LENSES AND ALLERGY
Diagnosing, Managing Allergy in Lens Wearers
With so many patients affected, practitioners need to have a strategy to keep these patients wearing lenses.
By Arthur B. Epstein, OD, FAAO
Dr. Epstein is a well known clinician, author, and lecturer. A senior partner of North Shore Contact Lens & Vision Consultants, Long Island, NY, he is also attending staff at North Shore University Hospital, NYU School of Medicine. Dr. Epstein has received speaking honoraria, research grants or served as a consultant for Alcon Labs, Ciba Vision, CooperVision, and Vistakon.
Allergy affects such a high percentage of patients that most eyecare practitioners quickly become familiar with the typical signs and symptoms of ocular allergy. Nearly constant direct exposure to the environment also makes the eyes even more sensitive and susceptible to allergic triggers compared to other parts of the body.
While the diagnosis of ocular allergy is usually simple and the management straightforward, ocular allergy can be complicated by other factors such as dry eye and ocular surface disease. The more complicated the overall condition, the more difficult the diagnosis and management.
After more than a quarter of a century of practice focused on contact lenses and anterior segment disease, I have learned that contact lenses can dramatically complicate a clinical picture. Is that mild papillary conjunctivitis due to the lenses or is it allergy? Is it solution sensitivity? For that matter, is the patient even using the solution I prescribed? Even simple questions like these can plague clinicians when the answers don't lead to effective treatment. Paradoxically, the worst affected patients are the most satisfied contact lens wearers. For them, allergy or anything that would prevent them from wearing their contact lenses can be a huge issue. The key to effective management of these patients is to fully understand allergy and how it interacts with and affects contact lens wear.
Physiology and pathology are logical disciplines. There are good reasons to explain almost everything the body does. Allergy should be no different, but oddly, allergy is one of few disorders that doesn't make much sense. Put simply, allergy is an overly exaggerated response to the most ordinary of things. And worse, it typically brings far more misery than benefit to affected patients. In fact, allergy can be life altering, and contact lens wear can make patients who are miserable from allergy even more miserable. Numerous quality of life studies as well as economic profiles have shown allergy to have significant personal and societal impact. That is generally true but even more so for patients who depend on contact lens wear and are tormented by allergy.
A little background will make it easier to understand the impact of allergy. Many allergists believe that the allergies we encounter today evolved from native defenses against parasitic infestation. Today's allergy sufferers are likely descendants of survivors of parasitic epidemics during biblical times.
More recent evidence is compelling. After largely eliminating parasitic roundworm infection of the residents of the tropical island Mauke in the 1970s, returning physicians found a five-fold increase in allergy among the islanders a few years later. Up until the eradication of roundworm infestation, allergy was virtually nonexistent on Mauke.
Often described as the hygiene hypothesis, early hygiene, specifically exposure to pathogens and allergy, are believed related. The inverse relation between allergy and parasitic infection observed on Mauke suggests that allergic response plays a still important protective role in humans, but only under the right circumstances. This explanation is also consistent with the genetic pattern of allergy. Most allergy sufferers have at least one if not both parents who either suffer from or have a predisposition for allergy.
Clinicians sometimes trivialize allergy as being more annoying than clinically important; however, consider that it represents a system intended to protect against life-threatening disease. Allergy can have powerful consequences even while we may not be fully aware of them. For example, many contact lens wearers abandon contact lens wear during allergy season. Most have not received effective treatment from their clinicians. However, once identified, most of these patients can be successfully managed and can continue to wear lenses even during the worst allergy periods.
A Slippery Slope: The Allergic Cascade
The allergic cascade has been well described, and most clinicians are familiar with it. However, there are elements that are poorly understood and, consequently, infrequently described. Some are especially pertinent to contact lens wearers.
As a brief review, immunologically, ocular allergy represents a type I hypersensitivity reaction. The primary actor in ocular allergy is the mast cell, after it is loaded with IgE. The appropriate IgE is created during a sensitization phase in which an allergen is processed and its signature is coded into the IgE.
