by Noelle La Croix, DVM, Dip. ACVO & Judy Seltzer, DVM, Dip. ACVD
Ocular and Dermatologic Disease
The lacrimal glands, conjunctiva, meibomian glands, cornea, and eyelid skin are all derived from the surface ectoderm of an embryo. The body’s skin is also derived from this embryonic ectoderm. Meibomian glands are greatly enlarged and modified sebaceous glands that lack hair follicles. Their development is quite similar to skin hair follicles. In addition to these analogous origins, ocular and dermatological health are often correlated. These relationships will be discussed in this article.
Blepharitis is inflammation of the eyelid margins, whereas dermatitis or eczema (Greek: “eruption”) is inflammation of the skin. Blepharitis causes cosmetic alterations and discomfort at the eyelid margins as well as disruption of the tear film. Meibomianitis (inflammation of the meibomian glands) is often asociated with blepharitis. Both disorders are additionally associated with keratoconjunctivitis sicca (dry eye). It doesn’t matter which condition develops first, and one disorder generally exacerbates the other (Figure 1). These eyelid margin diseases diminish lipid production on the ocular surface which amplifies tear evaporation with resultant dry eye. A dry eye’s ability to wash bacteria from the eyelid margins can be very limited. Bacterial colonization of both meibomian glands and eyelash follicles may follow causing further degradation of the tear film.
Dogs with blepharitis may maintain normal Schirmer tear test values and yet develop many of the characteristics of classic dry eye including corneal vascularization, lusterless corneas, corneal pigmentation, and corneal ulceration. The tear films of blepharitic patients are unstable because the meibomian glands fail to evenly spread lipids across the cornea with each blink. Blepharitis may be associated with epiphora because the aqueous portion of the compromised tear film is not retained by the cornea.
The appropriate treatment of blepharitis depends upon establishing its etiology (dermatologic disease), improving ocular hygiene, and re-establishing the tear film. Allergies are typically the root cause of blepharitis. The skin of allergy-induced blepharitic patients often reveals atopic signs (erythematous macules, patches, and small papules) and secondary symptoms including excoriations, self-induced alopecia, lichenification, and hyperpigmentation. These indications of systemic allergies require long-term systemic therapy. Blepharitis may also arise from, or be complicated by non-atopic sources including parasitic, bacterial, or yeast infections. Skin cytology, skin scrapings, and biopsies can be considered as further diagnostic tests.
Eyelid diseases are generally best treated with systemic (oral) medications. Prednisone is generally prescribed as an anti-inflammatory to lessen allergic responses. Antihistamines are usually not used for treatment of blepharitis as this class of medications can cause a drop in tear production. A broad spectrum oral antibiotic (often a cephalosporin effective against Staphylococcus pseudintermedius) is also prescribed for patients with associated pyoderma and/or meibomian gland impactions. Ocular hygiene can be improved by cleansing with daily eyelid scrubs (either diluted baby shampoo or commercially available eyelid/eyelash wipes). Lipids lost from the tear film can be replaced with petroleum-based ocular ointments applied three times daily. Similar ocular ointments with additional steroids or antibiotics can also be applied. Some cases will also require artifical tear supplementation of the aqueous tear film.
Clinical signs of blepharitis and meibomianitis should start to resolve within two weeks of treatment. However, these eyelid disorders are typically manageable but not curable. A veterinary dermatologist can help guide appropriate treatments for cases with recurrent blepharitis and/or meibomianitis. If you have further questions concerning blepharitis, meibomianitis, or dye eye disease, please consult with a veterinary ophthalmologist and/or veterinary dermatologist.
Noelle La Croix, DVM, Dip. ACVO
Judy Seltzer, DVM, Dip. ACVD
The Veterinary Medical Center of Long Island
75 Sunrise Highway
West Islip, New York 11795
(631) 587-0800, fax (631) 587-2006