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

Abstract

PurposeAssess aqueous tear production when measured with the dogs' eyelids open or closed.MethodsThirty healthy dogs (15 Shih Tzus, 15 Labrador retrievers) were recruited. With the order of testing randomized for each dog, two sessions (separated by 30 min) of STT‐1 testing were performed with the dogs' eyelids closed or open. Schirmer strip wetness (every 10 s for 60 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.ResultsSTT‐1 values were significantly higher in closed versus open eyes in Shih Tzus (18.6 ± 2.7 mm/min vs. 16.3 ± 2.5 mm/min; p = .002) and Labrador retrievers (21.6 ± 2.9 mm/min vs. 17.8 ± 3.2 mm/min, p < .001), findings that were also significant at times <60 s for either breed (p ≤ .004). Schirmer strips dislodged from six dogs with open eyelids and no dogs with closed eyelids. Maximal STT‐1 difference with closed versus open eyelids was 13 mm/min in Labrador retrievers and 7 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%).ConclusionsEyelids 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.