Meibomian gland dysfunction (MGD) is a common disease in ophthalmic clinic. This study aimed to explore ocular Demodex infestation on the microstructure changes of the meibomian glands (MGs) in patients with MGD by in vivo confocal microscopy (IVCM). We retrospectively reviewed 103 eyes of 52 patients with MGD and 62 eyes of 31 non-MGD patients. All enrolled patients underwent IVCM examination. The following IVCM parameters were recorded: the MG acinar density (MAD), MG acinar longest diameter (MALD), MG acinar shortest diameter (MASD), MG orifice area (MOA), severity of MG fibrosis (MF), MG acinar irregularity (MAI), meibum secretion reflectivity (MSR), inhomogeneous appearance of walls of acinar units (AWI) and periglandular interstices of acinar units (API), and the number of Demodex . The positive rate of Demodex infestation in MGDs was 89.32%, and statistically higher than control group (controls; P < .001). All parameters showed statistically significant differences between MGDs and controls ( P < .001), and Demodex- negative group and Demodex- positive group ( P < .05) in both MGDs and controls, except MAD ( P = .826) in controls. The number of Demodex was positively correlated with MALD, MASD, MF, MAI, MSR, AWI, and API in MGDs and controls ( P < .05), and negatively correlated with MAD and MOA in MGDs ( P < .05). MOA showed a strong significant correlation with the number of Demodex in controls ( P < .001), whereas there was no significant difference between the number of Demodex and the MAD in controls ( P = .448). Demodex can cause microstructural changes of MGs, which can cause or aggravate MGD, and the more the number of Demodex infestation, the more serious the structural damage.

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