The Effect of Demodex Infestation on Blepharitis and the Ocular Symptoms

Objective: This study aimed to determine the frequency of Demodex infestation of eyelashes in patients with and without blepharitis and to determine the effects of Demodex infestation on blepharitis and the ocular symptoms. Methods: The study included patients with chronic mixed (anterior + posterior) blepharitis who presented to our clinic. Patients with refractive error and no ocular disease were enrolled as the control group. From each participant, a total of 4 eyelashes were removed and were then examined under a light microscope for Demodex infestation. Symptoms, fluorescein tear breakup time, and ocular surface staining pattern were recorded. Results: The prevalence of Demodex infection in the blepharitis group was 67.2%, versus 54.9% in the control group (P=0.18). The incidence of itching in the blepharitis group was significantly higher in the Demodex (+) patients than in the Demodex (−) patients (P<0.001). Fluorescein tear breakup time in the Demodex (+) patients was significantly shorter than in the Demodex (−) patients (P<0.001). There was not a significant difference in the fluorescein staining pattern between the 2 groups (P=0.57). The incidence of advanced stage blepharitis was significantly higher among the Demodex (+) patients (P=0.007). The incidence of cylindrical eyelash dandruff in the blepharitis group was significantly higher in the Demodex (+) patients (P<0.001). There was a significant difference in meibomian gland dysfunction between the 2 groups (P=0.039). Conclusion: Demodex infestation must be investigated in patients with advanced stage blepharitis, itching, and shorter than normal fluorescein tear breakup time.