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In a Schirmer test, the eye is usually anaesthetised to prevent reflex tearing and then given several minutes for the anaesthetic to take effect. Excess tears and the anaesthetic are blotted. A tiny strip of filter paper is placed in the patient's eye just under the lower lid. After five minutes, the length of the paper that the tears have stained is measured. The greater the distance, the higher the natural tear production. A score of 15 or more indicates normal tear production.
Schirmer's test is often performed (or if not, should be performed) during the screening process for laser eye surgery in order to help determine whether there is a pre-existing aqueous tear deficiency which may place the patient at increased risk of severe dry eye syndrome as a complication.
There is much debate about the usefulness and accuracy of the Schirmer test, and there are many variations on the method for performing it. In general it can probably be assumed that while a Schirmer may produce a false "normal" result, a low score on a Schirmer test is a good indication that there is in fact an aqueous deficiency.
It should also be noted that many patients with symptoms of dry eye syndrome may have a normal aqueous tear production and normal Schirmer score. In such cases their symptoms may be caused by an unstable tear film. |
