Dry eye in dogs
The eyes are supposedly the window to the soul, but they’re also the window that allows our pets to see the world around them, providing your pooch with one of their most important senses. However, like any organ in the body, your pup’s eyes can sometimes become injured or ill.
One of the most common conditions that can affect your dog’s eyes is dry eye, medically known as “Keratoconjunctivitis Sicca” (KCS). Here’s everything you need to know about dry eye in dogs including what it is, which dogs are at risk, how it’s treated, and what the outlook is if your dog is diagnosed with the condition.
What is dry eye in dogs?
Dry eye is a pretty self-explanatory condition because it means that your dog has lost their ability to produce enough tears, so their eyes have literally become dry.
Tears play an important role in maintaining your dog’s eye health - losing the ability to create them will impact the comfort and condition of your dog’s eyes. In severe cases, it can lead to damage to the eye and loss of vision. Some dogs with dry eyes can produce a small amount of tears, whilst others aren’t able to make any at all.
Their tear gland produces a “tear film” made up of water, fats, and oils that’s spread over the eye to lubricate it so the eyelid can move smoothly and comfortably over the eye. Because this film is super slippery, it acts like a protective barrier. This film stops any nasties like germs or dust from getting into your dog’s eye because it slides off the slippery film and doesn’t touch the eyeball’s surface.
Tears also provide nourishment to the cornea, the clear front part of your dog’s eye, and the conjunctiva, which is the pink skin that surrounds the eyeball.
Without enough tears, your dog’s eyes will become dull and dry, and the tissues of their cornea will become irritated and inflamed.
As you might imagine, having dry eyes is very uncomfortable and blinking will become uncomfortable or even painful, as the movement of the eyelid over the eye will cause friction and further irritate your the eye.
If left untreated, dry eye will get progressively worse and eventually your dog can lose their vision. Leaving their eyes dry and irritated can also lead to other complications such as corneal ulcers.
What causes dry eye?
Dry eye is caused by a lack of tear production, but there are a number of different reasons why your dog has become unable to produce enough tears to keep their eyes lubricated and healthy.
The most common cause of dry eye is a fault in your dog’s immune response, causing the body's immune system to attack the tissues of the tear glands. Because the glands become damaged they can no longer produce enough tears. Not a lot is known about this cause of dry eye in dogs, but it’s believed to be an inherited issue and certain breeds of dog seem to be predisposed to the problem.
Another cause of dry eye in dogs is a problem with the nerves that stimulate a dog’s tear glands and ducts. If there is a defect or damage to these nerves they could stop stimulating the tear glands resulting in a halt to the production of tears. Trauma to the eye can also cause damage to the tear ducts and glands.
Some cases of dry eye are caused by illnesses that can dry out your dog’s eyes as a side effect. Conditions that affect a dog’s third eyelid (the nictitating membrane), such as cherry eye, can also lead to dry eye because the third eyelid is responsible for the production and spread of tears across the eye.
Historically, the treatment for cherry eye would involve the removal of the third eyelid and lacrimal gland, however, this severely impacts tear production and often causes dry eye in dogs. Nowadays, vets will instead surgically replace the eyelid and gland so a dog can still produce tears. Nevertheless, your dog’s tear production may still be impacted even after surgery to correct cherry eye.
Finally, there are some medications that can lower tear production as a side effect, including sulphonamides.
Are some dogs more at risk of dry eye?
A dog of any age or breed can develop dry eye, and it’s thought that around 1 in 250 dogs will develop dry eye as an average across the entire dog population.
Senior pooches are at greater risk of dry eye compared to young and adult dogs. A 12-year-old dog is 30% more likely to develop dry eye compared to a 3-year-old animal.
Another factor that can increase a dog’s risk of developing dry eye is their weight. Both underweight and overweight dogs are at greater risk of the condition when compared to a pooch that’s within the normal weight range for their breed and gender. Overweight dogs are 1.25x more likely to develop dry eye than a dog at a healthy weight.
As well as age and weight affecting a dog’s risk of dry eye, their breed will play a significant part. Some breeds are predisposed to dry eye and as many as 1 in 5 dogs of these high-risk breeds can be affected.
What breeds are at risk of dry eye in dogs?
American Cocker Spaniels are far more likely to suffer from dry eye than any other breed, with 1 in every 17 dogs suffering from the condition. Meanwhile, Bulldogs aren’t far behind and around 1 in 55 dogs will develop dry eye at some point in their life.
