Effects of Dry Eye
Dry eye (keratoconjunctivitis sicca or KCS) is a painful and potentially dangerous condition caused by the inadequate production of tears. The eyes of affected animals – especially the outer covering of their eyeballs (the cornea) and the lining of their eyelids (the conjunctiva) – become dry, rough, red, inflamed, sensitive and fragile. Unfortunately, this condition is quite common. Dogs with dry eye have varying degrees of discomfort, ranging from mild to extremely severe. Their eyes always are irritated, scratchy and red. In most cases, they probably also are itchy and painful. As the condition worsens over time, the cornea can ulcerate, which means that parts of it will break down and slough off from the inflammation and mechanical trauma caused by lack of adequate lubrication. Being in bright sunshine is uncomfortable for dogs with dry eye, because their eyes become hypersensitive to light. Affected dogs may develop sores around their eyes from rubbing and scratching in an attempt to get some relief from their discomfort. They may lose part of their vision in the affected eye or eyes. In extreme cases, they can become completely blind. Sometimes, dry eye is so painful that the dog will become frantic and virtually inconsolable.
Symptoms of Dry Eye
KCS can cause a number of different symptoms in dogs, all of which can be attributed to the dryness, scratchiness and pain associated with the condition. Owners may notice one or more of the following signs when their dog develops dry eye:
- Pawing or rubbing at the eyes (often persistent and frantic)
- Eye redness (conjunctival hyperemia; often pronounced)
- Dull, dry, lackluster look to the cornea, which is the outer surface of the eyeball (eyes lack their normal sheen)
- Ocular discharge (copious, thick, stringy, yellow-green gunk accumulates in the inner corners of the eyes; looks like mucus or pus; can be dry and crusty)
- Protrusion of the third eyelid (eversion of the nictitating membrane; “cherry eye”)
- Hypersensitivity to light
- Eyelid twitching (blepharospasm)
- Swollen, inflamed eyelids (blepharitis)
- Excessive blinking
- Ulceration or scarring of the outer surface of the eyeball (cornea)
- Impaired vision
The eyes of affected dogs may or may not be covered with a visible mucus film.
Dogs at Increased Risk
Dry eye can occur in any dog, at any age, but certain breeds are thought to be predisposed to developing this disorder. These include the West Highland White Terrier, American Cocker Spaniel, English Bulldog, Pug, Pekingese, Yorkshire Terrier, Miniature Schnauzer, Boston Terrier, Dachshund, Chihuahua, German Shepherd Dog, Doberman Pinscher, English Springer Spaniel, Lhasa Apso and Shih-Tzu. Females and neutered males are more commonly affected, especially female Westies. The reason for this association is not clear.
Other factors that can predispose a dog to developing dry eye are: previous surgical removal of the gland of the third eyelid (a common treatment for “cherry eye”); bacterial eye infections; injury to the tear glands; damage to the nerves that support the tear glands; middle ear infections; general anesthesia; adverse drug reactions; Addison’s disease (hypoadrenocorticism); Cushing’s disease (hyperadrenocorticism); distemper; congenital absence of tear glands (rare, but reported in small breeds); systemic metabolic disorders; and rheumatoid arthritis.