Dear Dr. Melin,
My dog, a 5-year-old Basset Hound, always seems to have red eyes. Is this a problem?
Thank you, Gary.
Depending on where the redness is, this can be a simple or complex problem.
If the redness is appearing on the lid itself, this could be a sign of skin allergies or infection of the glands of the eyelid. If the redness is involving the inside lining of the eyelids, this is called conjunctivitis.
Conjunctivitis is one of the most common disorders we see. Conjunctivitis means “inflammation of the conjunctiva.” Conjunctivitis can be caused by a variety of problems. Sometimes, it is something as simple as an irritant, like dust or debris in the eyes. In Basset Hounds, and other breeds of dogs that have been bred for a “droopy eye” appearance, the conjunctiva can dry out, leading to irritation.
Other times, there is an underlying infection or allergy that is causing the inflammation. Depending on the problem, simple conjunctivitis is sometimes treated with artificial tears (a good brand is “Genteal” eye drops for people), antibiotics or steroids provided by your veterinarian, or antihistamine eye drops (like the product “ Zaditor.”)
It is also important to note that conjunctivitis can accompany other more significant problems of the eye, so conjunctivitis that is not resolving should be investigated further.
Decreased tear production in the eyes, for example, can cause conjunctivitis as well as inflammation of other parts of the eye. The condition “dry eye” or keratoconjunctivitis sicca, is a serious problem in dogs. In this condition, the glands of the eye are not producing enough tears. The eye responds to this by producing a thick mucous to keep the eye moist. Dogs with dry eye are prone to secondary infections and ulcers of the eye. This condition can cause discomfort and if left untreated, dogs can develop irreversible pigmentation of the cornea leading to poor vision. A simple test called, called a schirmer tear test can determine if your dog has “dry eye.”
Corneal ulcers are also a common disorder in dogs. They are most often caused by trauma, such as a stick or a scratch. Dogs with ulcers will classically have a red eye, and will squint their eye because the eye is painful.
Ulcers are most commonly diagnosed by putting a drop of fluorescein stain in the eye. Fluorescein is taken up by the inner layers of the cornea but not a normal corneal surface making an ulcer show up distinctly as a bright green spot on the eye.
Another serious condition of the eye that can lead to redness is glaucoma. Glaucoma is caused by too much pressure in the eyeball itself. Glaucoma can cause inflammation of the conjunctiva and sclera and can make the eye look bigger than normal. It can also make the surface of the eye appear cloudy.
Some breeds of dogs such as Bassett Hounds and Cocker Spaniels have a genetic predisposition to glaucoma. Glaucoma is an emergency situation, requiring prompt medical attention in order to prevent permanent blindness.
Investigating the cause of your dog’s red eyes is important so that appropriate therapy can be instituted.
Dr. Eric Melin is a veterinarian at Westgate Pet Clinic in Linden Hills. Email pet questions to firstname.lastname@example.org.