Glaucoma in Dogs and Cats
Though different in the level of perception and sensitivity, the anatomy of a dog and a cat’s eye is pretty much similar to ours and is also prone to the same eye problems that affect us. These include problems involving the conjunctiva, the lenses, the cornea, and the internal pressure in the eye itself. Glaucoma, a commonly reported eye problem in humans, is also commonly seen in both dogs and cats. This article touches on the topic of glaucoma in pets, what happens when they develop this disease, the common causes of the condition, and the recommended treatment for it.
What is glaucoma?
Glaucoma is an eye disease characterized by an increase in the pressure inside the eye globe, called intraocular pressure. This often results in severe discomfort and can lead to serious complications if not addressed immediately and appropriately. The intraocular pressure can be measured by using an instrument called a tonometer.
How does glaucoma develop?
The anterior chamber of the eye produces a fluid called aqueous humor which serves as the eye’s primary source of nutrients and oxygen. Used aqueous humor is drained from the eye to give room to the newly produced fluid for constant nourishment of the tissues and components of the eye.
The pressure is maintained at a constant level when the rate of production and drainage of aqueous humor is the same. Improper drainage due to anatomical abnormalities causes a build-up of aqueous humor in the anterior chamber of the eye, resulting in an increase in the eye’s intraocular pressure and the development of glaucoma.
Glaucoma in dogs and cats has many causes and can be generally classified as primary and secondary glaucoma.
Primary glaucoma occurs in a generally healthy eye. There are no apparent signs of physical injury, but the development of the disease still occurs due to genetic predisposition. Certain breeds of dogs and cats are predisposed to developing glaucoma as they get older due to inherited physical and anatomical abnormalities in their eyes.
Dog breeds predisposed to developing glaucoma are the Akita, Bull Mastiff, Great Dane, Siberian Husky, Shih Tzu, Beagle, and many other breeds. In cats, the Siamese, Burmese, and Persians are highly predisposed to developing glaucoma as they get older.
Secondary glaucoma cases, on the other hand, are those that result from a primary ocular disease or injury to the eye. There are several causes of secondary glaucoma in both dogs and cats, the most common of which are:
- Uveitis - Described as inflammation of the eye, this is usually caused by infections or injuries on the corneal surface. The inflammation and damage result in debris and scar tissue obstructing the drainage of aqueous humor.
- Lens dislocation - Dislocation of the eye’s lens can block the drainage of the aqueous humor in the anterior chamber and cause an increase in intraocular pressure.
- Eye tumors - Small tumors inside the eye may block the drainage of the ocular fluid and result in the development of glaucoma.
- Lens rupture - When the lens gets damaged, the protein inside leaks and causes an inflammatory reaction which leads to swelling and blockage of the aqueous humor drainage.
Symptoms of Glaucoma in Dogs and Cats
An increase in the intraocular pressure causes severe discomfort in a dog or a cat. The most common signs seen in pets that develop this eye disease are ocular pain, excessive eye discharge, and a decrease in appetite due to severe pain and discomfort.
Physical changes on the affected eye include apparent swelling and bulging, redness of the eye’s sclera (the white part of the eye), and the cornea may become bluish or cloudy in appearance. If not addressed properly and immediately, a consistent increase in the eye’s intraocular pressure causes damage to the optic nerves at the back of the eye and causes blindness.
Acute glaucoma is always considered an emergency due to the risk of blindness. If you start to observe any of the signs mentioned in one of your pets, it’s best to visit your vet to have their eyes checked right away.
Diagnosing and Treating Glaucoma in Pets
It’s important that when you start to see signs of possible glaucoma, that you bring your pet to the veterinarian immediately. Acute glaucoma is often considered an emergency case since it progresses very quickly and can cause permanent eye damage if not diagnosed and treated immediately.
In dealing with glaucoma in pets, it’s important to reduce the intraocular pressure as quickly as possible to minimize permanent damage to the nerves and reduce the risks of blindness. Your vet will use an instrument called a tonometer to check your pet’s intraocular pressure and confirm if your dog or your cat has glaucoma.
Thorough ophthalmic examination is also needed to determine the underlying cause, as it is also important to address this while treating for glaucoma. Additional tests like fluorescein staining may be needed to check if there are physical damages on the surface of the eye.
Treatment for glaucoma usually involves analgesics to manage pain and discomfort brought about by the condition. These eye drops are formulated to either reduce the production of aqueous humor or stimulate drainage of the fluid to help bring down the intraocular pressure. Your vet will give you specific instructions on how often to administer the eyedrops for optimal results.
Frequent monitoring of the status and intraocular pressure level of the affected eye is important to make sure that treatment is working, and adjustments can be made if the patient is unresponsive to the treatment.
Treatment of underlying conditions in cases of secondary glaucoma is necessary for complete resolution. Additional eye drops to control infection and inflammation may be needed to completely treat secondary glaucoma in dogs and cats. Severe and advanced stages may require surgery.
Care must be taken to avoid injuries to the eye during the treatment of glaucoma. You may need to confine your pet to an enclosed space and make them wear an Elizabethan collar (cone) to prevent damage or injuries to the affected eye.
It’s important that you discuss the treatment and management plan with your vet in order to provide the best care for your pets with glaucoma. In severe or advanced cases of glaucoma, surgical intervention, in combination with medications, is sometimes necessary. This is usually performed by a veterinary specialist, and a referral is normally required from your primary vet.
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