Eyes: Dry Eye
Dry eye results from a deficiency in the liquid portion of tears. Tears are produced by tear glands around the eye and are spread across the surface of the eye (called the cornea) by blinking. This tear film has several functions:
- It lubricates and flushes debris from the eye
- It provides oxygen and nutrients to the cornea
- It contains anti-bacterial substances to help prevent infection
The most common cause of dry eye is the dog's own immune system mistaking the tear glands as foreign and attacking and destroying them, as it would an invading germ. The progressive loss of these glands results in tear production being reduced. Without the protection of tears, the eyes become dry and irritated, often develop infections and the cornea can become ulcerated. Eventually, the cornea can become permanently scarred, or develop blood vessels and pigments over its normally transparent surface, leading to blindness.
Your dog's breed and age also provide important clues. Dry eye is most common in middle aged and older dogs. The breeds of dog most prone to dry eye are: West Highland White Terrier, Cavalier King Charles Spaniel, Cocker Spaniel, Shih Tzu, Miniature Schnauzer, Pekingese, Bulldog, Pug and Lhaso Apso.
A vet will have some clue as to the presence of dry eye just by the appearance of the affected eye(s). To confirm the diagnosis, the vet will perform a Schirmer Tear Test which is the diagnostic test for dry eye.
Schirmer Tear Test
This involves placing an absorbent paper strip, containing a blue coloured indicator, under the lower eyelid for one minute. Any tears produced will be absorbed by the test strip. The blue indicator is carried by the tears along the test strip, thereby showing the level of tear production. A normal eye should have tears going up to or past the 15mm mark in 1 minute.
Common signs of dry eye which will alert your veterinarian to the disease include:
- Redness of the eyes due to inflammation - your dog may squint and rub at its eyes
- A thick sticky yellowish discharge from the eyes
- Ulceration of the cornea
- A dull or cloudy cornea early in the disease
- Blindness due to corneal pigmentation and scarring later in the disease.
Treatment of dry eye may be either medical or surgical. Medical therapy is usually effective and is commonly attempted prior to resorting to surgery. It may include:
- Artificial tears
- Corticosteroids in some situations
- Suppressing the local immune system of the eye (Optimmune, Cyclosporin)
- Treatments to increase tear production
The most effective registered therapy for dry eye is an eye ointment called Optimmune, which contains cyclosporin, an immune suppressant drug that is also used to prevent transplant rejection in humans.
Optimmune is the only registered product which treats the cause of the problem, not only the symptoms, by:
- Halting the immune destruction of these glands
- Helping to reduce inflammation of the eyes
- Stimulating the tear glands to resume normal tear production
The concentration of cyclosporin in Optimmune is just 0.2%, so it will not affect the immune function af the rest of the dog's body.
Optimmune is usually applied twice daily to the eyes for the remainder of the dog's life. It has been found to be effective in over 80% of dogs with initial Tear Test readings of greater than 2mm. 50% of dogs with readings of less than 2mm respond to Optimmune, therefore early diagnosis is vital.
- Ensure the eyes are clean before applying Optimmune as mucus and debris can prevent it from working optimally.
- Apply Optimmune twice daily, as close to 12 hourly as possible.
- If treating both eyes, always treat the "better" one first.
- To apply Optimmune, carefully pull down your dog's lower eyelid with one hand. Hold the tube of Optimmune in the other hand and rest it on top of the dog's head to steady yourself. Apply the ointment to the inside of the eyelid and allow the dog to blink to spread the Optimmune over the eye.
- Use only a 6mm strip of Optimmune in each eye per application. hsi is similar to a grain of rice in size. Squeeze the tube gently form the bottom- a small squeeze may yield a large amount of Optimmune!
- Squeeze to flatten the tube to get the last of the ointment out. Do not roll like a tube of toothpaste as the tube may split.
Deep corneal ulcer case due to dry eye