Photo Credit: by Moshe Harosh from Pixabay
Simple things, such as chasing a ball, set tails wagging. So if your best buddy is diagnosed with glaucoma, an eye condition that threatens eyesight, it’s natural to worry. This article is written for concerned owners and aims to explain what canine glaucoma is, the treatment options for the ‘bad’ eye, and how to protect the remaining ‘good’ eye.
What is Glaucoma in Dogs?
Canine glaucoma occurs when the pressure builds up inside an eye, a lot like blowing too much air into a balloon. This high pressure within the eye results in blurry vision, headaches, light sensitivity, and pain. If the condition remains untreated, it leads to blindness.
Eye Anatomy 101
A look at basic eye anatomy makes for a clearer understanding of glaucoma in dogs.
Eyeballs are not called ‘eyeballs’ for nothing. They are indeed a hollow ball which contains some fancy ‘technology’ such as a light-sensitive retina, self-adjusting lens, and a transparent packing (the aqueous and vitreous humors). Actually, these two humors both keep the eye in shape and nourish it – all clever stuff for something that’s transparent.
Now here’s the thing. Stare into those puppy-dog eyes and you’re gazing into aqueous humor. This fluid sits in the eye’s front chamber (anterior chamber) and fills the space between the lens and the cornea (the eye’s ‘window pane’).
A healthy eye has the perfect balance between the volume of aqueous humor produced and the amount that drains away: Think of this like a faucet running into an unplugged basin. If the drain is blocked, then water flows in faster than it can escape and the sink overflows. This is what happens with glaucoma in dogs, but instead of overflowing, pressure builds inside the eye causing it to stretch and putting delicate tissue under strain.
Why does the Drain Block?
Great question and thank you for asking!
Dog Breeds at Risk
Some dog breeds carry genes that code for subtle changes which make it harder for aqueous humor to drain away, much like a poorly designed storm drain that’s unable to cope with a cloudburst. These dogs tend to develop glaucoma in middle age, first in one eye and, sadly, a few months later in the second eye.
Breeds recognized as at increased risk of canine glaucoma include:
• Bassett hound
• Beagle
• Chow Chow
• Japanese Chin
• Pekinese
• Pug
• Shibu Inu
• Samoyed
• Shar Pei
• Shih Tzu
Glaucoma as a Complication
Another group of dogs may develop canine glaucoma as a complication of separate condition. Some examples include:
• Inflammation: Some infectious diseases cause inflammation inside the eye. This inflammation narrows the drainage system and stop aqueous humor escaping.
• Lens dislocation: If the lens pops out of position, it sits in the drainage system like a plug in a sink
• Cataracts: A lens that has formed into a cataract is stiff and swollen, which may interfere with the drainage angles inside the eye.
• Tumors: A tumor within the eye acts like blocked drain and causes pressure to rise.
• Bleeding: Bleeding inside the eye (as a result of trauma or if the dog doesn’t clot blood properly) clogs the drain like garbage in a plughole.
Signs of Glaucoma in Dogs
Prompt treatment of canine glaucoma may save the pet’s eyesight. This makes it vital for owners to recognize early warning signs of glaucoma and seek urgent veterinary attention.
Early signs of glaucoma to look out for include:
• The dog has one red, angry-looking eye
• The dog flinches away from bright light
• They act out of sorts
• One pupil (the dark circle surrounded by the colored iris) is larger than the other eye
• One eye looks physically bigger than the other
If you notice one or more of these symptoms, contact your vet immediately.
How Does the Vet Diagnose Glaucoma in Dogs?
The gold standard when diagnosing canine glaucoma is to measure the pressure inside the eye. However, this requires a piece of specialist equipment called a tonometer and may require referral to a veterinary ophthalmologist.
In first opinion practice, the vet can assess the patient to rule out other causes of red eye, and decide if referral is required. It may be that the dog simply has a nasty eye infection or has an ulcer on the cornea, and simple treatment is all that’s needed.
