VKC is a chronic allergic conjunctivitis affecting children and young adults, generally between the ages of 6 and 18. Patients often have concurrent allergic diseases such as seasonal allergies and asthma. The predominant symptom is ocular itching, as well as redness, mild photophobia, and a thick mucoid discharge. There is often a seasonal variation in symptoms with the spring and early summer being the worst period, hence the name "vernal" (springtime) keratoconjunctivitis.
On clinical exam, there are two forms of VKC. In the more common palpebral form, the predominant finding is giant papillary hypertrophy primarily affecting the upper tarsal conjunctiva. (See Figure 2.) The lower palpebral conjunctiva demonstrates a fine papillary response. The entire conjunctiva has a pale "milky" infiltrate that gives the conjunctiva a pink color, rather than the deep red seen in acute forms of conjunctivitis. A thick, tenacious mucoid discharge is often present. In the limbal form, the palpebral conjunctiva demonstrates a similar fine milky papillary response without formation of giant papillae. The predominant findings are gelatinous limbal papillae associated with epithelial infiltrates called Horner-Trantas dots, which are focal collections of eosinophils (Figure 10). The limbal form seems to be more prevalent in African American children. In either form, there is commonly a superior punctate keratopathy. In severely affected cases, the punctate lesions can coalesce into a sterile shield-shaped ulcer ("vernal ulcer") centered at the junction of the middle and upper third of the cornea (Figure 11).
AKC is similar to VKC, but has different demographic characteristics. Affected patients often suffer from atopic eczema from early childhood, but are free of ocular symptoms until early adulthood. They generally have eczema affecting the eyelids as well as other areas of the body. Ocular symptoms include itching, redness, and a mucoid discharge. Conjunctival involvement is characterized by papillary hypertrophy ranging from fine to giant papillae. While the upper tarsal conjunctiva predominates, the lower palpebral conjunctiva is more affected than in VKC, and giant papillae can sometimes be seen in the inferior conjunctiva, which never occurs in VKC. Thickening of the limbal conjunctiva is common. Conjunctival scarring often occurs from prolonged inflammation, resulting in symblepharon formation. Perhaps because of the longer duration of the disease, corneal involvement is more common in AKC than VKC, characterized by a superficial epitheliopathy eventually leading to vascularization and scarring. AKC patients are prone to early development of cataracts, have a higher incidence of retinal detachment, and often suffer more severe corneal infection with herpes simplex virus. Cicatricial ectropion may also occur due to prolonged eczematous skin changes.
There is no definitive diagnostic test for VKC or AKC. Diagnosis is made by identification of characteristic clinical findings, in the absence of any cause for secondary GPC. Conjunctival scrapings from actively inflamed eyes invariably demonstrate eosinophils. Patients with AKC may have high circulating IgE levels. Patients with atopic eczema frequently have skin colonization with Staphylococcus aureus, which can contribute to the keratitis when the eyelids are involved.
Treatment of both diseases is similar. Histamine release from mast cells plays a major role in the pathogenesis of both diseases. For that reason, topical mast cell stabilizers, such as cromolyn sodium and lodoxamide, are the mainstay of treatment, and are the preferred drugs for maintenance treatment because there are few significant side effects. Topical antihistamines and "antihistamines with mast cell stabilizing properties" (eg, olopatadine) are generally too weak for these diseases. Topical steroids are highly effective, but their chronic use must be balanced against frequent side effects, including ocular hypertension, cataract, and worsening of herpetic keratitis. For that reason, they are generally used for short "pulses" to treat flare-ups of the disease, or as part of initial treatment until the mast cell stabilizers can take hold. In addition, supratarsal injections of triamcinolone acetonide (Kenalog) are effective for acute flares of the disease. Topical cyclosporine has also proven to be effective for long-term treatment in recalcitrant cases. An alternative to topical cyclosporine is the dermatologic preparation of tacrolimus (Protopic), which is well-tolerated when used on the eye. In cases where staphylococcal exotoxin contributes to the punctate keratopathy, periodic local treatment with antistaphylococcal antibiotics can be useful.