Conjunctivitis in Cats

Conjunctivitis in Cats

Overview of Feline Conjunctivitis

Conjunctivitis is an inflammation of the conjunctiva, which is the tissue coating the eye and lining the eyelids. Normally, the conjunctiva is moist and glistening with tiny blood vessels coursing through the semilucent tissue. It serves as a protective barrier for the eye by trapping debris and helping to prevent invasion of viruses and bacteria.

Conjunctivitis is a common eye problem in cats. It may be the only eye disease present, or it may be associated with other diseases or eye problems.

Below is an overview of conjunctivitis in cats followed by in-depth detailed information about the diagnosis and treatment options for this disease. 


  • Viral eye infections, such as herpesvirus or calicivirus
  • Chlamydial eye infections
  • Bacterial eye infections
  • Corneal diseases
  • Abnormalities of tear production
  • Eyelid infections or abnormalities
  • Exposure to foreign material such as plant material, fibers, sand and chemicals
  • Environmental irritants
  • Trauma
  • Idiopathic, meaning that no cause is ever defined
  • What to Watch For

  • Redness of the eyes
  • Eye discharge
  • Swelling of the conjunctiva
  • Squinting or excessive blinking
  • Diagnosis of Conjunctivitis in Cats

    Conjunctivitis is usually diagnosed based on physical exam findings. Your veterinarian will probably perform the following tests:

  • Fluorescein staining to detect superficial abrasions or ulcers on the cornea
  • Schirmer tear test to determine if your cat is producing sufficient tears
  • Thorough exam of the conjunctiva, external eyelids, and the third eyelid

    In some situations, additional tests may be recommended, such as:

  • Bacterial cultures
  • Tests for viruses
  • Tonometry, which measures eye pressure (glaucoma test)
  • Conjunctival scrapings to evaluate the cells of the conjunctiva
  • Conjunctival biopsy (rarely performed)
  • Certain blood tests if the cat is also ill
  • Treatment of Conjunctivitis in Cats

    Treatment involves symptomatic therapy for the conjunctivitis and instituting treatment for any underlying causes.

  • The eye may be thoroughly irrigated to remove any irritating substance.
  • Foreign material should be removed.
  • Tear production abnormalities are treated with medication.
  • Eyelid infections and abnormalities may require either medication or surgery.
  • Since secondary bacterial infections are a common concern, antibacterial eye ointment is frequently prescribed.
  • In many cases, anti-inflammatory eye medications are also indicated.
  • Home Care and Prevention

    Once diagnosed and started on medications, the eyes should be checked frequently for improvement. Most cases of conjunctivitis improve within 24 to 48 hours after medication is begun. If you notice that your cat is not improving, consult your veterinarian.

    Unfortunately, many causes of conjunctivitis are not preventable but veterinary examination and treatment usually resolves the disease rapidly and maintains your cat’s eyes and vision.

    In-depth Information on Conjunctivitis in Cats

    Feline conjunctivitis is a common eye ailment, but unfortunately the exact cause of the conjunctivitis is often not defined. In cats, there are a variety of diseases that can result in conjunctivitis.

  • Upper respiratory infection. These infections usually involve viruses (especially feline herpesvirus and feline calicivirus), bacteria and chlamydial agents. Signs of conjunctivitis are often present in both eyes, and other signs such as sneezing, nasal congestion and discharge, lethargy, fever and decreased appetite may be noted.
  • Herpesvirus. Once a cat has been infected with herpesvirus the virus is rarely cleared from the body. Instead, the virus becomes latent (or quiet) and may cause repeated bouts of conjunctivitis throughout the cat’s lifetime. These recurrent bouts of conjunctivitis may be triggered by stress, illness, certain medications or other infections.
  • Exposure to environmental irritants or foreign material. Such irritants can include cigarette smoke, household chemicals and cleaners, dust, pollen, plant material, and sand.
  • Infection and inflammation of the eyelids and cornea. Because the conjunctiva is physically adjacent to both the eyelids and the cornea, any infection or inflammation of these tissues may result in conjunctivitis. Examples include corneal ulcers, certain forms of keratitis, blepharitis (inflammation of the eyelids), and skin diseases that affect the eyelids.
  • Allergies. Allergy-related conjunctivitis is uncommon; it is much more common in the dog.
  • Primary bacterial infections. Without associated eye disease, these infections are a rare cause of conjunctivitis. It is much more common for bacteria to take advantage of inflamed conjunctiva, and then to invade this inflamed tissue to create a secondary infection.
  • Trauma to the conjunctiva, eyelids, cornea or eye itself.
  • Inflammation from within the eye. Occasionally outward extension of inflammation can reach the conjunctiva, resulting in conjunctivitis. In these instances the inflammation within the eye is the primary concern.
  • In-depth Information on Diagnosis of Conjunctivitis in Cats

