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Conjunctivitis in Dogs

The conjunctiva is the moist tissue that covers the front part of the eyeball and lines the eyelids. Breeds that tend to have allergies or autoimmune skin diseases tend to have more problems with inflammation of the conjunctiva. They are also more likely to have dry eyes, the result of a disease in which the animal is allergic to substances in the environment, such as pollen, that would not normally cause health problems. Otherwise, there does not appear to be a breed predilection for this disease.

Conjunctivitis can affects both dogs and cats. If you would like to learn more about how this disease affects cats, please visit this page in the PetMD health library.

Symptoms and Types

• Squinting or spasmodic blinking (blephora)
• Redness of the moist tissues of the eye
• Discharge from the eye(s); it may be clear or may contain mucus and/or pus
• Swelling from fluid build-up of the moist tissue covering the eyeball
• Follicle formation; follicles are accumulations of lymphoid tissues located at the moist tissue surface of the eyelids, causing a cobblestone appearance; lymphoid tissue contains lymphocytes, a type of white-blood cell that is involved in allergies and act in response to irritants

Causes

Bacterial:

• Primary condition -- not secondary to other conditions, such as dry eye
• Neonatal conjunctivitis: newborn inflammation of the moist tissues of the eye - accumulation of discharge, often associated with a bacterial or viral infection; seen before the eyelids separate or open

Viral:

• Canine distemper virus

Immune-mediated:

• Allergies
• Follicular conjunctivitis
• Plasma-cell conjunctivitis -- inflammation of the moist tissues of the eye characterized by the presence of plasma cells, especially in German Shepherds
• Related to generalized (systemic) immune-mediated diseases in which the body's immune system attacks its own tissues

Cancer:

• Tumors (rare)
• Lesions that appear to be cancer, but are not cancerous. Inflammation of the border between the cornea (the clear part of the eye, located in the front of the eyeball) and the sclera (the white part of the eye); characterized by the presence of nodules, it is most commonly found in collies and mixed collies, and usually appears as a pink mass

Secondary to disease of the tissues surrounding the eye:

• Lack of normal tear film (dry eye)
• Lid diseases
• Lash diseases

Secondary to trauma or environmental causes:

• Foreign body in the moist tissues of the eye
• Irritation from dust, chemicals, or eye medications

Secondary to other eye diseases:

• Ulcerative keratitis
• Anterior uveitis
• Disease of the eye, in which the pressure within the eye is increased; known as glaucoma

Diagnosis

The first thing your veterinarian will look for is evidence of other ocular (eye) diseases. For example, the disease may not be in the conjunctiva but in other parts of the eye. Your doctor will conduct a complete eye exam. Different methods of examination may include a fluorescein stain, which is spread on the surface of the eye to make scratches, ulcers, and foreign material stand out under light. This is to rule out ulcerative keratitis. Foreign materials may also have gotten caught in the lids or eyelashes, so they will be examined thoroughly as well. A test for glaucoma will be conducted by determining pressures in the eye, and the nasal cavity may need to be flushed out to rule out disease there. If there is discharge from the eye a culture will be done to determine what the discharge consists of, since infection may be indicated, and a biopsy of conjunctiva cells may be collected for microscopal examination. A skin test may also be conducted if skin allergies are suspected to be the cause.