treatment plan

Ocular Allergy:
Second of a three-part series on OSD

BY BRUCE E. ONOFREY, RPH, OD
MARCH 1998

Ocular allergy, a component of ocular surface disease, begins with a response to the antigen, which can be plant pollen, animal dander, contact lens proteins or a variety of other substances. When susceptible individuals are exposed to an antigen, they produce IgE antibodies, which bind to mast cells. Upon re-exposure to the antigen, the mast cell explodes, releasing histamine. Histamine causes the early signs and symptoms of the allergic response, such as itching, redness and localized swelling.

Seasonal allergy and GPC are the most common forms of ocular allergy. Seasonal allergy, or hayfever, is classically triggered by pollens released throughout the year. Hallmark symptoms include bilateral itching, watering and hyperemia.

Giant papillary conjunctivitis (GPC), vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC) are forms of allergic disorders triggered by mast cell degranulation. Unlike simple seasonal allergy, which is limited to the classic histamine response, these conditions can produce significant tissue changes which may result in conjunctival and corneal scarring.

Therapeutic Options

Artificial Tears. Artificial tears help to normalize the tear film, dilute the level of antigens and enhance the efficacy of other therapies. Avoid recommending products that contain toxic preservatives.

Mast Cell Inhibitors. Mast cell inhibitors are of limited benefit for acute symptoms but can prevent subsequent attacks. Dosage ranges from two to four times daily and can be adjusted as needed. Bausch & Lomb's Crolom (cromolyn 4%) and Alcon's Alomide (lodoxamide 0.01%) are equally effective in controlling mast cell degranulation.

Antihistamines. Acute allergic attacks associated with mast cell degranulation and histamine release require agents that block the H-1 histamine receptors. Over-the-counter topical products contain either antazoline (0.5%) or pheniramine (0.3%), and can be quite effective in controlling the itching, redness and edema of acute allergic attacks. All OTC products also contain sympathomimetic decongestants, which help to reduce edema and redness through vasoconstriction but can also produce rebound hyperemia and are contraindicated in patients with elevated blood pressure. The only topical antihistamine without a decongestant is the prescription drug Livostin from CIBA Vision (levocabastine). All OTC oral antihistamines produce significant anticholinergic side-effects including dryness and drowsiness. While the first non-sedating antihistamines, Seldane (terfenedine 60mg) and Hismanal (Astemizole 10mg) were welcomed additions to the treatment of allergy, their use led to several deaths in individuals who took them with macrolide antibiotics or antifungal agents. The newest non-sedating antihistamine compounds do not produce drug interactions, and these include Claritin (loratadine 10mg), Allegra (Fexofenadine 60mg) and Zyrtec (cetirizine 5mg and10mg).

Patanol from Alcon (Olopatadine) is the ideal topical agent for the management of allergic eye disease because it blocks H-1 histamine receptors, thereby limiting acute histamine-driven symptoms, and it also prophylactically inhibits mast cell degranulation. Effective dosage is two times a day.

NSAIDS and Steroids. Allergan's Acular (ketorolac 0.5% ) has been shown to help manage inflammation associated with the allergic response. In advanced cases, topical fluoromethalone compounds like Eflone (CIBA Vision) or Flarex (Alcon) can be used.

Dr. Onofrey, editor and author of various ophthalmic texts, practices in Albuquerque.