What is glaucoma?
Glaucoma is a painful condition characterized by increased intraocular pressure within the eye, caused by inadequate fluid drainage. Glaucoma can progress very quickly, and often leads to optical nerve and retinal damage in dogs. It is estimated that 40% of dogs will be left blind in the eye which is affected by glaucoma.
Glaucoma in dogs is caused by insufficient drainage of fluid from the eye. There are two types of glaucoma, each defined by the cause of the condition; primary glaucoma and secondary glaucoma.
What causes primary glaucoma in dogs?
Primary glaucoma occurs in dogs due to inherited abnormalities in the drainage mechanism of the pet's eye. A number of breeds show an increased risk of primary glaucoma including (but not limited to) Boston terriers, cocker spaniels, shar-peis, beagles, basset hounds, Siberian huskies, Labrador retrievers, samoyed, toy poodles, and great danes. Each breed has its own unique traits that make dogs of that breed more susceptible to developing glaucoma.
Primary glaucoma rarely affects both eyes equally or at the same time. The condition typically occurs in one eye months or even years before it affects the second eye.
What is the cause of secondary glaucoma in dogs?
Secondary glaucoma (the most common type of glaucoma) is sudden and acute. It occurs as a result of an injury to the eye or disease. The most common causes include: damage to the lens of the eye, inflammation of the interior of the eye, severe intraocular infections, anterior dislocation of the lens (blockage caused by the lens falling forward in the eye), tumors, and intraocular bleeding. This type of glaucoma can cause severe pain and is more likely to be noticed by pet owners than primary glaucoma, which can cause subtle but chronic symptoms.
What are the signs and symptoms of glaucoma?
Dogs suffering from either primary or secondary glaucoma may experience one or more of the following symptoms:
- Watery discharge from the eye
- Eye pain (eye rubbing or turning away when being pet)
- Bulging of the eyeball (whites of eye turn red)
- Cloudy, bluish appearance to eye
- Dilated pupil – or pupil does not respond to light
- Loss of appetite
- Lethargy
- Swelling of the eye
- Less desire to play
- Vision loss
Chronic glaucoma can take some time to develop and begin causing symptoms, but acute glaucoma occurs very suddenly. If your dog is showing any of the symptoms listed above contact your vet immediately or visit the nearest emergency veterinary hospital for urgent care. Early diagnosis and treatment are your dog's best bet for good treatment outcomes.
How is glaucoma in dogs diagnosed?
Your vet will measure the pressure within your dog's eye using an instrument called a tonometer.
If your dog is experiencing blindness due to glaucoma a veterinary ophthalmologist may use electroretinography to determine wether surgery can help to restore vision to the eye.
How is glaucoma in dogs treated?
Following diagnosis, your vet will prescribe drugs to help reduce pressure within the eye as quickly as possible. Reducing the pressure quickly may help to prevent permanent blindness in some dogs.
Typically, painkillers are also prescribed in order to help your dog feel more comfortable.
Other medications may be prescribed to both promote drainage and decrease fluid production as a way of reducing intraocular pressure.
Can dogs have eye surgery for glaucoma?
In many cases surgery will also be an essential part of the treatment for advanced cases of glaucoma. Depending on your dog's circumstances, your vet may recommend one of three surgical options.
If your dog still has their vision or there is a chance their vision will return, a veterinarian may recommend transscleral or endoscopic diode laser cyclophotocoagulation or aqueous shunt implant (gonioimplant).
Transscleral or Endoscopic Diode Laser Cyclophotocoagulation
Cells of the cillary body (the tissue inside the eye behind the iris that produces fluid) are destroyed using a laser. The procedure may control eye pressure for a period of 6 months. Potential complications include post-operative spikes in pressure, significant inflammation, corneal ulcers and intraocular bleeding.
Aqueous Shunt Implant (Gonioimplant)
A small tube or shunt is implanted inside the eye, sitting partially inside the eye and partially outside the eye under the conjunctiva. The shunt allows fluid to exit the eye when pressure increases above a specific level. While the success rate for this procedure designed to control pressure is similar to laser surgery, a shunt is not permanent and may only be effective for a few weeks, or up to a few months.
Potential complications include scarring surrounding the shunt, which may lead to fluid backing up in the eye and the shunt dislocating. General anesthesia and overnight monitoring will be needed after surgery.
If there is no chance of vision returning, or there is minimal to no response to medical treatment and the primary goal is to relieve pain, there are two surgical options:
Enucleation (Eye Removal)
As a last resort, your dog may need eye removal surgery to address glaucoma. A veterinarian removes the eye and the eyelids are permanently closed. A silicone implant may be placed in the eye socket to prevent a sunken appearance, provided there is no cancer or infection in the orbit.
This procedure rarely requires dogs to be hospitalized overnight, and general anesthesia will be used. Following the surgery, your dog will be prescribed oral antibiotics and pain medications. There is low risk for infection to develop around the orbital implant, or the body may reject the prosthesis. A second surgery would likely be needed to remove the prosthesis should infection or rejection occur.
Evisceration with Intrascleral Prosthesis
A cosmetic alternative to enucleation, this surgery involves making n incision through the conjunctiva and sclera (white shell of the eye) and removing the contents within the eye. A prosthesis is placed within the eye before the conjunctiva and sclera are sutured closed. Your dog will then have what appears to be a functional, though non-functional, eye and will be able to move the eye and blink.
For your dog to be eligible for this procedure, they must have a healthy cornea and normal tear production. They will need post-operative therapy and topical medications may be needed long-term.
If your dog has permanently lost their vision your vet may recommend surgery to remove the eye in order to relieve pain.
Regular eye examinations will be an essential part of your pet's ongoing care and treatment for glaucoma. Regular appointments allow your vet to monitor symptoms and keep the condition under control over the long term.
What is the prognosis for dogs with glaucoma?
Your dog's prognosis will depend on many factors, including how promptly the glaucoma is treated and your dog's response to medication.
If treatment was administered late or proves ineffective, your dog may lose their vision. However, dogs with vision loss can continue to lead healthy, happy lives.
Ongoing treatment will be needed to prevent eye pressure from increasing in the future. In some cases, a serious health issue like cancer can trigger glaucoma. If this is the case for your dog, the underlying health issue will need to be addressed.
What is a veterinary ophthalmologist?
Working alongside your primary care veterinarian, our veterinary eye specialists provide care for all ocular diseases that can impact your dog. While some conditions may require surgery, many can be managed with medications alone.
Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.