What is Glaucoma?
Glaucoma is an eye disease associated with elevated pressure within the eyeball. A nourishing fluid called the aqueous humor normally maintains appropriate pressure, giving the eye its shape and firmness. The fluid, produced behind the iris by filtering blood, flows through the pupil and then reenters the bloodstream. But a buildup of fluid, generally thought to be because it isn’t flowing out of the eye properly, puts too much pressure on the eyeball. This damages eye tissue, including the optic nerve, causing pain, headaches and complete or partial blindness. The condition usually starts in one eye and later affects the other eye.
“Glaucoma can be likened to a bathtub in which water is supposed to be flowing in and draining out, but there is a problem with the drain,” says Dr. Kirk N. Gelatt, a professor of comparative ophthalmology in the Colleges of Veterinary Surgery and Medicine at the University of Florida in Gainesville. “In a bathtub, the water overflows. But in the eye, there is no way for fluid to overflow, so pressure increases.”
What causes glaucoma in dogs?
Glaucomas are classified by three general causes:
- Primary Glaucoma – this canine glaucoma is unrelated to other health conditions. It is the most common type of glaucoma and is often linked to specific breeds. It generally appears when a dog is 4 to 8 years old.
- Secondary Glaucoma – glaucoma caused by another eye condition such as inflammation, lens luxation (the dislocation of the eye’s lens), injury, tumor, infection or previous surgery.
- Congenital Glaucoma – a rare condition caused by birth defects that cause the eye to develop improperly in puppies.
What dog breeds are susceptible to primary glaucoma?
While the disease is often seen in Cocker Spaniels, terrier breeds, Poodles, Beagles, Chow-Chows, Bassett Hounds and Dalmatians, primary glaucoma has been identified in almost every breed of dog, reports the College of Veterinary Medicine at North Carolina State University.
Symptoms of glaucoma in dogs
Any of the following symptoms in one or both eyes, even if the symptoms are temporary, can indicate glaucoma:
- Glassiness to eye
- Redness in the white part of eye
- Cloudiness of the eye
- Excessive tearing (weeping)
- Sensitivity to light
- Green or yellow eye discharge
- Bluish cast to eye
- Dilated pupil
- Desire for excessive sleeping
- Iirritability Behavior that indicates pain (hiding under the bed, acting frightened, avoiding being petted on the head)
- Behavior indicating vision impairment (bumping into things)
- Enlarged and bulging eyeball (late stage)
Glaucoma often manifests itself as a headache that won’t go away. Because dogs can’t say they’re in pain, they may act like they don’t want to be petted on the head or may simply lie around, avoiding people. “These are vague signs,” Gelatt says. “A lot of people would say, ‘Well, maybe he’s just grouchy today.’ And they don’t relate it to the eye.”
Diagnosing and preventing glaucoma in dogs
Veterinarians diagnose most dogs when the eye is enlarged. “When that is happening, the disease is moderately advanced, so your chances of successful treatment are low,” Gelatt says.
To detect glaucoma earlier, Gelatt recommends occasional tonometry measuring of pressure within the eye. Usually only board-certified veterinary ophthalmologists use the most accurate tonometers due to their cost to the veterinarian (about $2,500). But general veterinarians can perform the procedure with a $200 version of the more accurate high-end tonometer.
Not all veterinarians agree with such preventive screening, but Nicole MacLaren, a veterinary ophthalmologist at the Eye Clinic for Animals in Salt Lake City, Utah, goes further. Owners with a purebred dog of an at-risk breed should seek a gonioscopy when the dog is 6 months or older, she says. This procedure uses a contact lens, usually applied after numbing the eye with an anesthetic, to evaluate the drainage angle.
Several drugs and surgical treatments are available for other glaucomas depending on the eye’s drainage angle, pressure level and degree of vision loss. Preventive treatments may be performed in the “good” eye.
But medication alone will not resolve glaucoma problems in most dogs, so veterinarians sometimes use surgical techniques to try to maintain whatever vision the dog has.
- Laser surgery can reduce or halt fluid production by killing some of the fluid-producing cells.
- Shunts – small plastic tubes inserted in the eye provide alternative drainage.
- Cryosurgery – a non-invasive freezing technique also decreases fluid production by killing fluid-producing cells.
In most cases, vision eventually will be lost. “We don’t have a silver bullet yet,” Gelatt says. “Laser surgery and shunts are the most common in America, and neither is perfect.”
When vision is lost, veterinarians try to keep the dogs as pain-free and medication-free as possible. Several techniques are available, including:
- Injecting antibiotics into the eye to reduce fluid pressure by killing the fluid-producing cells.
- Injecting an antiviral drug into the eye to damage fluid-producing cells.
- Replacing the eye with a prosthetic (i.e., glass eye) which must be cleaned daily to avoid infection.
- Removing the contents of the eye and placing a silicone implant in the eye “she’ll.”
- Removing the eye and sewing the lids shut.
Eye removal is the only way to ensure the lack of pain, but most dog owners balk at the prospect of looking at an eyeless face, so veterinarians tend to treat blind dogs for pain. “We’re treating the patient because of pain, we’re treating the client because of cosmetics,” Gelatt says.
If you notice any potential signs of glaucoma, take your dog to your veterinarian immediately. If the diagnosis is glaucoma, have your veterinarian refer you to a board-certified specialist to further evaluate the animal and discuss treatment options.