Hopefully, you noticed that I took last week off from writing Vet’s View. I utilized the holiday weekend to spend some much needed time with my newly expanded family. I hope everyone had a wonderful Memorial Day Weekend and took some time to honor the men and women of our armed forces who serve our country and protect our way of life.
Keratoconjunctivitis sicca.
In order to keep their license to practice, veterinarians are required to receive a certain number of continuing education credits each year. We were at a meeting on Sunday and one of the lectures was about Ophthalmology. The lecturer mentioned that we, the general practice veterinarians, were under diagnosing a specific ocular disease in dogs. This is me doing my part to correct that.
Keratoconjunctivitis sicca, also known as dry eye, is an acquired change in either the amount of tear fluid or the quality of tear fluid produced by dogs. This condition can happen to any dog but certain dogs have a predisposition to developing dry eye. Any of the small dogs with eyes that enter a room before the rest of their body are at risk because they have so much eyeball surface to cover with tears compared to the size of their eyelids. Pugs, Boston Terriers and Shih-Tzus would be a few breeds that fit into this category. Dogs that are also prone to bouts of conjunctivitis due to either anatomy or predisposition to allergies are also prone to developing dry eye. This list includes several very different breeds; Cocker Spaniels, Staffordshire Terriers, Bloodhounds and Golden Retrievers would be a few of the dogs that make this list. It would not be unusual, however to diagnose Keratoconjuntivitis sicca in any breed of older dog.
A dog walks into a veterinary clinic, stop me if you’ve heard this one. A dog that has a history of several weeks, months or maybe even years of mucus discharge from each eye presents for diagnosis and treatment. The dog may also have conjunctivitis, corneal ulcers or inflammation of the cornea also known as keratitis. It may have a history of being treated for any or all of these conditions several times over the past few years.
After a complete physical exam your veterinarian says, “I think Fluffy should have a complete ophthalmic exam.” You think to yourself, “That’s why we’re here doc.”
The vet shines a light into both of your dog’s eyes to check the pupils response to light. Then he or she places two small strips of paper into the bottom lid of each eye. This is called a Schirmer tear test. We wait for one long minute and look at where the marker has moved. If it has moved more then 15 millimeters we have normal tear production if it does not we have an answer. If it moves less than 15 mm we have a diagnosis of dry eye. We have an answer. Does that mean if that test is normal we don’t have dry eye? Nothing is ever that easy and that’s one of the reasons we can’t stop the ophthalmic exam there. Next the vet will place a few drops of a stain called fluoroscein and then shines a black light in your dog’s eye to look for corneal ulcers. Sometimes these dogs have corneal ulcers and sometimes they do not. Right before your veterinarian looks for the ulcers he or she should just be staring at the eye for at least 30 seconds. It may look like we are taking time to think about what we are going to say when we don’t find anything wrong with your dog’s eyes but we are actually evaluating your dog’s tear film quality. The fluoroscein should leave a film on the eyeball that we can see clearly for at least 15 seconds although it’s better if it lasts for 20 seconds. A tear film that disappears before 15 seconds is an inadequate tear film and your dog has keratoconjunctivitis sicca. A dog with inadequate tear film may have had a normal Schirmer tear test and we would have missed it if we had stopped there. At this point your vet puts two different drops in Fluffy’s eyes. One is to dilate the pupil and one is to numb the cornea. As long as there are no ulcers on the cornea we will test the pressures inside your dog’s eyes with a device called a tonopen. Typically dogs with dry eye will have normal pressures but it is not uncommon for some dog’s to have multiple ocular issues such as dry eye and glaucoma. We wouldn’t want to miss something like that. Now is the fun part, my favorite part although I have to admit I’ve been in the habit of skipping this part to make the exam go more quickly. We use a hand held lens and standing at an arm’s length from your dog’s face with a light held against our temple we look at the back or your dog’s eye to evaluate the retina.
When discussing medical cases for education’s sake it is always best to give the dog or cat one problem. Since this article is about Keratoconjunctivitis sicca that is the problem we will give this dog. You may ask, “How does this happen doc?” There are many diseases with a clear cause and effect mechanism that is simple and straightforward to explain. This is not one of those diseases. Dry eye can be caused by certain medications. There are infections and anatomic and physiologic abnormalities that can cause dry eye. Dry eye can also be an immune mediated inflammation of the tear glands caused by the body reacting to the tear film as if it were a foreign invader. The end result in all cases however, is that inflammation blocks the production or outflow of tears and the cornea dries out and the dog is at increased risk of losing its sight.
Once a diagnosis of Keratoconjunctivitis sicca is reached and treatment begins that treatment is typically life long. The goal is to increase the body’s ability to produce tears and offer another lubrication source at the same time. We may use topical cyclosporine or a drug called tacrolimus to locally dim the body’s immune reaction. Both of these drugs are moderately expensive but very effective in treating this condition. We will also use artificial tears to provide much needed moisture to the eyes and prevent damage or injury. Again once you begin treating dry eye, stopping treatment for any reason will most likely cause the signs of the disease to come back.
So there you have it, my attempt to make people aware of an apparently under diagnosed condition in older dogs. Bring it up the next time you see your vet with your older dog.
Can you address the eyelid, droopy eye issues sometime? What the risks/treatment options are? That would be great!! Thanks!! Always love your articles!!
Posted by: C. Cook | 07/28/2011 at 07:57 PM