Blepharitis in Dogs
What is blepharitis?
Blepharitis means inflammation of the eyelid. In most cases, the inflammation affects the outer two layers of the eyelids; in some cases it may spread to involve the inner lining or palpebral conjunctiva. The outermost layer of the eyelid is made up of skin and hair follicles; the middle layer is made up of connective tissue, muscles, and glands such as the meibomian gland. The meibomian glands produce oily secretions that help lubricate the eyes, and the meibomian gland ducts drain out along the margins of the eyelids.
What are the symptoms of blepharitis?
Blepharitis can affect one or both eyes. The affected eyelid will be usually be red, swollen, and itchy, and the dog will squint or blink spasmodically (called blepharospasm). Often the dog will scratch or rub at its face and/or eyelids. This can lead to secondary trauma to the surrounding tissues. There may be a discharge from the eye and the discharge may be clear, mucoid, or purulent (containing pus). If the inflammation has been present for a while, there may be loss of pigment or hair.
The skin covering the eyelids may have dry crusts or flakes on its surface or small papules or pustules ('pimples') may develop on the surface. The papules, pustules and crusts may be single or multiple. One or more meibomian glands along the margin of the eyelid may become swollen or may produce a colored discharge. In more severe cases, the inflammation may spread and include conjunctivitis (inflammation of the conjunctiva), or keratitis (inflammation of the cornea).
What causes blepharitis?
Any condition that can cause irritation of the eyelids can lead to blepharitis. Common causes of blepharitis include congenital abnormalities, allergies, infections, tumors, and occasionally other inflammatory disorders.
"Any condition that can cause irritation of the eyelids can lead to blepharitis."
Congenital eyelid abnormalities that can predispose a dog to developing blepharitis include entropion, a condition in which the eyelid edges turn inwards, and developmental eyelash abnormalities such as distichiasis, ectopic cilia or trichiasis, three different conditions in which one or more eyelashes grow inwards towards the eyeball instead of outwards.
The shape of a dog's muzzle and face may predispose a dog to developing blepharitis. Dogs with prominent facial folds, extremely long and narrow muzzles, and dogs with short flat faces and lagophthalmos (bulging eyes) are more prone to develop this problem.
Allergies to insect bites, inhalant allergens, or food may cause blepharitis. Bacterial infections may cause localized abscesses of glands in the eyelids or generalized infections of the eyelids. In some cases, infection with staphylococcus bacteria ('staph') may lead to an allergic reaction, called 'Staphylococcus hypersensitivity'. Occasionally, a fungal infection may be the cause of blepharitis.
Localized blepharitis may be caused by a chalazion, an inflammatory enlargement of a meibomian gland associated with a reaction to the glandular secretions from the gland.
The most common tumors that cause blepharitis in dogs originate in the meibomian glands. These tumors may be benign 'sebaceous adenomas' or malignant 'sebaceous adenocarcinomas'. Another type of tumor, called a 'mast cell tumor' may also cause blepharitis.
Other causes of blepharitis include external trauma to the eyelids, localized mange (caused by either Demodex or Sarcopes mites), nutritional disorders such as zinc-responsive dermatitis or fatty acid deficiency, endocrine problems such as hypothyroidism, Cushing's disease or diabetes mellitus, and environmental irritants such as tobacco smoke.
In some cases, no underlying cause can be determined; this is called "idiopathic blepharitis".
Are any breeds of dogs more likely to have problems with blepharitis?
Dogs with any of the congenital abnormality or conformation shapes described above are more likely to develop blepharitis. Specific breeds include Shih Tzus, Pekingese, English Bulldogs, Lhasa Apsos, pugs, Golden Retrievers, Labrador Retrievers, Poodles, Chinese Shar peis, Chow Chows, Rottweilers, and collies.
How is blepharitis diagnosed?
Your veterinarian will conduct an eye examination to determine the extent of the eyelid involvement. The eye examination will often include testing such as a Schirmer tear test to assess the tear production in the eye, and collection of samples of cells or secretions to look for evidence of an infectious agent such as bacteria, fungi, or mites. Samples may be sent to a diagnostic laboratory for culture and sensitivity testing to determine the type of treatment that is needed. If your veterinarian suspects an allergy, further testing may be necessary to determine the specific allergic cause. For suspect tumors, a biopsy will be necessary to determine the nature of the tumor and the appropriate treatment. If there is no obvious reason for the blepharitis, your veterinarian will recommend blood tests to look for evidence of systemic disease.
What is the treatment for blepharitis?
Your veterinarian may recommend short-term symptomatic treatment for the inflammation, such as application of warm compresses for 5-15 minutes several times per day, and removal of any discharges using sterile saline eye drops or a commercial eye cleansing agent.
"However, any specific treatment for blepharitis will depend on the underlying cause of the disorder."
However, any specific treatment for blepharitis will depend on the underlying cause of the disorder. Surgery is the treatment of choice for correcting eyelid abnormalities or removing tumors. In some cases, this may require referral to a specialist. Bacterial infections will be treated with topical antibacterial ointments or drops, mange will be treated with antiparasitic medications, and allergic disorders can be controlled with oral broad-spectrum antibiotics and corticosteroids or other immunosuppressant medications along with avoidance of the allergen. Blepharitis that is secondary to an endocrine disorder will be treated symptomatically until the endocrine problem is controlled. Dietary supplements will be required for nutritional deficiencies.
If the blepharitis is idiopathic, the symptoms may be controlled with topical medications; in some cases oral immunosuppressants may be necessary.
What is the prognosis for recovery?
The prognosis depends entirely on the cause of the blepharitis. If a congenital abnormality is responsible for the problem and it is surgically corrected, the prognosis is excellent. Most eyelid tumors in dogs are benign and can be removed surgically with a good prognosis. For most other causes of blepharitis, the condition can be well-controlled medically but it often cannot be cured.