Glaucoma

GENERAL DESCRIPTION

Glaucoma is defined as an increase in the intra-ocular pressure of the eye.  If the eye cannot drain an adequate amount of aqueous humor fluid, this causes a back-up of fluid leading to a pressure increase.  The aqueous humor is the fluid found in the eyeball which provides nourishment to the interior eye structures and keeps the eyeball inflated. As this pressure increases, the risk of damage to the internal structures of the eye also increases.  Glaucoma can be considered an emergency situation because, as the pressure rises the incident of rendering the eye blind is quite likely.  Glaucoma is generally classified as primary or secondary. 

SOURCE & CAUSE(S)

Primary Glaucoma:

Is the result of increased intra-ocular pressure in an animals eye due to a breed disposition, or they are genetically inclined to develop glaucoma based on how their eye structures have developed.  The drainage pores might be too small or are at an angle not allowing for the proper amount of fluid to drain.  This causes a back up and thus increases the pressure.  Some of the most susceptible breeds include: Beagles, Cocker Spaniels, and Basset Hounds.

Secondary Glaucoma:

Secondary glaucoma is the most common glaucoma found in dogs and cats.  It is the result of increased intra-ocular pressure in the eye due to disease or injury. Some general causes include:

• Damage to the lens.  In a trauma to the eye the lens becomes damaged this allows proteins to leak into the eye and can cause a blockage of the drainage aqueous humor.
• Tumors which cause physical blockage of the drainage path.
• Some kind of Intra-ocular bleeding, which leads to a blood clot formation which can block the drainage of the aqueous humor.
• Intra-ocular infection with Uveitis (inflammation), which can result in debris and scar tissue blocking the drainage aqueous humor.

 SIGNS & SYMPTOMS

• Eye pain - usually presents with your pet rubbing eye or holding eye closed and squinting.  If you try to touch the area around the eye, your pet may move away and even growl to show that it is painful.
• Swollen eye - you may see a bulging eye and may also note that it is bloodshot.
• The cornea may appear to be shiny and a bluish-greenish color.
• Loss of appetite or lethargy will indicate that your pet is not feeling well.
• Blindness may occur rather quickly if the pressure is getting too high too fast.

DIAGNOSIS & TESTS

Diagnosis begins with a complete history and a physical exam.  Your veterinarian will most likely do the following:

• Eye exam with tonometer - This test will help your veterinarian determine the fluid pressure inside your pet’s eyeball. A pen-like instrument is touched to the eye multiple times and the eye pressure measurement will be displayed.
• Cat scan - This machine uses X-rays that rotate on a single axis around your pet as they slowly pass through a machine. Many images are taken gradually, and then combined, making a very accurate, clear image. Sometimes, contrast material can be used to differentiate certain tissues or blood vessels. In this case, your veterinarian will use the cat scan to look at all of the structures around the eye to evaluate the integrity of the eye as a whole, and to rule out any tumors that may be the cause of the increased pressure.
• Eye exam with opthalmoscope - Your veterinarian will likely perform a complete eye exam using an opthalmoscope with a light and high magnification to examine your pet’s eyes for any abnormalities and to comprehensively evaluate the integrity of the eye.
• Corneal stain - This will rule out any secondary corneal ulcer development that may be present from rubbing the eye.

NOTE:  There is a very high likelihood that your veterinarian will refer you to a veterinary ophthalmologist to diagnose and treat.  The opthalmologist will have all the specialized instruments for glaucoma.

TREATMENT & MANAGEMENT

The most important factor in treatment is reducing the intra-ocular pressure as quickly as possible thereby reducing the risk for more damage and blindness.  This can be done using some topical and oral medications.  The topical eye medications usually have to be given several times a day to be effective.  Surgery will most likely be the best way to treat and manage glaucoma.  In the most severe cases where blindness has developed and there is a high level of pain associated the glaucoma removal of the eye is recommended.

PREVENTION & HELPFUL TIPS

There is no prevention for glaucoma.  If you suspect your pet is having symptoms of glaucoma and you see an eye bulging, this is an emergency and you should contact your veterinarian ASAP!