Histamine release test and measurement of antigen-specific IgE antibody in the diagnosis of allergic conjunctival diseases

In-vivo diagnostic measurements of ocular inflammation

PURPOSE OF REVIEW

The diagnosis of allergic conjunctival inflammation is usually made on the basis of clinical signs and symptoms; however, in-vivo and in-vitro tests are indicated when patient management requires identification of the specific allergic sensitization. The purpose of this review is to describe recent and less recent methods to assess ocular allergic inflammation.

RECENT FINDINGS

In the non-active phase of the disease, the specific conjunctival provocation test can be used to identify local sensitivities to allergens. Although not highly specific, total IgE in tears may be measured with a simple local test by inserting a paper strip in the lower meniscus. Limited tear volume prohibits the use of specific IgE tests. The measurement of tear-specific inflammatory markers, such as eosinophil cationic protein, IL-4, IL-5 and eotaxin, may also be useful for the diagnosis of ocular allergy. Multiple cytokine assays of tear samples and new imaging techniques are exciting advances that might provide the in-vivo diagnosis of ocular surface inflammation.

SUMMARY

Whereas chronic, severe ocular allergic conditions have uniquely diagnostic signs and symptoms, the most common diseases, seasonal and perennial allergic conjunctivitis, have no specific pathognomonic signs. The diagnostic measurements of local inflammation may help in the management of ocular allergy.

[Ocular allergies]

Recent developments indicate that ocular allergy is more than an IgE-mediated allergic conjunctivitis. Ocular allergy is a disease affecting the entire ocular surface including conjunctiva, lids, cornea, lacrimal gland and tear film. Besides an IgE-mediated reaction, a complex chronic inflammation is involved in the pathogenesis of many ocular allergies. According to their pathogenesis and clinical picture, ocular allergies are classified into mild forms, such as seasonal and perennial allergic conjunctivitis as well as giant papillary conjunctivitis, and chronic, potentially blinding forms such as atopic keratoconjunctivitis and vernal keratoconjunctivitis. New therapeutics act on the entire inflammatory process or try to modulate the allergic reaction early and specifically. The association with non-ocular allergic symptoms requires an interdisciplinary approach.

Spectrum of ocular allergy

PURPOSE OF REVIEW

To elaborate and review the immunologic spectrum of the five basic types of ocular allergy.

RECENT FINDINGS

Perennial allergic conjunctivitis (PAC) appears to be an extension of seasonal allergic conjunctivitis (SAC) based on the similarity of clinical symptoms and the immune mechanism involved. T helper type 2 (TH2)-type cytokines, increased ratio of TH1/TH2 cytokines and increased statement of adhesion molecules all appear to play an integral role in the inflammatory process of SAC and PAC. Vernal keratoconjunctivitis (VKC), which is a pediatric disease, differs from SAC and PAC by its more severe and chronic nature. Increased numbers of T cells, eosinophils (along with the products of degranulation), chemokines and their receptors may contribute to the more serious symptoms of VKC. Atopic keratoconjunctivitis (AKC) is similar to VKC by the increased concentration of cytokines involved (i.e. interleukin-4 and -5). Despite clinical similarities with VKC, the presence of atopic dermatitis, along with some differences in clinical signs, make AKC a separate entity, which is sometimes referred to as an adult variant of VKC. Giant papillary conjunctivitis has similar cell involvement as VKC and AKC. However, giant papillary conjunctivitis differs from VKC and AKC by the clinical signs present (i.e. the presence of giant papillae) and the necessary concurrent contact lens wear.

SUMMARY

The important differences and similarities observed in these five types of allergic diseases might help to better treat the patients affected with these disorders.