Allergic Conjunctivitis

Mild allergic conjunctivitis.

Severe allergic conjunctivitis with watch-glass conjunctiva.

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.

Ocular Allergies: OTC or Rx? Even though there a dozen FDA-approved prescription topical medications to treat allergic conjunctivitis, the American public still purchases more than 40 million bottles of over-the-counter (OTC) ophthalmic preparations each year. More individuals use agents such as Opcon-A (Bausch & Lomb) and Visine-A (Pfizer) for allergy-related ocular itching than any of the prescription medications. OTC products combine a topical decongestant, such as naphazoline hydrochloride, with a topical antihistamine such as pheniramine maleate or antazoline phosphate. Patients are lured by the promise of "fast, effective relief from red, itchy eyes." As clinicians, we must ask, "Can they possibly work as well as drugs such as Patanol or Zaditor?" On the contrary, we know that the OTC preparations are generally less effective for managing ocular allergies, because the antihistamines in the OTC agents are not as potent and are formulated at much weaker concentrations than those in the Rx agents. In fact, we know that OTC agents can actually be harmful in some individuals. Studies have shown that chronic use of topical vasoconstrictors such as naphazoline can result in toxic, follicular reactions and contact dermatitis.1 So why do so many patients still use OTC eye drops? Most likely there are two factors at play: Cost and ignorance. On average, OTC drops cost about $5-$10 for a 15ml bottle, while newer drugs such as Patanol, Zaditor or Optivar may cost between $50 and $60 or more for a 5ml bottle. Patients see the cost savings, but they remain unaware that OTC drops are less efficacious and are potentially detrimental to their ocular health. It's our obligation to educate patients regarding the OTC products they may encounter, as well as prescribe the best and most appropriate therapies for them. Patients need to know that OTC allergy solutions may be fine on occasion for those who suffer a mild exposure, but should not be used in the continuous management of seasonal or perennial allergic conjunctivitis.   1. Soparkar CN, Wilhelmus KR, Koch DD, et al. Acute and chronic conjunctivitis due to over-the-counter ophthalmic decongestants. Arch Ophthalmol 1997;115(1):34-8.

Clinical Pearls:

• Advise patients with a history of seasonal allergic conjunctivitis to try to avoid the substances that precipitate symptoms. In severe cases, these patients may be treated four weeks in advance with loading doses of topical mast-cell stabilizers (Alomide, Alamast, Alocril or cromolyn sodium), or mast cell-stabilizing antihistamines (Patanol, Zaditor or Optivar) to retard the degranulation process.
• Follow patients on a topical NSAID agent for 1-2 weeks after starting therapy. Patients placed on topical steroidal preparations should return for follow-up one week after starting therapy.
• Optimal therapy for ocular allergies includes an antihistamine, mast-cell stabilizer and a steroid. This combination will address all aspects of the allergic inflammatory reaction.
• Newer mast-cell stabilizers (Alamast and Alocril) are patient-friendly in that they can be dosed bid (although Alamast is indicated for qid dosing).

Other reports in this section

• Conjunctival Neoplasms
• Allergic Conjunctivitis
• Vernal Conjunctivitis
• Acute Bacterial Conjunctivitis