(Dry eye is formally known as keratoconjunctivitis sicca or KCS)

Why Tears are Good

Tears consist mostly of water, but also of oil and mucus secreted by their respective eyelid glands. The water portion of tears is secreted by two lacrimal glands in dogs and cats: one just above the eye and another in the third eyelid (or so-called nictitating membrane).

“Conjunctivae” are the moist pink membranes of the eye socket. “Itis” means inflammation and “sicca” means dry. Keratoconjunctivitis sicca, abbreviated KCS, means there is an inflamed, dry cornea and conjunctiva. It occurs when there is a deficiency in the water portion of the tear film, which normally accounts for 95% of the tear volume. Without water, one is left with oil and mucus; hence, the gooey yellow eye discharge characteristic of this condition.

Why do Eyes Become this Dry?

There are many causes of dry eye. Some are:

• Canine distemper infection attacks all body interfaces with the environment including the eyes. Dry eye is part of the constellation of symptoms that can occur with canine distemper infection. 
• In cats, herpes upper respiratory infection can lead to chronic dry eye (see more on herpes conjunctivitis).
• There could be a congenital lack of tear-producing gland tissue (as described in certain lines of Yorkshire terriers).
• Exposure to sulfa-containing antibiotics, such as trimethoprim-sulfa combinations, can lead to dry eye. It can be either temporary or permanent and occurs unpredictably.
• Anesthesia will reduce tear function temporarily (thus eyes are lubricated with ointment by the attending nurse).
• During surgery for cherry eye, removal of the third eyelid tear-producing gland, instead of replacing the gland in its proper location, can lead to KCS. So can too much damage to the gland prior to proper gland replacement.
• A knock on the head in the area of one of the tear-producing glands can lead to KCS.
• The most common cause of KCS appears to be immune-mediated destruction of the tear-producing gland tissue. We do not know what causes this type of inflammatory reaction but certain breeds are predisposed: the American Cocker Spaniel, the Miniature Schnauzer, and the West Highland white terrier.

How We Make the KCS Diagnosis

The moisture of the eye will wet the paper. At the end of the 60-second period, the length of the moistened area on the paper is measured. A length of 15mm or more is normal. A length 11 to 14mm is a borderline result. A height of less than 10mm is dry. A height less than 5mm is severely dry.

Cyclosporine is an immunomodulating drug used to prevent organ transplant rejection in people and treat certain immune diseases in dogs and cats. When applied as an eye drop or ointment, it suppresses the immune destruction that is the most common cause of KCS, and tear production is restored.

The success of this treatment plus its convenient dosing interval (1 -3 times daily) has made this medication the primary treatment for KCS.

Animal hospitals used to make their own cyclosporine eyedrops out of oral cyclosporine and vegetable oil, but this largely ended when Optimmune® eye ointment (containing 0.2% cyclosporine) came out. Occasional patients simply do not show a good response to cyclosporine ointment but will respond when the concentration is increased. Higher-concentration products can easily be formulated by compounding pharmacies or one of the alternative medications listed below can be used. Treatment is almost always required for the lifetime of the pet.

After beginning cyclosporine eye drops or ointment, a recheck in three to four weeks is a good idea to check for improvement. If the Schirmer tear test is still showing poor results, the dosing frequency can be increased to three times a day; similarly, if excellent results are seen, the medication can be dropped to once a day.  Periodic rechecks are needed for dose adjustment and some dogs take as long as three to four months to show a response. Dogs with Schirmer tear tests as low as 2 mm still have an 80 percent chance of responding to cyclosporine. This medication has been a miraculous breakthrough in the treatment of KCS.

Tacrolimus is another medication that is an immune modulator. No commercial products are available for use in the eye, so they must be obtained from a compounding pharmacy. It is often tried in cases that are unresponsive or poorly responsive to cyclosporine. It is used in a manner similar to cyclosporine and is generally similar in cost.

Pilocarpine is a cholinergic drug, which means it works on the autonomic nervous system (the part that controls automatic functions such as glandular secretion). This medication can be given for the particular form of dry eye known as neurogenic KCS. In these cases, neurogenic stimulation of the tear gland is absent, so the pilocarpine is given in an attempt to stimulate the gland. Although the drug comes as an eye drop, for KCS it is actually given orally at an increasing dose until side effects are seen (diarrhea, drooling, vomiting). If side effects are encountered, the dose is reduced to that which the animal tolerates. It is continued indefinitely or until the neurogenic KCS subsides, usually twice daily. Neurogenic KCS typically affects only one eye.

Artificial tear solutions, gels, and ointments can be purchased in most drug stores. These can be combined with other therapies and are soothing. Their use is particularly important early in therapy until cyclosporine or tacrolimus takes effect and in eyes that do not respond to these latter medications. Over-the-counter products may be recommended two-12 times daily, depending upon their formulation and the severity of the KCS.

Topical antibiotics are often needed, especially when starting treatment for KCS because secondary infections are common with inadequate tears. These products do not increase tear production but help relieve the thick discharge.

Topical steroids may be beneficial in decreasing the inflammation associated with KCS. Typically they are combined with topical antibiotics in the same solution or ointment, especially when given to dogs.

