By Jennifer Coates, DVM
A dog’s eyes perform a nearly miraculous function – converting reflected light into nerve impulses that the brain uses to form images of the world. To do this well, all the various parts of the eye must be healthy. Unfortunately, a number of diseases can disrupt the way a dog’s eyes function. Let’s take a look at some of the most common eye problems dogs experience and how pet parents can manage them.
Dogs have three eyelids – two that are readily visible and an extra one, called the third eyelid, that normally hides from view below the inner corner of the eye. The third eyelid is home to a tear producing gland. Normally, this gland is also invisible, but some dogs have a congenital weakness of the ligaments that hold it in place. When these ligaments fail, the gland pops out of its normal location and looks a bit like a “cherry” stuck at the inner corner of the eye. Because this condition often has a genetic basis, both eyes are usually affected over time.
To treat cherry eye, a veterinarian will perform a simple surgery to attach the gland back in a more normal position.
The surface of the eye is covered with a clear, skin-like tissue called the cornea. Just like the skin, the cornea can be injured, and lacerations (cuts), punctures and ulcers are all quite common in dogs. Trauma is often to blame, like when a dog runs through tall grass and gets poked in the eye. In other cases, problems with the eyes themselves (like poor tear production or abnormal anatomy) can put dogs at risk for corneal damage. A dog with a corneal wound will often rub at the affected eye and squint because of pain. The eye may also be red and have excessive drainage.
Treatment for corneal wounds involves preventing or treating infections with antibiotic eye drops or ointments, managing pain and giving the cornea time to heal. In severe cases, surgery or other treatments may be needed to protect or repair the cornea and promote healing.
When dogs develop a disease called keratoconjunctivitis sicca (KCS) or dry eye, their tear glands produce fewer tears than normal. Tears perform important functions like removing potentially damaging material from the surface of the eye and nourishing corneal tissues. Unsurprisingly, a lack of tears can cause big problems including corneal ulcers, chronic drainage of mucus from the eyes and pain.
Mild cases of KCS can sometimes be managed with frequent application of an artificial tear solution, but medications that stimulate tear production (e.g., cyclosporine) are usually necessary. Surgery that redirects a duct carrying saliva so that it moistens the eye is an option in severe cases.
The conjunctiva are the mucus membranes that cover the inside of a dog’s eyelids, both sides of the third eyelid and some parts of the eyeball. “Conjunctivitis” or “pink eye” are interchangeable terms that simply mean “inflammation of the conjunctiva.” The symptoms of conjunctivitis include reddened and swollen conjunctiva, eye drainage and discomfort.
Conjunctivitis should be thought of as a symptom of disease, not a disease itself. Many conditions cause conjunctivitis in dogs, including physical irritation (like dust and inward growing eyelashes), infections (bacterial and viral are most common) and allergic reactions. Treatment depends on the underlying cause. Sterile saline eye washes are available over the counter and can be used to flush irritants from the eye. Bacterial eye infections usually resolve quickly when treated with an appropriate prescription antibiotic eye drop or ointment. The chances of catching pink eye from your dog is very low but it only makes sense to wash your hands thoroughly after applying your dogs eye medications. Make a veterinary appointment if your dog’s conjunctivitis worsens or fails to resolve over the course of a day or two.
Within the eye, the production and drainage of fluid is precisely balanced to maintain a constant pressure. Glaucoma occurs when this balance is disrupted and pressure within the eye increases. Symptoms include pain, eye redness, increased tear production, a visible third eyelid, corneal cloudiness, dilated pupils and in advanced cases, an obviously enlarged eye.
Call your veterinarian immediately if you are worried that your dog might have glaucoma because delaying treatment can result in blindness. Treatment may involve a combination of topical and oral medications that decrease inflammation, absorb fluid from the eye, lower fluid production within the eye and promote drainage of fluid from the eye. Surgery may also an option in some cases.
The lens is located in the middle of the eye and it is normally clear, but sometimes part or all of a lens develops a cloudy, opaque cataract. Cataracts block light from reaching the back of the eye resulting in poor vision or blindness, depending on their severity. Cataracts are often confused with a normal aging change that affects a dog’s lenses called lenticular sclerosis. Both conditions give the pupils (the normally black center to the eye) a white, grey, or milky appearance, but a veterinarian can tell the difference through a standard eye exam.
Cataract surgery is available for dogs when their vision is severely compromised. If this is not an option, it is important to recognize that most dogs adapt very well to having poor vision.
Some dogs have eyelids that roll inwards. This is called entropion. Entropion causes hair to rub on the surface of the eye, resulting in pain, increased tear production and eventually damage to the cornea. Entropion can be a congenital problem (dogs are born with it) or it can develop as a result of chronic squinting due to discomfort or eyelid scarring.
If entropion has occurred because of a condition that will resolve, a veterinarian can temporarily suture the eyelids into a more normal position (a procedure called eyelid tacking). Surgery to permanently fix abnormal eyelid anatomy is necessary in other cases.
Some eye diseases in dogs can be hard to spot. This is the case with progressive retinal atrophy (PRA), a condition that causes dogs to gradually become blind even though their eyes look quite normal. The first symptom of PRA is often difficulty seeing at night, but it is not unusual for dogs to behave normally until their eyesight is almost completely gone and/or they are taken to an unfamiliar environment.
Unfortunately, no effective treatment exists for PRA, but the condition is painless and dogs generally adapt extremely well to becoming blind.
Of course there are many more conditions that cause eye problems in dogs than can be discussed here. Because eye problems have a tendency to worsen quickly, it is very important to discuss any concerns that you might have about your dog’s eyes with your veterinarian as quickly as possible.