Ultrasound of the Lacrimal Gland in Healthy Shih Tzu Dogs and with Dry Eye Disease

Abstract

Dry eye disease (DED) is a very common disease in dogs, especially that of immune-mediated origin, with Shih Tzu dogs being some of the most affected. In this study, ultrasound changes of the orbital lacrimal gland (LG) were described in healthy Shih Tzu dogs and those diagnosed with different intensities of DED. For training purposes, a macroscopic and ultrasonographic study of the orbits of brachycephalic dog cadavers (n = 6) was conducted. Subsequently, thirty-five eyes from 23 male and female dogs aged between two and eight years, distributed into four groups according to the Schirmer tear test (STT-1), including a control group (CG, n = 10) (STT-1 ≥15 mm/min), early DED group (DED1, n = 8) (STT-1 between 14 and 11 mm/min), moderate DED group (DED2, n = 7) (STT-1 between 10 and 6 mm/min), and severe DED group (DED3, n = 10) (STT-1 ≤5 mm/min), were used. Ultrasound evaluation of LG showed a higher occurrence of glandular tissue heterogeneity (p=0.755) and the presence of hyperechoic areas (p=0.027) in dogs with DED3. The variables measuring the major axis were lower in dogs with DED3 (p=0.002). The area and perimeter were smaller in dogs with DED3 than in CG and DED1 groups (p<0.001) and the perimeter of the LG of dogs in the DED2 group was smaller than that of CG (p<0.001). The LG major axis (r = 0.56), area (r = 0.66), and perimeter (r = 0.66) decreased as the STT-1 of the different groups decreased. LG ultrasound of Shih Tzu dogs is a feasible technique that allows the evaluation of characteristics of the glandular tissue. The ultrasound could identify changes in texture, echogenicity, and size in LG of Shih Tzu dogs with immune-mediated DED.