Glaucoma in dogs may lead to eye deformity or permanent blindness. Here is all you need to know on symptoms, treatments and the best way to prevent your dog from canine glaucoma.
- What is Glaucoma in Dogs?
- What Causes Glaucoma in Dogs?
- Primary Glaucoma
- Common Breeds Affected by Primary Glaucoma in Dogs
- Secondary Glaucoma
- Luxation or displacement of the lens
- Intra-ocular bleeding
- Tumor / Cancer
- Damage to the lens
- Degeneration of the drainage angle
- Signs of Glaucoma in Dogs
- Gonioscopy and Ultrasound Biomicroscopy(UBM)
- Treatment of Glaucoma in Dogs
- Medication Therapy for Glaucoma in Dogs
- The medicines that help reduce aqueous humor production include;
- Carbonic Anhydrase Inhibitors
- Alpha Adrenergic Agonists
- The medicine used to increase aqueous humor outflow include;
- Prostaglandin Analogs
- Alpha Adrenergic Agonists
- Surgery for Canine Glaucoma
- Laser Surgeries
- Endolaser Cyclophotocoagulation
- Argon Laser Trabeculoplasty
- Laser Peripheral Iridotomy (LPI)
- Routine surgery
- Anterior Chamber Shunts or Gonio-implantation
- Surgery when the Dogs Eye Vision is Lost
- Intraocular Prosthesis
- Side Effects of Surgery
- Prevention of Glaucoma in Dogs
What is Glaucoma in Dogs?
A dog’s eye is just like another mammal eye, it contains a fluid that continually keeps the eye in its normal shape. This fluid “aqueous humor “created by inner cells of the eye exerts normal pressure in the eye “Intraocular Pressure (IOP)” giving the eye its ordinary natural shape. To keep the eye under normal pressure then there must be a right balance between aqueous humor drainage and production.
Glaucoma is the increase in pressure inside the dog’s eye from the aqueous humor fluid. It may be due to these two factors. One is excessive production of aqueous humor, and the other is problems with the fluids drainage. This increases the amount of fluids amount hence increase in eye pressure. Without proper treatment or any checkup, the condition will result in deformity of the dog’s eye shape; the eye becomes bigger and later permanent blindness of dog’s affected eye.
What Causes Glaucoma in Dogs?
Increased Intraocular Pressure” Glaucoma” in dogs. This can be classified into two ways.
- Primary Glaucoma- inherited Glaucoma
- Secondary glaucoma- from injury or infection in the eye.
Canine Glaucoma is one of the diseases that fall under the categories of hereditary diseases. The dog inherits the anatomical abnormality which is the deformity of the dog’s eyes drainage angle. Symptoms of primary glaucoma start getting more noticeable when the dog is older than two years. The main risk factors of primary glaucoma are Gender, Age, Gonadogenesis (Abnormalities in the drainage angle) and Breed. In most cases, primary glaucoma affects both eyes.
Common Breeds Affected by Primary Glaucoma in Dogs
Studies and records have shown that there are types of dogs that are more prone to get hereditary Glaucoma. Here some of the dogs:
- Cocker Spaniel
- Siberian Husky
- Chow Chow
- Basset Hound
- Shih Tzu
- Boston Terrier
Secondary Canine glaucoma is due to secondary causes that result in increased IOP. These include injury, infections like a fungal infection, inflammation, tumor, or luxation or displacement of the lens. Unlike primary glaucoma the effects of secondary glaucoma are not for both eyes, this is because it is rare for the causes to affect both eyes. Here is the list and description of secondary causes of glaucoma:
Luxation or displacement of the lens
This means that that the attachments that hold the lens together have broken or weakened, causing anterior dislocation of the lens. The lens moves forward physically rests against the iris blocking the drainage angle or opening.
Internal eye bleeding may clog the aqueous angle. blood clots clog the drainage pores. Intra-ocular bleeding is usually as a result of injuries to the eye.
Tumor / Cancer
Tumors are unpredictable, and they can also occur at any part of the dog’s eye. Some tumors can physically block drainage in the dog’s eye, hence causing glaucoma.
Uveitis is the swelling or inflammation of the uveal track “the middle layer of the eye”. This, as a result, blocks the drainage and in the end, increasing IOP. Uveitis has several types
- Anterior uveitis – affects the eye front.
- Posterior uveitis –has an impact on the back of the eye, the retina and choroid.
- Intermediate uveitis – inflammation of the vitreous cavity.
- Pan-uveitis – affects all layers of the uveal tract.
Uveitis may be due to eye surgery, cancer, autoimmune disorder or infections such as herpes zoster, brucellosis, etc.
