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Allergic Diseases of the Eye

The eye is one of the most sensitive organs of the body when it comes to manifesting allergic reactions. Airborne allergens can readily reach the ophthalmic conjunctiva, and systemic allergies are often manifested in the ophthalmic tissues. Because of these facts, recognizing and treating ophthalmic allergic conditions remains a major challenge for the clinician.

Inflammation in the eye is the result of numerous interrelated inflammatory pathways. (Graphic used with permission from E. Cook and H. Stahl, University of Wisconsin Medical School, Madison, WI)

At the recent annual meeting of the American Academy of Allergy, Asthma, and Immunology, Dr. Leonard Bielory of the University of Medicine and Dentistry of New Jersey reviewed the known causes, differential diagnosis, and treatment options for the management of ocular allergic events.

He pointed out several general considerations:

Avoidance of allergens remains the mainstay in the management of any ocular disorder.

Cold compresses provide considerable relief, especially from ocular pruritus. In general, he noted that all ocular medications provide additional subjective relief when refrigerated and applied cold.

Tear substitutes help in the direct removal and dilution of allergens. If these products are inadequate, ointments or time-released tear replacements can be used at night to moisturize the ocular surface during sleep.

Topical decongestants act as vasoconstrictors that are highly effective in reducing ocular redness. However, extended use of topical vasoconstrictors can lead to "rhinitis medicamentosa," a condition in the eye that is analogous to that observed to result from the overuse of

nasal vasoconstrictors. Symptoms can include increased swelling and rebound redness that may persist even after the drops are discontinued.

These drugs should not be used in patients with narrow angle glaucoma.

Newer topical antihistamines (i.e., olopatadine, levocabastine, cromolyn sodium, lodoxamide) when applied as single-agent therapy to the eye can effectively reduce redness and itching, but many of the older antihistamines (pyrilamine and pheniramine maleate) provide greater effectiveness when they are applied together with a vasoconstrictor.

Orally administered nonsteroidal anti-inflammatory drugs (NSAIDs) can reduce ocular signs of allergy. Similarly, topically administered NSAIDs such as flurbiprofen, ketorolac, and diclofenac can reduce

redness and itching. Other NSAIDs have been developed for the eye (i.e., indomethacin, sulindac, tolmetin), but these have been associated with a low to moderate incidence of burning and stinging.

When topically administered antihistamines, vasoconstrictors, or cromolyn sodium is ineffective, mild topical steroids can be considered.

They are highly effective in the treatment of acute and chronic forms of allergic conjunctivitis. However, they are associated with often potentially severe adverse reactions such as increased intraocular pressure, the development of underlying viral infections, and cataract

formation. New findings suggest that the transient rise in intraocular pressure that is seen in some persons may be a genetically influenced trait not observed in all persons. Although the effectiveness of various esters of the same corticosteroid base may vary, their ability to increase

intraocular pressure remains constant. These drugs should be avoided when herpetic infection may be present in the eye, because the infection can progress rapidly in the presence of a steroid.

Allergic conjunctivitis has been suppressed in animals by the oral administration of an antigen. Whether this will be effective in helping humans has yet to be proven. Oral and intranasal administration of retinal antigens and the S-antigen, as well as the use of crude retinal extracts, has been shown experimentally to inhibit autoimmune uveitis.

Some new therapies that are being investigated include:

Nedocromil: A potent inhibitor of various allergic inflammatory cells, it can stabilize mast cells and inhibit histamine release more effectively than cromolyn. Is more effective than placebo in improving clinical symptoms of seasonal allergic conjunctivitis.

Pentigitide: Also known as human IgE pentapeptide (HEPP), a synthetic peptide that duplicates a five amino acid sequence of the Fc region of the IgE molecule and that has a similarity to the first four amino acids in substance P. It has been reported to be effective in decreasing signs and symptoms of allergic conjunctivitis.

N-Acetylaspartylglutamic acid (NAAGA): A mast cell stabilizer that may control allergic conjunctivitis.

Cyclosporine: A cyclic peptide that has immunomodulating

activity via actions on interleukin-2 (IL-2). A 2% solution has been shown to decrease signs and symptoms of vernal

conjunctivitis. A new carrier (alpha-cyclodextrin) has been

recently developed that increases ocular penetration and

improves ocular tolerability.

FK506: May be effective in treating a variety ofimmune-modulated diseases such as corneal graft rejection, keratitis, scleritis, ocular pemphigoid, and uveitis. It inhibits the generation of cytotoxic lymphocytes and the production of IL-2,IL-3, and gamma-interferon.

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