A variety of mast cell subtypes have been identified. For the purposes of this discussion the primary subtypes of interest are the MC T and MC TC mast cells. The MC T subtype predominates in the lungs and the gut but may be found in the eye when affected by chronic allergy. The MC TC subtype is present on the external surfaces of the body such as the skin and the human conjunctiva. Knowing this is important as medications can be selective for mast cell type. Mast cell stabilizing medications designed to treat respiratory disease will often be ineffective on surface allergy due to the differences in mast cell subtypes involved.
The purpose of the mast cell is to protect surrounding tissue by mobilizing an immediate response to invading agents. In that sense it serves as a fortress containing large amounts of histamine and other potent mediators that are released immediately upon allergen challenge. In addition, an activated mast cell can synthesize a variety of pro-inflammatory mediators that can, in turn, mobilize a robust cellular response through the vascular system.
Of special note in contact lens wearers is the mast cell's sensitivity to mechanical stimuli. Greiner and colleagues (1985) described the effects of eye rubbing on mast cell degranulation and ocular inflammation. While inflammation plays an intuitive and more obvious role in conditions such as keratoconus, inflammation upregulated by contact lens wear and subsequent micro-trauma can worsen other conditions or confound their diagnosis and management.
Among the most important considerations in successfully managing ocular allergy is how the allergic response is regulated. Early theorists viewed allergy as a simple reaction driven solely by allergens and both acted and modulated locally. Modulation was through local responses such as coughing, tearing, or sneezing. These reflexive mechanisms are designed to rid an area of the offending allergen. While these reflexes are often effective; they lack the precision and specificity of central control. With little exception, functions important to the body are usually controlled centrally rather than locally. The eyes are so critical to survival that central control of ocular defenses would seem logical.
For example, we now know that lacrimal production is controlled through a central neural loop. Similar mechanisms influence other aspects of ocular surface function such as meibum production and the production of mucins.
Surface epithelium is able to modulate the allergic response through release of proinflammatory mediators. Responding to histamine released by mast cells, a broader systemic response can be mobilized and effectively controlled at the site of allergic challenge. Because contact lenses can cover a significant portion of the ocular surface, they may effect conjunctival-modulation of the allergic response. This may explain why some allergy patients seem to benefit from lens wear during periods of high allergen exposure.
Clinical Realities: Patient Encounters With Allergens
Allergy is a disorder of opportunity. As mentioned previously, a family history of allergy usually exists but the presence of an allergen that triggers the allergic response is essential. When recording the family history, it is important to always ask about possible allergens.
In eyecare settings a large percentage of allergy sufferers experience seasonal attacks. Seasonal allergic conjunctivitis (SAC) is heralded by the acute appearance of red, itchy, and watery eyes (Figures 1 and 2). Similarly, but with greater chronicity, perennial allergic conjunctivitis (PAC) occurs year round. In addition, a smaller number of patients may be affected by severe ocular allergy such as atopic keratoconjunctivitis or vernal keratoconjunctivitis.
Figure 1. Injection, inflammation, and tearing associated with ocular allergy.
Figure 2. Injection and vascularization response with ocular allergy.
With seasonal allergy, exposure to allergens usually occurs outdoors and is time dependent: the more prolonged the exposure, the more profound the allergic response. It is important to note that patients who have seasonal allergies often transport outdoor allergens inside the home on clothing or trapped in their hair. Some allergists recommend that patients shower upon coming home to wash away any lingering allergens.
In contrast, perennial allergic conjunctivitis occurs almost exclusively indoors. As a result, exposure periods are prolonged; however, the allergic response is typically milder. Because allergens are concentrated within a relatively small space, allergen control is often possible. Removal of carpets and other fabrics that tend to trap and concentrate allergens may be helpful, and patients may purchase special bedding that minimizes allergen contact. In more severe cases, treatment of the air using a HEPA filter can remove substantial amounts of sensitizing allergens.
