The Schirmer Tear Test: What is It?
The Schirmer tear test is a simple, quick, and non-invasive diagnostic test used to evaluate the production of tears in the eyes. It is primarily used to diagnose dry eye syndrome (keratoconjunctivitis sicca) and to assess tear production in various ocular and systemic conditions. Since adequate tear production is crucial for maintaining the health of the cornea and conjunctiva, the Schirmer test plays an essential role in ophthalmic diagnostics.
Purpose of the Schirmer Tear Test
Tears serve multiple vital functions for the eye, including lubrication, protection against infection, and providing essential nutrients to the cornea. The tear film comprises three layers: the lipid layer (produced by the meibomian glands), the aqueous layer (produced by the lacrimal glands), and the mucous layer (produced by goblet cells in the conjunctiva). Deficiencies in any of these layers can lead to symptoms of dry eye and ocular surface disease.
The Schirmer Tear Test is used to measure the aqueous component of tear production, which is the largest portion of the tear film and is crucial for maintaining corneal hydration and integrity. The test is a key tool in diagnosing:
1. Dry eye syndrome: A condition caused by decreased tear production or poor tear quality, resulting in irritation, inflammation, and damage to the eye surface.
2. Sjögren’s syndrome: An autoimmune disorder where the body’s immune system attacks its own moisture-producing glands, leading to dry eyes and dry mouth.
3. Other conditions: It is also used to monitor tear production in patients with blepharitis, keratitis, or those undergoing certain treatments like radiation therapy, which may affect tear production.
Types of Schirmer Tear Tests
There are two primary variations of the Schirmer Tear Test, each serving slightly different diagnostic purposes:
1. Schirmer I Test (Without Anesthesia)
This version of the test measures total tear production, including both basal and reflex tears. Basal tears are continuously produced to maintain eye moisture, while reflex tears are produced in response to irritation or stimulation (such as the sensation of the paper strip in the eye).
Procedure: No anesthesia is applied, and the strip is inserted as described above. The lack of anesthesia allows both basal and reflex tear production to be measured.
Interpretation: Normal tear production typically wets 10-15 mm of the strip after 5 minutes. If the wetting is less than 5 mm, it indicates inadequate tear production, suggestive of dry eye syndrome or related conditions.
2. Schirmer II Test (With Anesthesia)
In the Schirmer II test, topical anesthetic eye drops are applied to the eye before the strip is inserted. This eliminates the irritation from the paper strip, allowing for measurement of basal tear production only (since the anesthetic prevents reflex tearing).
Procedure: After applying the anesthetic, the strip is inserted, and the test is conducted as usual. The test measures only the basal tear secretion, which reflects the eye’s natural ability to produce tears without external stimulation.
Interpretation: In normal conditions, basal tear production should wet approximately 10 mm of the strip after 5 minutes. A measurement below 5 mm suggests a deficiency in basal tear production and may indicate more severe forms of dry eye.
How the Test is Performed?
The Schirmer tear test is performed by an ophthalmologist or optometrist. The procedure for the Schirmer tear test is straightforward and involves the following steps:
1.) Preparation: Before the test, the patient should remove any contact lenses and avoid using eye drops for at least 24 hours. The test should be performed in a quiet and well-lit room.
2.) Placement of the Test Strips: The test strips used in the Schirmer tear test are small strips of filter paper that are about 5mm wide and 35mm long. The strips are folded at the designated line and then inserted under the lower eyelid, with the shorter end pointing towards the nose. The strips should be placed in both eyes at the same time.
3.) Waiting Period: After the strips have been inserted, the patient is instructed to close their eyes and wait for five minutes. During this time, the strips absorb tears that are produced by the eye.
4.) Removal of the Test Strips: After five minutes have elapsed, the strips are removed from the patient's eyes. The amount of moisture on the strips is then measured to determine the amount of tears that were produced.
5.) Reading the Results: The test strips are examined and the length of the wet portion of the strip is measured in millimeters. A measurement of less than 10mm is indicative of dry eye syndrome. Measurements between 10mm and 15mm may indicate borderline dry eye, while measurements over 15mm are considered normal.
The Schirmer tear test is a simple and safe procedure that can be performed by a healthcare professional in an office setting. It is non-invasive and typically does not cause any discomfort to the patient. However, patients with sensitive eyes or eye infections may experience mild discomfort during the test.
Interpretation of Results
The results of the Schirmer tear test are interpreted based on the length of the wet portion of the strip and are used to diagnose and manage dry eye syndrome.
Interpretation of Schirmer Tear Test Results:
Normal Results
A measurement of over 15mm of wetting on the Schirmer tear test is considered normal. This indicates that the eyes are producing an adequate amount of tears to keep the eyes moist and comfortable. Normal results do not rule out other causes of dry eye, and further testing may be needed.