Damage to the lens
Damage to the eye lens causes leakage. This may cause inflammation, and/or blockage of the drainage angle.
Degeneration of the drainage angle
The tissue and cells of the drainage angle can wear out with age, or due to any damages and injury. This causes the two to lose their ability to work well. In the end, the cells and tissue lead to blockage of drainage angle and the fluid can’t get to the deeper reaches of the corner.
Signs of Glaucoma in Dogs
If you don’t watch for, do check up on your dog frequently some of the signs might go without unnoticed. Make sure you carefully examine your dog. If you see some of these symptoms take your dog immediately to the vet ophthalmologists. Glaucoma develops very fast. Here are the symptoms of canines with glaucoma:
- Increased production of tears.
- Dilated pupils.
- Cloudy, gray or bluish colored cornea.
- The dog avoids areas with light.
- Eye redness, the sclera looks red.
- The dog may partially and gently try to rub its eye closed.
- Bulging and swelling of the one eyeball.
- Lack of appetite.
- Degeneration of the eye.
- Sticking of the iris to either the cones or the lens
- Redness of blood vessels and congested vessels.
- Behavior changes.
- Depressed and agitation
- The dog stumbles and bumps into objects.
- Noticeable loss of vision.
- Possible construction of the eye
Behavioral change, depression, agitation, etc. may come as a result of the pain your dog is experiencing due to the disease.
Remember that some of the symptoms such as (tearing, redness, dilated the pupil, or squinting) are similar to other diseases or problems, that’s why the vet ophthalmologists do the diagnosis to determine if its glaucoma or another type of problem and later treat your dog.
Because irreversible blindness can occur immediately after symptoms or diagnosis, glaucoma is an emergency. Increased IOP should be reduced as soon as possible.
The best diagnosis is made through tonometry and gonioscopy.
A vet ophthalmologist diagnoses canine glaucoma. He uses a highly accurate applanation tonometer which measures pressure in the dog’s eyeball. The vet ophthalmologists can use any of the three types of tonometers:
- One a tonometer that blows air onto the eyeball, then he /she uses the indentation as a measure of the pressure in the eye.
- The other tonometer that’s used to press the small and flat disk against the dog’s eyeball to gauge the pressure.
Gonioscopy and Ultrasound Biomicroscopy(UBM)
The ciliary cleft and iridocorneal angle are measured using the techniques above. A goniolens is a tool employed in Gonioscopy technique to measure the drainage angle. It is a dome-shaped contact lens which is placed on the corneal surface. It allows the vet to see or visualize the drainage angle.
UBM is an ultrasound eye exam that is used for imaging of the interior parts of the eye. The ultrasound machine bounces high-energy sound waves off the eyes anterior segment. The echo pattern shows on the device’s screen reviling the details of the eye’s anterior segment.
Gonioscopy and UBM are very essential in preventing future risks or attacks of glaucoma by efficiently evaluating the nonglaucomatous eye.
After diagnosis treatment should be immediate, you can’t estimate time of disease development. Glaucoma causes and severity has a lot of variables making estimation a little challenging.
Treatment of Glaucoma in Dogs
There are several treatment options for Canine glaucoma. It typically depends on the severity stage of glaucoma and also on its cause. When the vet ophthalmologist is treating your dog is goals are:
- Reducing the aqueous humor production
- Increasing the drainage
- Reducing pressure in the eye.
- More important enabling clear visibility of the dog’s eye.
If all this has been done, surgery can be done to maintain visual possibility for your dog. If this is not possible then, pain relief surgery is done, or medicine is given to help reduce the pain your dog is filling.
Medication Therapy for Glaucoma in Dogs
The medication comes in the form of pills or eye drops, some increase drainage of aqueous humor while others decrease fluid production and some do both. Dogs get a lot of help with the drugs, but a combination of both medication and surgical therapy is what helps eradicate glaucoma completely.
The reason for this is because medicine is a temporary fix for glaucoma by keeping the disease in check. It helps to keep symptoms in control but eventually, they may not work.
The medicines that help reduce aqueous humor production include;
The medication reduces the inflow of aqueous humor in the eye and also its production.
Here are some examples of beta blockers:
Carbonic Anhydrase Inhibitors
This medication reduces aqueous humor fluid production. Here are some examples:
Alpha Adrenergic Agonists
It reduces fluid production and increases its outflow. Here are some examples:
The medicine used to increase aqueous humor outflow include;
Increase outflow of aqueous humor fluid, hence relieving pressure in the eye. Here are some examples:
Miotics cause the pupil to reduce in diameter which results in increased drainage of aqueous humor fluid. Here are some examples:
Alpha Adrenergic Agonists
It can also increase aqueous humor fluid drainage. Here are some examples:
The best chance to save your dog’s vision is the combining of both medications therapy CAM (Complementary and Alternative Medicine) and surgery.
