Schirmer tear test-1 with open or closed eyelids: An evaluation in brachycephalic and nonbrachycephalic dogs.

Abstract

PURPOSE: Assess aqueous tear production when measured with the dogs' eyelids open or closed. METHODS: Thirty healthy dogs (15 Shih Tzus, 15 Labrador retrievers) were recruited. With the order of testing randomized for each dog, two sessions (separated by 30&#x2009;min) of STT-1 testing were performed with the dogs' eyelids closed or open. Schirmer strip wetness (every 10&#x2009;s for 60&#x2009;s) and number of time(s) the strip dislodged during testing were recorded in each eye. Preferred STT-1 method was surveyed via a global Listserv of the veterinary ophthalmology community. RESULTS: STT-1 values were significantly higher in closed versus open eyes in Shih Tzus (18.6&#x2009;&#xb1;&#x2009;2.7&#x2009;mm/min vs. 16.3&#x2009;&#xb1;&#x2009;2.5&#x2009;mm/min; p&#x2009;=&#x2009;.002) and Labrador retrievers (21.6&#x2009;&#xb1;&#x2009;2.9&#x2009;mm/min vs. 17.8&#x2009;&#xb1;&#x2009;3.2&#x2009;mm/min, p&#x2009;<&#x2009;.001), findings that were also significant at times <60&#x2009;s for either breed (p&#x2009;&#x2264;&#x2009;.004). Schirmer strips dislodged from six dogs with open eyelids and no dogs with closed eyelids. Maximal STT-1 difference with closed versus&#xa0;open eyelids was 13&#x2009;mm/min in Labrador retrievers and 7&#x2009;mm/min in Shih Tzus. Survey results from 275 veterinarians showed STT-1 performed with "closed eyelids" (38.5%), "open eyelids" (26.9%), or "never paid attention, sometimes closed, sometimes open" (34.6%). CONCLUSIONS: Eyelids status (closed or open) during STT-1 testing had a significant impact on aqueous tear secretion in brachycephalic and nonbrachycephalic dogs, highlighting the importance of consistency when repeating STT-1 in a canine patient. STT-1 differences are likely due to sustained reflex tearing throughout the test duration when the dogs' eyelids are closed.