Glaucoma in Dogs
- Glaucoma in dogs occurs when excess fluid cannot drain from the eye.
- There are two categories of glaucoma in dogs—primary glaucoma and secondary glaucoma.
- Glaucoma can cause irreversible blindness if left untreated.
- Glaucoma cannot be cured with medical therapy alone, but it can be managed with daily medication.
Many people have heard of glaucoma in humans, but did you know that dogs can experience this condition too? This painful eye disease may be genetic in some dogs, while others acquire it due to underlying illness or injury.
Many dogs with glaucoma will eventually go blind in one or both eyes, so it’s important to identify and address this condition quickly.
What is Canine Glaucoma?
In the normal canine eye, the anterior chamber—located between the iris and the cornea’s innermost surface—is filled with a fluid called aqueous humor. This fluid is produced by a structure called the ciliary body, which is a circular structure located behind the iris.
As the ciliary body continues to produce new aqueous humor, excess fluid drains out at an angle, called the iridocorneal angle. This balance maintains the level of fluid in a dog’s eye and ensures that the pressure inside the eye remains constant.
Glaucoma in dogs occurs when excess fluid cannot drain from the eye due to a problem with the filtration angle. As the fluid accumulates, the pressure inside the eye increases. This pressure causes pain and damages a dog’s retina and optic nerve, ultimately leading to blindness if left untreated.
Types of Glaucoma in Dogs
There are two categories of glaucoma in dogs—primary glaucoma and secondary glaucoma.
Primary glaucoma is inherited and most commonly occurs in purebred dogs. Primary glaucoma usually occurs in both eyes, but one eye may develop the disease earlier than the other.
Secondary glaucoma develops due to an underlying disease or injury that blocks the drainage of the aqueous humor (fluid). Secondary glaucoma can occur in any dog, but some dogs are predisposed to develop conditions that lead to glaucoma. With this type of glaucoma, one or both eyes may be affected.
Symptoms of Glaucoma in Dogs
Glaucoma may occur in one or both eyes. Acute glaucoma comes on rapidly and owners may notice symptoms right away. In patients with chronic glaucoma, often the initial signs are subtle and may be missed by pet owners.
As the disease progresses, pet owners may notice symptoms such as:
- Redness and irritation of the eye
- Rubbing or pawing at the face
- Swelling of blood vessels in the eye
- Discharge from the eye
- Cloudy or bluish-colored cornea
- Swelling of the eyeball
- Dilated pupil
- Behavior changes such as lethargy or irritability
- Loss of vision
What Causes Glaucoma in Dogs?
Primary glaucoma is caused by an inherited abnormality in certain breeds. In some types of primary glaucoma, there is a defect in the shape of the iridocorneal angle that blocks the drainage of excess fluid.
In other cases, a buildup of abnormal compounds in the eye slows the flow of fluid. These conditions are genetic and most commonly occur in breeds including:
- Cocker Spaniels
- Basset Hounds
- Great Danes
- Jack Russell Terriers
Secondary glaucoma can be caused by any disease or injury which results in decreased fluid drainage and increased pressure in the eye.
Common causes of secondary glaucoma include trauma to the eye, tumors, advanced cataracts, uveitis (inflammation in the eye), and displacement of the lens which blocks the filtration angle. These conditions can occur in dogs of any breed.
Secondary glaucoma typically affects only one eye, although it is possible for both eyes to be affected in some cases.
Diagnosing Glaucoma in Dogs
Glaucoma can cause irreversible blindness if left untreated, so if your dog shows symptoms of this disease you should seek veterinary care right away.
In addition to a physical examination and a thorough ophthalmic exam, your veterinarian may recommend some of the following tests to help diagnose glaucoma:
Tonometry: Your veterinarian will use a special instrument called a tonometer to measure the intraocular pressure (IOP) for each of your pet’s eyes. This can look scary because the instrument must be pressed against the cornea to take a measurement, but your pet will be given numbing drops beforehand so the procedure is not painful. Often multiple measurements are taken from each eye and compared to determine whether the pressure is elevated in one or both eyes.
Gonioscopy: Your veterinarian may use a special lens, placed on your pet’s cornea, to view the iridocorneal angle of the affected eye. This can help your veterinarian determine whether the angle is malformed (primary glaucoma) or obstructed. This test may require referral to a veterinary ophthalmologist because it requires special equipment.
Blood work: In some cases, an underlying systemic disease may have caused your dog’s secondary glaucoma. Your veterinarian may recommend a full medical workup, including a complete blood count and biochemistry panel, to identify and address the underlying problem.
Glaucoma Treatment for Dogs
Acute glaucoma—which comes on quickly—is an emergency and must be treated rapidly in order to save your dog’s vision. Your dog may need to be hospitalized so that medications can be administered and intraocular pressure can be rechecked frequently.
A combination of topical and intravenous medications may be used to help bring your dog’s intraocular pressure down quickly. Once the initial crisis has been controlled, your dog will likely be sent home on maintenance medications.
Medications for Dog Glaucoma
Glaucoma cannot be cured with medical therapy alone, but it can be managed with daily medication. The goal of medical therapy is to improve fluid draining, reduce intraocular pressure, and delay the onset of blindness.
Your veterinarian may prescribe some or all of the following medications to control your dog’s glaucoma:
Prostaglandin Analogs. Topical prostaglandin analogs such as latanoprost help reduce intraocular pressure by increasing the outflow of fluid (aqueous humor). These drugs are typically prescribed as an eye drop that is administered once or twice daily.
Carbonic Anhydrase Inhibitors (CAIs). These drugs decrease the production of aqueous humor so that less fluid accumulates in the eye. They are typically prescribed as a topical eye drop that must be administered 2-3 times daily.
Beta-Blockers. Topical beta-blockers are prescribed to decrease the production of aqueous humor and reduce intraocular pressure. These eye drops are usually not adequate treatment by themselves and are often prescribed alongside other medications.
Glaucoma Surgery for Dogs
In some cases, surgery may be performed on the affected eye to open the filtration angle or to decrease the production of fluid. These procedures are most commonly used in cases of primary glaucoma in the hopes of preserving vision. This type of surgery is typically performed by a veterinary ophthalmologist.
Severe cases of glaucoma may necessitate surgical removal of the eye, a procedure called enucleation. This procedure may be performed if medical therapy does not help or if irreversible blindness has already occurred.
Many dogs quickly adjust to having only one eye. Removing the painful and diseased eye also significantly improves a dog’s quality of life.
General Cost to Treat Glaucoma in Dogs
The cost to treat glaucoma varies depending on the type of glaucoma and the severity. Glaucoma that can be managed at home with topical medications can be relatively inexpensive to treat.
Owners that elect to pursue surgery with a veterinary ophthalmologist should expect to pay several thousand dollars for this type of specialty procedure.
How to Prevent Glaucoma in Dogs
Some dogs with primary glaucoma do not develop clinical disease until later in life. In these cases, starting prophylactic medication before symptoms start can help delay the onset of clinical disease. Your veterinarian can help you determine if this type of preventive measure is a good choice for your dog.
Dogs with primary glaucoma should not be used in breeding programs because this condition is genetic. In some breeds, such as Beagles, a genetic screening test is available to help identify potential carriers.
- Anterior Lens Luxation