Background: Demodex mites are common ectoparasites of the skin that are implicated as a cause of blepharitis. However, it is difficult to differentiate Demodex infestation from other causes of blepharitis due to the lack of distinctive symptoms and requirement of a microscope examination to confirm the diagnosis.

Objective: To compare signs and symptoms between blepharitis patients with and without Demodex infestation.

Materials and Methods: Sixty-one consecutive patients with symptomatic blepharitis were enrolled. The patients completed the Ocular Surface Disease Index (OSDI) questionnaires and underwent standard eye examination, Schirmer I test, tear break-up time (TBUT), and ocular surface staining. Four eyelash samples were epilated from each eye and examined for Demodex mites using a microscope. Symptoms and signs of blepharitis between patients with and without Demodex infestation were compared.

Results: The prevalence of Demodex infestation among blepharitis patients was 63.9%, with an average Demodex count of 7.2 mites per patient. Common symptoms of Demodex blepharitis included ocular irritation (82.1%), itching (79.5%), and blurry vision (76.9%), but no significant difference was found when compared to non-Demodex blepharitis. Cylindrical dandruff (CD) was significantly more prevalent in blepharitis with Demodex infestation (74.4%) than those without (22.7%) (p<0.001). TBUT was significantly shorter in the blepharitis with Demodex infestation (3.6 second) than those without (4.3) (p=0.04). There was no significant difference in age, sex, duration of symptoms, OSDI score, Schirmer I test, ocular staining score, and severity of meibomian gland dysfunction between the two groups.

Conclusion: Symptoms of Demodex blepharitis are non-specific, similar to blepharitis without Demodex infestation. The presence of CD and short TBUT strongly suggest Demodex infestation and should warrant further diagnostic evaluation.

Keywords: Blepharitis, Cylindrical dandruff, Demodex, Demodicosis, Meibomian gland dysfunction

Received 14 Jun 2018 | Revised 12 Nov 2018 | Accepted 16 Nov 2018