Thelazia represent a genus of nematode parasites,( sometimes referred to as “eye worms”), which may affect the ocular and adnexal tissues of dogs and cats. The life cycle of these parasites comprises a definitive host (comprising a range of wild mammals including horses, ruminants & numerous wild carnivores) and an intermediate host (notably dipteran flies). After mating, adult female parasites produce immature (first stage) larvae, which are released into the pre-corneal tear film of the definitive host. Immature larvae are subsequently ingested by flies, where they develop to third stage larvae before again being released into the tear film. Adult parasites may be found in the conjunctival fornix, nasolacrimal system, under the third eyelid or in rare cases, inside the globe. Associated symptoms may include blepharospasm, conjunctivitis, chemosis, ocular discharge, third eyelid elevation and/or uveitis, all of which may be aggravated by self-trauma.