contact lens care and compliance
Understanding Seasonal Ocular Allergy
BY MICHAEL A. WARD, MMSC, FAAO
Spring is a time of renewal. Songbirds sing their loudest and most eloquent songs to mark their territory and to attract a mate. Flowers emerge from bulbs through the cool, damp soil that has slowly prepared since fall to present a kaleidoscope of colors that brighten our days. Grasses awaken from their dormancy to claim their space in the yard. Trees sprout new growth to repair the traumas from winter storms. Ah, the joys of spring…except for those who have seasonal allergies.
Seasonal allergies affect approximately 39 million Americans. Ocular symptoms of itchy, red, watery eyes occur in approximately half of the allergic population. In addition, approximately half of our contact lens wearers who suffer from seasonal allergies switch to glasses, at least temporarily. Seasonal allergic reactions can also create tear film instability and dryness symptoms. Inability to wear contact lenses can negatively impact patients' visual function at work and at play, as well as their emotional well-being. Understanding these inflammatory mechanisms can help us to better advise and manage our seasonal allergy patients.
The Allergic Reaction
Seasonal allergic conjunctivitis (SAC) and perennial allergic conjunctivitis (PAC) are caused by an immunoglobulin E (IgE)-mediated immediate hypersensitivity reaction to environmental airborne allergens such as grasses, tree pollens, mites, molds, and animal dander. Mast cell surfaces are coated with IgE molecules, each of which is specific to a given antigen. The ocular allergic response results from exposure of the conjunctiva to an environmental allergen. The allergen causes cross-linking of IgE on the conjunctival mast cells, leading to the mast cell degranulation cascade. Mast cells play a key role in initiating and mediating the pathogenesis of ocular allergic reactions.
These types of immediate hypersensitivity reactions are characterized by early phase and late phase responses. The immediate (early phase) response lasts clinically for 20 to 30 minutes, with symptoms and signs such as itching, chemosis, injection, and tearing. This mast cell response results in increased tear levels of histamine, prostaglandins, tryptases, and leukotrienes, with recruitment of eosinophils and neutrophils to follow. The late phase reaction occurs four to 24 hours following initial exposure. Recent laboratory studies indicate that conjunctival mast cells are essential for late phase eosinophilic inflammation. The late phase is associated with an altered balance between T helper type 1 (Th1) and T helper type 2 (Th2) cells and between Th1- and Th2-types of cytokines.
Advice for Seasonal Allergy Sufferers
Offer your seasonal allergy sufferers the following advice to help minimize their allergic response:
- Keep the humidity level below 50 percent to inhibit mold growth.
- Keep windows closed; high efficiency air filters and electrostatic air cleaners can remove pollen and dust to improve air quality in central air conditioning systems. Replace filters regularly.
- Wear a mask if working outdoors during high-pollen-count conditions.
- Shower immediately after outdoor exposure to remove pollens from clothes, hair, and skin. Don't wear your shoes inside.
- Wear goggles or close-fitting sunglasses when outside.
- Washing face and hands often with cold water can relieve symptoms. Cold compresses also help to relieve ocular itching. CLS
To obtain references for this article, please visit http://www.clspectrum.com/references.asp and click on document #172.
Mr. Ward is an instructor in ophthalmology at Emory University School of Medicine and director, Emory Contact Lens Service.