| 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:
Apply a modified sampling and counting method to 55 clinical cases. Patients were divided in to Group A (n=20) with diffuse CD, Group B (n=12) with sporadic CD, and Group C (n=23) with clean lashes or greasy scales, of which the latter was subdivided in C1 (n=15) without lid hygiene and C2 (n=8) using daily lid hygiene for the past one year. Each patient received routine complete eye examination and modified demodex counting. Survival time of demodex was measured under the microscope. Seven patients practiced daily lid scrubbing with baby shampoo and 9 patients with microscopically proven ocular demodex treated with lid scrubbing with 50% TTO.
Results:
Demodex was found in all of Groups A and B patients (n=32) with CD, which was significantly higher than 22% of Group C patients (n=23) without CD (p<0.001). The demodex counts were 4.1 ± 1.0 and 2.0 ± 1.2 per epilated lash with retained CD, which were significantly higher than 0.2 ± 0.5 and 0.2 ± 0.4 per lash without retained CD in Group A and B, respectively (each p<0.001), and than 0.01 ± 0.09 and 0.12 ± 0.41 per lash for Group C1 and C2, respectively (each p<0.001). Demodex was still found in CD fragment left on the lid skin after epilation. 5 Demodex brevis mites were found among the 422 demodex specimens. Demodex folliculorum survived for more than 150 min in 10% povidone iodine, 75% alcohol, 50% baby shampoo and 4% pilocarpine. However, the survival time was significantly shortened to within 15 min in 100% alcohol, 100% TTO, 100% caraway oil, or 100% dill weed oil. TTO’s in vitro killing effect was dose-dependant. Lid scrubbing with 50% TTO, but not with 50% baby shampoo, can further stimulate demodex to move out to the skin. The demodex count did not reach zero in any of the 7 patients receiving daily lid scrubbing with baby shampoo for 40 to 350 days. In contrast, the demodex count dropped to zero in 7 of 9 patients receiving TTO scrubbing in 4 weeks without recurrence.
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. Demodex is resistant to a wide range of anti-septic solutions. Weekly lid scrubbing with 50% TTO and daily lid scrubbing with tea tree shampoo is effective in eradicating ocular demodex.
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