September Pulse Article (PART 3 OF 12, NASOLACRIMAL AND CONJUNCTIVAL ABNORMALITIES)
September 20, 2018
This month, we look at some common ophthalmic presentations associated with the conjunctival and nasolacrimal tissues.
The conjunctival surfaces are richly supplied with the cellular components of the immune system and represent a first line of antigenic response. As a consequence,allergic conjunctivitisis not uncommon, particularly in those patients affected by generalized dermal allergic or atopic disease. Treatment comprises the avoidance of inciting allergens, systemic management of generalized atopy and the application of topical anti-inflammatory therapy, the type, frequency and duration of application being determined by the clinical picture.
Dacryocystitisdescribes inflammation of the nasolacrimal drainage structures, which comprise the eyelid puncta, lacrimal canaliculi, lacrimal caverns and the sinonasal ducts that exit to the external nares. Inflammation may be the result of infection, extension of inflammation from adjacent structures, neoplasia or entrapment foreign material. Primary aplasia or hypoplasia of any part of this system may also occur. Post-inflammatory scarring & fibrosis is a common cause of nasolacrimal non-patency, particularly in cats previously affected by herpesviral-associated disease. Medical therapy using topical and/or systemic antimicrobial and/or anti inflammatory agents as well as canulation, irrigation, stenting and/or surgical exploration may be indicated based on the severity of disease, diagnostic findings and response to therapy.
Herpesviral- associated conjunctivitisis highly prevalent, particularly among young cats, resulting predominantly from animal to animal contact. Affected animals may display a range of symptoms including sneezing, coughing, nasal discharge, pyrexia, inappetance, lethargy, conjunctivitis, chemosis and/or keratitis. Herpes viral disease should also be considered when investigating similar symptoms in canine patients. Accurate testing for the presence of FHV-1 and its correlation with ophthalmic disease is challenging, however, polymerase-chain-reaction assays, based on tissue samples, are currently considered most reliable. Topical and/or systemic antiviral agents may be administered where appropriate, including; (topical) trifluorothymidine, idoxuridine, cidofovir, & ganciclovir and/or (systemic) famciclovir.
Thelazia(“eye worms”), represent a genus of nematode parasites which may occasionally be found in the ocular and adnexal tissues of dogs and cats in southern California. 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 larvae, which are released into the pre-corneal tear film of the definitive host. Adult parasites may be found in the conjunctival fornix, nasolacrimal system, under the third eyelid or in rare cases, inside the globe. Resultant conjunctivitis is frequently aggravated by self-trauma. Adult worms are thin, linear, white to translucent in color and approximately 1-2cm in length. Treatment includes the removal of adult parasites, the topical administration of demeracrium bromide and/or systemic anthelminthic agents including the avermectins, praziquantal and/or mebendazole.
Neoplastic processeswhich may affect the conjunctival and nasolacrimal tissues include papillomas (notably viral papilomatosis in puppies), adenoma/adenocarcinoma, haemangioma/haemangiosarcoma, lymphoma and squamous cell carcinoma (notably in white or minimally pigmented animals). The management of each tumor type is beyond the scope of this brief clinical review however typically encompasses excision where possible in combination with adjunctive radio/chemo therapy where indicated &/or the involvement of a veterinary oncologist.
Dr Esson is a board-certified veterinary ophthalmologist with more than twenty years of clinical experience and multiple areas of interest & expertise. His clinicVeterinary Ophthalmic Consultingis family owned & operated and he takes great pride & pleasure in working closely with his friends and colleagues in the greater Southern California veterinary community.