Regardless of cause, ocular allergy may impact contact lens wearers more than other patients (Figure 3). However, properly managed ocular allergy should not be a contraindication to lens wear. Indeed, while soft lenses can act as a magnet for allergens and GP lenses may uncomfortably trap allergens underneath, the majority of lens wearers respond even to high levels of allergens much as any other patient would. And in some cases, as discussed previously, soft lenses may actually serve a protective function and mitigate some of the patient's suffering. For that reason alone it is critical that practitioners ask patients who are allergy sufferers and who wear lenses how they respond to allergen challenge. If patients are successful with lenses in place, there is no clinical reason why they cannot wear them.
Figure 3. Injection with low fitting soft lens in a patient who has ocular allergy.
The differential diagnosis of allergic conjunctivitis is usually straightforward. However it can be complicated by a variety of factors including contact lens wear. Ocular allergy is frequently episodic, and patients may not present with either clinical signs or symptoms in the controlled environment of an air-conditioned office.
A careful history is important, but it is imperative to observe for contributing factors. Dry eye and ocular surface disease can produce non-specific inflammation that can either mimic or exacerbate ocular allergy. A deficient tear film can potentiate allergy by concentrating allergens in the tears rather than flushing them away. Inflammation from lid or ocular surface disease can produce red eyes or exaggerate an allergic response.
While itching is a hallmark sign of all forms of allergy, patients who have lid disease may also complain of itching. In these patients itching can result from Staphylococcal overpopulation and high levels of Staph exotoxin. Likewise, dermatological conditions can also be associated with irritation, which can be perceived as itching.
Infection, especially low-level chronic bacterial infection, can be associated with a velvety papillary reaction that can be confused with a classical allergic response. However, in cases of bacterial infection, a somewhat mucoid rather than a serous discharge is usually observed. Viral infection usually presents with a follicular or mixed conjunctival response.
Contact lenses may be associated with irritation and itching. Sensitivity to contact lens solutions, although not as common today, may cause or contribute to the allergic response. Mechanical irritation due to a less-than-optimal fit can also lead to chronic inflammation and allergy-like red eyes. This is more likely encountered with GP and hybrid lenses than with modern soft or silicone hydrogel lenses.
Giant Papillary Conjunctivitis
If there is one condition that comes to mind for contact lens fitters when they think of allergy, it's giant papillary conjunctivitis (GPC). However, even though GPC isn't fully understood, it seems reasonably certain that it is not entirely allergic in nature. Research has shown no increase in mast cells, histamine levels, or any of the other findings associated with allergy. However, an increase in inflammatory cells suggests that GPC is an immune response most likely due to mechanical irritation of the conjunctiva.
Managing Types of Allergy
Contact Lens-Specific Minimizing potential sources of inflammation may help reduce the allergic response. Practitioners can accomplish this by ensuring an optimal fit and fitting slightly tighter to reduce lens movement. Minimize edge clearance as much as possible in GP lenses to prevent allergens from lodging beneath the lenses. More fastidious and frequent lens cleaning may also be beneficial including the use of MiraFlow (Ciba Vision), an alcohol-based surfactant cleaner. Increasing replacement frequency for disposable lenses is wise, especially during the height of allergy season. In fact, single-use lenses are ideal if they are available in an appropriate prescription. When all else fails for a patient who must wear GP lenses, the use of a soft piggyback carrier may help temporarily while the patient is brought under control medically. As many allergens are airborne, protective goggles or sunglasses worn over contact lenses may be helpful.
Systemic Allergy Therapy Many allergy patients take over-the-counter (OTC) or prescription systemic mediations. This can be especially problematic for contact lens wearers. Even modern allergy medications can reduce tear levels. This not only complicates lens wear, it can also lead to increased allergen levels in tears as well as concentrate inflammatory mediators. Whenever possible, avoid systemic treatment; however, if necessary, modern non-sedating and non-drying medications are preferred.
