Cat Schirmer Tear Test — Key to Diagnosing Dry Eye and Interpreting Results

Eye HealthDiseasesMeongsiljang Veterinary Advisory Board

The Schirmer tear test for cats is a diagnostic method that measures tear production and is used to evaluate symptoms of dry eyes or excessive tearing. For an accurate diagnosis, it must be performed by a veterinarian.

What is the Cat Schirmer Tear Test?

A veterinarian inserting a Schirmer test strip into a cat's eye

The Schirmer tear test is an important diagnostic method that quantitatively measures tear production in cats. - Schirmer Test: A special paper strip is placed in the lower conjunctival sac (inside the lower eyelid) for one minute, and the length of the strip wetted by tears is measured. The normal range is approximately 15–20 mm/minute. - Checking for Tear Deficiency: Very low tear production may indicate dry eye (keratoconjunctivitis sicca, KCS). - Cat-Specific Considerations: Even healthy cats can show low values below 5 mm/minute, so diagnosis should not be based solely on test results. - Comprehensive Diagnostic Criteria: Therefore, a comprehensive evaluation is made by considering clinical signs along with other tests, rather than relying on a single test. - Veterinary Collaboration is Essential: Interpretation of test results requires professional judgment.

Main Causes of Abnormal Tear Production

Abnormal tear production in cats, particularly decreased tear production seen in dry eye (keratoconjunctivitis sicca), can result from various causes. - Immune-mediated diseases: Immune-mediated conditions that directly affect the lacrimal gland tissue are the most common cause. - Trauma, inflammation, or corneal damage: Injury or inflammation damaging the lacrimal glands or cornea can disrupt tear production. - Drug-induced effects: Certain medications, such as sulfonamides (sulfa drugs), etodolac, and atropine, may reduce or worsen tear production. - Congenital or genetic factors: Inherited or congenital conditions can lead to abnormalities in the tear film. - Neurological factors: Problems with the nerves that regulate tear secretion can also decrease tear production. - Tear drainage issues: Blockage of the nasolacrimal duct can prevent tears from draining properly, causing them to accumulate around the eyes.

An anatomical diagram showing the tear secretion structures in a cat's eye

Key Symptoms and Signs

When a cat’s tear production is abnormal, you may notice constant tearing and dampness around the eyes, or conversely, sticky discharge adhering to the eye area when tear production is insufficient. - Mucous discharge: In cases of keratoconjunctivitis sicca (dry eye), thick, sticky, mucus-like discharge often accumulates around the eyes, resembling crusty eye boogers. - Conjunctivitis and redness: The eyes may appear red and inflamed, and the cat may blink frequently or keep the eyes closed. - Signs of discomfort: The cat may repeatedly scratch or rub its eyes. If pain is present, the third eyelid (nictitating membrane) may protrude. - Corneal changes: If left untreated for an extended period, pigmentary keratitis (pigment deposition on the cornea) or corneal vascularization (new blood vessel growth) may develop. - Immediate veterinary care required: If these symptoms persist, consult a veterinarian for a proper diagnosis.

A Persian cat with darkened fur around the eyes due to tear stains

When Immediate Veterinary Attention is Necessary

If your cat is unable to open its eyes, has severely swollen eyes, is producing tears mixed with blood, or repeatedly scratches or rubs its eyes, immediate veterinary attention is necessary. These symptoms may indicate corneal damage, severe inflammation, infection, or blockage of the tear ducts. Delayed treatment can lead to vision loss, so early diagnosis is crucial.

Diagnostic Procedures and Testing Methods

Veterinarians use a combination of tests to comprehensively evaluate a cat’s eye condition. - Schirmer Tear Test: This basic test quantitatively measures tear production by recording how much moisture a paper strip absorbs over one minute. - Corneal Staining: A dye is applied to check for any damage to the cornea. - Lacrimal Duct Contrast Study: This procedure confirms whether tears are draining properly and identifies any blockages. - Blood and Hormone Tests: These help assess for endocrine or systemic diseases. - Imaging Studies: In complex cases, CT or MRI scans can be used to analyze the structure of the lacrimal system in detail. - Need for Multi-Step Evaluation: Accurately identifying the cause requires performing multiple tests together.

