Cat Health

Cat Runny Eyes: How to Discover the Cause

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With their beautiful, uniquely colored irises and vertical pupils, a cat’s eyes do not seem to bear much resemblance to yours.

After all, cats can see in the dark and have that odd reflective glow at night.

However, there are not many structural differences between a cat’s and a human’s eye. Cats can suffer from the same eye ailments as any person.

Cat runny eyes occur from several causes, many of which may be familiar from your own experiences.

When you have a cold or are ill, your eyes will water.

Cats, likewise, suffer watery eyes from upper respiratory infections and other viruses. They can also experience runny eyes from allergies, ocular foreign bodies, and trauma, like you or I.

We cover the more common causes of runny eyes in cats that affect the outer tissues or conjunctiva as well as the inner structures. You will read about the signs, a few diagnoses, and some treatments

How do you categorize watery eyes in cats?

Watery eyes for cats occur either from contagious diseases, most commonly viral, or noninfectious issues.

Noninfectious causes of runny eyes run the gambit from irritants like hairs to trauma, allergies, and hereditary diseases.

The other categorization of cat runny eyes is whether your pet is producing too many tears or there is an obstructive process going on. For example, dry eye can paradoxically cause excessive tearing.

Your cat does not produce enough lubrication, so the resulting discomfort and irritation cause a flood of tears to compensate.

Swelling and redness of the conjunctiva, also known as conjunctivitis or pink eye, obstructs normal tear flow and will cause swelling. Viruses cause runniness as secretions increase from the nose and eyes.

You can classify cat runny eyes based on signalment

You may be unfamiliar with the term signalment. A cat’s signalment refers to her identifying information such as age, breed, and gender.

This information can be as helpful as the history in determining why your pet may have runny eyes.

Whether your cat is a male or female may not be very relevant in watery eye symptoms, but his or her breed can be very instrumental.

Flat-faced or brachycephalic breeds usually have watery eyes because of the shape of their faces.

Age is also an important factor as young cats may be more susceptible to viruses and older cats are more likely to experience dry eyes.

Why does your cat have runny eyes?

There are many causes of runny eyes in cats. It is easy to think of them in several different broader categories.

Structural Causes

Cats with round heads and flat faces are likely to have watery eyes. Usually, tears would drain into a cat’s nose. Since brachycephalic cats do not have a significant muzzle, tears will drain down their faces.

Moreover, the shape of their heads makes for shallow eye sockets, allowing tears to frequently spill across the lids. Since the eyes protrude, their chronic exposure also leads to chronic inflammation and excessive tearing.

Persian cats with their exaggerated flat-faced and dome-headed features are particularly vulnerable to runny eyes, but there are other brachycephalic breeds.

  • Exotic shorthair
  • Scottish Fold
  • Himalayan
  • Ragdoll
  • Burmese

This video shows the Persian cat confirmation with the dome-shaped head, flat face, and prominent protruding eyes.

A show cat with daily grooming will not show the excessive tearing that is a frequent trait of the breed.

Inflammatory

If the eyes become inflamed, they cause blepharospasm (excessive blinking, spasm of the eyelids) and copious tears.

Viruses

Viruses that cause upper respiratory infections are among the most common causes of cat runny eyes.

Concurrent sneezing, nasal discharge, and fever further support a diagnosis of feline upper respiratory infection or cat flu.

Often infected cats will have conjunctivitis that leads to even more drainage. As the viral infection progresses, opportunistic bacteria can cause the ocular drainage to become thick and pus-like.

Feline Calicivirus

Calicivirus usually affects the nose and throat of cats and leads to secondary conjunctivitis. Common in kittens, calicivirus infections will present with both a runny nose and eyes.

Although the discharge starts out clear, it can often become green-tinged or yellowish over a few days.

The virus is highly contagious and usually airborne, traveling several meters with sneezing and coughing.

Moreover, infected cats can shed the virus for two to three weeks, and the organism can live on exposed surfaces for at least several days.

The disease is usually respiratory, but some strains may affect the joints or other organs. Kittens suffer more severe symptoms than adults.

An important source of infection is the carrier cat which sheds the virus with no outward signs. Some cats become carriers for a few months after their apparent recovery.

A definitive diagnosis is through viral isolation or identification via specialized laboratory methods, but most veterinarians advise treatment based on presumption.

The persistence of symptoms or suspicion of other systems being involved may trigger your veterinarian to perform other tests such as radiographs and blood chemistries.

If the virus spreads to the lungs, your vet will likely prescribe a transtracheal wash to nail down the diagnosis and design a more effective treatment. Otherwise, treatment is usually supportive and outpatient.

Eye drops can make your cat more comfortable, and oral antibiotics may help prevent the secondary onset of a bacterial infection in kittens.

Herpesvirus

Feline rhinotracheitis is like calicivirus in many ways. It affects the nose and throat, causing an upper respiratory infection that can be particularly severe in kittens. However, the virus only lives in secretions.

Once these dry on exposed surfaces, the organism dies. Therefore, herpes viruses only live for a few hours in the environment.

Herpesvirus-1 is the most common cause of conjunctivitis in cats. It also causes inflammation of the cornea and decreased tear production or dry eye, both setting the infected cat up for corneal ulcers.

Eye drops are helpful to reduce inflammation and treat ulcers to prevent permanent scarring.

