Eyeworld

88 | EYEWORLD | MARCH 2021 C ORNEA by Ellen Stodola Editorial Co-Director About the physicians Vincent de Luise, MD Assistant Clinical Professor of Ophthalmology Yale University School of Medicine New Haven, Connecticut Henry Perry, MD Chief, Cornea Service Nassau University Medical Center East Meadow, New York Scheffer Tseng, MD, PhD Chief Technology Officer TissueTech Miami, Florida Elizabeth Yeu, MD Assistant Professor Eastern Virginia Medical School Norfolk, Virginia D emodex mites can cause a number of problems, including ocular issues. Several physicians discussed symp- toms, what to look for, and ways to treat an infestation. According to Vincent de Luise, MD, there are two species of Demodex that cause human disease: Demodex folliculorum and Demodex brevis. These mites are acarids, a type of arach- nid, in the phylum Arthropoda, and in the same taxonomic class as spiders, he said. D. folliculorum is the most common para- site in man, said Henry Perry, MD, adding "the parasite is virtually ubiquitous in our skin by age 45." D. folliculorum and D. brevis mites are com- mon on human eyelids and lashes, Dr. de Luise said. He noted that D. folliculorum mites are the larger of the two species and usually inhabit hair follicles, whereas the smaller D. brevis mites are usually found in and around piloseba- ceous glands and meibomian glands. "Demodex folliculorum finds its primary habitat at the base of the lash follicle, where it feeds on follicular and glandular epithelial cells, causing direct mechanical damage and microscopic epithelial abrasions that can lead to epithelial hyperplasia and hyperkeratinization." Dr. de Luise said it has been estimated that 45% of adults with blepharitis harbor Demodex mites. Although Demodex occurs more commonly in the older age groups, the most severe cases of Demodex are in children, Dr. Perry said. "The older the patient is, the more likely to find Demodex, but in children who have rosacea, the presence of Demodex is alarming," he said. It can cause significant ocular issues, including loss of vision or permanent scarring depending on the severity of the rosacea and infestation. Presentation and symptoms Dr. de Luise said that Demodex can present with a number of ocular conditions, including anteri- or blepharitis, posterior blepharitis, meibomian gland dysfunction (MGD), oculocutaneous ro- sacea, and keratitis. "There is also a correlation between Demodex infestation and acne vulgaris, as well as an association with oculocutaneous rosacea," he said. "Because the Demodex mite lives within sebaceous glands and the eyelash follicle is a modified sebaceous gland, the Demodex mite can commonly infest and overgrow within the eyelids," said Elizabeth Yeu, MD. Demodex blepharitis accounts for approximately 45–50% of blepharitis. Patient complaints vary, Dr. de Luise said, with symptoms of irritation, discomfort, itching, burning, and foreign body sensation often elicited. Signs of Demodex infestation include collarettes and crusting or matting of eyelashes, tearing, and blurry vision. When patients come in complaining of itchy, burning eyes, many of these patients have MGD, blepharitis, or dry eyes, Dr. Perry said. "We start trying to look for the factors that are making them worse." He said that during examination, one thing to check for is dandruff at the base of the eye- lashes. There's a particular type, called cylindri- cal dandruff, that's like a pipe stemming off the eyelashes. It grows in a circular fashion around the eyelashes and usually starts at the base of the eyelash. This cylindrical dandruff is the pri- mary sign of D. folliculorum, Dr. Perry said. To diagnose, Dr. Perry said he will take an eyelash and examine it under a light micro- scope. He is often able to see the organism and diagnose this way. He noted that cylindrical dandruff presence on its own is not enough for a definitive diagnosis. "The clinical finding of the collarette, or cylindrical dandruff at the base of the lash, may Demodex update: background, signs and symptoms, and treatment Phase contrast Demodex folliculorum with eight legs, head, and body Source: Henry Perry, MD

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