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Dog: Keratoconjunctivitis sicca

General information

Other common/scientific names: KCS, dry eye

Tears are essential to the health of the eye. Not only do tears provide lubrication to the eye but they also supply anti-bacterial proteins, salts, sugars and oxygen to nourish the eye. Tears flush away irritants and infectious agents. Tears are produced by two glands: one just above the eye (lacrimal) and another in the third eyelid (nictitating membrane).

Keratoconjunctivitis sicca or KCS basically means the eye is dry. Kerato refers to the cornea or the clear covering of the eye. The conjunctiva is the lining of the inner surface of the eyelids and the exposed surface of the eyeball. And “ itis” means inflammation while sicca means dry. So, keratoconjunctivitis sicca basically means a dry eye with resulting inflammation to the cornea and conjunctiva. This dry eye is caused by inadequate production of tears or poor quality of tears and/or defective tear production.

Without tears, the eye becomes dry and irritated. The conjunctival tissues become reddened and inflamed. The cornea becomes thickened and scarred. Blindness can result.

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Abb. GGT8V4DS: Schematic illustration of the eye, side view, showing the gland of the third eyelid.

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Abb. GGT8YE4D: Schematic illustration of the eye, front view.
The lacrimal gland is shown on the outside, upper corner of the eye.

Causes

There are several causes of KCS in dogs. These include:

  • Immune-mediated destruction of the tear producing gland
  • Medications such as certain antibiotics, antihistamines and anti-inflammatories
  • Anesthetic agents can cause temporary KCS
  • Radiation for treatment of nasal and head tumors
  • Congenital lack of tear producing tissue inherited in Yorkshire terriers and Pugs
  • Removal of the third eyelid (nictitating membrane)
  • Trauma to the eye or face resulting in nerve damage to nerves which innervate the lacrimal system
  • Breed predisposition in the Cocker Spaniel, Lhasa Apso, Bulldog and Miniature Schnauzer
  • Canine distemper virus

Cardinal symptom

red eye

Symptoms

Clinical signs of KCS include a reddened conjunctiva, thick yellow ocular discharge, increased blinking and eye pain. Advanced cases of KCS develop keratitis or inflammation of the cornea. These cases show signs of corneal ulcers and corneal erosions, resulting in the cornea becoming thickened and discolored with edema, vascularization and pigment.

Diagnosis

Chronic KCS can be diagnosed by physical examination but in early stages it can look like simple conjunctivitis. In either case, it is important to measure the tear production. This test is called the Schirmer Tear Test. This test consists of inserting a strip of a special type of paper into the lower eyelid. The strip is held in the eyelid for one minute and the tear fluid is absorbed onto the strip. The height of the tear fluid or the height of the moistened area on the strip is measured.

Diagnosis should also be aimed at finding the underlying cause.

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Abb. GG92HMAI: Schirmer Tear Test.
This is a photograph of the test strip inserted into the lower eyelid. The moistened area is measured to determine tear production.

Treatment

Mild or borderline cases of KCS can be treated with artificial tear drops to replace tear production. Eye medications containing antibiotics, anti-inflammatories and compounds aimed at dissolving the thick discharge can also be used. However, in severe cases, the preferred treatment is an ocular medication which suppresses the immune destruction and allows tear production to be restored.

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Abb. GG92M6TT: Application of artificial tears.
This is a photograph of applying artificial tears to a dog’s eye. The dog’s head should be tipped upward to allow the drops to fall into the eye. Place your hand on the dog’s face, under the eye to steady your hand if the dog moves and prevent touching the eye.

Dogs which do not respond to medical treatment of KCS can undergo a surgical procedure called parotid duct transposition. The parotid gland produces saliva which is carried to the mouth via a long duct or tube. This surgery involves carefully moving this duct to deliver saliva over the dog’s eye. While saliva is a reasonable substitute for tears and lubrication of the eye, this is an expensive and specialized procedure. This surgery should be performed by a veterinary ophthalmologist.

Prognosis

Mild cases of KCS which respond well to medications have a good prognosis. However, depending on the cause, KCS can be a chronic condition requiring daily medication of your dog. This can be time consuming and frustrating. If the cornea is damaged and scarred, prognosis will also depend on the extent of damage. Severe corneal scarring can result in impaired vision.

Tips

It is important to administer all medications as recommended by your veterinarian. If you have difficulty applying eye medications to your dog, consult your veterinarian.

Update version: 4/24/2014, © Copyright by www.enpevet.de
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