An estimated 20 percent of the U.S. population experiences allergies - and this percentage seems to be growing. Some surveys (Gallup Poll 2003-4) suggest that this number may be as high as 50 percent of the population and that 90 percent of these individuals experience ocular symptoms as well. Moreover, studies have shown that eye allergies are under reported.

Along with these statistics, patients in our practices report significant negative effects from increased healthcare-related costs due to decreased productivity and quality of life. In fact, consumers' out-of-pocket costs and the indirect costs of productivity reductions and lost workdays have had an economic impact estimated to be at least $5 billion a year.

Within this population of allergy sufferers are many of our patients who wear contact lenses of all types. We, as practitioners, must be cognizant of our patents' trials and tribulations in attempting to wear contact lenses in the midst of suffering symptoms of allergic rhinitis, allergic conjunctivitis and dry eye-related allergies. Let's examine the effect of this problem on our contact lens wearing population, which is more than 30 million in the United States alone.

In one study, allergic rhinitis patients reported being bothered by their allergy symptoms, both nasal and ocular, on an average of nearly four days during the week before they were questioned. Each patient reported experiencing ocular symptoms on at least one day of that week, and approximately 20 percent reported experiencing ocular symptoms every day of that same week.

As contact lens wearers, these individuals would experience continuous ocular symptoms during their entire wearing schedule each week and would eventually either give up on contact lens wear or, at best, become partial wearers who might wear their lenses only on social occasions. But even these individuals most likely would not be comfortable in this situation, and eventually they, too, would choose to give up on contact lens wear if no long-term solution was found.

It's become increasingly evident in clinical practice that there's no one solution for any contact lens wearer experiencing ocular allergy. Many contact lens wearers blame the contact lens fit for the problem. Many blame dryness as the cause, and others realistically know that the root of their problems lies in the systemic allergic response and its further effects on their eyes.

As practitioners, we have a treatment goal with any allergic patient, contact lens wearer or otherwise. That goal is an approach that targets all aspects of the allergic response with optimal efficacy, immediate onset, extended duration and the utmost comfort and safety. This may involve a pharmacologic approach, holistic approach, allergen avoidance approach or an environmental lifestyle change approach. When the complication of contact lens wear is also present, further changes may be necessary in contact lens material, lens type or lens solution to try to enhance wearing comfort.

It's important to understand the allergic cascade and ocular allergy mechanism of action when dealing with contact lens patients. Most of the allergy we deal with as ophthalmic practitioners is of the Type I hypersensitivity variety mediated by the immunoglobulin IgE. There are four phases of this complex process: sensitization; mast cell degranulation; activation, or early phase; and late phase response.

Active ocular allergy is a specific and narrowly focused form of ocular inflammatory disease. The primary cell involved is the mast cell, of which there are some 50 million in the human eye. During allergic episodes, mast cells move or migrate to the superficial tissue layers where they are degranulated by immune or mechanical stimuli. Once degranulated (Figure 1), histamine, the principal mediator of allergic conjunctivitis, releases into the blood stream and causes vasodilatation and erythema, increased vascular permeability (edema) and neural stimulation (itching - the hallmark of allergy) (Figure 2).

Other pre-formed mediators are also released during this cascade: tryptase, chymase and heparin to mention a few. In addition, other newly formed mediators are also released: prostaglandins, leukotrienes, cytokines, etc. All of these play a role in the allergic response, but to reiterate, the principal mediator is still histamine.

We see allergic patients seasonally (SAC), episodically (EAC) or perennially (PAC) depending on what allergen affects them. These are generally acute conditions, but if an individual is affected by more than one entity, this condition may be present all year. Of the chronic allergic conditions we see giant papillary conjunctivitis in contact lens wearers more than we see either vernal keratoconjunctivitis or atopic keratoconjunctivitis. Patients have also reported ocular symptoms from unilateral irritation of the nasal mucosa. In the nasal-ocular reflex (also called the ocular-nasal reflex), allergens in the nose stimulate inflammatory mediators, which in turn stimulate the trigeminal ganglion. This often results in ocular vasodilatation, erythema, plasma leakage and tearing. In this situation a nasal anti-inflammatory agent may offer relief of both nasal and ocular symptoms.

Any of the above conditions may occur in contact lens wearers, complicating what may be an ill-fitting lens, an improper lens material for that patient or an incorrect contact lens solution for that type of lens or patient (Figure 3). Our job is to rule out the obvious and to investigate the not-so obvious to properly diagnose the condition for each individual patient.

Complicating this further is the condition of dry eye syndrome, which practitioners must differentially diagnose before applying any treatment regimen. It used to be said that if the eye burns, it's dry eye; if the eye itches, it's allergy; and if the eye has mucus discharge, it's bacterial until proven otherwise. While this old adage still may hold some water, the diagnosis is much more complicated than that because of the various mechanisms of action described above in the allergic cascade.

