My Dog Has Red Eyes – Now What?

By Dr. Jillian Rankin

Soooo your cute little innocent and lovable companion has red eyes… Now what? Do you start searching his dog bed for contraband? Do you stop him from seeing the neighbours sketchy looking dog because he must be a bad influence? Do you ask your friend Karen from Pilates class, because she seems to know everything, so she must know this too? The answer to all of these is… no! When it comes to addressing red eyes in our dogs there’s only one right answer… GO TO THE VET!

Seeking a veterinarians expertise about Fluffy’s red eyes, will address the root cause of the red eye and help educate us as owners!

So, without further delay, here are some of the more common reasons for red eyes, and what to expect when visiting the vet with our red-eyed furry friend!

What is red eye?

Similar to people, when a dog’s eyes become inflamed, they become red. This inflammation, affecting one or both eyes, may be due to a variety of reasons ranging from mild allergies to glaucoma, which can lead to blindness. This redness may or may not be accompanied by discharge, and may involve the surface of the eye, or may be a sign of something more systemic. If you notice redness that lasts more than 24 hours, then it’s time to take your dog to the vet. The veterinarian can then work with you and fluffy in order to diagnose the issue with the eye before it gets worse!

Types of red eye in dogs


What is it: Inflammation of the eyelid

Causes: Any condition that can cause irritation of the eyelids can lead to blepharitis. Common causes of blepharitis include congenital abnormalities, allergies, infections, tumors, and occasionally other inflammatory disorders.


What it is: Inflammation of the conjunctival tissue (the mucous membrane that covers the eyeball and lines the eyelids).

Causes: Any condition that can cause irritation of the conjunctival tissue.
Common causes of conjunctivitis include viral infections (eg. distemper virus), immune-mediated disorders, tumors of the eyelids or conjunctiva, breed-associated conditions, tear film conditions (eg. dry eye), eyelid abnormalities (eg. entropion or ectropion), eyelash disorders (eg. distichiasis and ectopic cilia), obstructed ducts, as well as trauma to the eye or irritation from foreign bodies, smoke, or environmental pollutants, ulcerative keratitis, anterior uveitis, as well as glaucoma.

Chronic Superficial Keratitis (Also known as pannus)

What is it: A progressive inflammatory disease of the cornea. Characterized by infiltration of the cornea by vessels and granulation tissue and/or pigmentation.

Causes: Immune-mediated and animal may be at an increased risk with ultraviolet radiation exposure.


What is it: Any other disease process that affects the eye or surrounding tissues of the eye that results in redness or irritation, and may lead to more serious consequences such as blindness, if left untreated.

Types: cellulitis, abscesses, neoplasia (i.e. cancer), ulceration, glaucoma, uveitis et al.

What are the more serious causes of red eye in dogs

Once at the vet, all red eyes will be evaluated for 3 key ocular diseases that may cause vision loss in an eye:

1. Corneal ulceration

What is it: An open sore on the outer layer of the cornea

Causes: Often caused by infection, trauma or secondary to abnormal wound healing from an underlying disease process.

2. Glaucoma

What is it: Increased pressure within the eye, known as the intraocular pressure (IOP)

Causes: May be primary (due to anatomical abnormalities in the drainage angle in the eye) or secondary (due to a disease process or injury to the eye)

3. Uveitis

What is it: Inflammation of the interior of the eye, or severe intra-ocular infections that results in debris and scar tissue that blocks the drainage angle in the eye.

Causes: Most often due to a systemic cause including infectious, autoimmune or neoplastic. But may be considered non-systemic if there is evidence of cataracts (lens-induced uveitis), corneal ulceration, intraocular neoplasia, or other external evidence of trauma.

Keratoconjunctivitis Sicca (Also known as KCS or Dry Eye)

What is it: A disease that occurs when the eye does not produce enough tears.

Causes: Immune-mediated, hormone imbalances, chronic infections or inflammation, secondary to adverse reactions of certain medications. Also may be due to inappropriate removal of the third eyelid leading to reduced tear formation months to years later.

Diagnosis of red eye in dogs

A few basic diagnostic procedures can quickly assess whether one or more of these diseases are present

Physical examination of the eye

The veterinarian will use various instruments to assess both the anterior and vitreous chambers of the eye as well as the reflexes of the eye.

Schirmer tear test (STT)

This test aids in diagnosing conditions associated with decreased tear production (eg. dry eye).

Fluorescein stain

This test is an excellent way to assess whether your pet has corneal ulceration.


This is a test that measures the pressures inside the eye and is critical for the diagnosis of glaucoma and uveitis.

Once a thorough examination and diagnostics are completed, the eye’s condition will be classified as either extraocular (conjunctival or corneal), intraocular (glaucoma or uveitis), or as an ocular manifestation of systemic disease. Then, based on this information, the veterinarian will suggest the most appropriate diagnostics and/or treatment plan for your lovable furry family member.

Treatment of red eye in dogs

Some common treatments for dogs with the examination finding of red eye include:

Medicated drops

May be prescribed as an aid in treating for bacterial infections, to allow for anti-inflammatory effects and to help control pain in the eye.

Oral medication

May be prescribed in order to treat an underlying disease process that could have initiated the red eye to begin with.


May be necessary for certain conditions, based on the findings of the ocular examination.

Referral to an Ophthalmologist

A specialist referral may be appropriate for more complicated or unique cases.

Overall, your veterinarian will work with you to help make the best decisions around your dog’s treatment, your furry family member will receive the best care possible and so you don’t have to feel alone in trying to figure out why your pet is in pain and discomfort.

We share because we care about your pet, but please don’t rely on Dr. Google to diagnose your pets! If your pet has red eyes, please call us at 403-615-8016 to book an examination.