Ocular Tonomtery for Dogs & Cats

Understanding Ocular Tonometry for Pets

Ocular tonometry for pets is a simple task that is easy to perform in your vet’s office without pain or trauma for your pet. However, it can reveal very serious issues that can result in pain or even blindness if they go undiagnosed. Here's what you need to know about ocular tonometry for your dog or cat and how to know whether your pet may need this test.

What is Ocular Tonometry for Pets?

Ocular tonometry for pets is a test measuring your dog or cat’s eye pressure, also known as intraocular pressure. This test is done to find signs of eye disorders. It is a relatively simple procedure in which your veterinarian will use a tonometer, which is a handheld device that is held to the eye to monitor pressure.

OKC Vet Campus - ocular tonometry is a test that exmaines eye pressue in cat or dog - pug dog ready for an ocular tonometry test.

The tonometer has a very small probe that makes gentle contact with your dog or cat’s cornea. It is so mild that it usually doesn't even cause your animal to respond. Sometimes an anesthetic eye drop is used to numb a pet’s eyeball before the procedure is performed to reduce sensation even further.

What is a Normal Reading?

A normal reading is typically considered between 15 mmHg to 25 mmHg for dogs and 17 mmHg to 20 mmHg for cats. If the reading is any higher, your veterinarian may recommend further tests or treatment.

What Ocular Diseases Does Ocular Tonometry Test For?

The most common eye disorder that ocular tonometry tests for is glaucoma. Glaucoma describes a number of conditions of the eye, all of which are caused by high eye pressure and damage the optic nerve.

Ocular tonometry can also test for uveitis, which is inflammation of the eye. Uveitis often causes the eye to be red and can cause blurred vision and pain. Sometimes uveitis is caused by an infection or injury, while other times it is an autoimmune or inflammatory disease that is at fault. Sometimes no cause can be identified at all.

A high ocular tonometry may indicate glaucoma or uveitis.

A low reading can indicate dehydration, which may be secondary to other issues going on with your pet.

What is the Difference Between Primary and Secondary Glaucoma?

Glaucoma is a serious condition regardless of its cause, but primary or secondary glaucoma may have slightly different treatments.

Primary glaucoma develops for unknown reasons. It may be genetic in some pets, particularly some breeds of cats.Secondary glaucoma develops for known reasons and is more common in a number of breeds of dogs. The most common reasons for secondary glaucoma include injury to the eye, diabetes, a tumor, or a cataract.

Regardless of whether glaucoma is primary or secondary, it generally has the same symptoms such as cloudiness, redness, and irritation. However, secondary glaucoma may be accompanied by other signs.

We may also conduct different tests to understand the underlying causes of secondary glaucoma. For instance, if trauma to the eye is believed to be at fault, we may also conduct a Fluorescein Staining test to look for scratches to the cornea.

Why is Ocular Tonometry for Pets Important?

An eye pressure test is extremely important for your dog or cat in order to detect and treat ocular diseases. Diseases like glaucoma and uveitis can be very painful in and of themselves.

Furthermore, if untreated, high eye pressure can cause secondary issues such as causing your pet to go blind. A high reading may indicate that eye fluids are not draining normally. This can cause fluids to build up and make the optic nerve deteriorate.

Other diseases may also be underlying the high eye pressure. Cancer, retinal detachment, lens displacement, or cataracts can all result in a high reading. It is very important for your veterinarian to determine what is going on to cause the high reading and treat the source of the problem.

When is Ocular Tonometry for Pets Necessary?

You may know that your pet is suffering from some pain or pressure in the eye because it is visibly red or cloudy or because your dog or cat is pawing at the eye or rubbing it against things. You may also notice some lack of vision. However, if the issue is only occurring in one eye, you may be very unlikely to notice it since dogs and cats are very good at compensating for partial blindness or complete blindness in one eye with the healthy eye.

Many of the signs that there is an issue with your pet’s eye pressure don't occur until the disease is fairly advanced. For this reason, your veterinarian may recommend that eye pressure is tested at regular visits, particularly if your pet has had an issue with eye pressure in the past or they belong to a breed that is more prone to issues.

Untreated, high ocular pressure can progress extremely quickly. Unless eye pressure is reduced, your pet can go blind suddenly. This blindness will be irreversible. Therefore, it is absolutely essential that ocular tonometry is conducted whenever high eye pressure may be suspected.

Breeds That May Require Regular Eye Pressure Measurement

Inappropriate pressure in the eye and issues like glaucoma, uveitis, or dehydration can occur in any dog or cat. However, there are some breeds that may be more likely to have serious issues with eye pressure and therefore require checking eye pressure more often. Here are some of the breeds that are most likely to require regular checks to make sure problems don't develop:

These breeds may be vulnerable to secondary glaucoma:

  • Cocker Spaniel
  • Dalmatian
  • Boston Terriers
  • Great Dane
  • Chow Chow

These breeds may be more likely to inherit primary glaucoma:

  • Siamese
  • Burmese

Does an Ocular Tonometry Test Hurt?

The ocular tonometry test requires that a probe touch your pet’s cornea, with sounds like it may be painful. However, the vast majority of dogs and cats don't react to the test at all. In pets that are more sensitive or have had a reaction to the test before, an anesthetic eye drop may be applied to completely eliminate a reaction to the test. However, most of the time this test is regularly performed without the need for anesthetic drops.

Does My Pet Have to be Sedated?

Unless your pet has a severe aversion to being restrained, sedation will not be necessary for an ocular tonometry test. This test is not painful and can be conducted very quickly with just a gentle contact of the probe to your pet’s cornea. However, some pets are very reactive to being restrained in any way and may require sedation in order to get the probe near enough to the eye safely in order to conduct the test.

What Other Tests May be Conducted For Pet Eye Problems?

If you believe that your dog or cat has an issue with their eye because they are displaying signs of pain or irritation like rubbing or pawing at the eye or because you can see that the eye is red or cloudy, there are a couple of other tests that we may conduct to find out exactly what is going on.

Schirmer Tear Test
This test is conducted to find out if your pet is producing sufficient tears to lubricate the eye and keep it healthy. Dogs and cats that don't produce sufficient tears may have very dry eyes, also known as keratoconjunctivitis sicca. This can result in a number of problems like chronic irritation of the eye, inflammation, and pain. If untreated, it can result in issues with the cornea that can eventually result in infections and vision loss.
The Schirmer Tear Test is conducted by putting the end of a strip of filter paper underneath the lower eyelid. This paper is designed to absorb tears. It is put in place for exactly sixty seconds and then the amount of tears that have been absorbed are compared to standard values to see if your pet is producing sufficient tears.

Fluorescein Staining
Fluorescein Staining is done to find any injuries to the cornea. Such injuries are common when the cornea has been scratched or injured in some traumatic way or if ulcers have developed. This is a very simple and nonpainful test.
A simple green-tinted dye is dropped into your dog or cat’s eye, making any corneal injuries clearly visible. If your pet’s eye has suddenly become swollen or red or if you know that they have had some sort of traumatic injuries like a scratch from another animal, we will very likely conduct a Fluorescein Staining test.

Ocular Tonometry for Pets at OKC Vet Campus

Whether your pet belongs to a breed that is prone to eye pressure issues, showing irritation or signs of blindness in one or both eyes, or your pet has had issues with eye pressure in the past, it is a very good idea to have an ocular tonometry test performed. Issues like uveitis, glaucoma, eye pressure elevation, or low eye pressure need to be identified and resolved promptly to keep your pet happy and healthy. Contact OKC Vet Campus today to have your pet tested.