Hom, Milton M.*; Mastrota, Katherine M.†; Schachter, Scott E.‡
Demodex folliculorum and Demodex brevis are ectoparasites with a prevalence of 100% in patients aged 70 years and older.1 Demodex is regarded as the most common ectoparasite in humans.2 Demodex folliculorum resides in the lash follicles and relies on sebum as its main source of food.3 Despite high prevalence, little attention has been paid to the mite among eye care practitioners. The purpose of this case series is to explore the diagnosis of demodicosis with a clinical sequence within multiple optometric practices.
Demodex colonization in humans is high (20 to 80%) and reaches 100% in elderly people.4–7 Alejo et al.8 described D. folliculorum in the lids of 50% of randomly chosen Filipino patients at the Philippine General Hospital. Demodex is considered to be acquired soon after birth. It has been found to be present in young infants.9 Numbers vary from study to study, but studies agree that the prevalence of Demodex trend increases with age. The prevalence is only about 13 to 20% in patients younger than 20 years and approaches 95 to 100% by age 71 years.1,4,10 Not only does prevalence increase with age, but average numbers of Demodex per patient also increase.5 Gutierrez9 estimates that every person carries a colony of 1000 to 2000 mites and is part of the normal skin fauna where there are hair follicles.4,9 Thousands often exist on one person, and the mites show a high propensity to reproduce. Coston11 states “Consider the scrambling of this microscopic octopoded mob while the host sleeps: males seeking, finding, breeding females; gravid females seeking new follicles; inhabitants of follicles sweeping feces outside.”
Clinical sequence was followed for all of the cases, modified from Liu et al.12:
1. Clinical history: a high index of suspicion when anterior blepharitis, meibomian gland dysfunction (MGD), dry eyes, and/or ocular allergy is present.
2. Slit lamp examination: typical cylindrical dandruff (CD) at the root of eyelashes.
3. Microscopic confirmation: detection and counting of Demodex eggs, larvae, and adult mites in epilated lashes.11,12
Several studies have connected Demodex with blepharitis. Sumer et al.13 showed that 62.9% of chronic blepharitis patients had Demodex. Alejo et al.8 diagnosed 88% of the blepharitis patients with Demodex. De Venecia and Siong14 found that 95% of anterior blepharitis and 97% of anterior and posterior blepharitis had Demodex. Zhao et al.15 performed a meta-analysis of 11 articles and found Demodex and blepharitis to have a statistically significant association.
Dry eyes are a classic symptom of MGD and blepharitis.16,17 Demodex has been reported to increase Ocular Surface Disease Index scores.6 What is interesting is Demodex has been associated with dry eye but not necessarily with aqueous tear deficiency based on Schirmer scores. Some studies have shown normal Schirmer test scores with patients with mite infestation.6,18 In fact, aqueous deficient dry eye has been theorized to interfere with Demodex. The mite may thrive better with normal tear volume as opposed to a tear-deficient state.19 The other major category for dry eye is evaporative. There is support for evaporative dry eye and Demodex. With respect to MGD, De Venecia and Siong14 found 85% of MGD patients had Demodex. Kheirkhah et al.20 found that five of six patients with Demodex and corneal findings displayed MGD.
For ocular allergy, there are positive correlations between mite infestations and conjunctival papillary reactions. Groups with conjunctival papillary hypertrophy often have allergies that may be caused by Demodex.6 The debris and wastes from the mites may elicit an inflammatory response.12 The presence of papillary conjunctivitis and itching can lead a clinician to diagnose ocular allergy instead of Demodex.
SIGNS AND SYMPTOMS OF DEMODEX
The main symptoms are ocular dryness, severe itching, burning, foreign body sensation, crusting, and redness of the lid margin and blurry vision.5,12,18 The most common eye symptoms were itchiness and foreign