Demodex: Raiders of the Lash Follicles!

What are Demodex? They are mites, which are microscopic creatures with eight legs. They belong in the same class of animals as spiders. While most have heard of house dust mites, few have heard or come across demodex, except maybe dog owners. This is despite Demodex infesting many of us, only we are unaware of their presence most of the time.

Demodex are readily accessible to inspection by most ophthalmologists. When they infest the lash follicles, they are visible on high power with the slit lamp microscope. Typically, infested eyelashes have a large amount of debris and anterior blepharitis. To visualize the mites themselves, all debris and dandruff like material are first cleaned with an alcohol swab. Then, pulling lightly on the lashes causes the demodex tails to poke out of the follicular opening, and further twirling the lash will cause the mass of demodeces to come out and lie on the skin surface. They look like tiny shiny rod shaped objects. They can then be scooped up with the tip of a forceps and touched lightly on the sticky side of a cellophane tape. They are then stuck on a microscope slide and observed using a compound microscope.

It has become apparent to us that most people with blepharitis, especially anterior blepharitis and lots of debris near the eyelashes also have lots of demodex. Coincidence? Several papers by Scheffer Tseng have now come out about the pathological role of demodex in ocular surface disease. The role of demodex in posterior blepharitis and meibomian gland disease is less certain. This is often seen without demodex infestation of the lashes. It could be that there is deeper infestation within the meibomian gland itself, by Demodex Brevis, but we won’t know for sure unless we can somehow visualize the interior of the gland or maybe test the meibum by PCR for the demodex.

If you have Demodex, what do you do? Many patients have only a few Demodex in the odd follicle or are asymptomatic, and in such cases simple lid hygiene may be sufficient. But if there are many, and the eyelid is itching or inflamed, then steps should be taken. Tea tree oil has been advocated as being an effective mite killer-but that would only work for the ones on the lashes. At Jerry Tan Eye Surgery, we used to apply 50% tea tree oil to the eyelashes over several sessions but found that it caused significant discomfort even when we managed to avoid getting it in the eyes. In the majority of patients, the mites could not be eradicated with tea tree oil treatments even though their numbers were reduced. We have now specially compounded a medicated cream which paralyses the mites and that, most important of all, does not irritate the eyes. Mites could no longer be found in the eyelashes after nightly application of this cream for one month. We have seen marked improvement in lid crusting, redness, and itching with this treatment in all our patients in whom we found significant Demodex infestation.

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