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Alex Muntz, Christine Purslow, James Stuart Wolffsohn, Jennifer P Craig; Improved Demodex diagnosis and grading using a novel in situ technique. Invest. Ophthalmol. Vis. Sci. 2019;60(9):6794.
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© ARVO (1962-2015); The Authors (2016-present)
Clinical diagnosis of Demodex by eyelash epilation has been criticized for yielding low mite numbers even in cases of heavy infestation. Current and alternative techniques were compared and the optimum proposed for the clinical diagnosis of Demodex.
Fifteen participants with previously confirmed ocular demodicosis and/or anterior blepharitis featuring typical cylindrical dandruff eyelash crusting and 7 controls were enrolled. Demodex presence on each eyelid of every participant was assessed using 5 consecutive techniques, on up to four different eyelashes for each test, performed in the following order: in situ, using fine-point forceps and 25-40x slit-lamp magnification, by eyelash rotation as proposed by Mastrota (ROT); by removing cylindrical dandruff and exposing the eyelash insertion point at the lid margin (CDR); and by laterally tensioning the eyelash (ELT) following CDR. The typical appearance of cigar-shaped mite tails protruding from each assessed eyelash follicle (Figure 1) was observed, video recorded, and graded by mite tail count from 0 (no mites), 1 (1-2 mites), 2 (3-4 mites) to 3 (>5 mites) and averaged per participant for each assessment technique. Next, eyelashes were epilated, and mite presence evaluated using bright-field microscopy at 10, 20 and 40-times magnification (EPI). Finally, eyelash follicles were imaged using in vivo confocal microscopy and the images visually inspected for mite presence.
The highest numbers of mites in Demodex patients were identified by ELT, averaging a clinical grade (mean±SD) of 2.4±0.7, versus CDR (1.7±0.9) and ROT (0.8±0.7) (all p<0.002). An average of 1.0±0.8 mites/lash were identified by EPI. Demodex failed to be conclusively identified in known positive cases using in vivo confocal microscopy.
A novel technique for the clinical diagnosis and grading of Demodex in situ is presented. By removing cylindrical dandruff and applying static, lateral tension to the eyelash without epilation, large numbers of mites are visible at the exposed eyelash follicle. The proposed method is convenient for both clinicians and patients, allowing rapid, efficient evaluation of large numbers of eyelashes without discomfort to the patient, and requiring only forceps and 25-40x slit-lamp biomicroscope magnification.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
Two Demodex tails protruding from an eyelash follicle during ELT
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