Signs and Symptoms: The human allergic response has various objective signs and physical symptoms. Ocular allergic conditions vary from the subtle signs of itchy, watery eyes with mild hyperemia to extensive inflammatory interactions between the ocular coats and adenexa. Symptoms typically include itching, burning and tearing of the eyes with watery discharge. In most cases the patient will report a history of allergies. The important observable clinical signs include tissue swelling (chemosis); red, edematous eyelids; conjunctival papillae; and a lack of a palpable preauricular node.
Pathophysiology: The allergic response is an overreaction of the body's immune system to foreign substances known as immunogens or allergens. The response can be innate or acquired. The key component of the ocular allergic response is the mast cell. When mast cells interact with specific allergens they open like a lock being opened by a key--this is known as degranulation--discharging chemical mediators into the surrounding tissues. The primary chemical mediators include histamine (which is responsible for increased vascular permeability, vasodilation, itching, bronchial contraction and increased mucus secretion); neutral proteases (which generate other inflammatory mediators); and arachidonic acid (a crucial component of the cyclooxygenase pathway).
Management: Because there are many levels of ocular allergic reactions, management is primarily aimed at reducing symptoms. The most effective treatment for allergic conjunctivitis is to eliminate the potentially offending allergen, although this is not usually possible. Cold compresses, artificial tears and ointments soothe, lubricate and wash away or dilute the antigens on an as-needed basis.
Topical decongestants produce vasoconstriction, reducing hyperemia, chemosis and other symptoms by retarding the release of the chemical mediators into the tissues from the blood stream. The topical antihistamines--Emadine (emedastine, Alcon) and Livostin (levocabastine, Novartis)--and oral antihistamines are also excellent therapies. Mast-cell stabilizers--Alamast (pemirolast, Santen), Alocril (nedocromil, Allergan), Alomide (lodoxamide, Alcon) and cromolyn sodium--inhibit release of the histamine, but will take longer to relieve symptoms. The dual action medications--Patanol (olopatadine, Alcon Laborato-ries), Zaditor (ketotifen, Novartis) and Optivar (azelastine, Bausch & Lomb)--combine antihistamines with mast-cell stabilizing properties. Clinicians use them widely for managing symptoms associated with seasonal allergies.
The topical nonsteroidal
anti-inflammatory drugs--such as Acular (ketorolac, Allergan) and Voltaren
(diclofenac, Novartis)--may offer relief in moderate cases; topical steroids--such
as Pred Forte (prednisolone, Allergan) and Lotemax (loteprednol 0.5%,
B&L)--are typically reserved for more severe presentations. Alrex
(loteprednol 0.2% B&L) is a topical steroid specifically indicated
for the management of allergic ocular reactions. It is effective even
in severe ocular allergic responses and appears to be safe for long-term
management of ocular allergies. Still, you should monitor IOP in patients
who take the drug for 10 days or more.
Other reports in this section
& Eyelashes | Conjunctiva
& Sclera | Cornea
Uvea | Vitreous & Retina | Optic Nerve & Brain | Oculosystemic Disease
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