Dry Eye From an Unwelcome Visitor
By William L. Miller, OD, PHD, FAAO
This month we will look at a cause of blepharo-conjunctivitis and dry eye disease. This particular vector is related to an infestation of mites that live on the lash follicles and in the associated sebaceous glands. The condition is generally referred to as Demodicosis and involves two species of mites: Demodex folliculorum or Demodex brevis. Although controversial as a cause for blepharitis, a recent metanalysis supported the supposition that Demodex can be a cause of chronic blepharitis (Zhao et al, 2011).
Rarely seen in children, Demodicosis frequency increases as patients age with a large majority of patients over the age of 45 experiencing varying degrees of infestation. A study published nearly 50 years ago observed Demodicosis in 84 percent of patients with a mean age of 61 and in 100 percent of patients over the age of 70 (Post and Juhlin, 1963). In addition to blepharitis, Demodex can also cause dermatologic manifestations mostly affecting the scalp, face, and upper aspect of the chest.
Ocular Signs and Symptoms
Some patients may be asymptomatic, but when symptomatic they may complain of typical blepharitis symptoms such as burning, itching, redness, and foreign body sensations. All of these signs could also be confused with those of dry eye disease patients. Patients who have Demodicosis will also exhibit signs that are similarly found in the course of other causes of blepharitis and/or meibomian gland dysfunction. Keratin sleeves at the base of the lashes are also a common manifestation of Demodex overgrowth.
For a more definitive diagnosis, which may be prudent in chronic cases of blepharitis that are unresponsive to traditional therapy, the lash(es) can be epilated and microscopically examined using a viscous solution or fluorescein-laden drop of saline. If present, the mites will be clinging to the lashes (Figure 1). Because their presence can be common, overpopulation is defined as six or more mites per 16 lashes or when more than four or five are clinging to one lash. (Coston, 1967).
Figure 1. Eyelash with attached Demodex. Photo provided by Associate Professor IB Kjellevold Haugen, PhD, and Professor JR Bruenech, PhD, Biomedical Research Unit, Faculty of Health Sciences, Buskerud University College, Norway.
If traditional treatment such as lid scrubs and antibiotic therapy has not been initiated, proceed with that prior to starting the ensuing modes of therapy.
Additional treatment beyond what is typically undertaken for blepharitis may consist of the simple application of bland ointment to the lashes and lid margins in an effort to eliminate the mites' ability to breed. Because many of the topical therapies for dermatologic use are not safe around the eye, modern therapies have focused on the use of 50% tea tree oil along with lid massage and tea tree oil ointment for use overnight. Recent studies using ivermectin, an oral medication used by dermatologists to treat rosacea, have been reportedly successful in eradicating the mites when other therapies and approaches have failed (Holzchuh et al, 2011; Filho et al, 2011). CLS
For references, please visit www.clspectrum.com/references.asp and click on document #200.
|Dr. Miller is an associate professor and chair of the Clinical Sciences Department at the University of Houston College of Optometry. He is a member of the American Academy of Optometry and the AOA where he serves on its Journal Review Board. He is a consultant or advisor to Alcon and Vistakon and has received research funding from Alcon and CooperVision and lecture or authorship honoraria from Alcon and B+L. You can reach him at firstname.lastname@example.org.|