Allergic conjunctivitis 1342401 221400668 2008-06-24T10:14:08Z Mikr18 2274343 moved awkward templates {{Cleanup|date=May 2008}} [[Image:Oedema.JPG|thumb|Allergic Conjunctivitis]] '''Allergic conjunctivitis''' is [[Allergic Inflammation|inflammation]] of the [[conjunctiva]] (the membrane covering the white part of the eye) due to [[allergy]]. Although [[allergen]]s differ between patients, the most common cause is [[hay fever]]. Symptoms consist of redness (mainly due to [[vasodilation]] of the peripheral small blood vessels), [[oedema]] of the conjunctiva, [[itch|itching]] and increased [[lacrimation]] (production of [[Tears|tear]]s). If this is combined with [[rhinitis]], the condition is termed '''allergic rhinoconjunctivitis'''. The symptoms are due to release of [[histamine]] and other active substances by [[mast cell]]s, which stimulate dilation of blood vessels, irritate nerve endings and increase secretion of tears. Treatment of allergic conjunctivitis is by avoiding the allergen (e.g. avoiding grass in bloom during the "hay fever season") and treatment with [[antihistamine]]s, either topical (in the form of [[eye drop]]s), or systemic (in the form of tablets). [[Cromoglicate]] is sometimes used topically. [[Azelastine]] is available as a nasal spray and eye drops. ==Signs and symptoms== The [[conjunctiva]] is a thin membrane that covers the eye. When an allergen irritates the conjunctiva, common symptoms that occur in the eye include: ocular itching, eye lid swelling, tearing, photophobia, watery discharge, and foreign body sensation.<ref name= "Bielory"> Bielory, L. and M.H. Friedlaender, Allergic conjunctivitis. Immunol Allergy Clin North Am, 2008. 28(1): p. 43-58. </ref> <ref name= "Cunningham"> Cunningham, E.T. and E.W.M. Ng, Recent advances in ocular therapeutics. International ophthalmology clinics,. 2006, Philadelphia: Lippincott Williams & Wilkins. xiv,158 p. </ref> Itching is the most typical symptom of ocular allergy and more than 75% of patients report this symptom when seeking treatment.<ref name= "Cunningham"> Cunningham, E.T. and E.W.M. Ng, Recent advances in ocular therapeutics. International ophthalmology clinics,. 2006, Philadelphia: Lippincott Williams & Wilkins. xiv,158 p. </ref> Symptoms are usually worse for patients when the weather is warm and dry, whereas cooler temperatures and rain tend to assuage symptoms.<ref name= "Bielory"> Bielory, L. and M.H. Friedlaender, Allergic conjunctivitis. Immunol Allergy Clin North Am, 2008. 28(1): p. 43-58. </ref> A study by Klein et al. showed that in addition to the physical discomfort allergic conjunctivitis causes, it also alters patients’ routines.<ref name= "Cunningham"> Cunningham, E.T. and E.W.M. Ng, Recent advances in ocular therapeutics. International ophthalmology clinics,. 2006, Philadelphia: Lippincott Williams & Wilkins. xiv,158 p. </ref> The study showed that patients limited certain activities such as going outdoors, reading, sleeping, and driving. Therefore, treating patients with allergic conjunctivitis can improve their everyday quality of life. ==Pathophysiology== The ocular allergic response is a cascade of events that is coordinated by [[mast cells]]. When a particular allergen is present, sensitization takes place and prepares the system to launch an antigen specific response. TH2 differentiated T cells release cytokines, which promote the production of antigen specific IgE. IgE then binds to IgE receptors on the surface of mast cells. Then, mast cells release [[histamine]], which then leads to the release of cytokines, prostaglandins, and platelet activating factor. Mast cell intermediaries cause an allergic inflammation and symptoms through the activation of inflammatory cells.<ref name= "Cunningham"> Cunningham, E.T. and E.W.M. Ng, Recent advances in ocular therapeutics. International ophthalmology clinics,. 2006, Philadelphia: Lippincott Williams & Wilkins. xiv,158 p. </ref> When histamine is released from mast cells, it binds to H1 receptors on nerve endings and causes the ocular symptom of itching. Histamine also binds to H1 and H2 receptors of the conjunctival vasculature and causes vasodilatation. Mast cell derived cytokines such as chemokine interleukine IL-8 are involved in recruitment of neutrophils. TH2 cytokines such as IL-5 recruit eosinophils and IL-4, IL-6, and IL-13 which promote increased sensitivity. Immediate symptoms are due to the molecular cascade. Encountering the allergen a patient is sensitive to leads to increased sensitation of the system and more powerful reactions. Advanced cases can progress to a state of chronic allergic inflammation.