Demodex Mite Infestation and its Associations with Tear Film and Ocular Surface Parameters in Patients with Ocular Discomfort.

PURPOSE: The presence of Demodex species can be associated with blepharitis. Their pathogenic potential in meibomian gland dysfunction is discussed herein. The purpose of this study was to determine the prevalence of Demodex mites in eyelashes of Austrian patients with ocular discomfort and to evaluate associated changes of the lid margins and meibomian glands.

DESIGN: This is a case-control study.

METHODS: Two hundred twenty-nine consecutive patients with ocular discomfort from an Austrian dry eye clinic were investigated for the presence of Demodex mites on sampled eyelashes. Associations of a mite infestation with individual dry eye and lid parameters were assessed. Lid margins were evaluated for scales, vascularization, Marx line, expressibility and quality of meibum, and drop-out of meibomian glands.

RESULTS: Demodex mites were identified in 40.2% of patients suffering from ocular discomfort (mean mite count 3.3 ± 2.9 per patient). Infestation with mites was associated with the presence of significantly more cylindrical scales (sleeves), a higher Marx line score, and a lower quality of meibum compared with mite-free patients. There were no significant associations with the expressibility and the drop-out of meibomian glands.

CONCLUSION: The prevalence of Demodex mites in patients with ocular discomfort is high. The mean mite count per patient in this Austrian dry eye unit population is lower compared with previously published data from Asian regions. The infestation of the eyelids with Demodex species is associated with changes of the anterior and posterior lid margin, suggesting a pathogenic role in blepharitis and meibomian gland dysfunction.