Winky, Blinky, and Pinky
So far this year at our house we have treated a spot of ringworm, dealt with a flea infestation, tested for Lyme after deer tick bites, nit-picked our way through two bouts of lice, and coped with recurrent upper respiratory infections and stomach bugs... and I'm talking about the people, not the pets. So when I heard that there were a few cases of pinkeye at school, I didn't want to add that to our list of minor but decidedly inconvenient woes. I also prepared myself for the onslaught of calls from pet-owning parents, wondering if their kids caught pinkeye from Blinky the Burmese or Winky the Weimaraner.
The moniker "pinkeye" is a descriptive term that lumps together any problem that results in inflammation of the delicate membranes lining the eyelids and part of the eyeball, called the conjunctiva. When the conjunctiva becomes inflamed, we add the suffix "-itis" to create the technical term "conjunctivitis." I'm not a human physician so I'm not supposed to give human medical advice, but I can tell you that the contagious form of human pinkeye that kids pass around at recess is commonly caused by either a bacterial or a viral infection, which look exactly the same.
Pediatricians typically prescribe antibiotic eye drops or ointments to cover the possibility of bacterial infection. For viral infections, we depend on the person's immune system to fight off the bug all on its own. In either case, pinkeye commonly resolves in a few days. Frequent hand washing can limit the spread, but pinkeye is just one of those ubiquitous facts of elementary school, like skinned knees and homework, to which parents must resign themselves.
So your kid's been sent home from school with a raging red eye and you notice that Winky the Weimaraner looks a bit weepy as well. Aha! You knew you shouldn't have let your spouse talk you into getting a dog! See what he's done? He gave the kid pinkeye! Wrong. Conjunctivitis in dogs is rarely caused by infection, and almost never by anything contagious to people.
So, what does make Winky weep? The most common causes of canine conjunctivitis are allergies or trauma, including local irritation caused by functional diseases such as inadequate tear production, or conformation problems such as abnormal eyelashes or rolled eyelids that rub on the corneas. Your veterinarian will begin by taking a close look at Winky's eyes. Sometimes there is an obvious irritant, like on those Shih Tzus and Lhasa Apsos who get tufts of fur caked with ocular discharge in the corners of their eyes. These tufts dry into pointed little spears that stick straight up and poke the puppy in the eye. Ouch. This problem can be managed by good grooming.
Other breeds may be prone to eyelid abnormalities. The lids may roll in or droop excessively. Both conditions may lead to irritation and conjunctivitis. A closer exam with an ophthalmoscope may reveal abnormal eyelashes growing from the inner lid margins. These can be very tiny, requiring the expertise and equipment of an ophthalmologist to discover them. They can then be permanently removed.
Inadequate tear production is another common cause of canine conjunctivitis. Technically called keratoconjunctivitis sicca, "dry eye" is diagnosed with a simple yet elegant procedure, the Schirmer Tear Test. A thin strip of special paper is tucked into the rim of the lower eyelid. Tears seep down the length of the strip. By measuring the number of millimeters of the strip that become wet in 60 seconds, we can assess if Winky is making enough tears to adequately lubricate his eyes. If not, they will become dry and irritated. Voila! Conjunctivitis. Treatment consists of daily application of ointments or drops designed to stimulate tear production.
Once tear production is determined, the next step is to check for corneal ulceration. In other words, is the clear surface of the eyeball damaged? A few drops of Fluorescein dye are placed onto the cornea, then rinsed off with saline or artificial tears. If the corneal surface is damaged, it will retain a fluorescent green color.
Treatment of corneal ulcers is a whole other article but if Winky has an ulcer, there will likely be concurrent conjunctivitis. Besides treating the ulcer directly, your veterinarian will look for the initiating cause. If Blinky the Burmese scratched Winky in the eye, that's a simple explanation. However, in the case of recurrent corneal ulcers, there may be underlying problems such as dry eye.
Speaking of Blinky, could it be the cat that gave your kid pinkeye? Probably not. Although almost all cases of feline conjunctivitis are, in fact, caused by infection rather than allergy or trauma, the specific organisms involved do not typically affect people. The most commonly implicated bugs in cats are chlamydia and feline herpesvirus. I know you've heard of people getting chlamydia, but Blinky gets a different species of chlamydia than we do. Theoretically cat chlamydia can infect people, but it is rare for it to cause clinical disease, unless the human in question is immunosuppressed.
Your child is far and away more likely to have caught pinkeye from his classmate than his kitty. Chlamydia can be treated with topical antibiotics in the eye, but many cats continue to be asymptomatic carriers. If Blinky has a recurrent problem, or lives with an immunosuppressed person, this carrier state may be eliminated with several weeks of oral antibiotics. I know you've also heard of people getting herpesvirus, but again, we are talking a cat-specific strain that is not contagious to humans. Feline herpesvirus is not curable. Symptoms may be intermittent and variable in severity. Response to topical antivirals is unpredictable, and these medications can be quite expensive. Interferon is helpful in some cases as is the use of the amino acid L-lysine, which appears to inhibit virus replication. Unfortunately there is no treatment that is reliably effective in controlling the signs.
Sometimes conjunctivitis is caused by straightforward irritation. Smoke from the fireplace. Paint fumes. Strong cleaners. Scented candles. Tobacco smoke. Sand and saltwater. This may be exacerbated by allergic reactions. Diagnosis is made based on history, and ruling out other things. A way to confirm such suspicions is to remove Winky and Blinky from the environment and see if their conjunctivitis resolves. Or remove the irritant from the household. These types of conjunctivitis may be treated with drops or ointments that contain corticosteroids that reduce the inflammation but it is important to minimize ongoing exposure to whatever is initiating the reaction.
Finally, a very red eye can sometimes be a symptom of glaucoma, i.e. increased intraocular pressure. Glaucoma can lead to permanent blindness if not detected and treated promptly. So don't hesitate to get your pet to the vet to be checked... and don't blame Winky and Blinky for your child's pinkeye. Check with your pediatrician. Wash your hands. Don't rub your eyes. And be glad it's not lice.