Ocular Demodex: a systematic review of the clinical literature

Abstract

Purpose: There is increasing clinical and research interest in the potential contribution of Demodex to ocular surface disease. The aim of this systematic review was to summarise and synthesise current clinical evidence relating to the aetiology, diagnosis and treatment of ocular Demodex. Recent findings: A comprehensive literature search was performed in OVID Medline, OVID Embase, and clinical trial registries, for studies published between 1990 and August 2019, examining Demodex on the ocular surface. The review included primary clinical research studies and systematic reviews of primary clinical research studies, where Demodex was considered in the context of the ocular surface and/or adnexa. Studies were categorised using the National Health and Medical Research Council evidence hierarchy. Risk of bias assessment was performed using validated tools for studies categorised as providing Level I or II evidence. A total of 87 studies were eligible for inclusion, including two systematic reviews. Most studies (60%) were observational, describing the prevalence of ocular Demodex in different clinical populations. There was a high degree of variability in the epidemiological data derived from cross-sectional aetiology studies. There was mostly consistent evidence to support an association between ocular Demodex and chronic blepharitis. Seven diagnostic test-accuracy studies were identified, which considered a range of techniques, including slit lamp examination for cylindrical eyelash collarettes and/or eyelash manipulation techniques, light microscopic evaluation of epilated eyelashes and in vivo confocal microscopy. There is currently no accepted gold-standard diagnostic method for ocular Demodex. For intervention studies, there was one systematic review, 11 published randomised trials, six trial registry entries, and nine case series. Despite a number of recent trials, the appropriate treatment regimen for ocular Demodex (including the optimal criteria and timing of an intervention) is not clearly established. Conclusions: This comprehensive narrative synthesis has captured the landscape of clinical evidence relating to the prevalence, aetiology, diagnosis and treatment of ocular Demodex. There remain opportunities to enhance understanding of its role in ocular surface disease, best diagnostic approaches and optimal treatment protocols.

Safety and efficacy of lotilaner ophthalmic solution, 0.25% for the treatment of blepharitis due to demodex infestation: A randomized, controlled, double-masked clinical trial

“…Despite its high prevalence among blepharitis patients, Demodex mite infestation is an oftenoverlooked cause of chronic blepharitis [12][13][14]. When assessed in community populations, the prevalence of ocular Demodex reportedly ranges from 16% to 70% [15]. The rate of infestation increases with age, reaching 84% of the population by the age of 60 and 100% in those older than 70 [9,16,17].…”

“…Demodex mites are microscopic ectoparasites of the phylum arthropoda with a semi-transparent, elongated body and four pairs of legs [9,15,18]. Demodex folliculorum and Demodex brevis are known to inhabit human skin [9,15,19].…”

“…Demodex mites are microscopic ectoparasites of the phylum arthropoda with a semi-transparent, elongated body and four pairs of legs [9,15,18]. Demodex folliculorum and Demodex brevis are known to inhabit human skin [9,15,19]. These mites tend to gather in the face, cheeks, forehead, nose, and external ear tract, where they find a favorable habitat for breeding and active sebum excretion provides nutrition [20].…”

“…These mites tend to gather in the face, cheeks, forehead, nose, and external ear tract, where they find a favorable habitat for breeding and active sebum excretion provides nutrition [20]. While D. folliculorum is approximately 0.3 to 0.5 mm long and mostly exists in clusters in the eyelash follicles, D. brevis is typically smaller (0.2 to 0.3 mm long) and resides deep in the sebaceous glands of the eyelids and the lobules of meibomian glands [15,20]. D. folliculorum mites consume epithelial cells at the eyelash follicle, induce epithelial hyperplasia and hyperkeratinzation, subsequently leading to the formation of collarettes (cylindrical dandruff) and redness, potential eyelash loss and/or misdirection [3,18,19].…”

“…A number of proposed treatments, including 1% sulfur ointment [21,22], 1% mercury oxide ointment [22][23][24][25], pilocarpine gel [26,27], and iodized solutions [27,28], have been found to be largely ineffective. Treatment with the oral antiparasitic drugs ivermectin and metronidazole and lid wipes containing tea tree oil (TTO), a natural oil distilled from Melaleuca alternifolia, have shown varying levels of success [3,4,15,18,20,29,30].…”