Borderline Results
A measurement between 10mm and 15mm of wetting on the Schirmer tear test is considered borderline. This suggests that the eyes may not be producing enough tears, and the patient may experience some symptoms of dry eye. Additional tests may be needed to confirm the diagnosis.
Abnormal Results
A measurement of less than 10mm of wetting on the Schirmer tear test is considered abnormal. This indicates that the eyes are not producing enough tears, and the patient may have dry eye syndrome. Further testing may be needed to determine the underlying cause of the condition.
Interpreting the results of the Schirmer tear test is only one part of the diagnostic process for dry eye syndrome. A comprehensive evaluation of the patient's symptoms, medical history, and other diagnostic tests may be needed to confirm the diagnosis and develop an effective treatment plan.
It is important to note that the Schirmer tear test is not always accurate, and false positive or negative results may occur. Additionally, the test may not be helpful in cases of evaporative dry eye, a condition in which the tears evaporate too quickly due to an issue with the oily layer of the tear film.
Clinical Applications of the Schirmer Tear Test
The Schirmer Tear Test has a wide range of applications in ophthalmology and beyond. Some of the most common uses include:
A. Diagnosis of Dry Eye Syndrome
Dry eye syndrome is a common condition that can cause discomfort, visual disturbances, and even damage to the ocular surface if untreated. Patients with dry eyes typically report symptoms such as burning, redness, a gritty sensation, and blurred vision. The Schirmer test helps quantify tear production, guiding diagnosis and treatment decisions.
- Mild Dry Eye: Tear production is between 5-10 mm.
- Moderate to Severe Dry Eye: Tear production is below 5 mm, indicating more significant tear deficiency.
B. Sjögren’s Syndrome
Sjögren’s syndrome is an autoimmune disorder characterized by dry eyes and dry mouth due to the immune system’s attack on moisture-producing glands. The Schirmer test is an important diagnostic tool for detecting reduced tear production in patients with Sjögren’s syndrome, often in combination with other diagnostic tests like salivary gland biopsies and serological markers.
C. Pre- and Post-Operative Assessment
Patients undergoing certain eye surgeries, such as LASIK or cataract surgery, may be evaluated with a Schirmer test to assess baseline tear production. Some procedures can exacerbate dry eye symptoms, and the Schirmer test helps identify individuals at risk of post-surgical dry eye complications.
D. Contact Lens Fitting
Contact lens wearers are at risk of developing dry eye due to the disruption of the tear film by the lens. The Schirmer test is sometimes used to assess tear production in individuals considering contact lenses to ensure that their tear production is sufficient to support comfortable lens wear.
E. Radiation Therapy
Patients undergoing radiation therapy for head and neck cancers may experience reduced tear production due to damage to the lacrimal glands. The Schirmer test can help monitor tear function in these patients, allowing for timely interventions to manage dry eye symptoms.
Treatment for Dry Eye Syndrome
Treatment for dry eye syndrome will depend on the underlying cause and severity of the condition. Common treatments for dry eye syndrome include using artificial tears, using warm compresses to stimulate tear production, using a humidifier to increase moisture in the air, and avoiding environmental factors that can contribute to dry eyes, such as wind and low humidity. In more severe cases, prescription medications or procedures may be necessary to improve tear production and manage symptoms.
Limitations of the Schirmer Tear Test
Although the Schirmer test is widely used, it has certain limitations:
1.) Subjectivity and Variability: Results can vary depending on the patient’s environment, stress levels, or even the time of day. Variability between measurements can affect the reliability of the test.
2.) Discomfort: The insertion of the filter paper can cause irritation, triggering reflex tearing and potentially skewing results, particularly in the Schirmer I test. Patients may also find the test uncomfortable.
3.) Inability to Measure Tear Quality: The Schirmer test measures tear quantity but does not assess tear quality or the composition of the tear film. Deficiency in the lipid or mucous layers of the tear film, which are critical to preventing tear evaporation, cannot be detected by this test.
4.) Not Specific for Dry Eye Causes: While the test identifies reduced tear production, it does not distinguish between different causes of dry eye, such as evaporative dry eye (due to meibomian gland dysfunction) versus aqueous-deficient dry eye.
Summary
Schirmer tear test is a useful tool in the diagnosis of dry eye syndrome and can help healthcare providers determine the best course of treatment for their patients. If you are experiencing symptoms of dry eyes, such as discomfort, burning, itching, or redness, it is important to seek medical attention and undergo appropriate testing to determine the underlying cause of your symptoms and develop an effective treatment plan.
