In all species, including cats, the surface of the eye is coated by a thin film of tears, critical for comfort, eye health, and vision. The tear film improves vision, provides corneal lubrication, nutrition, and protection from infection, and flushes debris from the ocular surface. The tear film is composed of three layers: an outer lipid layer, a middle aqueous layer, and an inner mucous layer. Abnormalities in these tear layers are associated with rapid evaporation of the tears and drying of the conjunctiva and cornea, which is highly painful and potentially blinding. Tear film abnormalities are an important part of many common feline diseases such as dry eye, feline herpesvirus, Chlamydia and Mycoplasma infections, where they lead to increased discomfort and exacerbate inflammation. Despite this, current understanding of the feline tear film and methods of assessing it are rudimentary.
Although “artificial tear” eye-drops provide temporary relief in such conditions, they require accurate and convenient tests to identify the affected tear film layer and for monitoring response to treatment. Recently, new, non-painful, tests have been developed for diagnosing and monitoring tear film disorders in humans. It is predicted that these tests will have similar value in cats. Therefore, in this study the researchers will establish normal values for these new tests in cats. This information will be of immediate use to veterinarians worldwide because it will allow early diagnosis and treatment of tear film abnormalities in cats, which will minimize ocular pain and the potential for severe or chronic complications.