Our 'Clinical Pearl of the Month' column is where we present a clinical pearl to provoke thought and discussion.
The Demodex mite is an eight-legged ectoparasite that resides in our hair follicles and sebaceious glands, including our eyelashes. Every adult will have some demodex mites, but presence of blepharitis indicates they simply have too many. Demodex infestations increase with age, affecting 84% of the population at age 60, and 100% of those older than 70 years old.
It is contracted and spread by either direct contact or dust containing eggs. Two species are found on humans:
- the shorter Demodex brevis (0.2mm long) which tends to live inside the lashes' sebaceous glands and meibomian glands, and is suggested to be associated with posterior blepharitis
- and the slender, tapered Demodex folliculorum (0.4mm long), which bury themselves face down in the lash root, associated with anterior blepharitis
There are multiple types of blepharitis, each with their own path to effective treatment.
How do I diagnose Demodex Blepharitis?
Patients suffering from a demodex infestation may complain of crusted or matted eyelashes, tearing, burning, madarosis, and foreign body sensation on the base of their eyelashes. It is important to rule out other sources of anterior surface inflammation as there are many crossover symptoms to a myriad of conditions. N.B. Demodex mites are found in both symptomatic and asymptomatic individuals, and there is poor correlation between Demodex infestation and symptoms, as paralleled in other anterior segment conditions such as blepharitis.
A definitive diagnosis can be made through lash sampling. Select an eyelash with cylindrical dandruff as it is more likely to yield results. Mount the lash onto a coverslip with a droplet of oil.
However, this is not always practical in a clinical setting. Some signs which may be noted on routine clinical examination include cylindrical dandruff, eyelash disorders such as madarosis, and lid margin thickening and erythema. Inflammation of the lid margin can spillover and result in blepharoconjunctivitis and corneal inflammation.
What is that classic cylindrical dandruff?
This fine waxy, dry debris is considered pathognomonic of Demodex. The clear cylindrical dandruff classic of Demodex blepharitis is through to be a product of the mites' claws scraping around the eyelash follicle. Demodex infestation can cause increased keratinisation near the base of the eyelashes. As the keratinisation is mixed with lipids, it produces the classic clear cylindrical dandruff.
What is the lifecycle of Demodex?
Understanding the lifecycle is important to how we tackle demodex. A demodex mite lives around 2-3 weeks. A female will lay 15-20 eggs inside the hair follicle. These eggs turn into larvae and subsequently develop into an adult mite. They are fast little creatures, walking around 10 millimeters/hour.
Ok, I've heard enough, how do I treat my patients of these mites?
Long-term lid hygiene is required as Demodex is a chronic condition requiring chronic therapy. Prior to initiating therapy, there are several effective in-office demonstrations that have proven to increase compliance among patients with Demodex, as many lid therapies targeted specifically for Demodex cause ocular discomfort contributing to therapy dropout.
The most effective and commonly used agent for demodex is tea tree oil. Tea Tree Oil (TTO) is currently the most effective in-office and at home treatment option. The TTO stimulates the mite to exit the hair follicle and migrate to the skin before mating. Studies have shown that concentrations of TTO as low as 5% (applied 2x/day) and as high as 50% (applied in office once a week) to the base of the eyelashes and lids, is effective in reducing Demodex infestation.
There is no one single treatment method that fully eradicates the Demodex after 4 weeks of therapy. It is a chronic condition that requires long-term treatment. Here are some common treatments you can implement in practice.
- Commercial eyelid cleansers (foam or wipes) used 2x/day: Patients are instructed to clean the lids and lashes, as well as smear the lid cleanser onto the eyelash roots of the lid margins. They can also be instructed to use the wipes on their eyebrows, forehead and cheeks as well as demodex live in those regions. The foam/scrubs are meant to be left on the skin to dry. Examples of lid cleansers include: Blephadex, Cliradex, Oust Demodex, Ocusoft Lid Scrub Plus
- In-office high concentration TTO: A weekly office lid scrub with 50% TTO solution is to stimulate the migration of mites out of the lash follicle. Anaesthetic is instilled in both eyes and then the eyelashes are thoroughly debrided with a cotton bud soaked in 20-50% tea tree oil. 100% tea tree oil solution causes intense patient discomfort and toxicity to the ocular surface. A 50% TTO mixture can be prepared by diluting the tea tree oil in macadamia oil. Caution must be taken in those patients with nut allergies and allergy to tea tree oil. This is then followed by daily home therapy with eyelid cleansers 1-2x/day.
- Microblepharoexfolation: This involves a high-speed rotary sponge (BlephEx) soaked in a lid cleanser. It removes the biofilim on the surface of the lids and lashes, removes the cylindrical dandruff and helps to remove the mite eggs at the base of the eyelash follicle. This is a powerful tool to kickstart treatment and may need to be repeated at 3-6month intervals for those with severe blepharitis.
- Other hygiene measures: All makeup should be discarded, hot water should be used to wash clothers and linens dried on the high-dryer setting.
- Aiding compliance: Compliance tends to be simple once the patients can see photos of their mites. This can be taken through the slit-lamp or in free space if the infestation is severe enough. A digital microscope can also be used to take photographs and video of an extracted eyelash.