and travoprost.
- Carbonic Anhydrase Inhibitors: These medications decrease the production of fluid inside the eye. They are often used in combination with prostaglandin analogs. Examples include dorzolamide and brinzolamide.
- Beta-blockers: These medications decrease the production of fluid inside the eye. They are often used in combination with prostaglandin analogs or carbonic anhydrase inhibitors. Examples include timolol and betaxolol.
- Alpha-2 Agonists: These medications work by reducing the production of fluid and increasing the outflow of fluid from the eye. Examples include brimonidine.
- Miotics: These medications increase the outflow of fluid from the eye. They are less commonly used in dogs due to their potential side effects. Examples include pilocarpine.
It’s important to note that not all dogs with glaucoma respond to medications, and some may require additional treatment such as surgery to manage their condition. Additionally, regular monitoring of IOP is necessary to ensure that the medications are effectively controlling the IOP and preventing further damage to the eye.
Surgical Interventions
There are several surgical interventions that may be used to manage glaucoma in dogs, depending on the severity of the condition and the response to medical treatment.
- Gonioimplant Surgery: This procedure involves the placement of a small silicone tube into the eye to improve the drainage of fluid and reduce intraocular pressure. It is typically used in dogs with advanced glaucoma that are unresponsive to medical treatment.
- Cyclophotocoagulation: This is a laser procedure that is used to reduce the production of fluid inside the eye by destroying part of the ciliary body that produces the fluid. It is typically used in dogs with advanced glaucoma that are unresponsive to medical treatment or are not candidates for gonioimplant surgery.
- Enucleation: This is the surgical removal of the affected eye. It is typically used as a last resort in cases where medical and surgical interventions have been unsuccessful and the eye is causing significant pain or discomfort.
- Evisceration: This procedure involves the removal of the contents of the eye while leaving the outer shell intact. It may be performed in cases where the eye is painful or causing discomfort, but there is still some vision present.
- Partial or Complete Corneal Transplantation: These procedures involve the replacement of the damaged cornea with a healthy cornea from a donor. They may be used in cases where the cornea is damaged due to glaucoma or other underlying conditions.
- Gene Therapy: Experimental procedures using gene therapy to replace faulty genetic material in ADAMTS10 POAG Beagles has shown some promise in limited clinical trials but therapies are likely many years from widespread use.
Long-term Prognosis
The long-term prognosis for dogs with glaucoma depends on several factors, including the underlying cause of the glaucoma, the severity and duration of the condition, the response to treatment, and the presence of any other concurrent medical conditions.
In general, glaucoma is a progressive and potentially blinding disease that can cause irreversible damage to the optic nerve if left untreated or poorly managed. Dogs with secondary glaucoma that are diagnosed early and receive appropriate treatment have a better prognosis than those with advanced or long-standing disease. Dogs with primary glaucoma have a poor prognosis and will likely be blinded by the disease even with the best care and may require bilateral enucleation.
Regular eye examinations and monitoring of intraocular pressure are important in the long-term management of glaucoma in dogs to detect any changes in the condition and adjust the treatment plan as needed. Your veterinarian or a veterinary ophthalmologist can help you develop an appropriate management plan for your dog with glaucoma and provide guidance on long-term prognosis.