Demodex folliculorum and Demodex brevis are ectoparasites that inhabit the skin of humans. They have been related to alterations in the ocular surface, such as, dysfunction of Meibomian glands, blepharitis, chalazion, etc. Ocular demodicosis is characterised by the pathognomonic presence of cylindrical dandruff at the base of the eyelashes, and various symptoms including, among others, itching, lacrimation, and hyperaemia. A bibliographic review was carried out on the role of Demodex spp. in ocular disease, including publications made by the scientific society between 2005 and 2018. A significant relationship was found between prevalence and incidence of Demodex spp. in eye diseases. D. folliculorum is usually found more frequently than D. brevis in ocular infestation, with the prevalence or incidence of infestation by both species increasing with the age of the patient. In patients with blepharitis or other infectious diseases of the ocular surface, unresolved with antibacterial treatment, the search for Demodex spp. should be considered.