The short answer is yes, dogs can get glaucoma! Glaucoma in dogs is a painful eye condition that needs immediate veterinary attention. 

We’re going to explore what causes glaucoma in dogs, how to recognise the symptoms, and how to manage this condition. Read on to find out more… 

What is glaucoma in dogs? 

The term glaucoma refers to an increase in intraocular pressure (the pressure inside the eyeball). This can affect one or both eyes. As well as being very painful, this increase in pressure can lead to damage of the optic nerve and retina (at the back of the eye), which could cause vision loss. 

Glaucoma occurs when there is a decrease in drainage of aqueous humour, the liquid found inside the eyeball. This liquid is what gives the eye its shape and size. Aqueous humour also contains nutrients and oxygen which help the eye to function properly. It is produced by a structure called the ciliary body, which also contains suspensory ligaments that hold the lens in place. Small muscles in the ciliary body pull on these ligaments to change the shape of the lens, which helps your pet focus their eyesight. 

In a healthy eye, the ciliary body continuously produces fluid, and excess fluid drains from the eye through something called the iridocorneal angle, an area between the cornea and iris. This drainage ensures that normal pressure is maintained within the eye. 

Simply put, glaucoma occurs when there is inadequate drainage of fluid from the eye, causing pressure within the eyeball to rise. There are several reasons why this might occur. 

What causes glaucoma in dogs? 

As we’ve discussed, glaucoma is caused by reduced drainage of fluid from the eye, not an overproduction of fluid. Glaucoma can be divided into primary and secondary causes. 

Primary Glaucoma 

Anatomical abnormalities in the eye can cause primary glaucoma. Affected pets have an issue with their drainage angle. This condition is hereditary, and some breeds are more commonly affected than others, including (but not limited to!): 

  • Alaskan Malamutes 
  • Beagles 
  • Cocker Spaniels 
  • Flat-coated retrievers 
  • Great Danes 
  • Miniature Pinschers 
  • Samoyeds 
  • Shar Pei 
  • Welsh Springer Spaniels 

The British Veterinary Association is working hard through its nationwide eye scheme to reduce the number of inherited eye conditions in dogs. Reputable breeders should have their dogs examined for eye problems, thereby screening them before breeding. This will increase the chances of healthy puppies being born. Always check with your breeder as to whether this has been done before purchasing your puppy. 

Secondary Glaucoma 

Disease or injury in the eye can cause secondary glaucoma. This is the most common cause of glaucoma in dogs. Possible eye issues that can lead to reduced drainage of aqueous humor and an increase in intraocular pressure include: 

Uveitis – Inflammation of the inside of the eye can cause debris and scar tissue, which can block the drainage angle in the eye. Severe intraocular infections can also do the same. 

Tumours – A tumour in the eye can cause a physical obstruction, affecting the amount of fluid that can drain from the eye. 

Lens damage – If the lens in the eye ruptures, then proteins from inside the lens can leak out. This causes inflammation, swelling and blockage of the drainage angle. Lens damage can occur through trauma or because of issues like cataracts. 

Intraocular bleeding – A bleed in the eye can lead to a blood clot forming. This can block aqueous humor from draining effectively. Bleeding in the eye can occur from trauma or from hypertension (high blood pressure), a condition that can damage the very delicate blood vessels in the back of the eye. 

Anterior dislocation (luxation) of the lens – In lens luxation, the lens in the eye can fall forwards (anterior dislocation), the drainage angle in the eye can become blocked. 

What are the symptoms of glaucoma in dogs? 

Glaucoma can affect one or both eyes. If your pet has acute glaucoma (sudden onset), you may notice the following symptoms:

  • Pain in the eye/s – your dog may rub at their eye excessively, shy away from being stroked, and hold their eye partially closed 
  • Watery discharge from the eye 
  • A visibly swollen or bulging eyeball 
  • Inflammation and reddening in the white (sclera) of the eye 
  • A bluish, cloudy tinge to the cornea 
  • Reduced appetite, reluctance to interact, and lethargy 
  • Blindness 

Acute glaucoma is a medical emergency and requires immediate veterinary attention. Unless the intraocular pressure inside the eye is reduced quickly, blindness will occur. 

Chronic glaucoma can be a bit more subtle, with symptoms creeping on gradually over a longer period of time. 

How do vets diagnose glaucoma in dogs? 

There are several reasons why your dog may have a sore eye, so an accurate diagnosis from your vet is crucial. They will want to rule out other causes of an inflamed or watery eye such as a corneal ulcer or conjunctivitis. 

