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By knowing the signs and symptoms of Demodex, ophthalmologists can better diagnose and offer treatments for blepharitis.
Take-home message: By knowing the signs and symptoms of Demodex, ophthalmologists can better diagnose and offer treatments for blepharitis.
Reviewed by Esen K. Akpek, MD
Baltimore-Infestation of Demodex, an ectoparasite often found on human skin, appears to play a part in blepharitis cases-both in younger and older patients (and everyone in between).
The clinical significance of such an invasion of mites in blepharitis is up for debate, largely because the infestation also can appear in individuals with no symptoms, according to Esen K. Akpek, MD, professor of ophthalmology, Johns Hopkins University School of Medicine, Baltimore.
Dr. Akpek said whether the infestation is significant enough has a tie-in to incidences of blepharitis, and this has led to it sometimes being missed when drawing up differential diagnoses of chronic blepharokeratoconjunctivitis.
Demodex is often observed in individuals over age 70. The infestation rate is reported to accelerate with age. However, the literature also points to chronic blepharokeratoconjunctivitis being linked to demodicosis in children.
“Most everyone above a certain age has Demodex. However, most [do] not react to the presence of this microorganism,” Dr. Akpek said.
Overall, whether impacting young or old individuals, infestation of Demodex has been tied to several skin problems, including perioral dermatitis, pityriasis, and rosacea.
Simple hygiene measures can prevent demodex infestations. Courtesy of Esen Akpek, MDWhen affected by Demodex, Dr. Akpek says, “If patients perform daily hygiene measures, they will be fine. This means scrubbing the lids with a detergent such as baby shampoo.”
She likens the hygiene measure to brushing teeth twice and flossing once a day.
“Some people do not wash their faces, [so] the microorganism overgrows and causes trouble,” Dr. Akpek said. “Some people are highly sensitive to the presence of the microorganisms and react with a delayed cell-mediated hypersensitivity, then get, for example, corneal involvement.”
As for cases involving children, Dr. Akpek said it is important for ophthalmologists to anticipate this condition.
“It is easy to diagnose if they suspect [it],” she said. “Just lid hygiene [alone is] mostly adequate, but sometimes oral antibiotics are necessary.”
To watch video of a magnified demodex egg hatching, click here.
To date, two species of Demodex have been detected in humans-Demodex folliculorum and Demodex brevis. The former shows up in the lash follicle while the latter buries itself in sebaceous and meibomian glands. Transmission occurs via direct contact.
Demodex mites feed off meibum and Demodex folliculorum feed on epithelial cells around the hair follicle, which can result in broken or loose lashes, Dr. Akpek explained. Further damage from the mite’s claws can result in epithelial hyperplasia and reactive hyperkeratinization near the lash base, which can lead to cylindrical dandruff.
Due to Demodex brevis being able to block the meibomian gland openings, this can set the stage for posterior blepharitis, according to Dr. Akpek. When dealing with chronic infestation with Demodex, this can then cause recurring and difficult-to-manage chalazia. Another way the Demodex mite can trigger blepharitis is by housing bacteria on the surface, namely Streptococci and Staphylococci.
According to Dr. Akpek, primary demodicosis symptoms are burning and itching, foreign body sensation, redness and crusting of the lid, and blurred vision. When diagnosing Demodex blepharitis, she says cylindrical dandruff is a classical sign pointing to the condition. When the lash follicles continue to be infested, this can lead to misalignment of lashes or trichiasis.
“Trichiasis may induce trauma to the corneal epithelium, causing punctate epithelial erosions followed by corneal ulceration and pannus formation in severe, long-standing cases,” she says.
If the meibomian gland opening is blocked, this can result in distention, enlarged glands, and edema.
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Additionally, she said chronic granulomatous hypersensitivity responses in meibomian glands may lead to hordeolum or chalazion.
The presence of a mechanical blockage and delayed host immune hypersensitive reaction is a recipe for lid margin inflammation.
“Demodicosis can cause various sight-threatening corneal lesions, including superficial corneal vascularization, marginal infiltrates, phlyctenule-like lesions, and eventual scarring,” she said.
Diagnose and treatment
During a slit lamp exam, Dr. Akpek recommends looking for the telltale sign of cylindrical dandruff at the base of eyelashes as indicative of demodicosis.
Further, confirming via microscope the presence of Demodex eggs, larvae, and full-grown mites in epilated lashes will enable the ability to properly diagnose.
Start with warm compresses and scrubs for the lid, Dr. Akpek said. Treatments of demodicosis have included mercury oxide 1% ointment, camphorated oil, pilocarpine gel, and sulfur ointment.
“Most of these treatments involve spreading an ointment at the base of the eyelashes at night to trap mites and prevent mating,” she said.
Recent studies point to tea tree oil has a possible option to eliminate the mites, larvae, and eggs.
“Tea tree oil also leads to alleviation of symptoms and resolution of the ocular surface inflammation,” Dr. Akpek said.
“It is easily treatable. Always look for it and treat first,” she said. “If the patient symptoms are not better even after Demodex is gone, then look for other reasons for ocular surface inflammation.”
She added that because Demodex plays a role as vector of the skin organisms, comorbidity associated with a symbiotic relationship of Bacillus oleronius in mites may warrant potential use of oral antibiotics such as tetracyclines or macrolides as a tactic to kill the symbiotic bacteria.
As take-away points for physicians she recommends to “always look for Demodex in any blepharitis patient and treat it. This is easy to do [and] it might be helpful to the patient.”
Looking forward, she said she likes the procedural treatments for meibomian gland dysfunction such as intense pulsed light and LipiFlow thermal pulsation system. However, there is still no cure, she added.
Esen K. Akpek, MD
This article was adapted from Dr. Akpek’s presentation at Cornea Subspecialty Day during the 2015 meeting of the American Academy of Ophthalmology. Dr. Akpek reports grant support from Allergan.