Treating ocular allergies is a routine part of a comprehensive ophthalmology practice. Most of the allergic conjunctivitis that we see is seasonal, but other types include perennial, medication allergy, giant papillary conjunctivitis (GPC), atopic keratoconjunctivitis (AKC), and vernal keratoconjunctivitis (VKC). The hallmark of allergic conjunctivitis is red, itchy eyes. Many of these patients also have eyelid swelling, conjunctival edema, and tearing. The main goal of treatment is to relieve the symptoms, but for the chronic forms of allergic conjunctivitis it is also necessary to control the inflammation.
It is estimated that up to 25% of the US population have allergies, and 90% of patients with systemic allergies have ocular symptoms. This is most commonly seasonal or perennial allergic conjunctivitis, occurs in patients of all ages, and is associated with allergic rhinitis. The acute phase of allergic conjunctivitis is mediated by a type I hypersensitivity reaction in which airborne allergens (i.e., pollen, mold, dander, dust mites, etc.) cross-link the IgE receptors on mast cells, resulting in mast cell degranulation with release of a host of inflammatory mediators and preformed substances such as histamine, eosinophil chemotactic factors, platelet-activating factor, major basic protein, and prostaglandins. The later, chronic phase involves other allergic inflammation. The symptoms (itching and redness) of allergic conjunctivitis are attributable to histamine receptor activation.
Acute allergic conjunctivitis can also be triggered by direct contact with a toxic stimulus, most commonly a topical medication (i.e., neomycin, aminoglycosides, antivirals, atropine, miotic agents, brimonidine, apraclonidine, epinephrine) or chemical substance (preservatives [thimerosal]), which causes a follicular reaction.
The chronic forms of conjunctivitis (GPC, AKC, and VKC) are less common but can be more difficult to treat. The majority of GPC is found in contact lens wearers, but it can also occur in patients with an ocular prosthesis, foreign body, or exposed suture. Those with atopy (a hereditary allergic hypersensitivity, which is a clinical diagnosis consisting of rhinitis, asthma, and dermatitis) are at higher risk for developing GPC. In addition to itching, the characteristic signs include giant papillae on the upper palpebral conjunctiva, ropy discharge, blurry vision, and contact lens discomfort followed by intolerance.
AKC is a rare form of allergic conjunctivitis that occurs in adults and is also associated with atopy. AKC has similar features as VKC but the papillae are smaller, and there is milky conjunctival edema, thickened and erythematous eyelids, and corneal neovascularization. AKC is also associated with cataracts and keratoconus.
VKC is a very rare form of self-limited, seasonal, allergic conjunctivitis that occurs in children during warm months and lasts for approximately 5-10 years. It is more common in males, and is associated with a family history of atopy. Ocular signs include intense itching, ropy discharge, giant papillae (cobblestones), Horner-Trantas dots (collections of eosinophils at the limbus), shield ulcer, and keratitis. Microscopic examination of a conjunctival scraping that reveals more than two eosinophils per high-power field is pathognomonic of VKC.
The first step in treating allergic conjunctivitis is to identify and remove or avoid the inciting agent. This may require referral to an allergist for patch testing to determine the causative allergens. Supportive measures such as lubricating eye drops, cold compresses, and systemic antihistamines may also be helpful.
The standard ophthalmic treatment is symptom relief with a topical antihistamine preparation usually in combination with a mast cell stabilizer. There are many choices and the response to any given medication can vary from patient to patient. Therefore, I will often do a trial in the office, prior to instilling any diagnostic eye drops, by applying a drop of one product in the patient's right eye and a drop of a different product in the patient's left eye. I then ask the patient which eye feels more comfortable and prescribe the corresponding medication.
The choices of topical allergy drops are antihistamines (Emadine, Livostin, Lastacaft), mast cell stabilizers (Alamast, Alocril, Alomide, Crolom), antihistamine-mast cell stabilizer combinations (Optivar, Patanol/Pataday, Zaditor, Alaway, Elestat, Bepreve), NSAID (Acular), steroid (Alrex), and vasoconstrictors (with or without an antihistamine [Naphcon, Vasocon, Opcon]). Higher potency steroids are often necessary to control the late phase inflammation in the more severe and chronic types of allergic conjunctivitis. In addition, topical cyclosporine can be used for AKC and VKC, and supratarsal steroid injections may also be considered.
As we are well aware, steroids have the potential to cause increased IOP and cataracts, which becomes more concerning with chronic therapy. New compounds are therefore being developed that will hopefully reduce or eliminate these adverse effects. For example, prednisporin is a combination of low concentration prednisolone and cyclosporine. Selective glucocorticoid receptor agonists are partial steroid agonists that have anti-inflammatory properties without the adverse effects. Small molecule inhibitors of intracellular protein kinases may also suppress chronic inflammation without the steroid side effects. Finally, sustained release agents and implants (i.e., punctal plug or contact lens delivery systems) may prove to be a more efficient method of providing current and future medications.