Redness in your pet’s eyes is a vague, non-specific sign that could signal a temporary, harmless irritation, or the start of a more serious disease process. A visit to your primary veterinarian can identify and treat minor red eye problems, but a visit to Veterinary Vision Center is warranted if the redness is not responsive to first-line treatments, if your pet is squinting or in pain, or if the redness goes away but keeps coming back.
Almost any eye disease or condition can cause redness, and determining the exact cause will require a thorough ophthalmic examination by our team. In most cases, redness is caused by one of the following common eye conditions.
#1: Conjunctivitis in pets
The conjunctiva is the clear-to-pinkish tissue that lines the inside of your pet’s eyelids and covers the white portion (i.e., sclera). The conjunctiva contains many blood vessels, and irritation or infection can cause redness, inflammation, and swelling. Environmental allergies in dogs commonly cause seasonal conjunctivitis that may be accompanied by hair loss. Conjunctivitis may also lead to thick eye discharge, squinting, or eye rubbing.
The most common cause in cats is infection, usually with herpesvirus. Other causes in pets can include:
- Follicular conjunctivitis — This immune overreaction occurs in young dogs, who often outgrow the condition by 2 or 3 years of age.
- Irritants — Dust, wind, pollen, smoke, or cleaning fumes can easily irritate your pet’s eyes.
- Bacterial infections — Bacterial conjunctivitis is common in young pets, and can be secondary to other problems like dry eye.
Conjunctivitis is treated with topical eye drops or ointments that contain antibiotics, antivirals, and steroid anti-inflammatories.
#2: Uveitis in pets
The uvea includes structures in the anterior chamber (i.e., the front eye portion), and uveitis describes inflammation inside this chamber. Unlike surface eye inflammation, uveitis can signal an underlying systemic disease, commonly including infection, cancer, or an immune system problem. The inflammation can also clog the eye’s drainage system and lead to glaucoma, followed by vision loss. Uveitis may cause squinting and a cloudy or blue cornea, as well as redness.
If your pet has uveitis, your veterinarian will order additional tests, including specialized blood and urine screenings, to determine the underlying cause. Treatment is directed at the underlying cause, decreasing inflammation, and preventing secondary glaucoma using oral and topical medications.
#3: Glaucoma in pets
Many purebred dogs inherit primary glaucoma, but dogs or cats can also acquire the disease secondary to other eye diseases or following surgery or trauma. Glaucoma involves a rise in eye pressure because fluid cannot drain properly, and the increased pressure leads to optic nerve damage and ultimate vision loss.
Glaucoma usually starts in only one eye, which may become red, cloudy, and swollen, and the pet will lose vision if the pressure is not controlled quickly. Topical medications can treat glaucoma for a few months or years, but eventually stop working. At that time, pets require a surgical procedure to preserve vision, or to relieve pain in a blind eye.
#4: Dry eyes in dogs
Dogs with red, itchy, dull-looking eyes accompanied by thick, green-yellow discharge may be suffering from dry eye disease (i.e., keratoconjunctivitis sicca [KCS]), which is common in certain dog breeds, diabetic dogs, and dogs with thyroid problems. Diagnosis can be made with a simple, in-office test called a schirmer tear test, and treatment involves topical medications or surgery. Dry eye cannot be cured, but can be controlled with life-long medications.
#5: Corneal ulcers in pets
A corneal ulcer is a scratch or abrasion on the eye’s outer clear covering (i.e., cornea). Ulcers can occur secondary to dry eye disease, other eye surface diseases, eye injuries, or spontaneous age-related conditions. If the abrasion becomes infected with aggressive bacteria, the ulcer will “melt” and cause a deep hole or complete eye rupture, which more likely will affect flat-faced, bug-eyed breeds, such as Boston terriers, shih tzus, and French bulldogs.
Superficial ulcers are treated with topical antibiotics to prevent infection until the cornea can heal on its own. Deep ulcers may require emergency grafting surgery to prevent eye rupture and subsequent vision loss.
#6: Pet eye trauma
Blunt eye trauma from a fall, accident, dog bite, or ball can lead to red, inflamed eyes. Most pets who sustain eye trauma have other associated injuries and need prompt emergency treatment and stabilization, followed by specific eye treatments. If eye trauma causes too much damage, the eye may be removed for the pet’s comfort.
Any change to your pet’s eyes could signal a serious problem, and should be evaluated by the Veterinary Vision Center team. Contact us to schedule a visit or to learn more about possible red eye causes in pets.