e that time, several studies show an association between Demodex and rosacea.33,34,36–41 For years, skin biopsy was the definitive dermatological test for Demodex. One study performed skin biopsy on rosacea patients and normal subjects. Rosacea patients had an average of 12.8 mites per square centimeter of skin; significantly greater than 0.7 mites per square centimeter in normal subjects.40 A meta-analysis has added further support to the association. Zhao and colleagues41 performed a meta-analysis of 48 separate studies done in 10 different countries on 28,527 subjects. Rosacea patients are seven to eight times more likely to have Demodex infestation.41
There are two bacterial links that may explain the connection between Demodex and rosacea. Bacillus oleronius has also been detected inside the digestive tract of the mites.12 Li et al.19 looked at 59 rosacea patients and found a significant correlation among serum immunoreactivity to bacillus antigens, Demodex infestation, and facial rosacea.19,26 Their study confirms the presence of bacillus in both the gut of the mite and rosacea patients. The second bacterium implicated is Staphylococcus epidermis, which was found in the pustules of the rosacea patients, but not in healthy (rosacea-free) skin. The theory is that Demodex serves as a carrier of Staphylococcus to areas where the bacteria can proliferate on the host.26 Once Demodex mite infestation establishes in the face, it is likely to spread and flourish in the eyelid.3
A 53-year-old woman with moderate dry eye signs and symptoms has been taking topical steroid–antibiotic combination off and on for the past 2 years. She is also taking 4% cromolyn eyedrops four times a day. The patient has a history of allergies. Meibomian gland dysfunction grade 2 OU is present. Cylindrical dandruff, eyelid edema, greasy oily debris, and telangiectasia were present in both eyes. On epilation of lashes, a mite appeared on the lash (Figs. 6, 7).
Patient 5 Discussion
The appearance of an actual mite on the surface in Figs. 5 and 6 is a rare occurrence. As stated previously, Demodex is highly photophobic and avoids light. Coston11 writes that he has seen hundreds of mites appear in severely infested lids but has never seen a mite emerge completely.
Two modern techniques allow imaging of Demodex in vivo. Sattler et al.34 used confocal laser scanning microscopy to view lesional skin in 25 patients with rosacea. If imaged partially sideways, the mites were detected as lengthy cone-shaped structures similar to their appearance under the light microscope.34 The high-definition optical coherence tomography imaging is another new technique for detecting mites. The detection rate of Demodex mites by high-definition optical coherence tomography in infested patients was significantly higher than in healthy controls.36 Maier et al.36 imaged 20 rosacea patients and found 192 mites versus 13 mites seen in the control group. Both techniques are noninvasive compared with traditional methods such as epilation or skin biopsy.
Demodicosis can manifest itself in many patients in different ways and needs to be diagnosed properly.42 To paraphrase Forton et al.,33 although Demodex are greatly underdiagnosed, they nevertheless concern the daily practice of the eye care professional.
Milton M. Hom
1131 East Alosta Ave
Azusa, CA 91702
We acknowledge Jerry Paugh, Alan Sasai, and Leonard Bielory for their encouragement and enthusiastic support.
Received February 4, 2013; accepted March 6, 2013.
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