Adjunctive Therapy As discussed, many conditions can worsen ocular allergy. In particular, dry eye can ramp up surface inflammation as well as concentrate allergens in the tear film. Part of the allergy workup is evaluating tear and ocular surface health and function. Meibomian gland dysfunction can lead to excessive evaporation and decreased tear volume. In addition, meibum may serve as an immune barrier. Manage existing lid disease with warm compresses and lid hygiene. Topical azithromycin (Azasite, Inspire Pharmaceuticals) can reduce Staph overpopulation as well as reduce inflammation while increasing meibum production. Topical steroid-tobramycin combinations (Tobradex, Alcon) may also be helpful. Application directly to the lids using a cotton swab or little finger, with air drying, is an effective application approach. Oral tetracycline class antibiotics have also been used with good success and improved meibum quality and production. Other therapies that stabilize the tear film such as Systane Ultra (Alcon) and Blink Tears (Abbott Medical Optics) may be helpful in increasing tear volume and ocular surface integrity.
Topical Allergy Therapy The mainstay of ocular allergy treatment for more than a decade has been topical antihistamine-mast cell stabilizer combination drops. The first drug in this class was Patanol (olopatadine 0.1%, Alcon). Other drugs with similar mechanisms of actions include ketotifen, azelastine, Elestat (epinastine 0.05%, Inspire), and more recently Bepreve (bepotastine 1.5%, Ista Pharmaceuticals). Pataday (olopatadine 0.2%, Alcon) is a once-daily topical combination agent. Alcaftadine 0.25% is a topical combination product currently in development by Vistakon Pharmaceuticals.
Older topical therapies, which included antihistamines Livostin (Novartis) and Emadine (emedastine, Alcon) and a variety of mast cell stabilizers such as cromolyn and nedocromil, have been superseded by the combination agents and are rarely used. More recent research has suggested that the available mast cell stabilizers are ineffective on normal conjunctival mast cells but may still be of value in chronic ocular allergy where mast cell populations include susceptible subtypes.
Currently available combination agents are potent antihistamines with sufficient activity to compete with high levels of histamine. Their mast cell stabilizing ability derives from a property of antihistamines, termed the biphasic effect. First described by Mota and Dias DaSilva in 1960, this non-specific effect stabilizes cell membranes at lower drug concentrations and perturbs and disrupts them at higher concentrations—hence the biphasic effect. At commercial concentrations only olopatadine 0.1% and 0.2% and (reportedly) alcaftadine 0.25% demonstrate mast cell stabilization. This may explain the market dominance of olopatadine over the past decade.
As no single medication is completely effective with every patient, other medications including Elestat and Bepreve can be effective anti-allergy strategies. Bepreve has been demonstrated (but not approved) to reduce conjunctival edema in an animal model. Both of these medications are potent antihistamines and mast cell stabilizers at their systemic (non-ophthalmic) concentrations.
Medical management of contact lens wearers who have allergy depends upon the wearing schedule and sustained effectiveness of the medication. Topical medications deliver the highest concentration of medication to the affected site and have the lowest potential for side effects. For example, the drying effects common to oral antihistamine agents are not observed with topical agents. Dosing is an important issue as convenience often makes the difference between compliant successful therapy or contact lens complications and discontinuation. Although some clinicians will use topical allergy medications concurrently with soft and GP lenses, such use is not approved and may be associated with issues linked to preservatives. With the introduction of Pataday, once-a-day dosing provides effective therapy and may be ideal for lens wearers. I prefer administration in the morning to obtain peak concentrations during periods of greatest exposure. Some contact lens patients do well with b.i.d. dosing using other agents instilled prior to lens application and after removal.
Contact lenses are amazing medical devices that can bring about life-changing good. Because allergy is so common—affecting approximately 25 percent of our patients—many contact lens wearers are affected. It is critical that contact lens practitioners understand allergy and how to manage it. For some patients, it can mean the difference between success and failure. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #173.