Red Eye in Dogs

Cecilia de Cardenas
Nov 11, 2008
3 min read
Image: Photo Grapher / via Image Bank

Inflammation of the Eye in Dogs

Red eye causes the dog's eye to become inflammed and, well, red. This inflammation may be due to various factors, including excess blood in the eyelids (hyperemia) or in the eye's blood vessels (ocular vasculature). This occurs when vessels expand in response to extraocular or intraocular (outside of, and within the eye, respectively) inflammation, or a passive accumulation of blood.

The condition described in this medical article can affect both dog and cats. If you would like to learn more about how red eye affects cats, please visit this page in the PetMD health library.

Symptoms and Types

The most common signs of red eye in dogs is redness and inflammation affecting one or both eyes.


There are various factors which may contribute to a dog's red eye, such as inflammation of the eyelid, cornea, sclera, conjunctiva, ciliary body, and iris. Other causes include:

  • Glaucoma
  • Orbital disease
  • Hemorrhage at the front of the eye
  • Hemorrhage within the eye from newly formed or existing blood vessels


Your veterinarian will perform a complete physical exam on your pet, including a blood chemical profile, a complete blood count, a urinalysis and an electrolyte panel. You will need to give a thorough history of your dog's health, an onset of its symptoms, and possible incidents that might have precipitated this condition.

Red eye is often a visible symptom of an underlying systemic disease, sometimes of a serious nature. Consequently, bloodwork is essential for ruling out or confirming an underlying disorder.

In order to rule out cancer and infectious causes to the red eye, X-ray imaging can be used for visual inspection of the chest and abdomen. Just as useful for diagnostic purposes are ultrasound images of the eye, which can be performed if the eye is opaque, and tonometry -- measurement of the pressure inside the eyes using a tonometer.

If there is pus-like discharge from the eye, or long-term disease of the eye, your veterinarian will perform an aerobic bacterial culture and sensitivity profile.

Other tests your veterinarian may choose to perform are a Schirmer tear test to verify normal tear production; a cytologic (microscopic) examination of cells from the eyelid, conjunctiva, and cornea; and a conjunctival biopsy (tissue sample) if there is chronic conjunctivitis or mass lesions.

Fluorescein staining of the cornea, which uses a non-invasive dye to coat the eye, making abnormalities more visible under light, can also be used for the detection of foreign material, ulceration, scratches, and other lesions on the surface of the dog's eye.

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