It is said that the eyes are the windows to the soul. Unfortunately, those windows can become cloudy and dirty. What kinds of problems can lead to eye disorders? Since this series is on the causes of commonly seen symptoms, I’m going to limit my discussion to the things that pet owners are likely to notice.
The most common eye-related symptoms we see can be collectively described as “red eye”. The eye becomes red and irritated, often resulting in a mucusy or “goopy” discharge. Depending on the source of the problem, the pet may be uncomfortable and may squint or rub at the eyes. Several very different disorders can lead to these symptoms, and each one is diagnosed and treated very differently.
The first of these is conjunctivitis, which can also be called “pinkeye”. Before you panic, this is different than the pinkeye syndrome we see in humans. We don’t consider it contagious to other pets, let alone to people, so you can’t catch it from your dog or cat. In our feline patients conjunctivitis is often caused by a viral upper respiratory infection (such as herpes or calici virus). Bacterial infections can affect both dogs and cats and may be started by something irritating in the eye, such as dust, pollen or other small particles.
An ulcer or scratch on the cornea is not uncommon and can be extremely painful. This type of injury can be very serious, potentially even resulting in a rupture in the eye in the worst cases. Damage like this is one of the main reasons we urge people to bring their pets in quickly for anything related to eyes. You can’t see a small scratch without special stains and can’t see the extent without staining.
Then there is glaucoma. As in humans, this disease results in an increased pressure of fluid within the eye, leading to pain, redness, and eventually blindness. Even if vision is lost, it is important to get the pressure under control for the pet’s comfort.
Lastly we can see “dry eye” or keratoconjunctivitis sicca (the fancy medical term– say that ten times fast). For various reasons tear production can decrease or even stop, resulting in a lack of lubrication in the eye. The eye becomes very uncomfortable and irritated, and the body produces excessive mucus as a secondary lubricant. This is a chronic disease that will need life-long treatment and cannot be cured.
As with most problems, a vet can’t confirm a diagnosis without tests to rule in or out a given diagnosis. There are three tests we do for almost every “red eye” case. A fluoroscein stain is absorbed in the inner layers of the cornea, allowing us to see whether or not an ulcer or other injury is present, as well as its size. Tonometry measures the pressure of the eye and is a screening for glaucoma. A tear test (with a strip of specialized absorptive paper) measures tear production, letting us know if it’s abnormally low. Doing all three may be necessary since you can have multiple problems at the same time. For example, decreased tear production can result in a corneal abrasion.
Next let’s talk about “cloudy eye”. Haziness in the eye can be the result of fluid buildup in the cornea, or a problem in the lens. Corneal fluid is often secondary to an injury to the surface of the eye but can also indicate deeper inflammation due to certain systemic illnesses or immune disorders. A cloudy lens is generally one of two problems. Most people are familiar with cataracts, which can develop secondary to other diseases such as diabetes, can be genetic and develop at a young age, or can be a gradual onset in older pets. There is another condition called sclerosis that is an age-related thickening of the lens and happens in most older dogs. Sclerosis doesn’t normally result in blindness, but can cause some vision problems. It’s important to let your vet determine whether or not the problem is fluid, cataracts, or sclerosis, as they have very different causes and outcomes.
As always, if you have concerns about your pet’s health, have them seen by your vet. I especially emphasize this recommendation when it comes to eye problems since too long of a delay can result in permanent blindness.