Occurring in both humans and dogs, glaucoma is a serious eye disease in which the pressure within the eye becomes abnormally high. Glaucoma is a debilitating condition that you might associate most with the older human generation, but in the canine world, dogs of all ages are susceptible.
It’s a severe condition, with several cases often leading to total vision loss, so it’s essential to know what to look out for so you can seek urgent treatment. We’re going to equip you with all the knowledge you need on glaucoma, what it is, what causes it, the symptoms to look out for and the subsequent treatment and care your dog will need.
Hopefully, the more knowledge that dog owners have about the disease, the sooner the symptoms will be recognised. Consequently, this means a quicker diagnosis and treatment to prevent more dogs suffering from vision loss.
Glaucoma is a painful eye disease that can potentially lead to total vision loss. It occurs when there is an excessive build-up of fluid (called aqueous fluid) leading to increased pressure within the eye. This pressure is referred to as intraocular pressure (IOP), and when too much fluid is produced, or not enough fluid is drained out of the eye, the IOP can become way too high and trigger glaucoma.
When the eye can’t properly drain the unnecessary aqueous fluid, the retina and optic nerve will start to deteriorate and could become damaged beyond repair. Humans and dogs share a similar eye structure, both needing the retina and optic nerve to facilitate our vision. The retina operates by converting what we see in front of us into messages that travel via the optic nerve to the brain which subsequently produces our vision.
Unfortunately, this means that damage to the retina and optic nerve due to the increased pressure will often result in blindness. Around 40% of dogs affected with glaucoma suffer from blindness in their affected eye.
Intraocular pressure is the fluid pressure within the eye and is maintained by having the appropriate amount of aqueous humour fluid within the eye. Aqueous humour fluid is a transparent, runny substance and it’s situated in between the anterior and posterior chambers within the eye.
The anterior chamber is located between the iris (the coloured section of the eye) and the cornea (the front of the eye) and the posterior chamber is behind the iris and in front of the lens - the fluid sits right in the middle of these. Dogs and cats tend to have around 1ml more aqueous fluid in their eyes than humans.
The fluid is packed with oxygen and plenty of nutrients to maintain the eye’s pressure, and it helps to deliver all the necessary nutrients to structures in the eye such as the lens and cornea. If there’s any extra fluid, it will be constantly drained out of the iridocorneal angle, also referred to as the drainage angle, which is located between the cornea and the iris. This is how the equilibrium of pressure is constantly maintained, preventing the onset of glaucoma.
As we know, glaucoma is caused by the insufficient drainage of the aqueous humour fluid. However, this can be categorised into two types, primary glaucoma and secondary glaucoma.
Primary glaucoma is all down to genetics. Some dogs have anatomical irregularities within their eye structure that have an impact on the iridocorneal angle, meaning that the adequate amount of aqueous fluid can’t be drained properly. Nothing else triggers primary glaucoma, such as an underlying illness or injury, it’s just the result of unfortunate genetic anomalies.
Although this can occur at absolutely any age, the majority of dogs suffering from primary glaucoma get diagnosed pretty early, usually between about 3-7 years old.
Unlike primary glaucoma, secondary glaucoma occurs as a result of another coinciding eye condition that has an influence on the drainage angle. Typically, it’ll mean the drainage angle is obstructed, limiting the amount of fluid that can be filtered out. Secondary glaucoma is much more prevalent in dogs than primary glaucoma.
Triggers for secondary glaucoma can include:
Uveitis (inflammation of the interior eye)
Intraocular infections which can cause scar tissue and debris to be left in the eye, blocking the drainage angle
Anterior dislocation of the lens. This is where the lens becomes dislocated, falling forward and blocking the drainage angle
A ruptured lens causes proteins in the lens to leak into the eye, resulting in a reaction, causing inflammation that will cause obstruction
Whether your dog is suffering from primary or secondary glaucoma, the disease will still occur in exactly the same way, with the failure to drain aqueous fluid and maintain the correct IOP.
Glaucoma in humans and dogs can be very similar, but sadly, our dogs experience the pain of the disease much more intensely than humans do. The pain will be severe, but our dogs are resilient, tough and like to try and mask their pain away from their humans. Therefore, it might be tricky to tell that they’re actually in pain, so you must try and look out for some of these symptoms:
Rubbing face against the floor
Pawing at eyes
Redness of eye
Hazy, cloudy ‘blue’ appearance to the eye
Avoidance of light
Weak blink response
Different size pupils
Dilated pupil that doesn’t constrict when light is shone into the eye
Appearance of vessels in the white of the eye
Bulging, swollen eye
Evidence of vision loss, such as bumping into furniture, not facing you when you’re speaking to them, unable to find their food and water bowls and walking with caution
It’s rare for a dog to experience glaucoma in both eyes simultaneously, it’s much more likely for your dog to experience it in one eye and then the other. However, this could take years for the other eye to become impacted by glaucoma.
As primary glaucoma is a disease caused by inherited genetic traits, there are some breeds that have the predisposition to develop glaucoma.
These breeds include Cocker Spaniels, Jack Russell Terriers, Chow Chows, Poodles, Huskies, Basset Hounds and Shar-peis. If you own any of these dog breeds, it’s imperative that you are aware of the glaucoma symptoms so you can quickly get your four-legged friend the treatment they need to hopefully avoid potential blindness.
As secondary glaucoma is a result of another eye condition, it means that any dog can be at risk of the disease if they’ve got another concurrent underlying condition.
