Schirmer tests are often used to determine the volume of aqueous tear production.
There are several types of Schirmer tests, and various techniques are employed in performing the tests. There is disagreement on which techniques produce the best results.
In 1903, Dr. Otto Schirmer, a German ophthalmologist, described three methods of measuring aqueous tear production. In each, strips of blotting paper were hung over the lid margin and, after a time, the wetted length of the paper was measured. The three methods were:
1. Strips of blotting paper were inserted for five minutes
2. The eyes were anesthetized before inserting the strips, and the nasal passages were stimulated.
3. Same as #2, except gazing at the sun replaced nasal stimulation
After the strip of paper is placed in the eyes, the eyes are held closed for several minutes. Alternatively, the head is held straight, and the patient is instructed to look up while blinking normally.
Variability in test results is considerable, and may be due to many factors including: the patient’s discomfort; trauma to the cornea or conjunctiva; variations in placing the strips of paper; uneven tear absorption by the paper strips; residual wetting by anesthetizing drops; variations in wetting patterns; stimulation of the lid margin; and the inability to control reflex tearing.
Some doctors have standardized Schirmer tests as follows:
- Type 1, without anesthetic
- Type 1, with anesthetic
- Type 2, with nasal stimulation
Some doctors use Type 1 tests to measure both reflexive tearing, the kind of tears produced when something gets in the eye, and basal tearing, the normal wetness of the eye. Type 1 tests are also often used in the diagnosis of Sjogren’s syndrome. Type 2 tests are used to measure reflex tearing. To stimulate the nasal passages, cotton swabs are placed into the nostrils to stimulate reflexive tearing. Some doctors push the cotton swabs further back into the nasal passages.
Some doctors perform the test several times in a row. A new strip of paper is placed inside the lower lid each time for a set amount of time, usually five minutes. Performing Type 1 (with anesthetic) tests several times in succession reduces the likelihood of measuring reflexive tearing or residual wetness from the numbing drops.
Generally speaking, Schirmer Type 1 values greater than 10 are considered normal. Anything below 10 indicates aqueous deficiency.
The Type 1 test with anesthetic was introduced in 1975. Even with the introduction of the Type 1 test with anesthetic, which produces a better measure of basal tears, Schirmer tests are often performed incorrectly — some doctors continue to rely only on the Type 1 test without anesthetic, which essentially measures only reflex tearing.
Reference
The challenge of dry eye diagnosis
Savini G, Prabhawasat P, Kojima T, Grueterich M, Espana E, and Goto E.
Clinical Ophthalmology
2008 Mar; 2(1): 31–55.
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