Surgery for Canine Glaucoma
Surgery is the best option for treating glaucoma. It lowers the cost of medicines and also offers a longer and sometimes permanent solution for your dog’s glaucoma problems. There are different types of surgery depend mostly on the degree of severity of glaucoma or if the dog’s vision has been damaged.
The most common type of surgery is laser surgery, which is used by vet ophthalmologists in preventing blindness and reducing the IOP to normal conditions.
The vet ophthalmologist direct laser beams through the white outer layer of the eye. It burns and destroys small areas of the ciliary body ”secretory epithelium” which is responsible for aqueous humor production, thus reducing its output. This type of procedure is done severally so as to control glaucoma permanently.
Argon Laser Trabeculoplasty
A high energy laser beam is used to open up clogged fluid channels of the eye. It then allows drainage of the fluid and hence helps the drainage system to work better. This type of laser surgery is used for primary open-angle glaucoma treatment. The procedure has been successful 75% of the times.
Laser Peripheral Iridotomy (LPI)
LPI is used to make a small hole in the iris, which helps aqueous humor to drain. It’s used in treating narrow-angle glaucoma.
Its alternative to laser surgery and medication
It involves placement of a small probe on the outer part of the eyeball which freezes the ciliary body. It destroys secretory epithelium and is done on numerous roles depending on the degree of pressure. After some time a second procedure is done in order restores normal intraocular pressure.
The vet ophthalmologist cuts a flap on the sclera, removes a tissue located around the eye and stitches the flap. A new opening is created to allow aqueous humor to drain and relieves the eye of pressure.
Anterior Chamber Shunts or Gonio-implantation
In this surgical procedure, a shunt (small tube) or valve-like device is implanted in the eye. This implant provides an outlet for the fluid drainage, thus minimizing IOP to its standard size.
Remember that most of these procedures have different side effects and can be used at various levels of glaucoma. The vet ophthalmologists will describe to you which is the best type of surgery and medicine to use after diagnosing your dog.
In some cases, medication is still needed even after surgery but not as constant or as aggressive as before the surgical treatment. Procedures may be repeated because glaucoma redevelops after some time.
Surgery when the Dogs Eye Vision is Lost
Some people may think it’s not important, but this type of treatment helps a lot. It assists prevent glaucoma to the other dog’s eye, and it also relieves the dog from irritation, uncomfortable and pain from the affected eye which has lost vision when medication isn’t helpful.
This is the complete removal of the eyeball. After this, an artificial eye may be inserted in the dog after the wound from surgery has healed or the skin will be the sutured then left, hair will grow over the surgical site over time. It’s painful for the dog, and it takes two weeks for the dog to heal.
Evisceration will remove the contents from the eye that brings about pain or irritation leaving the sclera. Then there is the placement of silicon Prosthesis in the eye. The eye will still move, and the shape of the eye is maintained. It’s an alternative procedure to Enucleation. It may be still painful to the dog but takes four weeks to heal. A side effect is an ulceration.
Side Effects of Surgery
Your dog is at risk of the following side effects:
For laser surgeries
- Blurred vision.
- Temporary eye irritation.
- Small danger of developing cataracts or shrinkage of the eye.
Surgeries involving cutting
- Blurred vision
- Retinal detachments “ Cyclocryothermy” surgery
- Bleeding in the eye
- Intraocular inflammation for “ Cyclocryothermy” surgery
Prevention of Glaucoma in Dogs
Because Canine glaucoma is seldom diagnosed in time, it leads to an average of 40 out of 100 dogs, lose their vision. So prevention measures and accurate early diagnosis which is guided by knowing glaucoma symptoms and your dog’s history will help a lot in stopping glaucoma.
- Frequent checkup for Breeds predisposed to glaucoma, elderly dogs, and dogs with any or both of its parents who suffered from glaucoma to avoid primary glaucoma
- Antioxidants might also help e.g. Beta-carotene, vitamins E, and C
- Reduce dog’s necks pressure from dog collars.
- Always check your dog for any eye injuries or scars which might later cause glaucoma
Sources and References
eyevet.info: Glaucoma in Veterinary Patients
1-800-petmeds: Glaucoma Treatment for Dogs
The Merck Veterinary Manual: Glaucoma
Pet Finder: Canine Glaucoma