The natural history of demodectic mites on the skin of the eyelid margin

Background Demodectic mites can be readily studied on the eyelid margin. Methods This was undertaken by scanning electron microscopy of the skin of the lid margin of full thickness eyelid specimens obtained by surgery. Results The whole life cycle of Demodex folliculorum, including the egg, nymph and adult stages was observed by electron microscopy of this region. The tails of adult mites protrude from hair follicles and also lie close to eyelashes either singly or in groups. Conclusions The eyelid littoral appears to be a significant site for egg laying by demodectic mites, and both intact and broken eggs have been seen. At the other end of the life cycle when adult mites die the protruding opisthosoma develops cracks in the carapace and the tail breaks off. Spillage of abdominal contents occurs which can carry fungi and bacteria on to the skin surface. All stages of the parasite including numerous casts of the ecdysed carapace contribute to debris found on the skin surface of the eyelid.