It is important to understand that any source of ocular irritation or pain can cause ocular discharge. Abnormal ocular discharge is not diagnostic of any one disease or disorder. In the simplest sense, ocular discharge represents the response of the eye to an irritation, injury, or an inability to drain tears or secretions properly. The exact cause can only be determined by a careful examination and appropriate diagnostic tests.

Observe your pet for any change in eye discharge. A minor amount of eye discharge is normal; however, any change from what is normal for your pet may be significant.

Decisive therapy for ocular discharge depends on identifying the exact cause of the problem. There are numerous possible inciting causes for ocular discharge. It is essential to distinguish a specific cause to provide the appropriate therapy.

Causes

Among the potential causes of ocular discharge are the following disorders:

Cilia (eyelash) disorders such as distichiasis, which are eyelashes that grow out along the edge of the eyelid and rub on the cornea; ectopic cilia, which are eyelashes that grow out from the inside of the eyelid rub and against the cornea; and trichiasis, which are lashes on the outer eyelids or face that are long enough to rub the eye.

Conformational eyelid defects such as inward rolling of the eyelids (entropion), outward rolling of the eyelids (ectropion) and congenital absence of a portion of the upper eyelid (eyelid agenesis).

Inflammation of the eyelids (blepharitis) or inflammation of the Meibomian glands within the eyelid margins from an immune-mediated disease, or a bacterial, fungal or parasitic infection

Prolapse (protrusion) of the tear gland of the third eyelid, often referred to as "cherry eye"

Tumors of the external eyelids and the third eyelid

Deformities or wounds of the third eyelid

Congenital deformities of the tear drainage pathway, including narrowing or closure of the holes in the eyelids the tears drain through (imperforate puncta)

Inflammation, infection or foreign material within the tear duct drainage system (dacryocystitis) obstructing the drainage of tears away from the eye

Keratoconjunctivitis sicca (dry eye syndrome)

All forms of conjunctivitis

Traumatic scratches, lacerations or ulcerations of the cornea, conjunctiva and eyelids

Trauma to the nose, palate or bones of the face around the eye

Certain forms of inflammation of the cornea (keratitis)

Certain congenital defects of the cornea and conjunctiva such as a dermoid, or a mass containing skin and hair

Anterior uveitis, which is inflammation of the iris and surrounding tissues in the front portion of the eye

Glaucoma, which is sustained elevation of pressure within the eye

Lens luxation or dislocation into the front chamber of the eye

Inflammation, infection, trauma, or tumor development in the soft tissues around the eye

Infection and abscessation of the roots of the back upper teeth