The prevalence of Demodex folliculorum and brevis colonization in patients presenting with blepharitis to an outpatient resident clinic

Philadelphia, PA

Purpose: To examine the prevalence of Demodex in two large, tertiary care, outpatient resident clinic settings; meanwhile, exploring demographic variables, use of ocular medications, and OTC cosmetic products with respect to prevalence. Lastly, analyze potential inadequacies in the rate of treatment amongst patients in the resident clinic setting.

Methods: A cross-sectional non-randomized, prospective study investigating the prevalence of Demodex folliculorum (DF) and brevis (DB) in patients presenting with blepharitis, and in control patients without clinical evidence of dry eye blepharitis syndrome (DEBS). Epilation of one eyelash from each lid was performed and studied under high power light microscopy. Each patient was questioned, or chart mined for relevant data including duration of DEBS, OSDI score, race, age, gender, disability status, use of medications, surgical history, previous ocular treatments aimed at improving DEBS, and OTC cosmetic products. For patients who tested positive, treatment was initiated with routine follow up.

Results: Average age for the sample population was 58.9 years, with the presence of blepharitis in 61.2%, DED in 67.9%, and Demodex in over half (55.1%) of individuals sampled. The presence of Demodex was independent of sex, race, number of clinic visits, concurrent pterygium, lid hygiene applications, OTC or Rx drops, while dependent on age (p=0.003), history of pterygium surgery (p=0.01), dermatochalasis (p=0.001), blepharitis (p<0.001), and DED (p=0.001). Of those patients currently undergoing some form of treatment for blepharitis, 51.4% were found to have Demodex, with only 3% undergoing adequate treatment. Given a strong association between patients who had previous history of pterygium surgery and the presence of blepharitis, a sub-analysis revealed blepharitis to be more strongly correlated with the presence of Demodex (p=0.01).

Conclusion: In the resident clinic setting, Demodex is grossly under diagnosed and responsible for acute and refractory blepharitis. In agreement with prior studies, we found a tightly positive correlation between Demodex and age. Although there is a strong association between Demodex and pterygium surgery, we believe this to be secondary to the high incidence of blepharitis in this subgroup. The causative mechanism should be explored further.