What is glaucoma in Shih Tzu? Causes Symptoms Diagnosis Treatment Prognosis Prevention. Our puppies use their eyes for many things – exploring the environment, playing fetch, and locating squirrels – so when issues like glaucoma in dogs arise, you’ll need immediate veterinary attention.
If you notice your Shih Tzu’s eyes are cloudy and he seems to be in pain, it might be glaucoma, a often painful eye condition that requires immediate diagnosis and treatment. Here’s what to expect if your dog is diagnosed with glaucoma.
What is glaucoma in Shih Tzu?
Glaucoma is an increase in intraocular pressure caused by the buildup of aqueous humor, an eye fluid that nourishes and provides oxygen to the entire eye. The fluid exits the eye through the filtration angle located between the iris and the cornea.
An equal balance between the production and drainage of aqueous humor keeps intraocular pressure within normal limits. Pressure increases when this balance is disrupted and aqueous humor does not drain properly. Increased pressure damages the retina and optic disc, leading to permanent blindness.
Glaucoma in Shih Tzu is classified as primary or secondary. Primary glaucoma is hereditary and involves a genetic malformation of the filtration angle, preventing adequate drainage of aqueous humor. Primary glaucoma can further be classified as “open-angle” or “closed-angle”. Open-angle primary glaucoma develops gradually, while closed-angle primary glaucoma (goniodysgenesis) develops rapidly.
Secondary glaucoma is the most common form of glaucoma in Shih Tzu and is caused by an underlying eye condition. Glaucoma can affect one or both eyes. Commonly, the unaffected eye will develop glaucoma within a year after the other eye develops glaucoma.
What causes glaucoma in Shih Tzu?
Glaucoma is caused by the blockage of drainage of aqueous humor from the eye. There are some genetically predisposed breeds to primary glaucoma, including Shih Tzu:
Cocker spaniel
Poodle
Beagle
Basset hound
Terrier breeds
There are several eye conditions that cause secondary glaucoma, including:
Eye inflammation
Lens luxation
Eye tumors
Eye trauma
Cataracts
What are the symptoms of glaucoma in Shih Tzu?
The early signs of glaucoma in dogs are difficult to detect. Glaucoma symptoms become more pronounced as the disease progresses, either rapidly or gradually. Symptoms may include:
Vision loss
Scratching the eyes
Redness of the eyes
Droopy eyelids
Cloudy and hazy blue eye
Bulging eye (buphthalmos)
Dilated, slow, and unresponsive pupil
Pain, demonstrated by squinting and excessive tearing
Secondary glaucoma causes additional symptoms:
Iris sticking to the cornea
Inflammatory debris in front of the eye
You may also observe more general symptoms:
Hiding
Reduced appetite
Reduced activity level
Head pressing to relieve pressure
Diagnosis of Glaucoma in Shih Tzu
Schedule an appointment with your veterinarian as soon as your Shih Tzu shows symptoms of glaucoma. After describing your dog’s medical history, inform your veterinarian about your dog’s symptoms and when they started, as well as any history of eye injuries or other eye problems.
Your veterinarian will then perform an ophthalmic examination. They will measure intraocular pressure using a tonometer. Normal intraocular pressure in dogs is 15 to 25 mm Hg. Pressure in Shih Tzu with glaucoma can reach 45 to 60 mm Hg. Your veterinarian will also examine your Shih Tzu’s eyes for other abnormalities.
Your veterinarian may refer you to a veterinary ophthalmologist for advanced eye tests. One such test is gonioscopy, which evaluates the filtration angle in dogs with goniodysgenesis. Another advanced eye examination is electroretinography, which evaluates retinal function.
Both eyes will be examined, even if only one eye is affected.
Treatment of Glaucoma in Shih Tzu
Glaucoma is treated as a medical emergency due to the risk of permanent blindness that can occur within hours if intraocular pressure is not reduced. Treatment through medication or surgery is expected to reduce intraocular pressure, reduce pain, increase drainage of aqueous humor, and decrease production of aqueous humor.
Some medications increase drainage of aqueous humor and decrease its production; others include analgesics. Both are administered as tablets or eye drops and are administered if there is no vision loss. If there is vision loss, surgical therapies become the best treatment option.
Cyclocryotherapy is a non-invasive surgical procedure that freezes aqueous humor-producing cells. Goniovalve surgical therapy creates another pathway for aqueous humor to exit the eye. Enucleation, or complete removal of the eye, is for end-stage glaucoma in dogs when there is permanent blindness.
Your veterinarian will determine the best treatment option for your Shih Tzu based on the type of glaucoma your dog has and how advanced it is. Treatment is usually long-term and requires regular monitoring of the affected and unaffected eye.
What is the prognosis for glaucoma in Shih Tzu?
Glaucoma has no cure. Long-term medical therapy often fails, and Shih Tzu become blind, necessitating surgery. Fortunately, dogs adapt very well to vision loss and can still enjoy their lives.
How to prevent glaucoma in Shih Tzu
Primary glaucoma cannot be prevented because it is hereditary. However, if you have a breed predisposed to glaucoma, regular eye monitoring can detect glaucoma early so that treatment can begin as soon as possible.
Preventing eye injuries is the primary way to prevent secondary glaucoma in Shih Tzu.