In differentiating dry eye from true allergy, you need to take some important steps. First and foremost, good history taking is paramount. Does the condition the patient describes involve itching vs. burning or dryness? If so, obviously the diagnosis would be more simplified and targeted to allergy. However, let's assume that you had nothing so specific to guide your initial impression. In this case, what would you do? A complete battery of dry eye tests would be in order, beginning with biomicroscopic evaluation of the tear layer for its composition (thickness, debris, meibomian gland oil and sebaceous secretions) as well as the tear meniscus for its apparent volume. Obtain a tear break-up time (TBUT) to help assess the quality of the tears. Next, stain the conjunctiva with fluorescein dye, use a Wratten filter and evaluate the cornea. Also evaluate whether the conjunctiva has dry spots or dry areas. Use lissamine green dye to additionally evaluate staining on the conjunctiva. Then use a Phenol Red Thread Test (Zone Quick) to evaluate the amount of fluid present in the conjunctival sac. I don't recommend a Schirmer analysis because I don't believe in its level of accuracy or repeatability.

These simple procedures will reveal if the patient's complaint truly results from a dry eye component or whether you can rule that out and direct your focus to allergy related issues.

Once you make the differential diagnosis, treatment for contact lens patients may be as simple as cold compresses and ocular lubricants. If this fails the next method of choice is to prescribe a multi-action eye drop that at least would stabilize the mast cell wall from further degranulation and additional release of histamine, along with an antihistamine to specifically bind with the histamine receptor and relieve the itch. These multi-action drops are highly prescribed. The most popular drugs in this category are Patanol (Alcon), Zaditor (Novartis), Elestat (Inspire Pharmaceuticals) and Optivar (MedPointe). Alcon has also introduced an ocular allergy eye drop approved for once-a-day dosing called Pataday.

Practitioners must treat every contact lens-wearing patient individually based upon his working and living environment, lens type, lens schedule and lens solution. Reduced wearing time may be necessary until the acute symptoms are alleviated, but patients remaining in lenses will probably also be on some ocular pharmaceutical agent as described above.

When deciding what pharmaceutical agent to use, you must be aware of your patient's wearing schedule and how acute the symptoms are so you don't prescribe an agent that could possibly exacerbate the problem. Topical ocular anti-allergy medications are generally more effective than systemic medications are for contact lens wearers. In our clinical practice, it appears that using these agents helps keep more patients in lenses during allergic episodes. Having noted that, it's also important to realize that many of our contact lens patients are also using systemic anti-allergy medications prescribed by their physicians as well as intranasal steroids for general allergic rhinitis symptoms. When this is the case, as it often is, I wouldn't counsel a patient to stop taking a systemic drug without first talking with his physician. The physician needs to know that even non-sedating antihistamines can cause drying, and this may complicate the treatment plan in the contact lens wearer.

As far as lens types and lens materials go, we need to assess whether the current contact lenses meet the intrinsic needs of the patient.

We all know that GP lens materials vary in Dk values, which will certainly affect oxygen transmission and ultimately long-term comfort. In the soft lens arena, we have daily wear lenses that have indications for allergic patients. We have lenses that have added properties such as phosphorylcholine to help address dryness and discomfort. We also have lenses that are aspheric in design and, by virtue of their added movement, aid with the oxygen pump upon blinking.

We now have several new silicone hydrogel contact lenses that have higher Dk values than older soft lenses, which again aids in oxygen transmission to the cornea. Because these silicone hydrogel lenses are traditionally lower in water content, lens manufacturers have incorporated additives to help create softer-feeling lenses or lower modulus, which may ultimately be more comfortable. Moreover, we now have contact lens solutions formulated for increased levels of moisturizing and comfort for longer wearing times.

All of these newer products have brought with them a level of awareness that we, as practitioners, didn't previously have. This has ultimately led to improvements in lens wearing comfort and longer wearing schedules for our patients, even for those who have ocular and systemic allergies.

The difficulty in determining what's best for each patient is in the proper diagnosis of the allergic condition in the first place. Once diagnosed, the practitioner needs to base the treatment plan upon the individual lens wearer and his individual desires and wishes.

No one approach will work for everyone. Much of this may be trial and error at the outset, but patience and persistence can prevail. You can attain the desired outcome with the patient once again becoming a happy contact lens wearer, symptom-free or controlled.

Finally, most of us in a primary care setting realize that getting to the proper end-point may involve increased costs to our patients. Of course there's a cost-benefit ratio to any treatment regimen, but for our contact lens patients, who have already spent and continue to spend lots of money on their lenses and solutions, it's imperative to remember that they want results.

When adding drug therapy for an existing contact lens wearer, I believe it's efficacious both from a treatment and monetary standpoint to prescribe the best drug for the patient, no matter what the cost. The bottom line is that our patients want to have the best effect. If a patient experiences a positive result from a particular drug and will ultimately be more comfortable in contact lens wear, he'll be less concerned about the cost.

Ultimately, what we're trying to provide to our contact lens patients is an overall improvement in their quality of life. When allergies begin to interfere with a patient's ability to wear contact lenses in addition to making him physically miserable, this quality deteriorates in some cases to what appears to be a point of no return.

It's critically important that we recognize our patients' symptoms and not treat these allergic conditions in a cavalier manner. A happy patient will refer many other patients to us to solve their problems as well. You can build a handsome practice when keeping this ultimate goal in mind.