High Prevalence of Ocular Demodex in Lashes With Cylindrical Dandruffs and in vitro and in vivo Killing Studies

Abstract

Abstract: : Purpose: To determine the prevalence of ocular demodex in lashes with cylindrical dandruff (CD) and to demonstrate in vitro and in vivo killing of demodex by different agents. Methods: Clinical data of 55 patients were retrospectively reviewed. They were divided in to Group A (n=20) with diffuse CD, Group B (n=12) with sporadic CD, and Group C (n=23) without CD, of which the latter was further subdivided in C1 (n=15) without and C2 (n=8) with daily lid hygiene for the past one year. After identifying the potential errors of the conventional demodex counting method, we modified it by adding 100% alcohol to dissolve CD and to stimulate demodex emigration from CD. We also evaluated in vitro killing of baby shampoo, povidion idine, alcohol, SDS, tea tree oil, caraway oil and dill weed oil, and a combination of them. Tea tree oil was then used as an office treatment to 4 patients with ocular demodex. Results: Demodex was found in all 32 patients (100%) of Groups A and B with CD, which was significantly higher than 22% of Group C (n=23) without CD (p<0.01). The average demodex counts were 4.1 ± 1.0 and 2.0 ± 1.2 per epilated lash with CD, which were significantly higher than 0.2 ± 0.5 and 0.2 ± 0.4 per lash without CD in Group A and B, respectively (p<0.01), and than 0.01 ± 0.09 and 0.12 ± 0.41 per lash for Group C1 and C2, respectively (p<0.01). Demodex was still found in CD fragment left on the lid skin after epilation. Among all tested solutions, only 100% alcohol, tea tree oil and caraway oil could kill adult demodex in 10 min in vitro. Weekly application of tea tree oil dramatically decreased demodex number and eradicate CD in one month, an efficacy unable to be achieved by shampoo alone in one year. Conclusions: Our modified sampling and counting method confirms that prior controversy is resulted from miscounting, and that lashes with CD is indeed pathognomonic for ocular demodex infestation. Lid hygiene with shampoo reduces demodex counts but does not eradicate demodex infestation. Tea tree oil has a superior killing effect on ocular demodex.

Keywords: cornea: tears/tear film/dry eye • microbial pathogenesis: clinical studies • microbial pathogenesis: experimental studies