Measuring tear production in birds

Measuring tear production in birds is an important diagnostic procedure that allows early detection of dry eye syndrome, i.e. decreased tear production that leads to changes in the cornea and conjunctiva of the bird. Dry keratoconjunctivitis is manifested by discharge from the conjunctival cavity of varying intensity from catarrhal to catarrhal-purulent, corneal edema, ingrowth of superficial blood vessels into the cornea, corneal dullness, and pigment deposition on the cornea (which is not very common in birds). Dry keratoconjunctivitis in birds often occurs after a severe inflammatory process in the lacrimal glands of birds. Inflammation of the lacrimal glands (dacryoadenitis), which arose for one reason or another, can lead to decreased tear production. In birds, pathologies of the lacrimal glands are quite common. The lacrimal glands may become infected with bacteria, leading to edema and abscess formation. Edema must be differentiated from possible neoplasia of the gland or periorbital area. Of the neoplastic causes affecting the lacrimal glands, adenocarcinomas of the lacrimal glands are the most frequently described. For quantitative measurement of tear production in birds, Schirmer test strips from various manufacturers are most often used, as well as a phenol red thread, which is most convenient for placement in the lower conjunctival fornix of small birds. When carrying out the procedure for measuring tear production, it is important to follow all the rules in order to obtain correct measurements. Measurement of tear production should be carried out before the use of any local solutions, since they artificially but temporarily increase the value of this test. In addition, some local solutions have a longer inhibitory effect. For example, local anesthetics or parasympatholytic drugs used to induce mydriasis will reduce the values of the Schirmer test. Manipulative procedures such as corneal or conjunctival scrapings, lacrimal irrigation, or application of bright light to the inflamed eye will result in artificially elevated Schirmer test values.