A veterinarian applying a fluorescent dye to a cat's eye.

Treatment Methods and Step-by-Step Management

Treatment is tailored to the underlying cause, with the primary goals of increasing tear production and protecting the cornea. - Stimulating tear production: Cyclosporine is a standard treatment for dry eye (keratoconjunctivitis sicca) because it stimulates tear production alongside its immunosuppressive effects. Tacrolimus may also be used. - Anti-inflammatory therapy: Topical corticosteroids may be used when necessary, but they are applied cautiously due to potential side effects such as delayed wound healing. - Tear film supplementation: Artificial tears or gel-based moisturizers are used to replenish the tear film and protect the cornea. - Long-term management: Most cases require consistent, lifelong eye drop administration and regular check-ups. Ongoing care is essential to prevent recurrence. - Surgical treatment: In severe cases involving lesions such as exposure keratopathy or ulcers, surgery to reduce the palpebral fissure (eyelid surgery) may be necessary. - Managing secondary infections: If a secondary bacterial infection is present, antibiotic eye drops may be used concurrently.

A veterinarian administering artificial tears to a cat’s eyes.

Home Care Points

Maintaining your cat’s eye health requires consistent daily care. - Daily eye cleaning: Gently wipe around the eyes with a soft cloth or specialized cleansing wipes. - Discharge management: Gently remove any crust or discharge to keep the area clean. - Nail care: Regularly trim your cat’s nails to prevent accidental scratches to the eyes. - Trimming facial hair: Keep hair around the eyes short to avoid obstructing tear flow. - Regular eye drops/medication: Consistently use prescribed artificial tears or medications without skipping doses. - Environmental hygiene: Minimize exposure to irritants such as dust, cigarette smoke, and perfumes.

A person gently wiping around a cat's eyes.

Breed-Specific Precautions and Prevention of Recurrence

Brachycephalic (flat-faced) cat breeds, such as Persians and British Shorthairs, are more prone to eye problems, including a higher incidence of corneal sequestrum, which is the deposition of black pigment on the cornea. Regular eye care and veterinary check-ups are essential for these breeds. Additionally, since normal cats can also show low values on Schirmer tear tests, test results must always be interpreted in conjunction with clinical symptoms. Ongoing management is necessary to prevent recurrence and progression.

Reviewed by a veterinarian

Dr. Tony — Punnawat Phongkittirak

Veterinarian

A veterinarian who majored in veterinary medicine at Khon Kaen University, Thailand, and completed the IVSA program at North Carolina State University in the United States. Drawing on clinical experience at animal hospitals, he works in the pet healthcare field and is dedicated to building a digital care environment that connects pet parents with veterinarians.

Frequently Asked Questions

Does the Schirmer test hurt?

Most cats tolerate the procedure relatively well. However, if a cat is in pain, it may evert its third eyelid (nictitating membrane), so we may use a topical anesthetic to properly examine the eye when necessary.

What problems can occur if the test results are low?

Low tear production may indicate dry eye (keratoconjunctivitis sicca), which can lead to corneal damage and pain. However, even healthy cats can show low values, so diagnosis is based on clinical signs in addition to test results, rather than relying on numbers alone.

How can I remove tear stains?

Gently wipe the area around your pet’s eyes daily with a soft cloth or special cleansing wipes. Avoid using regular wet wipes, as they can be irritating.

Can diet affect tear production?

There is limited evidence that pet food directly affects tear production. In fact, certain medications such as sulfonamides, etodolac, and atropine can reduce tear production, so please consult your veterinarian if your pet is currently taking any medications.

How often should Schirmer tear tests be performed?

Typically, the test is performed once when symptoms are present, or regularly as recommended by your veterinarian. If the condition recurs or is under treatment, periodic testing is necessary.

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References

[1] Esson, D.W. & Calvarese, S. (2022). Clinical Atlas of Canine and Feline Ophthalmic Disease, 2nd Ed. Wiley-Blackwell.

[2] Gelatt, K.N. et al. (2013). Veterinary Ophthalmology, 2nd Ed. Wiley-Blackwell.

[3] Ny, Y. et al. (2006). Medial canthoplasty for epiphora in dogs: a retrospective study of 23 cases. Journal of the American Animal Hospital Association, 42, 435–439.