    Diagnosing conjunctivitis is based on the physical exam finding of a red, inflamed conjunctiva, usually with associated tearing or other eye discharge. Diagnosing the underlying cause in order to provide precise treatment is difficult. Your veterinarian will probably perform the following tests:

  • A thorough eye exam to detect any foreign material such as sand, plastic or grass. It can also detect any abnormal eyelid conformation or inflammation of the eyelids, cornea, or within the eye.
  • An eye pressure test to detect glaucoma. This eye disease produces enlargement of the blood vessels under the conjunctiva and can easily be mistaken for conjunctivitis.
  • Schirmer tear test to determine if your cat’s eyes produce an adequate amount of tears. Inadequate tear production results in keratoconjunctivitis sicca (dry eye), which causes conjunctivitis.
  • Fluorescein staining to reveal corneal lesions. The test is done by placing a drop of dye on the surface of the eye, then flushing so the eye can be examined. If stain is present on the surface of the eye, there has been disruption of the surface of the cornea, such as an abrasion, scratch or ulcer.

    In addition to these tests, your veterinarian may recommend additional tests.

  • Conjunctival scraping and examination of the conjunctival cells to help identify the type of inflammation present and search for viruses
  • Certain blood tests if the animal is acting ill
  • In-depth Information on Treatment of Conjunctivitis in Cats

    Since many cases of conjunctivitis are mild and respond to topical anti-inflammatory medications, your veterinarian may chose to prescribe such a drug before proceeding with additional diagnostics. If the conjunctivitis does not resolve in five to seven days, or if it recurs immediately after the medication is stopped, further tests may be needed.

    If an exact cause can be determined, the specific treatment is instituted for that cause.

  • For cats with conjunctivitis associated with upper respiratory infection, supportive care is usually administered until the cat starts to recover. The eye is frequently treated with terramycin ointment or some other antibiotic to treat any chlamydial and bacterial agents involved.
  • For cats with chronic, recurrent conjunctivitis associated with feline herpesvirus, topical anti-viral medications may be instituted, although they are expensive. In addition, some of these cats respond to oral lysine given for long period of time.
  • Eye irritants such as pieces of sand, plastic, or grass can be flushed out of the eye using copious amount of sterile eye irrigation fluid. After removal of the offending foreign matter, a brief course of antibiotics or antibiotic steroids usually resolves the conjunctivitis.
  • Conjunctivitis due to environmental irritants can be difficult to treat unless the irritant can be removed. Owner’s should avoid smoking around the cat, should avoid the use of spray carpet cleaners and other agents that might linger in the environment. Furnace and air-conditioning filters should be changed regularly, and air filter or humidifiers may be helpful in some cases.
  • Corneal ulcers are generally treated with topical antibiotics and sometimes with pupil dilators. Many corneal ulcers heal within three to five days.
  • If dry eye is diagnosed, topical artificial tears and lubricants may relieve the conjunctivitis. Other potential medications include a trial of topical cyclosporine, which may increase tear production, anti-viral drugs for associated herpesvirus, topical antibiotics and anti-inflammatory drugs.
  • Allergic conjunctivitis is treated with topical steroids. This can alleviate some of the redness and inflammation. Removal of the item your cat is allergic to can also help eliminate the disease, but frequently this is not possible.
  • Inflammation of the eyelids and cornea must also be addressed.
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