The views expressed here belong to the author. They do not necessarily represent the views of Optometry Times or Multimedia Healthcare.
It is all too common for an asymptomatic patient to present exhibiting chronic dry eye and blepharitis signs, or for a patient to have previously been unsuccessfully treated by not having the actual cause identified.
The root of the problem may lie within the root of the eyelash follicle—an eight-legged obligate parasite.
Related: Diagnosing demodex
A 32-year-old female presented with bilateral worsening itchy eyes, intermittent blur, epiphora, and overall conjunctival injection. Upon slit-lamp examination, it was obvious this patient had false lash extensions capped on the ends of most of her upper lashes.
The patient reported she had avoided washing her eyelashes because she worried the lash extensions would be ruined. Because of this lack of hygiene, the patient created a perfect harbor for Demodex (D.) folliculorum to flourish.
Parasites in the lashes
Demodex is the most common microscopic ectoparasite living on the human skin and is often present in healthy, asymptomatic individuals. These parasitic mites are opportunistic and provide positive benefits by ridding the eyelash area of waste.
But while there are different Demodex species, only D. brevis and D. folliculorum are found on humans. Demodex is most often transferred between host via contact of hair, eyebrows, and sebaceous glands on the nose.2
The rounder female Demodex mite continues the life cycle by laying 15 to 20 eggs within the hair follicle, which develop into larvae that eventually become adults in about seven days. The life cycle of an adult is usually two to three weeks.1
Previously by Dr. Coats: Blog: Recognize the signs of SND in your patients
Over their lifespan, these eight-legged mites are capable of walking approximately 8 to16 mm/hour, and are typically more active in the dark, receding into the follicle with bright light.2
Slit-lamp observation with a high magnification (25x) provides a close look to visualize the mites’ tails at the base of the eyelash follicle.
In my practice, I find that D. folliculorum and D. brevis are frequently the culprit of chronic anterior blepharitis, worsened meibomian gland disease (MGD), and lipid tear deficiency. It is thought that Demodex feeds on skin cells and sebum of the lid margin and pilosebaceous glands, causing direct damage that can trigger an inflammatory cascade.
D. folliculorum mites are about 0.4 mm in length and usually live in clusters primarily on the face. D. folliculorum is often found within the lash follicle and is more associated with disorders of the eyelashes, contributing to chronic anterior blepharitis.1
D. brevis mites tend to be shorter—about 0.2 mm in length—and live in solitary. Feeding on sebaceous gland oils D. brevis burrows deep into sebaceous and meibomian glands, and is associated with causing posterior blepharitis, meibomian gland dysfunction, and keratoconjunctivitis.1
1. Liu J, Sheha H, Tseng SC. Pathogenic role of Demodex mites in blepharitis. Curr Opin Allergy Clin Immunol. 2010;10(5):505-10.
2. Rather PA, Hassan I. Human demodex mite: the versatile mite of dermatological. Indian J Dermatol. 2014 Jan;59(1):60-6.
3. Post CF, Juhlin E. Demodex folliculorum and blepharitis. Arch Dermatol. 1963 Sep;88(3):298–302.
4. Jarmuda S, O’Reilly N, Zaba R, Jakubowicz O, Szkaradkiewicz A, Kavanagh K. Potential role of Demodex mites and bacteria in the induction of rosacea. J Med Microbiol. 2012 Nov;61(11):1504-1510.