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Participate in Dry Eye Clinical Trial
There are three components to your pet’s tears. These include a mucus or mucin component to help spread the tears across the surface of the eye, an aqueous or liquid component comprising a majority of the tears, and a lipid component to keep the tears from evaporating off the surface of the eye. Keratoconjunctivitis sicca (KCS), also called "dry eye", is a disease resulting from a decrease in the aqueous component of your pet’s tears. This component is produced by the lacrimal gland and gland of the third eyelid. Tears function to provide lubrication to the surfaces of the eye, nutrition to the cornea, help protect against bacterial overgrowth, flush debris from the eye, and maintain an optically smooth surface for clear vision. When there is a deficiency in tear production, the surface of the eye becomes dry, causing discomfort and irritation. Chronic irritation of the corneal surface can create abnormal pigment changes, blood vessel growth, and scarring all of which can lead to vision loss. The corneal is also at risk of ulceration (a wound on the surface of the eye). The eye may also collect debris, and is at risk for bacterial overgrowth leading to infection of the conjunctiva or cornea.
What causes KCS?
The most common cause of KCS is "idiopathic" or unknown origin. In these cases, there is felt to be an immune mediated association with inflammation of the lacrimal gland. There is also a breed predilection with the Shih Tzu, Llasa apso, Pug, English bulldog, Cocker Spaniel, West Highland White Terrier, Miniature Schnauzer, Miniature Poodle, and Pekingese being the most commonly affected. However, KCS has been documented in almost every breed of dog. Other causes of KCS are numerous and include the use of certain antibiotics, trauma to the eye and lacrimal gland, trauma to the nerve that supplies the lacrimal gland (example – chronic ear infections, ear surgery), removal of the gland of third eyelid, systemic diseases such as hypothyroidism, and radiation therapy to the eye.
KCS occurs less commonly in cats with the Burmese being the most common breed recognized. It may also occur secondary to chronic feline herpes virus infection.
What are signs of KCS?
Your pet may show signs such as redness to the white part of the eye or sclera, squinting or rubbing at the eye from discomfort, a thick green-yellow discharge over and around the eye indicating a possible infection, as well as changes to the cornea that affect its clarity. The surface of your pet’s eye may no longer have a “glistening” appearance. Your pet may have an increase in the mucin component of the tears to try to compensate for loss of the aqueous component. This will create a milky to creamy white discharge that needs to be periodically cleaned from your pet’s eyes. KCS may affect one or both eyes.
How is KCS is diagnosed?
An eye exam and diagnostic tests will be performed to help confirm the presence of KCS and other secondary problems such as bacterial infections or corneal ulcers. These tests are not painful and help to determine appropriate treatment for your pet. The Schirmer tear test strip measures the amount of tears that are being produced. This involves placing a thin piece of special paper under your pet’s eyelid for 1 minute. The length of paper that is wet is then measured in millimeters. Normal tear production is greater that 15 millimeters in one minute. Fluorescein stain may be applied to determine if there are corneal ulcers present. A sample can be taken from your pet’s eye that is examined under a microscope to look for bacteria. If there is concern about a bacterial infection being present, then a culture may be taken to find out the type of bacteria present and what antibiotics are appropriate to use treat against that particular bacteria.
How is KCS treated?
Medical treatment is generally very effective. There are a number of different medications that may be prescribed that in combination will provide the best therapy for your pet.
Medications that increase tear production:
Cyclosporine or “Optimmune” is an ointment that stimulates the lacrimal glands to produce more tears. It also decreases inflammation of the glands and ocular surface. It is currently the most effective and commonly used therapy for treatment of this condition. It may take several weeks to months for it to reach its full effect. Cyclosporine is a safe drug to use topically and typically is associated with no systemic side effects. In some dogs, there may be mild ocular irritation noted. If irritation is noted when using this medication, please talk with one of our staff. This ointment is packaged in a container that is different than other ointments that you may have used in the past so please consult your veterinarian or staff on tips for application.
Pilocarpine is a medication that can also be used to increase tear production. It is generally used in cases where KCS is thought to be caused by damage to the nerve that supplies the lacrimal gland. It may be prescribed as a topical drop or oral medication depending on your pet’s particular needs. The topical application may be associated with mild ocular irritation. The oral medication can cause vomiting and diarrhea.
Medications that provide lubrication:
Artificial tears, while not a tear production stimulant, still keep the eye moist and lubricated, and are an important part of therapy. Artificial tears come in a variety of drop and ointment forms. Depending on the severity of your pet’s condition, we may recommend one form over the other, or a combination of a drop and ointment. The frequency of application will also vary with the severity of the KCS. It is important to remember that even though we may place your pet on a medication to increase the tear production, artificial tears may be needed in combination with those medications as tear production often does not return to completely normal levels, or it may take some time for those medications to have full effect. Therefore, the artificial tears will provide necessary lubrication and comfort in the meantime. There are a variety of artificial tears available over the counter, so if you are interested in obtaining your pet’s medications from a local drugstore, please check with one of are staff or your veterinarian for guidelines on the best product to purchase.
Antibiotics:
If your pet has a secondary bacterial infection, then antibiotics may be used as part of your pet’s therapy. While your pet’s tears are below normal production, they may be at risk to develop periodic infections that need to be treated. This is typically evidenced by a green to yellowish discharge coming from the eye. Remember, that your pet may have an extra creamy discharge that is not associated with an infection, so you should have one of our staff or your veterinarian evaluate the discharge to confirm the need for antibiotic treatment.
Surgical treatment for KCS:
Surgery is also available should medical treatment fail. Surgery involves transposing or moving the duct for the salivary gland that empties into your pet’s mouth to the eye. After this surgery, the eye will be lubricated with saliva instead of tears when your dog salivates. It will be necessary to feed your dog several small meals a day. Surgical treatment is reserved for dogs that do not respond to, and are still not comfortable with medical treatment alone. There are complications associated with this surgery including mineral deposits from the tears that build up on the cornea, skin infections around the eye due to overflow of saliva onto the face, or scarring or closure of the duct after surgery. Most pets continue on some type of topical medication after surgery.
What is the prognosis for KCS?
With proper management and treatment, the prognosis is very good. Pet’s who have a very low tear production (< 5 mm/min) generally have a poorer prognosis of responding to medical treatment. Treatment of KCS is usually required for the rest of your pet’s life.
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