A sight for sore eyes: conjunctivitis in dogs
MARLOE, a Chocolate Labrador Retriever, was just four months old when she first developed the problem with her eyes. It seemed to happen suddenly: one morning when she woke up, there was a white sticky discharge from both eyes. At the same time, her eyes seemed to be itchy: she kept rubbing them with both front feet. At first, her owner thought that she might be having a simple, mild problem that would go away by itself. She tried cleaning Marloe’s eyes with cotton pads and lukewarm, slightly salty water, and this seemed to soothe Marloe’s discomfort temporarily. But when she still had the problem a few days later, it was time to go to the vet to get help for her.
My first impression was that Marloe was suffering from a common problem to affect both animals and humans: conjunctivitis. By definition, this means inflammation of the lining of the eye, known as the ‘conjunctiva’: this is the membrane that covers the white of the eye, and extends to cover the entire inner surface of the eyelids. If you pull down the lower eyelid, or if you lift up the upper eyelid, the red fleshy tissue that you can see is the “conjunctiva”. When this becomes irritated, it becomes “inflamed”, which means it becomes red, sore and itchy. The big question that remained, however, was what was causing this irritation to Marloe’s eyes?
There are four main causes of conjuctivitis: viruses, bacteria, environmental irritants and allergies. In cats, viruses and bacteria are the most common causes, causing an infectious condition that often spreads from cat to cat. In contrast, conjunctivitis in dogs is rarely infectious: individual dogs tend to be affected, rather than every animal in the household. Conjunctivitis in dogs is more likely to be caused by irritants and allergies, so I asked Marloe’s owner some questions about anything that Marloe might have come into contact with that could have provoked a reaction.
It turned out that Marloe had been for a long beach walk on a windy day, just before her eyes started to itch. It seemed likely that whipped-up sand could have caused an initial irritation to her eyes, and subsequently bacteria could have moved into the irritated area, perpetuating the problem. My first choice of treatment was an ointment that included an antibiotic to clear up any bacterial infection with some anti-inflammatory steroids to ease the redness and itchiness. Marloe responded quickly to this treatment: within a couple of days, her eyes returned to normal.
I’d hoped that Marloe’s sore eyes would have been permanently cured by this treatment, but within a few days of the ointment finishing, the problem recurred. It was mild enough, but there was a white discharge every morning, and she began to rub her eyes again. And she had not been anywhere near a beach this time. So what was going on?
This time, I examined her eyes even more closely, to see if there were any clues as to possible causes. I used small strips of filter paper to measure the amount of tears that Marloe was producing. Some dogs don’t produce enough tears to keep the eye moist, suffering from a problem known as ‘ keratitis sicca’ or ‘dry eye’. Affected animals are prone to continual eye problems because of the lack of lubrication in the eyes. One answer is the regular application of drops of artificial tears from a bottle. As it happened, Marloe’s tear production was normal, so this was not the problem in her case.
Next, I used a magnifying lens to examine the lining of Marloe’s eyes in closer detail. I checked carefully for tiny ingrow- ing hairs on the inside of her eyelids. If these are present, they can cause a continual lowgrade irritation, but in Marloe’s case, there were none. However under magnifcation, I could see something else: tiny pinpoint-sized nodules on the inner lining of the corners of her eyes. These characteristic nodules are made of lymphoid tissue: the eye-equivalent of miniature swollen tonsils. This finding was highly suggestive of a common problem in young dogs, known as ‘follicular conjunctivitis’. The precise cause is usually difficult to find, but it’s often thought to be an allergic reaction to something in the dog’s environment. It could be house dust, pollens or floor cleaners. It’s important to check for obvious substances that might be involved, but as is often the case, there was nothing in Marloe’s home that stood out.
There’s a simple, practical answer: the daily use of anti-inflammatory steroid eye drops. These dampen down the allergic reaction, relieving the itchiness, stopping the discharge and returning the eyes to normal. Most young dogs grow out of the problem as they mature, so the drops just need to be used for a few months.
Luckily, Marloe is an exceptionally good natured dog, and her owner has trained her to accept drops into her eyes by doing it as gently as possible, and by giving her treats and praise every time. At first, the drops had to be applied five or six times daily, but since the worst of the soreness has resolved, twice daily application has been enough to keep things under control.
Marloe is now eight months old, and her owner’s plan is to carry on with the twice daily drops for another two months. At that stage, with luck, she’ll have grown out of the sensitivity, and Marloe will be able to live an eye-drop-free life.
Marloe had a discharge from both eyes every morning