An eye infection is a relatively general description of a medical condition that may result in discomfort, discharge and abnormal appearance of a dog's eyes and surrounding tissue.

Conjunctivitis

This is generally the most common type of eye infection seen regularly in dogs. Conjunctivitis is characterized by the inflammation of the portion of the eye called the conjunctiva. The conjunctiva is the thin, clear membrane that protects the eye as well as the inner eyelid. The cause of this condition is most commonly a viral infection, an allergic reaction, or a bacterial infection.

The most common bacteria that cause conjunctivitis are streptococci and staphylococci. In Allergic conjunctivitis, the cause may be any number of airborne irritants that are causing an allergic reaction. Conjunctivitis that is caused by a virus is usually a result of a respiratory infection, flu, or other viral conditions. Regardless of the specific cause, this is the condition that manifests with all of the general symptoms of an eye infection, without any secondary symptoms.

Blepharitis

Blepharitis is a condition that usually manifests as an inflammation of the eyelids. The most common cause of this condition is a bacterial infection, which causes the subsequent inflammation of the eyelid. Other causes include demodectic mites, sensitivity to the sun, trauma, and other eye diseases. Though this condition may affect humans as well as dogs, it is occasionally seen in cats and other mammals.

Ulcerative Keratitis

In the condition of Ulcerative Keratitis, a dog's eye is subject to inflammation of the cornea. This is usually characterized by specific erosions of the cornea, though may also manifest as ulcers. This condition can be caused by several factors, though is commonly caused by keratoconjunctivitis sicca.

The common name for keratoconjunctivitis sicca is "Dry Eye", and is characterized by a deficiency of tears, usually caused by abnormalities in the tear ducts. Other causes of this condition include herpesvirus, trauma(where eye is punctured), other disease affecting the eyes/tear ducts, and facial nerve paralysis.

Juvenile Cellulitis (Puppy Strangles)

This is a condition that usually manifests as blisters around the eyes, in addition to blisters around the lips, mouth, nose and ears. These blisters will cause irritation to the eyes, resulting in many of the common symptoms of an eye infection. The blisters will eventually become ulcerated, and a dog will have other secondary symptoms, such as enlarged lymph glands and anorexia. This condition is caused by a bacterial infection.