What is a Schirmer's test? Is it reliable?

(posted apr 2003)

Schirmer’s test is meant to determine your tear production. It is done with a long narrow sterile strip of special paper which has a pre-printed measuring line (in milligrams), which is placed just inside the lower lid margin for 3-5 minutes. The paper soaks up tears as they are produced and the doctor reads how many milligrams of tears each eye produces during the designated time period by seeing how far down the paper strip they reach. A reading of less than 15mm can indicate low tear production and a reading of less than 10mm is definitely indicative of a problem.

HOWEVER, this test is often not done properly, and when it is not done properly it almost always OVER-estimates your tear production.

First, your eye needs to be anaesthetised. Normally, if someone sticks a foreign object in your eye, your eye will react to it by producing what is called reflex tears. It’s your eye’s way of washing itself out. These tears are quite different from your normal tears. If your eye is not properly anaesthetised, the nerve endings will send an SOS to the brain "Pain! Probably foreign object! Make tears! FAST!" and, presto, lots of tears, but that isn’t really telling you anything useful about your normal tear production function. So, the eye needs to be anaesthetised, and you should wait about 5 minutes for the anaesthetic to take full affect.

Second, after the drop has taken effect, the lower part of the eye needs to be blotted. This sounds like a very simple thing, but all too often the first 10mm of the strip soaks up anaesthetic, resulting in an excellent Schirmer’s result that... just doesn’t happen to be particularly accurate.