Ocular allergy in the Asia Pacific region

Allergic conjunctivitis (AC) represents a spectrum of disorders, comprising seasonal allergic conjunctivitis (SAC), perennial allergic conjunctivitis (PAC), atopic keratoconjunctivitis (AKC), vernal keratoconjunctivitis (VKC) and giant papillary conjunctivitis. Of these ocular allergy types, SAC and PAC are the most common.The most striking difference within this group of ocular diseases is that SAC and PAC remain self-limited without ocular surface damage, while AKC and VKC can compromise the cornea, causing ulcers and scarring and can ultimately lead to vision loss. Data on AC in the Asia Pacific is scarce however some understanding of prevalence of the condition has been obtained from the International Study of Asthma and Allergies in Childhood (ISAAC) studies and more recently from the Allergies in Asia Pacific study as well as some information from individual country surveys. Unfortunately none of this data has been collected using validated survey instruments specifically designed for AC. Surveys such as ISAAC have been predominantly concerned with respiratory allergic symptoms with questions added that incorporate some ocular symptoms. These questionnaires do not detect individuals who may have AC in the absence of allergic rhinitis. Using hospital ophthalmology outpatient populations for prevalence studies of ocular allergy immediately introduces a bias towards the more severe, complex forms of the condition as patients with the milder forms of SAR and PAR will rarely present to a hospital outpatient clinic. There is a real need for the development of validated questionnaires specifically addressing ocular allergy. There are no widely accessible studies examining prevalence of the complex forms of ocular allergy (AKC, VKC) in Asia Pacific region. This review will provide an overview of ocular allergy, its classification, clinical presentation and differential diagnosis, and will also discuss what is known about the epidemiology of ocular allergy in the Asian Pacific region.