If you’re able to recognise the signs very early on in the condition, you might be able to get a speedy diagnosis and treatment plan so you can prevent your pet from having any further vision troubles. However, time is of the essence here, a dog presenting symptoms will need to get medical attention urgently.
When you reach the vet, they’ll likely want you to provide a detailed account of your dog’s overall medical history, the symptoms they’re currently experiencing and a timeline of when you first noticed the symptoms to now. This will help the vet determine between primary and secondary glaucoma if that’s what they think is causing the symptoms.
A full ophthalmologic (eye) exam will then be conducted, alongside a test of the eye’s intraocular pressure using a tonometer. This is a handy little tool that checks for the pressure levels inside the eye, identifying if glaucoma is present. Tonometers can come in various forms, there are ones that directly press the onto the eyeball, ones that just touch the eyelid and ones that don’t even need to touch the eye at all. A small puff of air will be blown onto the eye which can help measure the pressure levels. Overall, tonometry is a painless, non-invasive process.
If the glaucoma is acute, where it appeared suddenly and severely, the pupil will have a delayed, slow response to light, the blink response will be weak and the cornea will be cloudy. In cases of chronic glaucoma, where the disease has been present for quite some time, the pupil will have absolutely no reaction to the light, the blink response will be totally nonexistent and the cornea will be extremely hazy.
In some cases, an X-ray of the eyeball may need to be performed to detect injuries, abscesses or tumours. Electroretinography is another test that will be performed once glaucoma has been detected, it’s used to determine whether the eye will remain blind despite treatment.
After all this testing, the vet will be able to diagnose glaucoma and differentiate between primary and secondary glaucoma, at which point treatment can begin.
The aim for treatment is to ease the pain caused by glaucoma and regain equilibrium of eye pressure, by either reducing how much fluid is created within the eye or by boosting how much is drained out of the eye.
If your dog is diagnosed with secondary glaucoma, there is the possibility of curing the disease, as long as you can treat the initial underlying condition that triggered glaucoma in the first place. For instance, if the glaucoma was triggered by cataracts, and these can be removed surgically, this removal will need to go ahead first to prevent glaucoma from progressing.
For primary glaucoma, there will sadly be no full cure. However, there are a few options for treatment which will help you and your dog manage the condition so they can live happily and healthily. Treatment methods will all depend on the severity of the disease, and the options are usually medication, cyclocyrotherapy and surgery.
Your pet will be provided with medication to decrease the intraocular pressure in the eye so it can return to the appropriate level as quick as possible. Medication usually comes in the form of topical drops or an ointment, with a goal of reducing inflammation.
Oral medications can also be administered, but these are more to lessen the pain and discomfort that comes with the condition, rather than used to treat glaucoma itself.
In extremely severe cases, hospitalisation might be necessary to supply your dog with an injected medication which should lower the intraocular pressure faster.
This procedure utilises extremely cold temperatures to destroy the ciliary body, which is situated in the anterior chamber of the eye and is where the aqueous fluid is produced. Aqueous fluid will continue to be produced, this procedure will just lessen the amount, allowing intraocular pressure to be maintained. If the symptoms are detected early enough, this can really slow down or prevent the disease from progressing even further.
Unfortunately, ongoing, long-term cases of glaucoma may require complete removal of the affected eye. If the disease has become advanced, there’s more likelihood that the optic nerve will be unsalvageable, causing total blindness.
When the eye is removed, the surgeon will close up the empty socket or fill the space in the eye cavity with an orb. To prevent any more injury to the eye, your pet will need to wear a protective cone for a while so they’re unable to itch their eyes. Your dog probably will experience some discomfort in the following days after surgery, but medication will be supplied to relieve the pain.
Dogs suffering from primary glaucoma usually respond really well to treatment, however, after many years of constant treatment and management, they may stop responding to it anymore. As a result, they may eventually lose their sight anyway.
As unfortunate as it is to lose their vision, our dogs can luckily cope really well without their sight. After all, their primary sense is their keen sense of smell, which they predominantly use to navigate their way around the world.
Your blind dog can still enjoy and live life to the fullest, you can help out by keeping all furniture in the same place to avoid bumps in the road, increasing how much you chat to your dog to reassure them that you’re there and trying to play plenty of mental enrichment games that allow them to use scent. On a walk with your dog, make sure you give them the time to sniff out everything on the ground, walks are their chance to ‘see’ the world!
Unfortunately, glaucoma in dogs can’t really be prevented. Primary glaucoma is impossible to stop as it’s an unchangeable result of your dog’s genetic makeup. However, secondary glaucoma can be prevented by keeping on top of your dog’s eye health. Regular check-ups at the vet, trying to avoid them getting injured and seeking out treatment quickly if you spot any signs of an eye condition are the best things you can do to help prevent glaucoma.
Glaucoma is a debilitating disease, often leading to total vision loss. Luckily, our clever canine friends are adaptable, tough and wouldn’t let something like that stand in their way. No matter what the outcome is, your dog will still enjoy playtime, walkies and will still greet you with a waggy tail.
Knowing the signs and symptoms of the eye condition is the best thing owners can do, especially if your dog is a breed susceptible to glaucoma. If you can seek a diagnosis and treatment quickly, your pet will have the best chance of keeping their eyesight.
Written by: Dr Andrew Miller MRCVS
Andy graduated from Bristol University in 2010 and sees nutrition as a foundation for our pet's wellbeing and takes a common-sense approach. We are what we eat, and it shouldn't be any different for our pets.