When most owners think of emergencies related to their pet, they envision their pet being hit by a car, being attacked by a large dog or wild animal, having seizures or ingesting a toxin. These scenarios are easy to recognize as true emergencies. However, emergencies that especially concern veterinarians are those that are not so obvious, and the owners may not realize their pet needs medical attention immediately. There is no better example of this than glaucoma.
Glaucoma in pets — as in humans — is caused by a sudden build up of fluid pressure inside the eye. As the pressure builds, the pet endures extreme pain. The vision parts of the eye, the retina and optic nerve, are especially sensitive to this build up in pressure. Unless glaucoma is treated quickly, permanent loss of vision can occur in the eye.
Cells within the eyes produce a fluid called aqueous humor. This fluid is what maintains the shape and nourishes our eyes. The aqueous humor circulates through the eye and then leaves through a drainage angle into the bloodstream. The flow of the fluid is much like that of water running from a faucet into a drain in a sink. In glaucoma, the “drain” becomes partially or completely clogged, yet the “faucet” steadily keeps flowing, thus leading to increased pressure inside the eye.
Glaucoma is referred to as being primary or secondary. Primary glaucoma is an inherited condition commonly occurring in breeds such as the Cocker Spaniel, Beagle, Bassett Hound, Chow Chow, Shar Pei, Shih Tzu and arctic breeds (Siberian Husky and Elkhound). Primary glaucoma is rare in the cat. The disease tends to develop when the dog is two to three years of age or older. Initially, only one eye will be affected but most will be affected in the second eye within six months to a year.
In secondary glaucoma, another condition or disease results in the development of glaucoma. Common causes are inflammation of the eye (uveitis), advanced cataracts, cancer in the eye or displacement of the lens from its normal position (lens subluxation). Glaucoma in cats is almost always secondary to chronic uveitis from trauma, infectious diseases or cancer.
How will you know if your pet has glaucoma? Unfortunately, you won’t. Your veterinarian diagnoses glaucoma by measuring the pressure within the eye. Using non-invasive, non-painful tools, they can get quick, accurate results to determine if emergency treatment is needed.
However, there are warning signs to watch for if your pet is developing glaucoma. Because glaucoma is painful, those may be the first symptoms you see — pawing at the eye, tearing, winking or squinting. The “white” of the eye will look red, pupils may be dilated and the cornea (glassy part of the eye) will become cloudy. As the disease progresses, you will notice that the eye will look larger than the other due to the increased fluid.
Treatment for glaucoma will depend on the cause but the goal is to decrease the amount of fluid being produced (slow the faucet), increase the fluid going out of the eye (open the drain), and provide pain relief. Our goal is to save your pets’ eye! Most therapies will involve topical eye drops but your veterinarian may do emergency intravenous or oral medications to alleviate the pressure quickly.
Your veterinarian will monitor eye pressures regularly to see how well the treatments are working. If medical treatment is ineffective, veterinary eye specialists can offer surgical procedures such as cyclophotocoagulation and gonioimplantation. Cyclophotocoagulation uses lasers to destroy the cells producing fluid, while gonioimplantation employs shunts in the drainage angle to increase fluid drainage. These options are excellent for long-term control of glaucoma but can be costly.
Ultimately, if medical treatment isn’t helping your pet and one cannot afford a specialist, the best option is removal of the eye. As more and more pressure builds, vision will be lost and the eye will be a constant source of pain. Eye removal, or enucleation, is well tolerated by pets. However, if a client is uncomfortable with enucleation, in some cases an intraocular prosthesis can be inserted. In this procedure, the internal contents of the eye are removed and replaced with a silicone ball.
Glaucoma is an emergency! Rule of thumb, as taught to me in veterinary college, any “red” or “cloudy” eye should be checked immediately for glaucoma. If you notice these symptoms in your pets’ eye, don’t wait till tomorrow to have him checked. That one day may make the difference in saving your pets vision.
Dr. April Shattuck is a 2004 graduate from the Ohio State College of Veterinary Medicine, an army wife and proud mother of two beautiful daughters. She practices small animal emergency medicine at the West Central Ohio Veterinary Emergency Services hospital. Any comments or questions may be directed to her at firstname.lastname@example.org.