Objective:To analyze the morphological changes and features of meibomian gland in patients with meibomian gland cyst under in vivo confocal microscope (IVCM). Methods:A cross-sectional study was performed.A total of 34 patients (34 eyes) with meibomian gland cysts and 18 control subjects (18 eyes) in the outpatient department without meibomian gland cysts treated in Shantou International Eye Center from September 2018 to April 2019 were included into the meibomian gland cyst group and control group accordingly.All the subjects underwent routine ophthalmologic examination and IVCM examination.IVCM test indicators included the opening area of meibomian gland, the longest diameter and the shortest diameter of meibomian gland opening, the morphology of glandular tube and acinus adjacent to the meibomian gland opening.The measurement indexes of the meibomian gland cyst group and the control group were compared and analyzed.This study followed the Declaration of Helsinki and was approved by the Ethics Committee of Joint Shantou International Eye Center of Shantou University and The Chinese University of Hong Kong (No.EC20171103[6]-P01). Written informed consent was obtained from each patient before examination.Results:The opening of the meibomian glands of the 34 subjects in the meibomian gland cyst group were all enlarged irregularly with smooth boundaries, and emboli in the openings were observed in 70.59% (24/34) of patients.The longest diameter, the shortest diameter and the area of meibomian gland openings were (148.12±70.16)μm, (114.77±52.38)μm and 9 239.11(5 506.96, 24 111.36)μm 2 in the meibomian gland cyst group, respectively, while (59.35±16.78)μm, (41.98±11.77)μm and 2 094.19 (1 432.28, 2 945.65)μm 2 in the control group, respectively.Compared with the control group, the longest diameter and shortest diameter in the meibomian cyst group were longer, and the area of meibomian gland openings in the meibomian cyst group was larger, and the differences were statistically significant (all at P<0.01). Adjacent to the opening, there was cystic dilation of glandular tube containing accumulated secretion of different characteristics detected in the 61.76% (21/34) of patients in the meibomian gland cyst group, and the dilated glandular tubes were with flat edges.The boundaries between the dilated glandular tubes and surrounding acini were clear. Conclusions:In vivo confocal microscope can detect the morphological changes of meibomian glands in patients with meibomian gland cyst, including enlarged opening with embolus, cystic dilation of glandular tube with clear boundary and accumulated secretion.