What Is Dry Eye Syndrome in Dogs?
Dry eye syndrome in dogs, medically termed Keratoconjunctivitis Sicca (KCS), refers to a condition characterized by reduced tear production. Tears play a vital role in maintaining the lubrication, comfort, and overall health of a dog’s eyes. They contain essential components such as antibacterial proteins, mucus, white blood cells for infection defense, and enzymes to keep the eyes clear and free from debris and irritants.
A dog’s tears consist of three layers:
- The lipid (fat) layer
- The aqueous (water) layer
- The mucin layer
Among these layers, the lacrimal and third eyelid glands primarily produce the watery component of tears in dogs. However, in dogs affected by dry eye syndrome, these glands produce insufficient or no tears, while the glands responsible for the lipid and mucin layers continue to function. Consequently, affected dogs often have dry yet sticky eyes filled with mucus.
Symptoms
Dogs suffering from dry eye syndrome may display a range of symptoms, including:
- Eyes that appear red, inflamed, irritated, and painful
- Swelling and redness of the conjunctiva, the tissue surrounding the eye
- Increased squinting and blinking
- Dryness evident on the surface of the cornea, the clear outer dome-shaped part of the eye
- Presence of mucous-like discharge on the cornea, which may exhibit yellow or green coloration if a secondary bacterial infection is present
- Observable abnormalities and irregularities on the cornea, such as heightened vascularization (an abnormal increase in blood vessel growth around the affected area) and pigmentation as the eye endeavors to heal and safeguard itself
- Potential impairment of vision leading to blindness
Causes
Dry eye syndrome in dogs can stem from various underlying causes, which veterinarians can identify through a comprehensive examination and review of the dog’s medical history. Some potential causes include:
- Immune system dysfunction: In many cases, dry eye syndrome occurs when the immune system mistakenly attacks and damages the lacrimal and third eyelid glands. The exact reason for this immune response remains unclear.
- Medications: Certain medications may trigger dry eye syndrome as a side effect, typically soon after the dog begins taking them. While discontinuing the medication might resolve the issue, permanent damage could occur. It’s important to discuss potential side effects with your vet.
- Genetic factors: Some breeds, notably Yorkshire terriers, may inherit congenital alacrimia, a genetic form of dry eye syndrome typically affecting one eye.
- Endocrine conditions: Systemic diseases like hypothyroidism, diabetes, and Cushing’s disease often lead to reduced tear production.
- Infectious diseases: Canine distemper virus, leishmaniasis, and chronic blepharoconjunctivitis are among the infectious diseases linked to dry eye syndrome.
- Medical interventions: Surgical removal of the third eyelid gland, as seen in cases of cherry eye, or local radiation therapy for tumors, can result in permanent damage to tear-producing glands.
- Neurological issues: Nerve damage, often secondary to inner ear infections, can impair tear production.
- Traumatic injuries: Severe inflammation or injuries, such as those sustained in accidents or wounds, can lead to dry eye syndrome by damaging the tear-producing glands.
- Transient causes: Anesthesia and medications like atropine can temporarily reduce tear production, with tear production typically resuming once these factors are removed.
Diagnosis
Veterinarians employ the Schirmer Tear Test (STT) to diagnose dry eye syndrome and assess the production of aqueous tears in dogs. This test is straightforward and painless, involving the placement of a special paper strip in the lower eyelid. Over a period of 60 seconds, the paper absorbs moisture and tears from the eye. Subsequently, the veterinarian measures the tear production on the paper. A tear production rate of over 15 millimeters per minute is considered normal, whereas less than 10 millimeters suggests dry eye syndrome. To ensure accuracy, your vet may repeat the test.
Following the STT, your veterinarian might conduct a fluorescein stain test to detect corneal ulcers. This test involves applying a fluorescent stain that causes ulcers to glow bright green under a black light. Additionally, the vet may assess intraocular pressure to identify inflammation or glaucoma, which are frequently associated with dry eye syndrome and require concurrent diagnosis and treatment.
Treatment
The treatment plan for dry eye syndrome in dogs depends on the diagnosis and the pet’s medical history, which your veterinarian will assess. Treatment options may encompass:
- Lacrimostimulants: Ophthalmic cyclosporine or tacrolimus are commonly prescribed medications to stimulate tear production. Cyclosporine, applied directly to the eye, helps prevent immune system damage to the lacrimal and third eyelid glands, facilitating tear restoration. Tacrolimus is considered if cyclosporine proves ineffective.
- Lacrimomimetics: Artificial tears serve to moisturize the eye’s surface, enhance comfort, and assist in flushing out debris and allergens. These eye lubricants are typically used alongside primary medications for dry eye syndrome, such as cyclosporine, especially during the initial stages of treatment when tear production is not fully restored. Always follow your vet’s instructions regarding the use of artificial tears.
- Antibiotics: Broad-spectrum topical antibiotics may be necessary to treat bacterial infections and corneal ulcerations associated with dry eye syndrome. Dogs with dry eye syndrome related to nervous system issues may receive treatment with pilocarpine, a medication that stimulates glandular secretion.
- Surgery: Dogs that do not respond to conventional treatment methods may require parotid duct transposition surgery. This procedure redirects saliva glands from the dog’s mouth to the eye, enabling saliva to function as tears.
Living and Management
Your veterinarian will conduct the Schirmer Tear Test (STT) every 3-4 weeks initially to assess the effectiveness of the medication and treatment plan for your dog. If tear production remains inadequate, adjustments to dosing frequency and medications may be made. Typically, most dogs with dry eye syndrome show improvement within 12 weeks, with many experiencing positive changes within the first 6 weeks. Once your dog achieves adequate tear production, periodic rechecks every 3-4 months are advisable.
The majority of dogs respond well to available treatments and regain normal vision and a pain-free quality of life. Regular monitoring and prompt veterinary care are crucial. For dogs with an STT measurement ranging from 2 to 14 millimeters per minute, there is a greater than 80 percent chance of achieving normal tear production. In more severe cases, where the STT response falls between 0 and 1 millimeter per minute, the rate of full recovery drops to less than 50 percent.
Dry Eye Syndrome in Dogs FAQs
Is dry eye in dogs treatable?
While certain types of dry eye syndrome can be reversed, the most common causes typically require ongoing management through medication.
Do dogs with dry eye syndrome experience discomfort?
Yes, without adequate tear production, dogs’ eyes can become irritated, inflamed, infected, and may even develop ulcers. These conditions are extremely uncomfortable and painful for your dog.
Can I administer over-the-counter eye drops to my dog?
Over-the-counter artificial tears and eye lubricants play a crucial role in maintaining the comfort and health of your dog’s eyes, especially in the early stages of dry eye syndrome. It’s essential to use products specifically approved for dogs and to consult with your veterinarian before selecting any eye drop options.
