Schirmer strip wetting length varies by commercial manufacturer

Abstract

Objective To determine whether wetting length of Schirmer tear test (STT) strips varies by commercial manufacturer of test. Animals Studied Ten normal female beagle cross‐breed dogs. Procedures Schirmer tear test strips from four commercial manufacturers were used to assess wetting lengths in‐vitro when exposed to a set volume of water over 1 minute. Digital photography was used to assess the total surface area of Schirmer strips from each manufacturer. Schirmer tear test type 1 was performed on normal dogs over 1 minute with STT strips from the same four commercial manufacturers in a randomized crossover design. ANOVA was used to detect differences between strips from different manufacturers. Results Significant differences in wetting length were found between STT strips from different manufacturers in‐vitro (P < .0001) and in‐vivo (P < .0001). STT wetting lengths for the in‐vitro experiments (mean ± SD) were 21.2 ± 0.8 mm (Amcon Laboratories), 27.8 ± 2.7 mm (Merck Animal Health), 30.0 ± 1.7 mm (HUB pharmaceuticals), and 31.5 ± 2.3 mm (Gulden Ophthalmics). STT wetting lengths for the experiments in live dogs (mean ± SD) were 17.5 ± 3.4 mm (Amcon Laboratories), 24.8 ± 3.9 mm (Merck Animal Health), 26.5 ± 3.7 mm (HUB pharmaceuticals), and 24.0 ± 3.9 mm (Gulden Ophthalmics). The surface area of STT strips were found to vary between different manufacturers. Conclusions Schirmer tear test type 1 results in dogs are affected by choice of STT strip commercial manufacturer. It is proposed that guidelines are created for the standardization of future STT strip production.

Influence of Schirmer strip wetness on volume absorbed, volume recovered, and total protein content in canine tears

“…However, it is possible the frequent collection of tears (10 sessions/day) might have affected the aforementioned outcomes; sessions were separated by ≥1 h, providing ample time for tear fluid dynamics to be restored, 9 albeit the time it takes for baseline protein composition to be restored in canine tears is unknown. Another limitation is the focus on a single manufacturer of Schirmer strips; in a recent study, Lewin et al showed variability in wetness lengths among different manufacturers of Schirmer strips in dogs, 10 and the same may be true for the outcomes evaluated in the present study. The study also focused on a single canine breed (beagles) with healthy eyes.…”

Pre-analytical sample handling effects on tear fluid protein levels

“…García-Porta et al found that there is also a difference in weight between different strips and that thicker strips have a slower migration, but more fluid is taken up 9 . Lewin et al demonstrated significant differences in wetting length between strips from different manufacturers 20 . Variability between manufacturers is important in tear fluid research (when normalizing protein results for migration lengths) and even more important when using migration lengths as a measure of tear production in regular care (DED diagnosis, monitoring) and in (multicenter) clinical trials.…”

A review of diagnostic tests for qualitative and quantitative tear film deficiency in dogs

“…There are several factors that can influence STT‐1 results and should be accounted for when this diagnostic test is performed in dogs, including: manufacturer of Schirmer strip, position of the strip in the eye, skull conformation, age, body weight, time of day, ambient humidity/temperature, endocrinopathies (e.g., diabetes mellitus), ocular surgeries (e.g., phacoemulsification, transscleral cyclophotocoagulation, excision of third eyelid), medications (e.g., atropine, sulfonamide), sedation, general anesthesia, and hospitalization in intensive care units 5–9,29,35–62 . The reference values in normal dogs vary from 18.89 ± 2.62 to 21.7 ± 4.9 mm/min 5,37,63–65 .…”