History
Symptoms of demodicosis include ocular irritation, itching, and scaling of lids. Past ocular history may consist of recurrent failed treatment of blepharitis.
Physical
Gross observation may reveal the following:
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Lid thickening
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Scaling of lids
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Madarosis (loss of lashes)
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Conjunctival inflammation
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Meibomian gland dysfunction
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Rosacea: The results of the study by Moravvej et al [7] conclude that the prevalence and the number of Demodex mites in rosacea patients are higher than in control subjects, supporting the pathogenic role of Demodex mites in rosacea.
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Decreased vision
Slit-lamp findings are as follows:
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A collar of tissue around the base of the eyelashes
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Follicular distention
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Cornea - Superficial corneal vascularization, marginal corneal infiltration, phlyctenule-like lesion, superficial corneal opacity, nodular corneal scar
Causes
Demodex species specific to humans occupy two periocular sites hidden from external observation. They are small in size and can move across the skin surface.
D folliculorum is found in hair and eyelash follicles associated with pilosebaceous glands in the eye or elsewhere on the face and the body. A single follicle may contain as many as 25 D folliculorum organisms.
D brevis leads a much more solitary lifestyle in the body's sebaceous glands, the meibomian gland, and the gland of Zeis.
D folliculorum measures 0.3-0.4 mm in length, whereas D brevis is one-half the size of D folliculorum (0.15-0.2 mm) with a similar head and thorax structure but a shorter abdomen.
The eight legs of this arachnid are segmented and provide locomotion at a rate of 8-16 mm/h.
D folliculorum and D brevis, also known as follicle mites, are believed to be more active in the dark, although capture in daylight is possible.
The bright light of the day and especially the biomicroscope cause the mite to recede into the follicle. Therefore, the mite can be observed only when an epilated lash is viewed under a low-power microscope.
The life stages of D folliculorum begin with copulation at the mouth of the follicle. Reproduction is believed to occur in darkness, which is significant in symptomatology and treatment.
Following copulation, the female burrows back into the follicle near the pilosebaceous gland's opening and lays her eggs.
Spickett reported the life cycle of D folliculorum and estimated that only 14.5 days elapse from the ovum to the adult stage, including 120 hours as an adult. Females may live an additional five days after oviposition. [4]
Sexes are separate; sexual maturity is reached in the larval form (neoteny).
Females are territorial; they remain in their follicles and wait for the nomadic philandering males that travel over the skin's surface from one follicle to another to seek females.
Adults reside in the follicle parallel to the hair shaft, head inward, often with the tail end (opisthosoma) protruding onto the skin's surface at the eyelash's base.
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Illustration of Demodex folliculorum. Reprinted with permission from Antoine Morin, BIODIDAC, University of Ottawa.
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Eyelid section shows Demodex folliculorum (M) in the hair follicle. Note mite mouthparts (arrow) embedded in epithelium and straplike layers of keratin (hematoxylin and eosin, X400). Reprinted with permission from Elsevier Science.
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Section of sebaceous gland of an eyelash shows Demodex brevis (M). Note gland cell (C) destruction (McManus, X375). Reprinted with permission from Elsevier Science.
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Cross-section through small hair follicle of the eyelid. Note distension, hyperplasia, and moderate epithelial keratinization caused by the activities of Demodex folliculorum (arrow) (hematoxylin and eosin, X375). Reprinted with permission from Elsevier Science.
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Section of eyelid shows eyelash (L), cuffing (C), and small segment of Demodex folliculorum (M). Note layering of cuff (Masson, X275). Reprinted with permission from Elsevier Science.
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Demodex folliculorum.
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Demodex along the shaft of the cilia.
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Demodex along the shaft of the cilia (higher magnification).
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Backsides of numerous pubic crabs with infestation of the lashes and secondary blepharitis. Reprinted with permission from HD Riley, OD, Indiana University School of Optometry.
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Phthiriasis (Phthirus pubis) pubic crab lash infestation and secondary blepharitis. Reprinted with permission from HD Riley, OD, Indiana University School of Optometry.
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Phthiriasis (pubic lice). Reprinted with permission from HD Riley, OD, Indiana University School of Optometry.
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Demodex infestation is an under diagnosed cause of chronic blepharitis. Image courtesy of Rendia, Inc. Copyright 2017 Rendia, Inc.
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Blepharitis secondary to Demodex infestation. Image courtesy of Rendia, Inc. Copyright 2017 Rendia, Inc.
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A novel in-office treatment using a mechanical rotating handpiece with a microsponge tip combined with PolyaminopropylBiguanide foam solution removes oil, scurf, and debris; exfoliates the eyelids, and claims to decrease Demodex infestation. Image courtesy of Rendia, Inc. Copyright 2017 Rendia, Inc.
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Intense pulsed light. Courtesy of OPTIMED (https://www.optimed.co.uk/), E-referral and patient engagement platform.