Brachycephalic breeds are also more likely to suffer from dry eye compared to mesaticephalic or dolichocephalic breeds of dog (that means pups with longer snouts). Your squashy-faced pup is 3.6x more likely to develop dry eye compared to a pooch with a long snoot.
Spaniels are also at high risk of the condition – they’re over 3x more likely to suffer from dry eye compared to other breeds.
While some breeds are at a higher risk of dry eye, some have a much lower risk than average and are less likely to develop dry eye compared to the general doggy population. Breeds like the Labrador and the Poodle are less likely to develop dry eye compared to other breeds.
The breeds at risk of developing dry eye are:
- American Cocker Spaniels
- West Highland White Terriers
- Yorkshire Terriers
- Cavalier King Charles Spaniels
- English Cocker Spaniels
- English Springer Spaniels
- English Bulldogs
- Lhasa Apso
- Shih Tzus
- Miniature Schnauzers
- Boston Terrier
- English Bull Terrier
- Basset Hounds
Symptoms of dry eye in dogs
The telltale signs of dry eye in dogs are red, dry, irritated eyes with yellow/green mucus around their eye that looks a little bit like snot.
The symptoms of dry eye in dogs include:
- Dull, dry eyes (no shine)
- Red or bloodshot eyes
- Excessive blinking
- Pawing and rubbing at the eyes
- Thick yellow-green discharge around and on the eye
The snotty mucus around the eye is actually all the oils and fats that would normally be in your dog’s tears. Usually, these oils and fats mix together with water to create the tear film. However, because a dog with dry eye can’t produce enough liquid, their tear glands instead create this thick and gunky mixture of fats and oils. This goop is still secreted onto the eye, but it can’t be spread properly nor can it lubricate the eyeball because there’s next to no fluid.
In severe cases of dry eye a dog might suffer from corneal scarring, known as “hyperpigmentation”, and the clear cornea of the eye will start to develop a dark film covering it. A dog’s blood vessels can also grow into the cornea, known as neovascularization.
Because your dog’s eyes are so important it’s always best to take your dog to the vet for an optical examination if they ever show any signs of discomfort in their eyes or any changes in their vision. As with many health conditions, cases of dry eye and other eye conditions that are diagnosed and treated early have the best chance of recovery.
Diagnosing dry eye
If you suspect dry eye or any issue with your dog’s eyes, it’s important you take your pooch to the vet for an eye exam. Your vet will talk to you about your pup’s symptoms and examine their eyes for any physical signs or abnormalities that might indicate dry eye or another condition.
To diagnose dry eye, your vet will conduct a Schirmer tear test (STT). This test involves getting a small strip of special paper and putting it behind your dog’s lower eyelid. Don’t worry, the test is completely harmless and only lasts for a minute.
The tiny bit of the paper is folded so it will sit behind your dog’s eyelid and collect any tears flowing from the tear duct. As the paper soaks up the tears, it changes to a blue colour. There are measurements marked along the paper strip and as the tears wet the paper, the blue stain will move along the measurements to show the volume of tears your dog is producing. Normally a healthy dog will create about 15mm of tears in a minute. If your dog produces much less than this, they will be diagnosed with dry eye.
As well as the STT test, your vet might carry out a fluorescein stain test to assess the condition of your dog’s eye and look for any other problems like corneal ulcers. This test involves putting a harmless, fluorescent dye into your dog’s eye which they examine under a blue light. The dye collects in abnormalities, like ulcers, making them super visible. The dye will last for a little while, so your dog might have a slightly yellow-green eye for a bit but it should all wash away on its own before the end of the day.
If your dog’s eye is very swollen your vet might measure the pressure of your pooch’s eye to make sure they're not suffering from glaucoma.
What happens if dry eye isn’t treated?
Dry eye will not get better on its own, and if your dog’s dry eye is not treated their condition will worsen. The inflammation in your pup’s eye will become more severe, and the blood vessels could grow into the clear cornea. The cornea will also become pigmented and cloudy.
Dry eyes are not only repeatedly irritated with every blink, but the lack of tears means their eyes aren’t protected from dust or debris. Dogs suffering from dry eye are also at greater risk of eye infections and corneal ulcers, which can seriously damage the tissues of the eye. Deep ulcers can actually cause eyeballs to burst, which will require the eye to be surgically removed.