<ref name= "Cunningham"> Cunningham, E.T. and E.W.M. Ng, Recent advances in ocular therapeutics. International ophthalmology clinics,. 2006, Philadelphia: Lippincott Williams & Wilkins. xiv,158 p. </ref> ==Types== ===Seasonal Allergic Conjunctivitis (SAC) and Perennial Allergic Conjunctivitis (PAC)=== Both SAC and PAC are two acute allergic conjunctival disorders.<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> SAC is the most common ocular allergy.<ref name= "Bielory"> Bielory, L. and M.H. Friedlaender, Allergic conjunctivitis. Immunol Allergy Clin North Am, 2008. 28(1): p. 43-58. </ref> <ref name= "Buckley"> Buckley, R.J., Allergic eye disease--a clinical challenge. Clin Exp Allergy, 1998. 28 Suppl 6: p. 39-43. </ref> Symptoms of the aforementioned ocular diseases include itching and pink to reddish eye(s).<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> These two eye conditions are mediated by mast cells.<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> <ref name= "Buckley"> Buckley, R.J., Allergic eye disease--a clinical challenge. Clin Exp Allergy, 1998. 28 Suppl 6: p. 39-43. </ref> Non specific measures to ameliorate symptoms include: cold compresses, eyewashes with tear substitutes, and avoidance of allergens.<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> Treatment consists of antihistamine mast cell stabalizers, dual mechanism anti-allergin agents, or topical antihistamines.<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> Corticosteroids are another option, but considering the side effects of cataracts and increased intraocular pressure, corticosteroids are reserved for more severe forms of allergic conjunctivitis such as Vernal Keratoconjunctivitis and Atopic Keratoconjunctivitis.<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> ===Vernal Keratoconjunctivitis (VKC) and Atopic Keratoconjunctivitis (AKC)=== Both VKC and AKC are chronic allergic diseases where eosinophils, conjunctival fibroblasts, epithelial cells, mast cells, TH2 lymphocytes aggravate the biochemistry and histology of the conjunctiva.<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> VKC is a disease of childhood and is prevalent in males living in warm climates.<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> AKC is frequently observed in males between the ages of 30 and 50.<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> VKC and AKC can be treated by medications used to combat allergic conjunctivitis or the use of steroids.<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> ===Giant Papillary Conjunctivitis (GPC)=== GPC is not a true ocular allergic reaction and is caused by repeated mechanical irritation of the conjunctiva.<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> Repeated contact with the conjunctival surface caused by the use of contact lenses is associated with GPC.<ref name= "Buckley"> Buckley, R.J., Allergic eye disease--a clinical challenge. Clin Exp Allergy, 1998. 28 Suppl 6: p. 39-43. </ref> ==Treatment== A detailed history allows physicians to determine whether the presenting symptoms are due to an allergen or another source. Diagnostic tests such as conjunctival scrapings to look for eosinophils are helpful in determining the cause of the allergic response.<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> Antihistamines, medication that stabilizes mast cells, and non-steroidal anti-inflammatory drugs (NSAIDs) are safe and usually effective.<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> Corticosteroids are reserved for more severe cases of ocular allergy disease and their use should be monitored by an ophthalmologist.<ref name= "Ono"> Ono, S.J. and M.B. Abelson, Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol, 2005. 115(1): p. 118-22. </ref> When an allergen is identified, the patient should avoid the allergen as much as possible.<ref name= "Buckley"> Buckley, R.J., Allergic eye disease--a clinical challenge. Clin Exp Allergy, 1998. 28 Suppl 6: p. 39-43. </ref> ==References== <references/> {{disease-stub}} {{Allergic conditions}} [[Category:General practice]] [[Category:Ophthalmology]] [[ca:Conjuntivitis al·lèrgica]] [[pl:Alergiczne zapalenie spojówek]] [[tr:Alerjik konjonktivit]]