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Glaucoma is defined as an increase in intraocular (within the eye) pressure. Normal intraocular pressure ranges from 15-25mmHg. Aqueous humor is the fluid that circulates within the eye and regulates pressures. The aqueous humor is constantly being produced and drained from the eye. Therefore, the ocular pressure is dependent upon the rate of formation and ease of drainage of the aqueous humor. Glaucoma can be broken down into two types: primary and secondary.

Primary Glaucoma

Primary glaucoma is classified as increased pressure without any obvious ocular disease. Beagles, cocker spaniels, basset hounds, springer spaniels, samoyeds and siamese cats are more prone to primary glaucoma.

Secondary Glaucoma

Secondary glaucoma occurs as a sequelae to a primary ocular disease. Some examples of primary ocular diseases are: lens luxation, hyphema (blood in the eye), trauma, neoplasia, pigment deposition and complications from anterior uveitis. Anterior uveitis refers to inflammation in the front portion of the eye.

Signs & Symptoms of Glaucoma

Early signs (within the first 2-3 hours of onset)

Pain characterized by excessive tearing, squinting and 3rd eyelid protrusion

Red eye

+/- cloudy eye

+/- blind eye

Advanced signs (hours to days after onset)

Pain persists

Marked red eye

Corneal opacity (cloudy eye)

Dilated pupil

Blind eye

Chronic signs (days, weeks to months after onset)

Less pain but still uncomfortable

Enlarged globe (big eye)

Cloudy cornea +/- white striations

Blind eye


Glaucoma is confirmed by measuring the intraocular pressure (IOP) using tonometry. There are several methods of tonometry. We use a tool called a Tonopen which uses applantation tonometry to measure IOP. First, topical anesthetic is applied to the eye, then the Tonopen is lightly tapped on the corneal surface. A numeric reading corresponding to IOP is given. If the IOP is increased and clinical signs are supportive, a diagnosis of glaucoma is made.

There are specialized techniques performed by veterinary ophthalmologists to assess the possible cause of glaucoma.


Glaucoma therapy needs to be instituted immediately to increase the likelihood of maintaining a visual eye. Acute glaucoma is an emergency, requiring prompt medical treatment. Initially, treatment goals are as follows: reduce inflammation, reduce aqueous production, assist aqueous outflow and increase absorption of fluid from the eye.

The medications that achieve these processes are typically a combination of oral, topical and intravenous medications. Treatment of acute glaucoma does require hospitalization and close monitoring. Once medical treatment is instituted there are several options for glaucoma patients including: continued medical therapies, several surgical procedures, enucleation (removal of the eye), chemical ablation (injection of a substance into the globe destroying the tissues).

Not all options are available for every patient, advantages and disadvantages of each option/procedure are very dependent upon the individual case. Short of enucleation, both the remaining surgical procedures and continued medical therapies require diligence, continued care and sound finances. In some cases of primary glaucoma, medical treatment will be instituted in the other eye to slow the onset of glaucoma in the “good eye”.

The goal of all the treatments is to keep the patient as comfortable as possible as glaucoma can be a very painful disease.

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