Glaucoma is an uncommon disease in dogs and cats. Simply put, it means an increase in the pressure inside the eyeball, leading to internal damage, pain, and loss of vision. There are two categories of this condition, primary and secondary, and different circumstances lead to these afflictions. Technically, these are separate diseases, leading to a final common condition known as glaucoma. The primary condition is due to acquired defects if the drainage system in the eye keeps the pressure within its normal range. Secondary glaucoma is caused by any other ocular disease, leading to inflammation that leads to increased pressure within the eye. These causes can be cataracts, systemic bacterial or fungal diseases, FIV or feline leukemia infection in cats, lens luxation, eye tumors, or cysts.
In both dogs and cats, there is a variable age of onset that is dependent on the cause of the disease. In young animals, a congenital condition may be the cause of glaucoma, most likely due to the incomplete formation of part of the eye. Primary glaucoma can be found in middle-aged to older dogs (average age 8 years old), it is rare in cats. In some dog breeds, primary glaucoma occurs more often in females. With secondary glaucoma depending on the cause, the age of onset varies. For instance, with a lens luxation leading to glaucoma, a young to middle age dog may be affected. Also, a tumor arising inside an eye can lead to glaucoma, which would usually affect an older animal (greater than 7 years old).
There are genetic and breed predispositions to both types of glaucoma. The top dog breeds affected by primary glaucoma include American cocker spaniel, basset hound, chow, shar-pei, Siberian husky, Cairn terrier, Boston terrier, and miniature poodle. In cats, the Siamese breed is known to have inherited primary glaucoma. Terrier breeds are at risk for secondary glaucoma due to lens luxation. Lastly, golden retrievers are known to acquire secondary glaucoma due to pigmentary uveitis (an inner eye inflammation).
What happens with glaucoma? Regardless of the cause, the inner pressure becomes greater, and damage to the inner parts of the eye, and pain result. The eye becomes red in the sclera (the white part of the eye) and cloudy in the cornea (the clear part of the eye). The animal may be visibly blind in the eye (bumping into objects, disoriented). Also, the pupil may be dilated, and the animal seems noticeably painful or stressed. The eye may or may appear larger than normal, depending on how long the condition has been present. The diagnosis is any measurement of the intraocular pressure above a certain level is considered glaucoma.
Once it is diagnosed, the primary goal of treatment is to reduce the pressure of the eye, relieve pain, and possibly restore vision. Medical treatments are of varying types of eye drops, some relieving pressure, and some anti-inflammatory. Surgical procedures to place shunts in the eye, or remove the lens can be performed. Also, removing the entire eye may be necessary if the pressure is uncontrollable medically. Sometimes, if the pain is still present and vision is lost, injections of medication into the eye can be performed to decrease the pressure, leading to pain relief. The success of the medical treatments is highly dependent on if the condition is diagnosed early, so that vision may be able to be restored. Unfortunately, in most cases of primary glaucoma, the prognosis for the eye is poor. In most cases we have seen at St. Francis, removal of the eye has been the end result, as most medical treatments are not successful long-term. Medical treatments for the other eye would be started immediately to try to prevent that eye from developing the same condition.
Glaucoma in dogs and cats is an uncommon condition only seen at our veterinary hospital a few times a year. It is, however, an emergency case due to the fragile nature of the eye. If we see this disease, we often refer to a veterinary ophthalmologist to further investigate the cause of glaucoma and for more advanced treatment. Fortunately, we have excellent veterinary ophthalmologists nearby in Matthews to help us if needed. If you suspect your animal of having this condition, please call us right away. As always, we appreciate our clients and your wonderful pets!
Dr. Jaime Kozelka
St. Francis Hospital for Animals