Surgical Solutions

Parotid duct transposition is a surgical solution to unresponsive, severe KCS, although it is a delicate procedure, usually done by a veterinary ophthalmologist. The parotid duct is the salivary gland on either side of the face/cheek. It produces saliva that is carried to the mouth via a long duct. This duct can be carefully dissected out and moved to the outer corner of the inside of the lower eyelid in order to deliver saliva to the eye. Saliva is a reasonable substitute for tears, although in time some mineral deposits may form on the eye surface. Mineralization of the cornea can range from mild to severe and there is no good way to predict whether mineralization will be a problem prior to the transposition of the duct. The eye may water uncontrollably when the dog is fed and facial wetting may be objectionable in some cases.

Most of us know that sun exposure can be damaging to the skin. We get wrinkles, sunburn, and even sun- induced skin cancers. Dogs have similar issues.

Pets like to sunbathe just like people do. Many like to lie happily on their backs and soak up the damaging UVB light. UVB light is pretty unpleasant stuff.  For one thing, UVB light induces the inflammatory response of skin cells, damages the skin’s immune cells, and induces mutations in skin cells of DNA. At first, the skin becomes pimply and red, but then plaques of thick skin develop and spread. Skin cancer can form, and not all forms of skin cancer stay confined to the skin.

Dogs at Risk

Most of the time, a good fur coat is all the protection a dog needs to avoid damage from the sun. After all, protection from the environment is what fur is all about. There are two problems, however: the tummy (which is sparsely furred in most dogs), and short white fur (which sunlight readily penetrates). This puts the pit bull terrier at special risk but any dog with similar hair length (greyhound, pointer, Dalmatian etc.) can have a problem with too much sun exposure, on the tummy or otherwise.

What Does it Look Like? 

The white fur becomes patchy, and the skin below becomes red and irritated. In contrast, if there are adjacent patches of dark fur, the coat is lush and normal with no patchy hair loss, and the skin underneath is not inflamed. Passing your fingers across the fur from white to colored will yield a dramatic difference in skin texture as the colored fur is protective against the sun.

Infection (usually a pimply red rash) is common in many skin conditions, including this one, so sometimes a course of antibiotics can make the underlying sun-induced situation more clear. Biopsy of sun-induced skin damage is very characteristic and should be able to settle any questions.

Courtesy Morguefile

Treatment

As long as skin cancer has not actually cropped up, treatment focuses on inflammation and reducing sun exposure.

Antibiotics

Most actinic dermatitis cases have a hefty secondary Staphylococcus infection and need a couple of weeks of antibiotics.

Topical Steroids

If the skin has a lot of inflammation and discomfort, a week or so of topical steroids can relieve this. Be sure to use a product made for animals as human products are not made with the expectation that they will be licked.

Vitamin A

Protocols using daily Vitamin A have been shown to reduce the development of skin cancer and lessen damage from the sun. Your veterinarian can tell you what to get.

Pentoxifylline

This medication can improve circulation to the skin, thus assisting with perfusion and healing.

Reduce Sun Exposure!

If possible, keep the pet indoors during the hours of 11 a.m.—2 p.m.

• Beware of outdoor areas featuring large spaces of white concrete. This type of flooring is highly reflective of sunlight and will expose a tummy to sunlight even without sunbathing.
  
• Use sunscreen on the pet’s skin but be careful of human products as they have irritating scents and the potential for toxicity (zinc oxide can be toxic if licked). For dogs, Epi-Pet® can be purchased at many outlets. Dermoscent SunFree lotion is made for both dogs and cats. 
  
• Sunsuits and even a T-shirt are better than nothing. Leg holes can be cut out so that the tummy and back are well covered. This will, unfortunately, leave the legs vulnerable. Surfing dogs have used canine sunsuits for years, protecting the whole body. Unfortunately, most of the companies that make these are in Australia, but some American companies sell appropriate protective dog clothing.       

Pre-Cancer and Cancer

If sun-induced dermatitis does not respond to treatment or you find growths or “blood blisters,” a biopsy is probably in order. The biopsy will identify sun-induced tumors as well as skin in a precancerous state. Any tumors should be removed as soon as possible. Any skin in a precancerous state needs attention.

Tumors

The sun can induce squamous cell carcinoma or hemangiosarcoma in the skin. Surgery is often curative, especially if performed early, but the problem is that multiple areas of tumor can arise, and in an area like the belly, there is only so much skin that can be removed. Your veterinarian will guide you, but many dogs must come in monthly as new skin tumors appear. Small tumors can be removed with a local anesthetic. Your veterinarian will determine your best protocol. You may wish to discuss with your veterinarian whether a referral to an oncologist is in your and your pet’s best interests.

Precancer

Remove growths wherever possible and implement some sort of prevention for the rest of the skin, which is undoubtedly in a precancerous state. Obviously, the treatments listed above should be used, but some extra steps may also help.

Non-Steroidal Anti-Inflammatories

These not only help with pain but can also inhibit sun-induced cancers. Never use a human product in your pet without specific instructions from your veterinarian, as many human NSAIDs are toxic to animals.

Imiquimod

This is a topical ointment with anti-tumor effects. It can be expensive for a larger dog, but the ointment can cover a large expanse of sun-exposed tummy. This medication should not be licked by your dog, so special wraps may be needed if it is used.

If you have a light-coated, short-haired dog, be careful of sun exposure because the fur is likely not enough protection alone. Any “blood blisters” on the skin, especially the tummy, should be seen by the veterinarian. Time in the sun should be fun for everyone, including the family dog.