AIM: To investigate the effect of Demodex infection on ocular surface function in patients with meibomian gland dysfunction(MGD).

METHODS: Totally 94 patients with MGD were enrolled in the Ophthalmology Clinic of Zhujiang Hospital of Southern Medical University from April 2018 to September 2018. The patients were conducted a series of tests for Ocular Surface Disease Index(OSDI), Schirmer I test(SⅠt), tear film break-up time(BUT), corneal fluorescence staining(FL), tear height, superior meibomian gland loss score, inferior meibomian gland loss score, total meibomian gland loss score, and demodex count. The difference between above indicators in the positive group and in the negative group was calculated, and the correlation between demodex count and above ocular surface parameters was analyzed.

RESULTS: All 54 patients were tested positive for Demodex, and the positive rate was 57%, which was not significantly correlated with age. The positive rate of Demodex in males was higher than that in females. The superior meibomian gland loss scoreandtotalmeibomian gland loss score \〖2.00(1.00, 2.00)vs 1.00(1.00, 1.50),P=0.02; 3.00(2.00, 4.00)vs 2.00(1.00, 3.00),P=0.04\〗in positive group were significant higher than that in negative group. There were no significant differences in OSDI, S I t, BUT, FL, and inferior meibomian gland loss score between two groups(all P>0.05). Demodex count showed mild to moderate correlations with superior meibomian gland loss score(r_s=0.37, P=0.03)and total meibomian gland loss score(r_s=0.44, P=0.01)in Demodex-positive group. While there were no significant correlation between demodex count and other parameters.

CONCLUSION: Demodex mites have a certain effect on the ocular surface functions of MGD patients and it was positive correlate with the loss of meibomian glands.