Both of these can lead to scarring, and along with hyperpigmentation, this can cause vision loss. In the worst-case scenarios, dogs can go blind as a result of dry eye and secondary infection.
Treatment for dry eye in dogs
The aim of treatment for dry eye in dogs is to stimulate tear production and to replace the missing tear film on your dog’s eye. There is no complete cure for dry eye and it will affect your dog for the rest of their life - dogs diagnosed with the condition will require treatment for the rest of their life. Luckily, most dog’s respond very well to treatment and can live a normal, happy life with normal vision.
Your dog will need two different medications in tandem to treat their dry eye, one to improve their tear production, and one to replace their tears.
It’s typical for dogs to be prescribed cyclosporine or pilocarpine to stimulate the production of tears. Cyclosporine is useful for dog’s suffering from dry eye as the result of an auto-immune response because it suppresses the immune response to stop it from attacking your dog’s tear glands. Pilocarpine meanwhile is used to stimulate the nerves that trigger tear production, basically getting the nerves to tell the glands to make more tears.
Your dog will also be prescribed artificial tears. You should always use the ones prescribed by your vet and never use artificial tears manufactured for human use. The ones your vet will give you are especially formulated for use in animals and safe for your dog. Even if your dog is receiving a tear production stimulant, artificial tears are important for maintaining the moisture in their eye.
You will often need to use a dog-safe eyewash before you put in artificial tears. These drops will help to clean away any dirt, debris, or discharge in your dog’s eye so it’s nice and clean. This will help to reduce irritants in the eye before the artificial tears are applied. These will normally need to be applied twice a day, but some formulations need to be applied up to four times a day.
As well as treatments to replace the tears, some dogs might be given oral antibiotics or an antibiotic ointment to clear away any infection in their eye. Your vet might also prescribe anti-inflammatory medication to help reduce the swelling in your pup’s eye.
Surgery for dry eye in dogs
In some cases, your vet may suggest that your dog has a surgical procedure to treat their dry eyes. This surgery is complex and comes with several side effects, so it is often not pursued unless all other treatment options have failed.
The surgery involves moving the salivary duct from its usual position by the ear and stitching it into the lower eyelid, so that saliva can be secreted into the eye instead of tears. This surgery usually offers some relief to dogs with dry eye as it will moisten the eye and make it more comfortable, but it’s far from a perfect fix because saliva can irritate the eye and some pups will still need daily medicine to manage other aspects of their condition.
Home remedies for dry eye
There have been a handful of home remedy suggestions online for treating dry eye, but they’re few and far between and even holistic vets will suggest the traditional treatment. This is because there is no natural or DIY remedy that can effectively stimulate or replace the missing tears and protect their precious eyes.
That being said, it has been suggested online to apply a drop of castor oil onto a dry eye to help lubricate it, and this suggestion has been made for both humans and hounds suffering from dry eye. Although castor oil is a natural product and is sometimes used in eye drops, ophthalmologists discourage applying castor oil alone directly onto the eye, and it’s best not to put it in your pooch’s eye either.
There have been suggestions of using CBD oil to help modulate the immune system to stop it from attacking the dog’s tear glands. CBD oil does appear to have some repressive effect on the immune system, but further study is required to understand the role of CBD oil and immune response, and studies on the effects on a dog’s immune system are yet to be conducted. You can always discuss trying CBD oil with your vet, and they’ll be happy to talk you through any other treatment options and whether or not they might work for your pet.
The prognosis for dry eye in dogs
The prognosis for dogs suffering from dry eye is usually pretty good, although they will need to receive treatment for the rest of their life to replace the missing tears. Dry eye shouldn’t affect your dog’s life expectancy, and in many cases your dog shouldn’t even suffer from any loss of vision provided they receive regular treatment, which means your pooch can still enjoy a long and happy life.
Provided your pooch’s dry eye was diagnosed and treated early before complications like corneal ulcers and scarring could occur, they should be able to live out the rest of their life without any loss of vision.
On the other hand, if your dog has suffered from severe ulceration or scarring on their cornea they might lose some of their vision or suffer from blindness. It is rare, but some dogs will need to have their eye removed.
Typically though, a dog with dry eye can live a long and waggy-tailed life with normal vision as long as you apply their eye drops and give them their medication every day as directed by the vet.
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- New RVC research shows certain dog breeds are more prone to keratoconjunctivitis sicca Veterinary News, June 2021
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- Certain breeds more at risk of dry eye, study finds VN Online, June 2021