Itchy Eyelids? It Mite Be Infestation
BY WILLIAM D. TOWNSEND, OD
One of the conditions that we often fail to consider when we encounter patients with itchy, inflamed eyelids is mite infestation. Only two species of Demodex are known to affect humans. Demodex folliculorum is a 0.3mm-0.4mm long arachnid and lives in the pilosebaceous glands of the face and eyelids. Demodex brevis is about 0.2mm long, and is found in lash follicles, meibomian glands and Zeiss glands. Rather than living in colonies, it tends to inhabit sebaceous glands either singly or in small numbers. D. brevis appears to thrive on skin lipids, but its presence is often associated with dry skin. This species has been shown to cause plugging of the meibomian and other sebaceous glands, and has been found at the center of meibomian granulomas, suggesting that it may be one cause of chalazia. Both species are nocturnal and avoid bright light by retreating into the nearest hair follicle. Histologically, mite infestation is characterized by histio-lymphocytic infiltration, follicular inflammation and generalized edema of the follicle.
Infestation or Infection?
Patients with mite infestation may complain of itchiness that is worse in dim light, especially after going to bed or upon awakening. Brittle eyelashes that break easily or are easily epilated are also tell-tale signs. Patients may also report dry eye symptoms secondary to plugged meibomian glands. The probability of mite infestation tends to increase with age, as lid biopsies show that 84 percent of individuals over 61 have the condition. Slit lamp evaluation often reveals eyelid changes that are indistinguishable from seborrheic blepharitis. There is usually dermal scaling, redness and meibomian gland stenosis. Collarettes at the eyelash base are a diagnostic finding. Although careful evaluation may reveal the ends of the mites' bodies extending just past the opening of the follicles, observation is much easier by epilating several lashes, placing them under a microscope in immersion oil and observing them at 40x magnification.
Managing Mite Infestation
Treatment of mite infestation requires killing the adult mites and getting rid of the eggs before they hatch. Initiate in-office treatment by carefully swabbing volatile fluids such as alcohol or ether on the eyelid margin three times per week. It's important that these materials do not contact the cornea. In-home therapy includes brisk eyelid scrubs daily using baby shampoo or commercially prepared pads. Heavily coating the lid margins with 2% mercuric oxide or other viscous ointments is also an effective approach that appears to inhibit the reproductive activity of the adult mites and cut off oxygen to mites trapped in hair follicles. Mercuric oxide has a toxic effect on the organisms as well, but be sure to question the patient about mercury sensitivity prior to prescribing it.
Another means of treatment is 4% pilocarpine gel, which works by interfering with respiration. Pilocarpine can cause severe ciliary spasm, retinal tears and detachment in predisposed individuals, so patients should apply it directly to their eyelid with a cotton-tipped applicator.
Demodex infestation is common among patients, especially elderly ones. Be aware that it can contribute to blepharitis, meibomitis and rosacea.
Maintaining a high index of suspicion will help you diagnose this condition more quickly.
Dr. Townsend is in private practice in Canyon, Texas, and is a consultant at the Amarillo VA Medical Center. (firstname.lastname@example.org)