“Dry Eye” is a condition that vets see commonly in small animal practice. To use it’s proper name, “Keratoconjunctivitis sicca” (“sicca” means dry in Latin), is a chronic and debilitating condition, which occurs when there is a lack of sufficient tears to keep the eyes and surrounding soft tissues moist.
The eyes then become dry, and tacky, and this predisposes to infection and painful inflammation, which also involves the conjunctiva (and so conjunctivitis occurs). The mucus glands in the conjunctiva try to compensate by overproducing lots of sticky, green mucus.
The lack of ‘flushing’ effect from the absence of tear film prevents foreign material (dust, grass seeds, pollen etc) from being washed out of the eyes, and can predispose to potentially disastrous ulceration and rupture of the thin corneal surface.
The chronic stage results in the cornea becoming thickened and discoloured (pigmented), resulting in blindness.
The commonest cause is autoimmune disease (where the body’s own defence system does not recognise its own tissues as “self”, and fights against it by producing harmful antibodies), altho’ other causes exist (such as damaged or diseased nerves which normally stimulate the tear glands).
You or your vet may suspect “Dry Eye” when your pet gets recurring eye infections, or the eyes appear dry and ‘sticky’. A simple test (the Schirmer Tear Test) can be done rapidly in surgery, which confirms the level of tear production.
Previous methods of treatment were limited to various artificial tear drops, which had to be applied every hour to be vaguely effective! Not very practical, and poor compliance meant poor results.
Nowadays, modern treatments include ointments which “modulate” the immune response, stopping the harmful attacks on the tear glands, allowing them to recover if caught in good time. Clearly, the return of natural tears, produced continuously by the patient, is the best possible option.
Occasionally, medical options are unsuccessful (usually when the start of treatment is left too late); one interesting surgical option for these cases is to transplant one of the salivary gland ducts towards the affected eye, draining saliva onto the surface of the eye, which keeps the eye moist. This can be an expensive option, and has the bizarre side-effect of making the eyes run at feeding time!
If you suspect your pet has “Dry Eye”, make an appointment with your vet for a Schirmer Tear Test.