Ocular Demodicosis (Demodex Infestation) Clinical Presentation

Updated: Oct 30, 2017
  • Author: Manolette R Roque, MD, MBA, FPAO; Chief Editor: Hampton Roy, Sr, MD  more...
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Presentation

History

Symptoms of demodicosis include ocular irritation, itching, and scaling of lids. Past ocular history may include recurrent failed treatment of blepharitis.

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Physical

Gross observation may reveal the following:

  • Lid thickening

  • Scaling of lids

  • Madarosis (loss of lashes)

  • Conjunctival inflammation

  • Meibomian gland dysfunction

  • Rosacea: The results of the study by Moravvej et al [6] 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.

  • Decreased vision

Slit-lamp findings are as follows:

  • Collar of tissue around the base of the eyelashes

  • Follicular distention

  • Cornea - Superficial corneal vascularization, marginal corneal infiltration, phlyctenule-like lesion, superficial corneal opacity, nodular corneal scar

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Causes

Demodex species specific to humans occupy 2 periocular sites hidden from external observation. They are small in size and possess the ability to 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 sebaceous glands of the body and in 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 similar structure of the head and the thorax but a shorter abdomen.

The 8 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 back into the follicle. Therefore, the mite can be observed only when an epilated lash is observed 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; a fact that is significant in symptomatology and treatment.

Following copulation, the female burrows back into the follicle near the opening of the pilosebaceous gland and lays her eggs.

Spickett reported the life cycle of D folliculorum and estimated that only 14.5 days elapse from ovum to adult stage, including 120 hours as an adult. Females may live an additional 5 days after oviposition. [3]

Sexes are separate; sexual maturity is reached in the larval form (neoteny).

Females are territorial; they remain in their respective follicles and wait for the nomadic philandering males that travel over the surface of the skin from one follicle to another in seek of females.

Adults reside in the follicle parallel to the hair shaft, head inward, often with the tail end (opisthosoma) protruding onto the surface of the skin at the base of the eyelash.

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