Increased numbers of Demodex in contact lens wearers

The aim of this study was to determine if Demodex infestation is more frequent in contact lens wearers than in nonwearers. Secondary aims were to evaluate the effects of Demodex on the ocular surface (symptoms and signs) and to evaluate the ability of confocal laser scanning microscopy to detect and quantify the Demodex infestation compared with the conventional light microscopic technique.

Forty Asian female participants (20 nonwearers, 20 lens wearers) with a mean (± SD) age of 27 (± 9) years were recruited. Ocular comfort scores (Ocular Surface Disease Index, Ocular Comfort Index, and Dry Eye Questionnaire), vital staining (corneal, conjunctival, and lid wiper), tear osmolarity, tear breakup time, and meibomian gland evaluation were evaluated. Demodex was detected using in vivo confocal microscopy and conventional light microscopy.

The number of Demodex was higher in lens wearers than in nonwearers (7.6 [± 5.8] vs. 5.0 [± 3.1]; p = 0.02). Demodex was observed in a large majority (90%) of lens wearers and in 65% of nonwearers using confocal microscopy (p = 0.06). The detection rate was lower in both groups using conventional light microscopy (p = 0.003) where Demodex could only be confirmed in 70% and 60% of lens wearers and nonwearers, respectively. The number of Demodex tended to increase with age (ρ = 0.28, p = 0.08), but Demodex did not appear to affect ocular comfort or any clinical signs (p > 0.05).

Contact lens wearers harbor Demodex as frequently as nonwearers and in higher numbers, which is best detected using in vivo confocal microscopy. The significance of these findings is uncertain because no associations were found with any symptoms and signs of dry eye disease.