Abstract:

Objective To investigate the effects of Demodex infection on clinical symptoms， signs， and tear MMP?9 levels in patients with meibomian gland dysfunction （MGD）. Methods A total of 680 patients with MGD were selected from our hospital， including 162 males and 518 females， with an average age of （45.05 ± 15.41） years old. The patients were divided into two groups based on the presence of Demodex mite infestation： the Demodex positive group （340 cases） and the Demodex negative group （340 cases）. All patients underwent evaluations using the OSDI questionnaire， SPEED questionnaire， eyelid margin alteration score， corneal fluorescein staining score， tear MMP?9 measurement， meibomian gland orifice score， meibomian gland excretion ability score， meibomian gland secretion score， meibomian gland loss score， tear film breakup time （BUT）， and Schirmer I tear secretion test. The differences in these indicators between the two groups were compared. Results SPEED questionnaire score： Demodex positive group： （7.68 ± 2.80）， Demodex negative group： （6.28 ± 1.99）. There was a statistically significant difference between the two groups （t = 2.582， P = 0.012）. Eyelid margin alteration score： Demodex positive group： （3.63 ± 1.53）， Demodex negative group： （2.85 ± 0.77）. A statistically significant difference was observed （t = 2.861， P = 0.006）. Corneal fluorescein staining score： Demodex positive group： （2.25 ± 1.86）， Demodex negative group： （1.08 ± 1.33）. There was a statistically significant difference （t = 3.247， P = 0.002）. Tear MMP?9 content： Demodex positive group： （30.76 ± 43.14） ng/mL， Demodex negative group： （12.36 ± 12.10） ng/mL. A statistically significant difference was found （t = 2.598， P = 0.013）. No statistically significant differences were observed between the Demodex positive and negative groups in meibomian gland orifice score， meibomian gland excretion ability score， meibomian gland secretion score， meibomian gland loss score， BUT， tear secretion examination， and age comparison （P > 0.05）. Conclusions Demodex mite infestation in patients with MGD exhibits significant differences across various clinical indicators， notably in SPEED questionnaire scores， eyelid margin alterations， corneal fluorescein staining， and tear MMP?9 levels. These changes are associated with mechanisms including inflammatory responses， cellular damage， and immune dysregulation. Demodex mite infestation may significantly influence the clinical progression of MGD by exacerbating inflammation and symptom severity， potentially playing a crucial role in disease development.

Key words: meibomian gland dysfunction, demodex mite infestation, matrix metalloproteinase-9, dry eye disease