Tear clearance rate in dogs: Measurement using anterior segment optical coherence tomography

Abstract

Abstract Objective The tear clearance rate (TCR), determined using anterior segment optical coherence tomography (AS‐OCT) images, and its correlation with ocular surface parameters, including blink rate, Schirmer tear test‐1 (STT‐1) and tear film breakup time (TFBUT), were evaluated. Animals studied Left eyes of 20 client‐owned dogs with no ocular disease symptoms. Procedures The tear meniscus height (TMH) was evaluated using AS‐OCT images before the instillation of 5 μL saline (TMHbase), immediately post‐instillation (TMH0), 30‐s post‐instillation (TMH0.5) and at 1 min intervals for 5 min post‐instillation (TMH1, TMH2, TMH3, TMH4 and TMH5). The TCR was calculated using the formula [(TMH0 − TMH0.5)/TMH0]×100 (%). The eyes were classified into two groups with the median: ‘High TMHbase’ (n = 10) and ‘Low TMHbase’ (n = 10). Eyes with STT‐1 values ≥15 mm/min and TFBUT ≥ 12 s were assigned to the ‘Satisfied’ subgroup, whereas eyes not satisfying these criteria were assigned to the ‘Not satisfied’ subgroup. Results TMH0 was higher than TMH0.5 (p = 0.02), wherein TMH0.5 to TMH5 did not differ significantly. The TCR and blink rate were negatively correlated (p = 0.02). The ‘Not satisfied’ subgroup in the low TMHbase group had a lower TCR (p = 0.02) and higher blink rate (p = 0.04) than the ‘Satisfied’ subgroup. Conclusions TCR can be evaluated using AS‐OCT in dogs. Eyes with a lower TCR blink more frequently. TMH merits studying to understand ocular surface health.

Keywords

• blink rate
• dry eye syndrome
• Schirmer tear test‐1
• tear clearance rate
• tear film breakup time
• tear meniscus height