Allergic conjunctivitis overview

# Overview
Allergic conjunctivitis is inflammation of the conjunctiva (the membrane covering the white part of the eye) due to allergy.  Symptoms consist of redness (mainly due to vasodilation of the peripheral small blood vessels), oedema of the conjunctiva, itching and increased lacrimation. If this is combined with rhinitis, the condition is termed allergic rhinoconjunctivitis.

# Epidemiology and Demographics
Allergic conjunctivitis exhibits distinct epidemiological and demographic characteristics based on the populations studied and the presence of comorbidities. Females are more affected and children often have other co-existent allergic diseases. Intermittent episodes are common, with the chronic forms more encountered in clinical practice.

# Natural History, Complications and Prognosis
Allergic conjunctivitis is usually a non-progressive condition with a favorable prognosis, and rare but serious complications. Most symptoms are self-limiting, while in some subtypes, a temporal association can be found with the age group and specific triggers.
Complications include infections, scarring and can also damage the cornea and eyelids.
Long-term prognosis is influenced by the recurrence of the attacks and side-effects of treatment.

# Diagnosis

## History and Symptoms
Allergic conjunctivitis is frequently characterized by a personal history of allergies and/or atopy and occurrence of similar episodes in the past. Itchiness and diffuse bulbar and tarsal conjunctival injection are the most commonly reported symptoms and almost univerally present in all the subtypes. Other clinical features include eye pain, eye discharge, photophobia and abnormal vision.

## Physical Examination
Conjunctival hyperemia and discharge are found in the majority of patients on clinical examination. Specific signs include Horner-Tranta's dots, shield ulcers and cobblestone appearance in VKC, sandpaper like eyelid texture in AKC, and giant conjunctival papillae in GPC.

## Other Diagnostic Studies
Conjunctival scrapings from the papillae may yield an inflammatory infiltrate. Tear analysis may show raised levels of inflammatory mediators like histamine and prostaglandins.

# Treatment
Therapeutic interventions for allergic conjunctivitis target one or more points in the inflammatory response cascade. The most common treatment approach is use of a topical pharmacologic medication combined with cold compresses or artificial tears.Moderate to severe symptoms affecting quality of life may warrant more effective and longer-lasting treatment.A key limitation of many topical treatments is the need for multiple daily dosing for maintenance.Surgery is not routinely indicated for treatment of allergic conjunctivitis.Avoidance of the allergens is an important step for preventing allergic conjunctivitis.Early diagnosis and treatment constitute the secondary prevention of allergic conjunctivitis. It involves both pharmacological and non-pharmacological measures.In cost analysis from Turkish data, including direct costs of drugs and physician meetings, lowest treatment cost was established by fluorometholon (US$ 38.94) and followed by ketotifen (US$ 43.41),epinastine (US$ 43.60), olopatadine (US$ 44.05) and emedastine (US$ 44.92), respectively.Compared for incremental cost-effectiveness, emedastine was dominated by ketotifen and itself dominated olopatadine while ketotifen could be compared with fluorometholon and olopatadine.Emerging therapies for allergic conjunctivitis include immunomodulators as well as evaluation of novel enzymatic targets.