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 body sensation.20 Other reported signs and symptoms were subjective lash loss, heavy lids, and misdirected lashes.21
One notable characteristic of the infestation is the past unresponsiveness to conventional treatments for blepharitis, dry eye, and allergy. Patients will have a history of trying out different treatment strategies with little to no success. The failed treatments are typically for ocular surface conditions mainly because the infestation has many of the same signs and symptoms. Ineffective treatments include artificial tears, cyclosporine, antihistamines, doxycycline, lid hygiene, baby shampoo, and steroids.
CYLINDRICAL OR CUFF DANDRUFF
Cylindrical or cuff dandruff is a fine, waxy, sometimes dry, debris seen with slit lamp at the base of lashes contiguous with the lids. A smooth transparent collar of mite feces, keratin, and lipids surrounds the bases of lashes for 1 to 2 mm. This collar has the appearance of sometimes clear plastic insulation about the lash.11,22,23
One hundred percent of the patients with CD have Demodex infestation. Gao et al.24 found that the average count of Demodex was 12.9 mites per patient with CD compared with 0.35 mites without. The significant difference was more than 30 times higher when CD is present. Clinical severity judged by CD correlates well with greater numbers of Demodex.24
Demodex is extremely difficult to see with the naked eye and requires magnification. The size of a mite is about half the diameter of a grain of table salt.25 The bodies of both D. folliculorum and D. brevis are worm shaped. The gnathosoma is composed of the mouth and feeding parts. Gnathosoma has sharp stylet-like chelicerae used to cut and take food. Pedipalps are used to hold the food. The rest of the body consists of the head and neck area called prosoma or prodosoma. Adults have four pairs of legs in the prosoma. Opisthosoma forms the tail.26 The morphology has been described and measured by Desch and Nutting27 (Table 1; Fig. 1).
When viewing with the microscope, identification of Demod