Occurrence of Demodex species in patients with blepharitis and in healthy individuals: a 10-year observational study

Two Demodex species (eyelash mites)-D. folliculorum and D brevis-are believed to be associated with human skin and eye diseases. However, the clinical significance of infection with Demodex species remains controversial.

The aim of this study was to estimate the prevalence of ocular demodicosis in patients with blepharitis as compared with the prevalence in the healthy population in Poland.

This case-control prospective study was carried out from 2007 to 2016. The enrolled patients (668) were divided into 2 groups: the study group, comprising 553 patients with blepharitis (349 women and 204 men, aged 17-88 years), and the control group, comprising 115 healthy volunteers without a history of ocular pathologies (78 women and 37 men, aged 17-88 years). A sample of 10 eyelashes was taken aseptically from each eye of the examined person and later studied under a light microscope.

Demodex species were found in 62.4% (345/544) of the patients in the study group and in 24.3% (28/100) of the controls (P = .001, OR = 0.006). The overall prevalence was 55.8% (373/668) in all the examined participants. The presence of Demodex infection increased with age in both groups. No association of Demodex infection with gender was found (119/204 vs 226/349; P > .05, OR 1.086). A high mean number of mites was present more frequently in patients aged older than 50 years and in those who complained especially about itching (P < .05).

The prevalence of ocular demodicosis is significantly correlated with blepharitis and increases with age.