Infected cats usually become carriers for life but only shed the virus if it reactivates secondary to stress or another disease.

Like many viruses, a herpes diagnosis is presumptive but can be definitive through polymerase chain reaction amplification (PCR test).

Treatment, again, is supportive and usually outpatient, with aggressive intervention in the case of eye ulcers. L-lysine may have antiviral effects particularly helpful against herpes viruses. Fluorescein eye stains are crucial to diagnosing corneal ulcers.

Bacteria

Often, bacterial infections only invade a cat’s eye secondary to a virus, especially upper respiratory diseases.

Staphylococcus and Streptococcus are frequent culprits when you are dealing with a URI in a kitten.

Clustered and sphere-shaped bacteria, respectively, these organisms cause clear ocular and nasal secretions to become yellowish and purulent.

Chlamydophila felis is one of the rare bacterial causes of primary conjunctivitis in cats. Cats only contract the disease through direct contact, and the organism is species-specific.

Easily confused with a viral upper respiratory infection, Chlamydophila will cause red and inflamed tissues surrounding the eyes, swollen eyelids, and nasal and ocular discharge. It usually strikes kittens between five and twelve weeks old and does not exhibit the respiratory symptoms of the other URIs.

Medical professionals can definitively diagnose Chlamydophila with a bacterial culture.

Usually, treatment is presumptive with antibiotic eye drops and possible oral antimicrobials. Rule outs are allergies, a foreign body, mycoplasma, and viral upper respiratory infections.

Although sometimes suspected to be a primary cause of bacterial conjunctivitis in cats, Mycoplasma felis is most often a secondary pathogen.

It contributes to watery eyes, conjunctival swelling, inappetence, fever, and oral ulcers associated with viral respiratory infections.

Other viruses that can cause watery eyes in cats are feline leukemia, feline infectious peritonitis (FIP), and feline immunodeficiency virus (FIV). None of these are associated with upper respiratory infections.

The systemic illness causes the infected cat’s eyes to run. Excessive tearing results from the inflammation of the inner structures (uveitis) of the eye rather than the conjunctiva.

Fungus

Cryptococcus is a fungus that causes anterior uveitis or inflammation of the middle part of the eye.

As opposed to conjunctivitis, signs of uveitis are redness, tearing, and cloudiness. You may or may not also notice squinting. Your vet can diagnose the fungus through an antigen test, although the organism can be difficult to detect if it is localized.

Allergies

Allergies are another frequent cause of cats producing too many tears. Environmental allergies cause redness, swelling, and itching of the tissues around the eyes, leading to blepharospasm and tearing.

Cats may experience allergic reactions to different species of grasses and flowers, pollen, household cleaners, fungus or mold, dust, or even prescription eye drops.

Foreign Bodies

Cats have prominent eyes, but they are well-protected in most felines with high cheekbones and the deep-set of the socket. However, foreign particles can enter the eyes and range from dust to grass.

Most of the time you will notice a day or two of excessive tearing and possible blepharospasm and no visit to the veterinarian will be necessary.

However, other common substances such as plant material, seeds, and dirt can cause severe irritation to the conjunctiva.

Your cat may not be able to flush out all foreign bodies on her own. If your cat has eye issues that persist beyond 24 hours, you should take her to a veterinarian. Diagnosis is via a good ophthalmological exam with a special light.

Your veterinarian will flush the eye with saline and treat any associated injuries that may occur. Occasionally, anesthesia and minor surgery are required to remove an object from the eye.

If the foreign body causes a corneal ulcer or scratch, your veterinarian will address that as well.

Afterward, the goal will be to resolve the resulting inflammation. Some cats need an Elizabethan collar to prevent them from further injuring the eye through rubbing and scratching.

Trauma

Trauma to a cat’s eyes can take many forms. Flat-faced cat breeds are vulnerable to physical trauma because of the protruding nature of their eyes.

  • Cat fights – Scratch, puncture
  • Hit by car – Head injury, socket disruption, eye contusions
  • Chemical – Abrasions, burns, corneal ulcers
  • Eyelid injury – Lacerations, scrapes

There are conditions that cause cat runny eyes

  • Follicular conjunctivitis – Bump on conjunctiva that causes excess tearing and is secondary to inflammation; often seen with upper respiratory infections
  • Corneal sequestrum – An area of the cornea dies and shows up as a black spot; Causes tearing and redness; Most common in Persians and Himalayans
  • Eosinophilic keratoconjunctivitis – A form of dry eye caused by a proliferation of cell types know as eosinophils; Eosinophils also proliferate in allergic reactions; Cause squinting, redness, and runny eyes
  • Keratoconjunctivitis sicca – Dry eye whereby eyes do not produce enough aqueous tears; Cornea becomes excessively dry and may develop ulcers; Cat develops mucoid discharge, redness, and irritation; Diagnosed by Schirmer tear test; Watery eyes does not rule this condition out

What are examples of causes of cat runny eye?

This video is a good synopsis of several common causes of watery eyes in cats. You can see how some problems cause conjunctivitis or inflammation of the outer tissue.

Anterior uveitis, affecting the structure behind the cornea, exhibits cloudiness. You can also visualize the appearance of corneal ulcers

I have worked in the veterinary field with dogs and cats for several years.