Epidemiology

Conjunctivitis commonly affects men, women and children of all ages. It is usually treated by general practitioners and is estimated to account for almost 1% of all primary care consultations.[2] In England there are 13-14 cases in 1000 people per year.[3][4] The incidence rate appears to be higher in children aged <1 year old (80 cases in 1000 patient-years) than in children aged >4 years (12 cases in 1000 patient-years).[5] In the US, 3% of all accident and emergency department visits are ocular related, with 30% of these due to conjunctivitis. Two percent of all visits to primary care physicians are for eye conditions, with 54% of these being either conjunctivitis or corneal abrasion.[6]

Seasonal conjunctivitis represents more than 90% of cases of allergic conjunctivitis.[7][8][9][10][11]​​​ An online survey in the US found that the majority of patients with seasonal conjunctivitis report moderate to severe symptoms that significantly impair their quality of life.[12] Perennial conjunctivitis is less common, but 80% of these patients have seasonal flares.[7] Atopic allergic conjunctivitis disease is more common in adults, and vernal allergic conjunctivitis (a more severe, chronic form of allergic conjunctivitis) is more common in boys.[13]​ Atopic and vernal conjunctivitis together represent 2% of ocular allergic disease; atopic dermatitis occurs in 3% of the population, and 25% of these have ocular involvement.[8][9][10][11]​​​ Vernal keratoconjunctivitis is more common in males.[1][14]​​ Vernal keratoconjunctivitis prevalence varies widely geographically and has seasonal variation, greatest in hot, dry climates, highest incidence in African countries.[13]​​

The prevalence of vernal keratoconjunctivitis in Europe ranges from 1.2 to 10.6 cases in 10,000 population, although the prevalence of associated corneal complications is much lower (0.3 to 2.3 in 10,000 population).[15]

​Prevalence estimates, based on limited evidence, indicate that bacterial conjunctivitis is more common in children, and viral conjunctivitis is more common in adults.[16]

​Ocular cicatricial pemphigoid (a subtype of mucous membrane pemphigoid) and neoplastic conjunctivitis are rare.[17][Figure caption and citation for the preceding image starts]: Allergic (vernal) keratoconjunctivitisFrom the collection of Mr Hugh Harris; used with permission [Citation ends].com.bmj.content.model.Caption@eb70e08[Figure caption and citation for the preceding image starts]: Bacterial conjunctivitisFrom the collection of Mr Hugh Harris; used with permission [Citation ends].com.bmj.content.model.Caption@483efd77[Figure caption and citation for the preceding image starts]: Viral conjunctivitisFrom the collection of Robert Sambursky, MD; used with permission [Citation ends].com.bmj.content.model.Caption@2f6af71a

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