Demodex brevis and Demodex folliculorum are likely ubiquitous organisms associated with human eyelashes. However, they have also been implicated in the pathogenesis of external ocular diseases. This article reviews the current literature in regards to life cycle, morphology, pathogenesis and treatment of underlying Demodex spp. infestation and outlines the previously undescribed in vivo behaviour of the mites. Images were obtained from the epilation of lashes from 404 patients seen in clinical practice. Epilated lashes were placed on a microscope slide which had been coated with optically clear hypromellose/carbomer gel (Genteal gel, Novartis pharmaceuticals corporation, East Hanover, New Jersey). Adults were identified with either dark field or standard transmission microscopy at 40-100×. Eggs and other life-cycle stages were examined at 250× magnification, with transmission microscopy giving the best image resolution. The life cycle of the mite has been reviewed and simplified according to clinical observations. Clinical signs suggestive of underlying Demodex spp. infestation have been described, and their pathogenesis was explained based on the micrographic digital images obtained. The problem of symptomatic Demodex spp. disease likely reflects an imbalance in the external ocular ecology; however, the role of Demodex spp. as a commensal should not be overlooked. Treatment should not be aimed at total eradication of the mite but rather restoring the ocular ecology to a balanced state. By revisiting the life cycle of the mite, we can identify areas where possible intervention may be effective.
Demodex species (spp.) have previously been implicated in the pathogenesis of blepharitis. This study aims to correlate improvement in symptoms of external ocular disease with treatment of underlying Demodex spp. This is a prospective, observational case series of patients with chronic external ocular disease. Demodicosis was confirmed by microscopic examination of epilated eyelashes. The main outcome measure was response to the treatment (5 % tee tree oil) in regard to change in subjective symptoms utilising a symptom-based patient questionnaire assessment. Overall patients had a good response to the treatment in terms of improvement or resolution of symptoms, with 91 % of patients reporting at least some improvement in symptoms. The treatment of underlying Demodex spp. appears to result in improvement of symptoms in patients with long standing external ocular disease and underlying Demodex spp. infestation.
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