Dry eye in dogs, or Keratoconjunctivitis Sicca (KCS), is a common problem that can cause your dog significant ocular discomfort. In this article, we will explore the many causes of dry eye in dogs and the associated treatment options. In most cases, the prognosis is very good. If you suspect that your dog may have dry eye, please consult with your veterinarian as soon as possible.
What is the lacrimal system in dogs?
The lacrimal system is responsible for producing tears and keeping the eyes moist. Tears are composed of three layers: an inner mucous layer, a middle water layer, and an outer lipid (or fat) layer. Tears produced by the lacrimal system play an important role in keeping the ocular surface healthy. Tears supply the metabolic requirements of the cornea, which being avascular has no blood vessels. Without tears, the cornea would eventually lack substance, dry, and potentially become infected or even damaged.
What causes dry eye in dogs (Keratoconjunctivitis Sicca (KCS))?
Keratoconjunctivitis sicca or dry eye in dogs has multiple possible causes. Several breeds have a higher incidence of keratoconjunctivitis than others, suggesting a genetic predisposition, particularly for the immune-mediated form of the disease. The top breeds predisposed to KCS include the American cocker spaniel, English bulldog, Lhasa apso, Shih Tzu, West Highland white terrier, Cavalier King Charles spaniel, miniature schnauzer, pug, Pekingese, and Yorkshire terrier.
1. Immune-mediated disease - this is the most common cause of dry eye, or KCS, in dogs.
2. Endocrine disease - diseases such as hypothyroidism, diabetes, and Cushing's disease can all contribute to decreased tear production in dogs.
3. Neurogenic KCS - Any disorder that compromises the function of either the facial nerve (CN VII) or the trigeminal nerve (CN V) can result in decreased tear production in dogs.
4. Certain medications - topical atropine, trimethoprim-sulfadiazine (TMS) antibiotic, and sulfonamides can temporarily decrease tear production.
5. Iatrogenic KCS - removal of the 3rd eyelid (nictitans gland) can result in permanent loss of tear production.
What are the clinical symptoms of dry eye in dogs?
Keratoconjunctivitis sicca (KCS) is characterized by copious quantities of thick, ropey, ocular discharge. In addition, the most common clinical signs of dry eye in dogs include:
- Blepharospasm (squinting)
- Red-eye, especially of the conjunctival tissues
- Ocular discharge
Corneal pigmentation and scarring commonly occur in chronic cases. When the clarity of the cornea is diminished, vision is impacted. KCS can lead to blindness if it isn't treated properly.
How is dry eye in dogs diagnosed?
Dry eye in dogs is diagnosed by your veterinarian with a combination of a detailed ophthalmic examination and clinical tests. One common clinical test used to diagnose dry eye is the Schirmer tear test (STT). In this test, a strip of filter paper is placed under the lower eyelid and the amount of tears that wet the paper over a given period of time is measured. A Schirmer tear test result of less than 10 mm in 1 minute is considered diagnostic of dry eye in dogs (normal values are >15mm/min).
How is dry eye treated in dogs?
Fortunately, dry eye in dogs can be treated quite effectively with a variety of medications and therapies. The goal of treatment is to increase tear production and keep the eyes healthy and comfortable. The following treatment options have been successful in the management of dry eye in dogs.
1. Cyclosporine or tacrolimus - The use of topical immunosuppressive medicines to prevent autoimmune destruction of the glands that produce tears is an effective treatment for keratoconjunctivitis sicca. Optimmune® is a veterinary product that is approved for use in dogs with KCS.
2. Pilocarpine - This medication may be administered topically, or orally and is frequently prescribed for dry eye in dogs that are a result of neurogenic KCS.
3. Tear replacement therapy - Artificial lubricants are essential and designed to meet the individual needs of your pet. Determining which product is best for you depends on the severity of your dog's condition, and how it responds. Lubricant use ranges from every 4-6 hrs with most products, many medications can be purchased over-the-counter as well, each differing in composition or price depending on their viscosity level - more viscous preparations are suitable for overnight use because they stay on longer than thinner ones.
What is the prognosis for dry eye in dogs?
The prognosis for dry eye in dogs is very good when the condition is diagnosed and treated early. However, if left untreated, dry eye can lead to blindness. With appropriate treatment, most dogs will have a good quality of life. Typically, the disease requires lifelong therapy, although the number and frequency of medications can be reduced as it improves. To keep the disease in good control, frequent recheck visits with your veterinarian are necessary on a permanent basis.
In this article, we have learned that dry eye in dogs is common and can be treated successfully. If your dog has dry eye, it’s important to have the condition diagnosed by a veterinarian so they know which treatment option will work best for them. Dry eye in dogs can lead to blindness if left untreated, but with appropriate care, most symptoms improve over time. To keep dry eye under control, you should make frequent trips to the vet clinic as prescribed.