OBJECTIVE: To measure the eyelid margin thickness (LMT) in dogs with meibomian gland dysfunction (MGD) and evaluate its correlation with meibomian gland (MG) morphology. ANIMALS STUDIED: Fifty-nine client-owned dogs. PROCEDURE: The LMT was measured on slit lamp biomicroscopy images and divided into groups of 1 to 4, from the thinnest to thickest, based on quartiles. MG morphology, including distortion, thickening, shortening, and dropout, was evaluated using noninvasive infrared meibography. The LMT and meibography results were compared between the MGD and normal groups. Statistical analysis was performed to determine the correlation between LMT and MG morphology. RESULTS: The mean LMT was significantly greater in the MGD group (1.18 ± 0.19 mm) than the normal group (1.00 ± 0.13 mm) and was positively correlated with MG loss (p <
0.01). The LMT was thicker in dogs over 12 years (1.25 ± 0.20 mm). The LMT group 4 (≥ 1.26 mm) had the highest percentage of abnormal MG (95.7%) and MG loss area (37%). The total abnormal MG ratio and thickened MG ratio were significantly higher in the LMT group 4. LMT ≥ 1.20 mm was identified as a potential indicator for MG loss area of more than one-third. CONCLUSIONS: Eyelids with thick LMT had more abnormal MG morphology, including thickening and dropout. An LMT ≥ 1.20 mm could be a criterion to suspect MGD. Thus, the LMT could be a simple screening tool to predict MG loss and might aid in the diagnosis and early management of MGD with a sensitivity of 0.645 and a specificity of 0.768.