Assessment of meibomian gland morphology and tear-film lipid layer using noncontact infrared meibography and meibometry, respectively, and tear-film osmolarity in healthy dogs.

Objective: To further investigate quantitative and qualitative tear-film dynamics through tear-film osmolarity, meibometry, meibography, and non-invasive tear-film break-up time and to describe a survey of parameters in normal eyes of healthy non-brachycephalic dogs.

Animals studied: Thirty-two veterinary hospital staff and student owned dogs between 1 and 7 years with no known comorbidities or ocular disease.

Procedure: Complete ophthalmic examination, tear-film osmolarity (I-PEN® VET), meibometry (Meibometer MB560), meibography, and non-invasive tear-film break-up time (handheld Ocular Surface Analyzer) were performed. Significance threshold was 0.05. Q-Q plots and histograms were used to assess normality of measurements. Data were summarized descriptively with mean, standard deviation, median, and interquartile range (IQR). Pearson and Spearman's correlations were used to test for correlations between diagnostics with each other and tear-film break-up times.

Results: Thirty-two dogs (64 eyes) met the inclusion criteria. Mean tear-film osmolarity level was 293.6 ± 14.1 mOsm/L (IQR 282.5-302.3). Median meibomian lipid level was 30.4 Meibometry Units (MU) (IQR 11.5-59.1). Median percent loss of meibomian glands in the upper eyelids was 25.3% (IQR 13.5-26.8). Median percent loss of meibomian glands in the lower eyelids was 26.0% (IQR 13.5-52.3). Automatic assessment of meibomian gland loss showed that grade 0 was present in 4/128 (3.1%) eyelids, grade 1 in 78/128 (60.9%) eyelids, grade 2 in 30/128 (23.4%) eyelids, and grade 3 in 16/128 (12.5%) eyelids.

Conclusions: Tear-film osmolarity, meibometry, meibography, and non-invasive tear break-up time can easily be incorporated into routine ophthalmic examinations to provide clinical information about meibomian gland morphology and function.