As well as doing a general examination, your vet will need to measure the intraocular pressure of the eye/s. This is done using a tonometer, a small handheld device which is lightly pressed against the surface of the eye. Many first opinion practices have this tool, but not all, so your vet may need to refer you to another practice if they don’t have access to one. 

Normal pressure readings obtained by a tonometer typically range from 10–20 mmHg. Readings above 25 mmHg alongside clinical signs are consistent with glaucoma. 

As well as measuring intraocular pressure, your vet may suggest assessing your dog’s eye in detail. While some assessment can be done with a normal ophthalmoscope, your vet may need to refer your dog to a veterinary ophthalmologist for gonioscopy. 

During this procedure, the eye is numbed and a goniolens is positioned on the eye surface, and a focal light source (ideally a slit-lamp biomicroscope) is used to examine the iridocorneal angle to look for narrowing or closure that could be preventing fluid drainage. It can also look for issues like pectinate ligament dysplasia, which is something that can cause primary glaucoma in certain breeds. 

Other abnormalities like anterior lens luxation will also be assessed for. 

How is canine glaucoma treated? 

For dogs with acute glaucoma, the aim is to reduce intraocular pressure as soon as possible, to address pain and to try to prevent permanent optic nerve damage. 

You should be aware that, even if treated promptly, only about 50% of patients will regain their sight. This is because damaging undetected episodes of high intraocular pressure have often occurred prior to the current acute presentation. 

Treatment for acute glaucoma 

Typical treatment for acute glaucoma involves hospitalisation for treatment which could include:

Osmotic diuretics – A group of drugs that are commonly used, which reduce the amount of aqueous humor produced in the eye, effectively dehydrating the eye. 

Prostaglandin analogues – These help to increase the outflow of aqueous humor from the eye through their action on the iris and muscles of the ciliary body. 

Anterior chamber paracentesis – Depending on the vet’s experience and the patient’s temperament, a small gauge needle can be inserted into the eye to drain some fluid. This is usually performed under mild to moderate sedation. 

Pain relief – Glaucoma is a painful condition, so strong (usually opioid) painkillers are often used. 

Anti-inflammatories – Anti-inflammatory eye drops containing steroids are often used to help treat inflammation on the surface and in the anterior (front part) of the eye. Systemic anti-inflammatories can be taken by mouth to help treat the retina and optic nerve. 

Maintenance therapy for glaucoma in dogs 

Once intraocular pressure has been reduced, additional therapy is needed to keep it under control. You will need to continue administering these medications long term. 

Carbonic anhydrase inhibitors – These aim to decrease production of aqueous humor, with topical eye drops available, as well as oral medications. Eye drops will typically need to be administered 2 – 3 times daily ongoing, but your vet will advise your further. 

Beta blockers – Occasionally beta blockers are also needed which reduce the formation of aqueous humor, but care needs to be taken in dogs with cardiovascular disease or asthma. 

Surgery – Surgery may be required to treat certain cases of secondary glaucoma including lens luxation. 

What is the prognosis for dogs with glaucoma? 

The prognosis for glaucoma is variable, depending on the underlying cause of the glaucoma in the first place and how quickly treatment was started. Regular ongoing monitoring is likely to be needed to monitor your pet’s intraocular pressure and make therapy adjustments as needed. 

In cases of primary glaucoma, where there is an inherited issue with the eye, medication can start well but become less effective over time. If your dog is still visual, then referral to a specialist ophthalmologist may be recommended for advance surgical treatments like ciliary body lasar ablation and anterior chamber shunts. However, enucleation (surgical removal of the eye) is not uncommon in chronically blind patients, to relieve their pain. 

In secondary glaucoma, the prognosis is more favourable if the underlying cause can be removed or resolved, e.g. a treatable tumour, inflammation, or lens dislocation. Your vet or veterinary ophthalmologist will be able to advise you further on this. 

We can’t stress enough that time is of the essence when treating glaucoma. The longer the intraocular pressure is raised, the more likely that the delicate retina and optic nerve will be damaged, leading to blindness. But remember, despite everyone’s best efforts, some dogs will permanently lose their vision.   

Summary 

We know that a diagnosis of glaucoma can be daunting for pet owners. There is often a lot of technical terminology used, as well as unfamiliar drugs. Your vet or ophthalmologist specialist will happily discuss your dog with you, so don’t be shy and ask questions if you’re not sure about anything. 

The key takeaway message is that you must contact your vet immediately if your dog’s eye ever seems sore, swollen, or inflamed. It could save their eyesight.