Schirmer Tear Testing
In our animal patients, 5 minutes is typically not tolerated and a modified or Schirmer tear test (STT) is performed without anesthesia and for only 60 seconds. This measures reflex tearing in animals.
Most sources state that the reference range of Schirmer tear test (STT) values is 15 to 20 mm/min in most species. But when considering the STT results, you must consider several factors. First, older dogs frequently have STT values lower than 15 mm/min but have no clinical signs of keratoconjunctivitis sicca (KCS). In addition, some animals, especially cats, have very low values (many are 0) when they are stressed in a clinic environment yet have no clinical signs of KCS. Thus, we need to account for whether reduced tear production is meaningful based on two factors: 1) a lower-than-15 mm/min STT value and 2) clinical signs of KCS.