Overview of Red Eye in Dogs

Red eye is a non-specific sign of inflammation or infection.In dogs, it may be seen with diseases of the external eyelids, third eyelid, conjunctiva, cornea, and sclera. It may also occur with inflammation of the structures inside the eye, with glaucoma (high pressure within the eye) or with certain diseases of the orbit (eye socket). Either one or both eyes can become red, depending upon the cause of the problem.

Eyes become reddened when blood vessels of the conjunctiva (the pink lining of the eyeball and eyelids), sclera (white covering of the eye), or cornea (clear surface of the eye) become enlarged or more numerous.

What to Watch For

Redness of the eye or structures around the eye

Squinting, increased blinking, holding the eye closed

Pawing or rubbing at the eye

Possible decrease in vision or blindness

Possible cloudiness of the eye

Tearing or discharge from the eye

Possible systemic signs if the redness is associated with some sort of illness

Diagnosis of Red Eye in Dogs

Veterinary care includes tests to diagnose the condition causing the red eye and to define subsequent treatment. Your veterinarian will do a complete medical history and physical examination to try to determine if the problem involves only the eye(s) or if other changes are present in the animal.

A complete ophthalmic examination is required to determine the source of the redness and whether it involves inflammation of the external structures of the eye or the internal structures. Your veterinarian may refer your dog to a veterinary ophthalmologist for further evaluation using specialized instrumentation. The following tests may be performed during the eye examination:

Schirmer tear test to measure tear production

Fluorescein staining of the cornea to check for ulcers

Tonometry to measure the pressure within the eye

Examination of the interior of the eye under magnification

Taking scrapings of inflamed tissues (such as conjunctiva and cornea) for cytologic studies to determine the type of inflammation present

Examination of scrapings of the eyelids to look for parasites

Submission of samples for culturing bacteria and other agents

Biopsy of masses around the eye

Other tests may include:

A complete blood count and biochemistry profile if any systemic signs are present

Blood testing for the tick borne rickettsial and bacterial infections, for fungal infections and parasitic conditions, if the red eye is related to inflammation of the interior of the eye

X-rays of the chest and abdomen if an underlying systemic illness is suspected

Treatment of Red Eye in Dogs

The goal of therapy is to decrease any inflammation present and to address the underlying cause. It is very important that the cause of the inflammation or infection be diagnosed, so that specific treatment can be started.

Anti-inflammatory medication. The are two basic classes of topical anti-inflammatory medications that may be used to treat red eyes: nonsteroidal anti-inflammatory drugs and topical corticosteroids. These medications are not indicated when corneal ulcers are present, and must be chosen based on the underlying ocular condition.

The nonsteroidal anti-inflammatory drugs (NSAIDs) are agents similar in action to ibuprofen. They are beneficial in some forms of red eye and not in others. They are less potent than the topical corticosteroids.

The topical corticosteroids are used most commonly for conjunctivitis, anterior uveitis and some forms of corneal inflammation. A number of these drugs exist and have varying degrees of potency.

Systemic anti-inflammatory medications. Occasionally systemic anti-inflammatory medications are used in conjunction with topical medications. These include antihistamines for the treatment of allergic conditions, oral NSAIDs to alleviate pain and inflammation inside the eye, and oral corticosteroids. The use of these products depends on the underlying cause of the red eye. It is important to note that systemic corticosteroids should not be used if infectious diseases, such as fungal infections, the tick borne diseases, and toxoplasmosis, are the source of the redness.

An Elizabethan collar may be applied to prevent rubbing or pawing at the eye.

A topical antibiotic may be administered to treat or prevent infection.

Lubricant eye drops or ointment are sometimes given to protect the surface of the eye or to treat dry eye conditions.

Swollen tissues may respond to warm, wet compresses.

Other treatments may be administered, depending upon the underlying cause.

Home Care

Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up is important and may include the following:

Administer prescribed medications as directed and alert your veterinarian if you are experiencing problems treating your pet.

Ensure that your pet does not rub at the eye and cause more serious injury. If an Elizabethan collar is provided, have your pet wear it at all times.

Observe the eye closely. Signs that may indicate a worsening condition include more obvious redness, increased or altered discharge, pain or loss of vision. Blindness in just one eye may not be obvious because the animal may behave normally when only one eye is affected.

In-depth Information of Red Eye in Dogs

It is important to differentiate whether the enlargement of the blood vessels that cause an eye to appear red represent superficial or internal inflammation. Superficial inflammation often arises with surface irritation or infection. Internal inflammation is inherently more serious in that it involves deeper structures within the eye. Deep inflammation is more often associated with diseases that threaten vision.

