(KCS or "DRY EYE")
A common problem of animal eyes most common in dogs is keratoconjunctivitis sicca (KCS or "dry eye" syndrome). Some causes of "dry eye" include congenital disorders (puppies), surgical removal of the tear-producing gland of the third eyelid ("cherry eye"), administration of certain medications (e.g., sulfa antibiotics, Etogesic anti-inflammatory drug), and infections such as distemper. Most cases are considered "immune-mediated" and result from attack by the animal's own immune system on their own tear-producing glands. The disease is seen very commonly in certain breeds such as the Cocker Spaniel, Shih Tzu, Lhasa Apso, Bulldog, Schnauzer, and West Highland White Terrier.
The clinical signs of "dry eye" include large amounts of ocular discharge (that re-forms quickly after cleaning), redness of the eyes, rubbing at the eyes, cloudy eyes, and corneal ulcers. After an extended period of dryness, the surface of the eye (the cornea) begins to accumulate pigment and blood vessels. If this is allowed to progress, blindness can be the result! It is therefore important that the tear production be normalized rapidly.
Our treatment goals for KCS include stimulation of tear production, controlling secondary infections, and decreasing corneal scarring. Treatment is very effective if the condition is diagnosed early, but life-long treatment is usually required. The drug cyclosporine is anywhere from 50-90% effective in stimulating normal tear production in dogs, depending on the severity of the disease by the time of diagnosis. A newer KCS treatment, tacrolimus, is an option for severe cases including those where cyclosporine has failed. It is effective in some, but not all, of the cases where cyclosporine has failed. Cyclosporine and tacrolimus must be used as directed. If the medication is discontinued, the signs will usually recur. It can be more difficult, or impossible, to get controlled the next time around. It is very important to have your pet's eyes periodically monitored in order to evaluate the success of treatment and to determine if any changes in treatment are required.
Parotid Duct Transposition (PDT) Surgery
Parotid duct transposition is a surgery to reroute the duct of the parotid salivary gland to provide substitute lubrication to the eye with saliva in place of tears. This procedure is reserved for patients that are non-responsive to medical therapy for KCS or dry eye. These patients have little to no improvement in tear values as measured by a Schirmer tear test (STT) with a measurement of <5 mm/minute as opposed to the goal of a normal STT value of >15 mm/minute. Due to the extreme dryness, most patients will be uncomfortable as evidenced by frequent blinking, rubbing and squinting. They may also be experiencing decreased vision due to corneal pigmentation and scarring resulting from KCS.
Prior to surgery, a dental cleaning should be performed if needed to reduce bacteria in the mouth. Additionally, function of the salivary gland can be confirmed with a drop of atropine or other bitter substance on the gums and observation of the duct opening for saliva.
The PDT surgery is performed under general anesthesia with either an open or closed technique. The only difference is the open technique involves making an incision on the side of the face in addition to the one inside the mouth in the gum tissue above the upper premolars. The duct is cannulated with suture material and freed from surrounding tissue until it can be redirected into the conjunctival sac and sutured into place.
In general, the success rate is 80-90 % for flow of saliva and resolution of discomfort. The most common complication of PDT surgery is accumulation of calcium/mineral deposits on the cornea from the saliva. A topical medication called EDTA may be used to reduce the deposits. Other issues that can occur include too much flow resulting in facial dermatitis or stricture/obstruction of the duct.
After surgery, swelling of the face and lower eyelid/conjunctiva area is to be expected. Cold pack application for the first several days will help that resolve. Both topical and systemic antibiotics are prescribed to combat infection. An Elizabethan collar is required to prevent self -trauma and disruption or premature removal of sutures during healing. Frequent small feedings are recommended to keep the duct open and saliva flowing especially during the initial healing phase.