Facts about Dry Eye
What is tear film/tears?
Tears are produced by various lacrimal glands, and one of their most important jobs is to keep the ocular surface moist. Tears consist of more than just water — they also contain, for example, antibacterial substances. In addition, tears support the movement of the eyelids and nourish the cornea.
Tear production is measured using a quick, simple test (the so-called Schirmer tear test). The test is painless and takes only 60 seconds. A test strip is placed in the lower eyelid, and the value is read off the strip via a colour change. Normal tear production in dogs is 15 mm/minute or more.
What is meant by dry eye disease?
In so-called "dry" eye, tear production is reduced due to disease of the lacrimal glands. This can have various causes:
- Inherited in certain dog breeds (e.g. Pug, Cocker Spaniel, West Highland White Terrier).
- An immune-mediated process (the immune system turns against the body's own tissue).
- Removal of the gland of the third eyelid.
- A neurological disease affecting the nerve that stimulates the lacrimal gland.
- A side effect of certain antibiotics.
- Metabolic disorders (e.g. diabetes, hypothyroidism).
- Radiation to the head region (mainly for tumour treatment).
How do I know if my dog's eyes are dry?
When tear volume decreases, blinking becomes painful. Affected animals may blink or squint constantly, or in more severe cases not open their eyes at all.
Other symptoms:
- Reddened conjunctiva.
- Yellowish discharge from the eye.
- The ocular surface becomes cloudy.
- Blood vessels grow into the cornea.
- Deposition of brown pigment.
If left untreated, the disease can lead to blindness and even loss of the eye.
How can my dog be treated?
Dry eye disease is in every case an incurable condition that requires lifelong treatment.
In recent years, several immunomodulatory agents (ciclosporin, tacrolimus, pimecrolimus) have been discovered that also stimulate tear production. These must be given twice daily (every 12 hours), and generally reach their full effect after 3 weeks.
It's important to know that patients respond best to treatment when tear production is reduced but not yet at zero (0 mm/minute).
In addition to the medication that promotes tear production, the dog must also receive various eye drops or gels that serve as a substitute for natural tears.
What can be done if my dog's eye doesn't improve with treatment?
If medical treatment produces no improvement, it is possible to surgically relocate the duct of the parotid gland (a salivary gland) into the conjunctival sac.
This surgery is technically not simple and carries numerous risks, since the composition of saliva differs significantly from that of tears.
