Double hapten challenge in guinea pigs undergoing an ocular late-phase reaction

Ocular redness - II: Progress in development of therapeutics for the management of conjunctival hyperemia

Conjunctival hyperemia is one of the most common causes for visits to primary care physicians, optometrists, ophthalmologists, and emergency rooms. Despite its high incidence, the treatment options for patients with conjunctival hyperemia are restricted to over-the-counter drugs that provide symptomatic relief due to short duration of action, tachyphylaxis and rebound redness. As our understanding of the immunopathological pathways causing conjunctival hyperemia expands, newer therapeutic targets are being discovered. These insights have also contributed to the development of animal models for mimicking the pathogenic changes in microvasculature causing hyperemia. Furthermore, this progress has catalyzed the development of novel therapeutics that provide efficacious, long-term relief from conjunctival hyperemia with minimal adverse effects.

Animal models of allergic and inflammatory conjunctivitis

Allergic eye diseases are complex inflammatory conditions of the conjunctiva with an increasing prevalence and incidence. The diseases are often concomitant with other allergic diseases such as allergic rhinitis, atopic dermatitis and allergic asthma. Despite the disabling and prominent symptoms of ocular allergies, they are less well studied and further insights into the molecular basics are still required. To establish new therapeutic approaches and assess immunological mechanisms, animal models of ocular allergies have been developed in the past years. The major forms of allergic ocular diseases, seasonal and perennial allergic conjunctivitis, vernal and atopic keratoconjunctivitis and giant papillary conjunctivitis, each have different pathophysiological and immunological components. In contrast to these distinct entities, the current animal models are based on the sensitization against a small number of allergens such as ovalbumin, ragweed pollen or major cat allergens and consecutive challenge. Different animal species have been used so far. Starting with guinea-pig models of allergic conjunctivitis to assess pharmacological aspects, new models including rats and mice have been developed which mimic major features of ocular allergy. The presently preferred species for the investigation of the immunological basis of the disease is represented by murine models of allergic conjunctivitis. In the future, combined ocular, nasal and aerosolic challenges with allergens may provide a model of allergy that encompasses simultaneously the target organs eye, nose and airways with conjunctivitis, rhinitis and asthma.