But when a physical exam highlights signs of glaucoma, the vet may decide to start treatment for canine glaucoma anyway, ahead of seeing the specialist. This can help protect the eye from the high pressure damage that causes blindness.
Treatment for Glaucoma in Dogs
Treatment is broadly divided into emergency stabilization and long-term maintenance.
Emergency Stabilization
The problem with canine glaucoma is the build-up of pressure within the eye causes damage to the retina. If this pressure is high for long enough it causes blindness. Therefore, fast action to drop things down to normal eye pressure (or near normal) can be sight-saving.
Different clinicians use different techniques to provide this urgent drop down to normal eye pressure. This may involve an intravenous drug (mannitol) that removes fluid from inside the eye or topical drops (synthetic prostaglandins such as Travatan, Xalatan, or Latisse) which also bring about a rapid drop in intraocular pressure.
This initial treatment is often done as an in-patient, so that the eye pressure can be measured every hour. Once the pressure is off (literally) the dog is switched to maintenance therapy and this is where the owner steps back in.
Maintenance Therapy
If the glaucoma is a complication of a separate condition, then correcting this underlying problem may resolve the glaucoma. But for those dogs genetically predisposed to canine glaucoma there’s no cure, but the condition can be controlled. Once the problem develops, the aim is to control the pressure so as to reduce pain and prevent blindness. This is done at home with the use of eye drops (and why Azopt is so important).
Treating the ‘Bad’ Eye
Azopt is a hero medication belonging to a group of drugs known as carbonic anhydrase inhibitors. When the emergency med has done the heavy lifting and brought the pressure down from crisis point, Azopt drops help keep things under control in the longer term. One drop of Azopt is applied to the ‘bad’ eye, usually three times a day, to delay deterioration and maintain the dog’s ball chasing ability.
The good news is that as well as being a great weapon in the fight against glaucoma, Azopt drops are gentle on the eye and less likely to cause irritation than other cheaper options. (And this is where Canada Pharmacy Online brings sophisticated treatments such as Azopt within budget.) There are other products that do a similar job, but they can sting a little when applied…and no one wants their best buddy flinching from such vital treatment.
Protecting the ‘Good’ Eye
For those dogs that develop glaucoma as a complication, this usually only affects one eye. Sadly, the same can’t be same for those at-risk dog breeds. These four-leggers the other eye is likely to develop glaucoma within a few months of the first. However, you can go some way to protecting the ‘good’ eye with the use of preventative treatments.
Without treatment the average time for the second eye to develop glaucoma is eight months. But with daily application of a preventative such as Betoptic S this can delay onset of glaucoma in the remaining eye by four-fold, to around three years….definitely something worth woofing about.
The Blind Eye
Sadly, even though prompt treatment can protect eyesight for a while, many dogs do eventually lose their vision. Glaucoma in dogs can be a painful condition and if the eye is swollen then surgery may be necessary. It sounds extreme, but removing the diseased eye takes away a functionless eye that is a source of pain and the dogs do just great afterwards.
Azopt and Other Eye Drops
It’s not so long ago there was little or no good news for dogs with glaucoma. But hero meds such as Azopt, Travatan, and Betoptic make the future look brighter. Whilst there’s no guarantee of saving sight in the long term, these treatments may well buy the dog time and give their other senses a chance to adjust. So do your pet proud and give them a chance to chase that ball for a long time to come, with these safe, effective modern medicines.
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Dr Pippa is a veterinarian with over three decades of experience working in companion animal practice. She loves working with owners to give their animals the best possible health and quality of life. In addition to work in clinical practice and as a shelter veterinarian for the Cats Protection, Dr Pippa is a developmental editor for veterinary textbooks and a freelance veterinary copywriter with her work widely published in print and online. Dr Pippa is an advocate of Fear Free Practice. Twitter: @PetvetP
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