Glaucoma in Dogs

Overview

Glaucoma in dogs is common, and can rob your dog of his ability to see and have a wonderful life. Glaucoma is the condition of increased pressure in the eye. Eye pressure is normally regulated by fluid flowing into and out of the eye at a balanced rate. If too much fluid is made or too little fluid is drained, the pressure in the eye increases, causing damage to the retina and optic nerve. Glaucoma can be painful and approximately 40 percent of cases lead to blindness within one year.

If treatment is not started within hours of pressure increase, vision will likely be lost. Glaucoma is the elevation of pressure inside the eye, known as intraocular pressure (IOP) beyond a specific point at which vision is compromised or is no longer possible. Glaucoma is a frequent cause of blindness in both humans and animals

There are two main types of canine glaucoma;

Primary glaucoma is typically an inherited trait seen in certain breeds. These include Cocker Spaniels, Basset Hounds, Shiba Inus, Huskies, Chow-Chows and Shar-Peis.

Secondary glaucoma occurs when something obstructs the intraocular drain within the eye. It’s characterized by inflammation inside the eye and can result from bleeding in the eye—maybe from a blunt-force trauma (your dog ran into something)—retinol detachment, an intraocular tumor, lens fluctuations or some other reason the drain swelled or closed.

Glaucoma is more common as the age of the dog increases, primary glaucoma most commonly affects middle-aged to older dogs. Glaucoma is common in certain dog breeds that are genetically predisposed, such as Samoyeds, cocker Spaniels, poodles, chow chows, and Siberians. Unfortunately, 40 percent of dogs affected by glaucoma will become blind in the affected eye within the first year, regardless of medical or surgical treatment.

Vets will try to determine whether a dog has primary or secondary glaucoma to determine treatment and if the other eye will be impacted. Most dogs with early to moderate long-term glaucoma are not taken to the veterinarian because the early signs—sluggish to slightly dilated pupils, mild congestion of the veins in the conjunctiva, and early enlargement of the eye—are so subtle that owners are not aware of the changes.

Major causes glaucoma in Dogs

Glaucoma is caused by inadequate drainage of aqueous fluid; it is not caused by overproduction of fluid. Glaucoma is further classified as primary or secondary glaucoma. Primary glaucoma results in increased intra-ocular pressure in a healthy eye. Some breeds are more prone than others (see below).  It occurs due to inherited anatomical abnormalities in the drainage angle. Secondary glaucoma results in increased intra-ocular pressure due to disease or injury to the eye.

These are the most common cause of glaucoma in dogs. Other causes include:

• Uveitis (inflammation of the interior of the eye) or severe intra-ocular infections, resulting in debris and scar tissue blocking the drainage angle.

• Anterior dislocation of lens. The lens falls forward and physically blocks the drainage angle or pupil so that fluid is trapped behind the dislocated lens.

• Tumors can cause physical blockage of the iridocorneal angle.

• Intra-ocular bleeding. If there is bleeding in the eye, a blood clot can prevent drainage of the aqueous humor.

• Damage to the lens. Lens proteins leaking into the eye as a result of a ruptured lens can cause an inflammatory reaction resulting in swelling and blockage of the drainage angle.

Signs and Symptoms of Glaucoma in Dogs

Glaucoma causes pain that’s more severe in dogs than in humans. However, dogs do not show pain in the way humans can, so it may be difficult to detect when they are actually hurting. Clinical signs to look out for include:

• Eye pain: Rubbing up against the floor or another object or with the paw

• Redness of the eye

• Cloudy cornea

• Squinting

• Tearing

• Avoidance of light

• Weak blink response

• Fluttering eyelid

• Pupils appear different in size

• Appearance of vessels in the white of the eye

• Bulging swollen eye

• Vision problems: bumping into objects, difficulty finding things, walking cautiously.

As a dog ages, the clinical signs may occur in one eye and then the other. Rarely will it occur simultaneously in both eyes or with equal pressure. It can also be years before the second eye becomes affected. If you notice any signs and symptoms of glaucoma, have your dog checked out immediately. Time is of the essence when it comes to this condition. Not only is it painful, it will lead to irreversible blindness if left untreated.

Consulting a Vet for Proper Diagnosis

As irreversible eye damage and vision loss can occur within hours of symptoms, if any one of the symptoms are noted, visit your veterinarian immediately. Your vet will want to know onset of symptoms and any history of trauma or behavioral patterns associated with pain or vision loss. He will perform an ophthalmologic exam and may choose to treat your pet in the clinic or may refer you to veterinary ophthalmologist.

Tonometry

Intraocular pressure is measured with a tonometer. A drop of anesthetic may be put on the eye first. One type of tonometer blows a puff of air on the eye and measures the indentation. Another type presses a small plastic disk against the eyeball to measure pressure. The Mueller method uses an electronic tonometer.

In sudden glaucoma, the pupil has a sluggish response to light, the blink response is weak or absent, the cornea is swollen or cloudy, the eye is red, inflamed and tearing, and the pet may be squinting.

In chronic glaucoma, the pupil has no response to light and the blink response is absent. The cornea is cloudy and the eye is red and inflamed. Tearing is possible and vessels are seen on the cornea. The eye is often enlarged.

X-ray

Your veterinarian may want to rule out the presence of an eye abscess, injury or tumor. An x-ray or ultrasound will allow the space around the eye to be visualized.

How Can Glaucoma Be Treated?

Glaucoma cannot be cured; but it can be controlled if treated promptly. The common forms of treatment include:

• Medications: In the form of eye drops or pills

• Laser surgery: Surgery is reserved for patients whose pressures cannot be controlled with medications.

• Glaucoma Surgery (Endocyclophotocoagulation): Glaucoma surgery involves the destruction of the ciliary processes with a strong beam of light using an endoscopic tool in an attempt to reduce the fluid production in the eye. The benefits of this procedure include direct visualization of the ciliary body, eliminating destruction of surrounding tissues. We currently have an 85% success rate of controlling intraocular pressure for at least one year.

Patients are hospitalized for at least three days after surgery for close postoperative monitoring of eye pressures. Dogs are sent home with an Elizabethan collar to prevent them from rubbing the eye. At home, care involves applying eye drops several times daily for a few weeks, then slowly decreasing the frequency of medications over time. Some cases may also require oral medications. Normal activities can resume after two weeks.