Glaucoma is caused by increased pressure inside the eye. It can be painful and often causes blindness even with treatment. Acute glaucoma is an emergency, so dogs and cats with any signs of eye discomfort or vision loss need to be examined by a veterinarian right away.
 
Causes
Pressure inside the eye, or intraocular pressure, is controlled by a balance of fluid production and fluid drainage. In dogs and cats, glaucoma results from decreased fluid drainage.
 
Fluid drains out of the eye mostly at the angle where the clear cornea and the colored iris meet inside the eye. This area, called the iridocorneal angle, contains a sieve-like network of tiny ligaments and tissues that regulate fluid flow. Anything that interferes with the iridocorneal angle can cause glaucoma.
 
Primary vs secondary glaucoma
Primary glaucoma is caused by an inherited problem with the structure or function of the iridocorneal angle. Some of the dog breeds at increased risk are cocker spaniels, beagles, basset hounds, Siberian huskies, and Samoyeds. Primary glaucoma is a progressive disease. Affected dogs need lifelong treatment, and the chance they will eventually become blind is high. Primary glaucoma is very rare in cats.
 
Secondary glaucoma is caused by another eye disease (like uveitis, lens luxation, cataract, or cancer of the eye) that results in physical blockage of the iridocorneal angle.
 
Acute vs chronic glaucoma
Acute glaucoma is an increase in intraocular pressure for less than a day. Chronic glaucoma is an increase in intraocular pressure for longer than a day. The best chance for saving vision is to start treatment during the acute stage. However, the early signs of glaucoma can be subtle or mistaken for another eye problem, so glaucoma often isn’t diagnosed until it’s chronic.
 
Signs
Glaucoma causes the same signs of eye discomfort as other eye disorders. Animals with glaucoma can also have subtle behavior changes caused by eye pain. The signs usually start in only 1 eye but might not be noticed until chronic glaucoma has affected both eyes. These are some of the signs of glaucoma:

• Redness of the white part of the eye
• Squinting
• Clear, watery discharge from the eye
• Cloudy eye
• Enlarged eyeball (with chronic glaucoma)
• Vision loss (might not be obvious if only 1 eye is affected)
• Rubbing the eye
• Head shyness
• Reduced activity level
• Decreased appetite

 
Diagnosis
A high intraocular pressure measurement confirms the diagnosis of glaucoma. Devices used to measure intraocular pressure in animals are similar to those used in humans. Animals with glaucoma benefit from referral to a veterinary ophthalmologist to evaluate the iridocorneal angle and assess the risk of glaucoma in the other eye. Animals with secondary glaucoma usually need additional tests.
 
Treatment
Glaucoma is managed, not cured. The goals of treatment are to prevent pain, preserve vision as long as possible, and delay glaucoma onset in the other eye. Animals with acute glaucoma need emergency treatment to quickly reduce intraocular pressure, and they are typically hospitalized for intraocular pressure monitoring and pain management. Some patients need surgical treatment. Dogs with primary glaucoma need ongoing treatment with eye drops, oral medication, or both.
 
Once an eye with glaucoma is irreversibly blind and painful, the kindest option is surgery to remove the eye. Animals tend to do well with this surgery and feel much better after the eye is removed.
 
Prognosis
For dogs with primary glaucoma, the long-term prognosis for vision is typically poor. However, early diagnosis and treatment can help these dogs stay comfortable and able to see for some time. Blind animals can have a very good quality of life with care and environmental management.   
 
If secondary glaucoma is identified and treated quickly and the cause can be eliminated, the prognosis for retaining vision is better than with primary glaucoma.

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Warm weather brings some extra risks for pets. Some animals need protection from sunlight, and all animals need protection from hot temperatures.
 
Sun-Related Skin Conditions
Ultraviolet (UV) radiation in sunlight causes skin damage in animals just like it does in humans. Fur and melanin (dark pigment) protect the skin from UV rays, so animals with short white hair or no hair are at higher risk than those with thick dark fur. Most animals with sun-related skin disease spend a lot of time outdoors, but even indoor cats can develop skin disease caused by UV rays coming through windows.
 
Sun-related skin damage typically affects areas of the body that don’t have thick fur and are exposed to the sun. Any part of the body with thin or light-colored hair can be involved, but these are the most common areas:

• Dogs: top of the nose and front of the muzzle; also belly, chest, and inner thighs in dogs that lie on their backs in the sun
• Cats: ears, eyelids, nose, and areas of thin hair in front of the ears

 
Solar dermatitis, also called actinic dermatitis, is skin disease caused by exposure to UV radiation. It can be mistaken for allergic skin disease because the lesions are similar and it is often seasonal. Affected skin is red, painful to the touch, and scaly or flaky. Bumps and oozy lesions might develop. Over time, the skin becomes thickened and scarred. Because solar dermatitis usually causes a secondary skin infection, the lesions might improve with antibiotics, at least at first.
 
UV radiation causes mutations within skin cells, so solar dermatitis can transform into skin cancer (squamous cell carcinoma or hemangiosarcoma, for example). These cancers are malignant: they can spread throughout the body. Solar dermatitis and skin cancer are diagnosed with skin biopsy.
 
Heat Stroke
Heat stroke is a life-threatening risk to animals during warm weather. Unlike solar dermatitis and skin cancer, it doesn’t require direct exposure to UV rays. The outdoor temperature doesn’t even have to be very hot for an animal to develop heat stroke. The temperature inside a parked car quickly rises higher than the outside temperature, so animals inside parked cars are at risk even in moderately warm weather. Brachycephalic (short-nosed) animals like pugs and bulldogs are at especially high risk.
 
Signs of heat stroke include panting, dark red or purple gums, vomiting, collapse, and seizures. Heat stroke requires immediate first aid (cooling with water, not ice) and emergency veterinary care. For more information, see the blog post on heat stroke.
 
How to Protect Your Pet
The best way to protect animals is to minimize their exposure to UV rays and heat:

• Keep pets indoors from 9 am to 3 pm, when solar radiation is highest.
• Don’t let indoor pets that have solar dermatitis or skin cancer lie in sunbeams unless you have window protection that blocks both UVA and UVB rays.
• Consider using sunscreen that’s formulated specifically for animals. An alternative is sun-protective clothing, but be very sure it doesn’t overheat or annoy your pet.
• Don’t use human sunscreens on animals. Many contain zinc oxide or salicylates, which are toxic if licked.
• In warm months, walk dogs early in the morning or after sundown.
• To prevent burns to the paw pads, avoid walking dogs on hot pavement. Feel the surface with your hand; if it’s too hot for you to touch for more than a few seconds, it’s too hot for your dog to walk on.
• Never leave an animal in a car without air conditioning.
• Never leave a brachycephalic animal outdoors unsupervised in warm weather.
• Make sure animals always have access to drinking water.

 
Sources

• Koyner KS. Diagnosis and treatment of solar dermatitis in dogs. DVM360. August 1, 2007. Accessed June 2, 2023. https://www.dvm360.com/view/diagnosis-and-treatment-solar-dermatitis-dogs
• Pucheu-Haston CM. Solar dermatitis. World Small Animal Veterinary Association Congress proceedings 2017. VIN. Accessed June 2, 2023. https://www.vin.com/doc/?id=8506219

 
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