Evaluating the aqueous portion of tears in shih tzu dogs: comparing Schirmer tear test 1 with tear meniscus height

ABSTRACT The aqueous portion of the tear film has been characterized as an essential structure for ocular surface health. Among various assessment tests, some measure the aqueous portion, such as Schirmer Tear Test 1, Meniscometry using a strip, and the test to determine Tear Meniscus Height (TMH). Conversely, few studies have specifically evaluated tear meniscus height, especially those utilizing ocular surface analyzers. Therefore, the aim of this study was to comparatively evaluate the results obtained from employing Tear Meniscus Height (TMH) using an Ocular Surface Analyzer and Schirmer Tear Test 1 (STT-1) in Shih Tzu dogs. To achieve this, the eyes of 18 brachycephalic Shih Tzu dogs of both sexes and varying ages were assessed and compared. The results revealed that the TMH for the right eye was 0.59±0.29mm, and for the left eye was 0.88±0.27mm; p=0.0135. For STT-1, it was found that the right eye had a value of 19.06±4.87mm/min, and the left eye had a value of 23.11±4.80mm/min; p=0.0238. Furthermore, the Pearson correlation test applied between TMH and STT-1 yielded the following results for the right eye (r=0.601; p=0.008) and the left eye (r=-0.032; p=0.8979). The TMH shows potential as an alternative to STT-1 for evaluating the aqueous component of tear film in a similar manner. However, further research is warranted, particularly for establishing reference values for TMH and conducting a comprehensive comparison between STT-1 and TMH. This research is especially important for gathering information that can contribute to the understanding of ophthalmic and systemic conditions that directly influence the physiological composition of tears. Critical for establishing the values obtained when measuring the canine lacrimal meniscus using different techniques is the consideration of associated functional factors.