Visiting Veterinarian

The eyes have it

By Michele Gerhard Jasny V.M.D. - March 1, 2007

"I think she has something in her eye," Tillie's mom said as she walked into the exam room with her Australian Labradoodle. "Uh-huh," I nodded, not listening too closely. Every few weeks an owner arrives thinking her dog has a foreign body in the eye. It's understandable. Tillie was squinting. Her eye was red and weepy. "Let's take a look," I suggested, reserving judgment while enlisting help to hold this wiggling youngster still. The majority of eyes I see that look like Tillie's turn out to be corneal ulcers, not foreign bodies.

The clear surface of the eye is called the cornea. Think of it like a windshield. It is transparent so that light can get through. In order to stay transparent, it depends on several qualities. It has no pigment. It has no blood vessels. Its main substance, called the stroma, is organized in a very precise way to keep it clear and waterproof. When the corneal surface is damaged, this is called corneal ulceration or ulcerative keratitis and it compromises the integrity and function of the windshield.

The most common cause of corneal ulceration is simple trauma. The windshield gets damaged by something physically scratching it. Maybe Tillie ran into a branch while playing in the woods, or the cat clawed her. Trauma can also result from anatomical sources. Breeds like Shih Tzus and Lhasa Apsos grow tufts of hair on their little pushed-in muzzles that may poke their eyes. Eyelids that roll inward, or that don't close all the way, tiny eyelashes growing where they shouldn't, like on the inside of the lids, all these problems can lead to corneal damage.

Keratoconjunctivitis sicca is another cause of corneal ulceration. Commonly called "dry eye," the eyes stop making enough tears. Excessive dryness makes the eyes susceptible to damage. Dry eye can be caused by certain drugs, but is often idiopathic. In other words, it just happens and we don't know why. Diagnosis is with a simple procedure called a Schirmer Tear test. A piece of special paper is placed against Tillie's lower lid. As her tears moisten the strip, we measure how many millimeters get wet in 60 seconds. Even an eye that looks moist may be suffering from keratoconjunctivitis sicca and should be tested.

Once we've checked tear production, the next diagnostic step is application of a water-soluble dye called fluorescein. Since the surface of an intact cornea is waterproof, the dye should just roll off. If the surface is ulcerated, the dye will penetrate the damaged area, staining it brilliant green. Dye may also drip out of Tillie's nose. Don't worry about that. It just means her nasolacrimal duct is functioning properly. If the cornea is ulcerated, water gets into the stroma, and the eye may start to look cloudy. This is called corneal edema. Then, after a day or two, you may start to see little red blood vessels growing from the white of the eye toward the ulcer. This may look creepy but it is a good sign. In order to heal, those blood vessels need to reach the ulcer.

Treatment of a simple corneal ulcer is . . . well . . . simple. Topical antibiotics are used to prevent infection. Topical atropine will reduce pain and will also dilate the pupil, which prevents a possible complication called synechia. Since corneal ulcers, even small ones, can be quite painful, oral pain medications are sometimes indicated as well. The ulcer should be all healed up in seven to 10 days.

If Tillie's ulcer hasn't healed in a week, we now enter a realm that is frustrating for everyone. It even gets a new diagnosis - refractory corneal ulcer, also called persistent ulcer and Boxer ulcer. It is most common in middle-aged to older pets and, as you might have guessed by the name, certain breeds have a predisposition, including the Boxer, Corgi, Pekinese, and Lhasa Apso, as well as many others. We don't know for sure why some eyes don't heal readily, but these refractory ulcers usually have edges of unattached corneal epithelium making a sort of lip around the injury. Our next treatment is usually to debride this loose tissue.

In most cases we can do this procedure using only a topical anesthetic. We rub the edges of the ulcer with a cotton-tipped swab, sometimes dipped in diluted. By cleaning up the margins of the ulcer and slightly irritating the cornea, we hope to "wake up" Tillie's eye and get the healing process started. At this point, your vet may add a topical medication that actually contains salt to draw excess fluid out of the cornea. A change in antibiotic may also be advised. One study indicated that about 40 percent of refractory ulcers will heal after this debridement procedure. Your job for the next week is labor intensive. Eye medications need to be applied frequently as they eventually get watered out by Tillie's tears. Why can't we just give her pills? Because oral medications do not get into the eye very well. The only way to get adequate concentrations of medications where we want them to go is to put them right in the eye.

After another week or so of your tender ministrations, if the ulcer still is not healing, our next step is a procedure called a keratotomy. This is usually the point where owners freak out a bit. Understandable. A keratotomy involves scratching the surface of Tillie's eye with a needle. We either poke it in little dots (punctate) or scratch it like a tic-tac-to game (grid.) Again, most dogs require only topical anesthesia and a good assistant holding for this procedure but extra wiggly patients may need light sedation. Uncomfortable as it sounds, it's what is needed to stimulate Tillie's eye into action. Roughly 75 percent of cases will respond to this treatment and heal.

Not anticipating any serious problem with Tillie, I figured it was probably the usual simple corneal ulcer. I shone my bright light at her eye and began my spiel on corneal ulcers. But wait! Well, I'll be a monkey's uncle! Tillie actually did have something stuck in her eye. Tillie was a good patient. With a few drops of topical anesthetic and a good assistant, I was able to carefully dislodge a small brown splinter and remove it. Fluorescein stain confirmed a small area of resultant corneal ulceration. I sent Tillie home with a tube of eye ointment. A week later it was all healed, as it should be.

Other dogs are not so lucky, many having some version of refractory ulcers. Lily, the French bulldog, just had the cotton-swab debridement and Woody, the golden retriever, a grid keratotomy. We'll soon see if those procedures had the desired effect. Caesar, the bull mastiff, is healed up, for now, but we have to watch him closely, because of the conformation of his eyelids. Mai Mai, the Italian spinoni, has an underlying disorder of her corneas and will probably be on lifelong medication. Here's hoping that with the help of the ophthalmologists, and the good care of their dedicated owners, they will all do well. If you think your dog has something in her eye, consult your veterinarian. You might be right, like Tillie's mom. Or it might be a corneal ulcer. The eye is a delicate and crucial structure and it deserves careful attention for even the smallest injury.