Causes of Red Eyes in Dogs

Conjunctivitis is one of the more common causes of red eye in dogs. It may occur when the eye becomes exposed to environmental irritants (dust, smoke, cleaning agents, and chemicals), when the eye is dry, or when the lids do not protect the eye properly.

Conjunctivitis can also occur in association with allergies, skin diseases and other ocular diseases, such as eyelid deformities and diseases of the third eyelid.

Blepharitis is inflammation of the eyelids. Blepharitis can be part of a more widespread skin inflammation or may only involve the eyelids. Causes are numerous and include allergies, parasitic, fungal or bacterial infections, and certain immune diseases. Blepharitis usually also causes inflammation of the adjacent conjunctiva.

Inflammatory diseases of the third eyelid may also cause the eye to be red. See the related article on Protrusion of the Third Eyelid in the dog.

Keratitis is inflammation of the cornea. With keratitis, the blood vessels of the conjunctiva and sclera may be enlarged, and blood vessels may migrate from these tissues into the cornea. In general, keratitis is a more serious finding than conjunctivitis. Keratitis may be accompanied by ulceration or opacification of the cornea.

Anterior uveitis refers to inflammation of the inner vascular layer of the eye, including the colored iris and related structures. This is a serious and potentially vision-threatening disease. Uveitis may indicate that your dog has a systemic disorder that involves other organs within the body.

Glaucoma is an increase in intraocular pressure or pressure within the eye. Glaucoma is diagnosed by measurement of intraocular pressure with a special instrument called a tonometer. Glaucoma is sometimes a painful disease and may also be associated with anterior uveitis.

Infections, inflammation and tumors behind or around the eye, in the nose or face may also cause an eye to become red.

Diagnosis In-depth

Veterinary care includes diagnostic tests to determine the underlying cause of the red eye and guide subsequent treatment. Your veterinarian will do a complete medical history and physical examination to determine if the problem involves only the eye(s) or whether other changes are present in the animal.

A complete ophthalmic examination is required to determine the source of the redness and whether it involves inflammation of the external structures of the eye or the internal structures. Your veterinarian may refer your dog to a veterinary ophthalmologist for further evaluation using specialized instrumentation. The following tests may be performed during the eye examination:

Schirmer tear test to measure tear production

Fluorescein staining of the cornea to check for ulcers

Tonometry to measure the pressure within the eye

Examination of the interior of the eye under magnification

Taking scrapings of inflamed tissues (such as conjunctiva and cornea) for cytologic studies to determine the type of inflammation present

Examination of scrapings of the eyelids to look for parasites

Submission of samples for culturing bacteria and other agents

Biopsy of masses around the eye

If uveitis is the suspected diagnosis or if your pet appears unwell, then further tests are indicated to identify diseases that are systemic (involve other systems). Common tests include a complete blood count, biochemistry profile, serum tests for tick borne diseases, systemic fungal infections, and toxoplasmosis, and possibly X-rays of the chest and abdomen.

Treatment In-depth

Exact treatment requires establishment of a diagnosis. The following may be necessary:

An Elizabethan collar may be applied to protect the eye. Ocular inflammation may be irritating and pets can cause more serious injuries to their eye if they scratch it with their paws or rub it against carpet or furniture.

Infectious agents can be the cause of conjunctivitis or may worsen ocular inflammation. Therefore, your veterinarian may prescribe a topical antibiotic to treat or prevent infection.

Lubricant eye drops or ointments may be prescribed to reduce the dry feeling associated with some surface eye inflammation, or to treat any deficiency in the watery tears (dry eye).

Numerous topical anti-inflammatory preparations can be used to diminish inflammation (redness) in the eye. It is important to reiterate that although they may make the eye appear better, these treatments are non-specific and do not replace treatment of the inciting cause. They can also exacerbate a pre-existing condition or lead to other complications. They should be instituted only upon direction of your veterinarian.

Topical corticosteroids are the most commonly used class of anti-inflammatory agents for non-infectious forms of conjunctivitis, keratitis and anterior uveitis.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are a second class of anti-inflammatory drugs, and may be used sometimes in the presence of certain infections.

Topical antihistamines may be tried to control inflammation associated with allergies, but they frequently contain other products (vessel constricting agents) that can be irritating to animals. 

Occasionally systemic anti-inflammatory medications are used in conjunction with topical medications. These include antihistamines for the treatment of allergic conditions, oral NSAIDs to alleviate pain and inflammation inside the eye, and oral corticosteroids. The use of these products depends on the underlying cause of the red eye. It is important to note that systemic corticosteroids should not be used if infectious diseases such as tick borne diseases or fungal infections are the source of the redness.

Swollen tissues may respond to warm, wet compresses.

Other treatments may be administered, depending upon the underlying cause.