AIM: To observe the changes of microcellular structure of meibomian glands (MGs) in type 2 diabetes mellitus (DM), and to explore its correlation with the duration of diabetes. METHODS: The study assessed 132 eyes of 132 patients with type 2 diabetes mellitus (DM group) and 100 eyes of 100 non-diabetic participants (NDM group). All patients underwent the examination of the Keratograph 5M system to obtain the meibography which were used to evaluate the structure dropout of the MGs. And then laser scanning confocal microscopy (LSCM) was performed for observing the acinar cells and ducts of the MGs to obtain the following parameters: the MG acinar unit density (MGAUD), MG acinar longest diameter (MGALD) and MG acinar shortest diameter (MGASD). The examination results of the right eye were selected for analysis. RESULTS: Compared with that in NDM group, the meiboscore was significantly higher (Z=-4.057, P<0.001), and there were more MGs dropout in DM group. With the prolongation of the course of diabetes, the absence of MGs aggravated and the MGs dropout score increased (r=0.596; P<0.001). LSCM showed that there were various cytological alterations in acinar cells of MGs with the progress of diabetes duration, such as expansion, atrophy or fibrosis of MG acinar units, decreased density of MG acinar units, deposition of lipid substances, infiltration of inflammatory cells, proliferation of fibrous tissues, etc. And the opening of the glandular duct changed from smooth at the beginning to narrow, blocked, fibrotic and so on. Compared with that in NDM group, the MGAUD in DM group was significantly lower (Z=-9.713; P<0.001), the MGALD and MGASD were significantly larger (Z=-9.751, -6.416; P<0.001). With the duration of diabetes, the MGAUD reduced, the MGASD increased (r=0.860, 0.364, P<0.001); but the MGALD had no correlation with diabetic duration (r=0.133, P=0.151). CONCLUSION: With the progress of diabetes, the meibomian glandular acinar cells of diabetic patients show various manifestations. Those changes may result in the dysfuction of the MGs, tear film instability and dry eye symptoms in patients with type 2 DM.