An estimated 80 million Ameri-cans suffer from allergies -- and the number is climbing. As a result, you're probably seeing more patients with symptoms ranging from the mild itching associated with environmental allergens to the debilitating itching, pain and corneal disease associated with vernal keratoconjunctivitis.

Here, I'll review how to diagnose allergic conditions accurately and select the best treatment strategy for keeping your patients comfortable and satisfied.

Let's begin by taking a closer look at the different types of disease processes we typically encounter in these patients.

• Seasonal and perennial allergic conjunctivitis (SAC and PAC):
Most patients with ocular allergies have SAC or PAC, which produce similar signs and symptoms: conjunctival hyperemia, lacrimation, mild lid edema, mild photophobia and moderate itching. Slit lamp examination typically shows mild to moderate conjunctival papillae and che-mosis, or in more severe cases, mild scattered superficial punctate keratitis (SPK).
Although SAC sufferers may show signs and symptoms seasonally, PAC sufferers contend with their symptoms more chronically, most likely because of year-round exposure to an allergen.
• Vernal keratoconjunctivitis (VKC):
The intense itching and discomfort associated with VKC can be debilitating. Tearing and photophobia are also common. At the slit lamp, you may find large, "cobblestone" papillae of the tarsal conjunctiva (palpebral form) or significant papillary hypertrophy of the limbal conjunctiva (limbal form).
Although VKC usually affects older children and young adults, the limbal form typically occurs in younger pa-tients. In patients with the limbal form, you often find increased pigmentation at the limbus near the areas of papillary hypertrophy. Other slit lamp findings include white punctate lesions near the superior limbus, known as Trantas' dots; tenacious, ropy discharge; and corneal shield ulcers.
• Atopic keratoconjunctivitis (AKC):
Patients with AKC typically have conjunctival hyperemia, chemosis, keratitis, itching, tearing and photophobia. The eczematous appearance of the lid skin can help you differentiate this condition from other types of ocular allergic disease. Often, these patients later show corneal changes, including pannus, keratoconus and anterior polar cataracts.
• Imitators:
Irritative conjunctivitis (IC) and giant papillary conjunctivitis (GPC) don't result from ocular allergy, but they may mimic allergic conditions. Patients with IC typically have been exposed to nonspecific airborne environmental irritants, such as smoke. Patients may have conjunctival hyperemia, tearing and nonspecific irritation or discomfort, but they don't itch.
Patients with GPC exhibit conjunctival hyperemia, giant papillae of the tarsal conjunctiva, pannus, keratitis and a mucous discharge. GPC usually is found in patients wearing soft contact lenses -- typically in those who don't take care of their lenses properly, don't replace them as prescribed, or fail to remove their lenses and wear their glasses when signs and symptoms first surface.
In most cases, patients initially complain that they can't wear their lenses as long as usual, or that their lenses are coated. Itching is uncommon.

As you know, ocular allergies usually produce redness, itching and irritation. Before selecting the most appropriate treatment, take a careful history. (See "Pinpointing Your Patient's Problem" above, right.) Then, remember these points as you proceed:

• Diagnose correctly.
If your patient's eye doesn't itch, the condition probably isn't allergy-related.
• Don't make it worse.
If the patient has a red eye, don't use medications that can increase the redness.
• Protect your patient.
Remember that patients often store leftover medications at home and self-prescribe for other conditions affecting them or others. Be sure that your prescription won't be harmful if it's used inappropriately.

In children, opt for preservative-free, artificial tears for first-line treatment. (Adults may also benefit from this approach.) These solutions wash out accumulated antigens in the tear film and create a barrier to new antigens.

This intervention may be all it takes to relieve itching in a 2-year-old who's rubbing his eyes. Although children don't like eye drops, preservative-free tears are safe, they don't burn and they won't worsen the problem.

Here are some viable options to consider when treating SAC and PAC:

• Non-steroidal anti-inflammatory drugs.
These medications, which in-clude ketorolac (Acular), are painful when administered. They must be ad-ministered frequently and aren't always as effective at managing ocular allergies as other agents. Other drugs in this class include diclofenac (Voltaren), suprofen (Profenal) and flurbiprofen (Ocufen).
• Topical antihistamines.
Medications such as levocabastine (Livostin) have benefited some patients on a short-term basis; however, they must be administered frequently, and extended use causes redness. Other drugs in this class include ketotifen (Zaditor), emedastine (Emadine) and azelastine (Astelin). (Note: Ketotifen, a triple-action drug, was only recently approved. Its 8- to 12-hour dosing reduces the need for frequent administration.)
• Topical steroids.
All topical steroids, even in a reduced concentration, have a very limited role in treating SAC and PAC and should never be used as a primary treatment. Patients using these medications must be monitored on an ongoing basis because, as you know, steroids may increase intraocular pressure (IOL) in the short term and cause cataracts in the long term.
If you do use steroids, as indicated, you have some new options in this area. For example, many doctors use loteprednol etabonate ophthalmic suspension 0.2% (Alrex) as an effective bridge be-tween steroids and other treatments. Loteprednol's unique mechanism of ac-tion deactivates the drug after it accomplishes its therapeutic mission, minimizing IOL and immunosuppressive effects.
• Mast cell stabilizers.
These medications may effectively control some cases of ocular allergy, but they're less effective in primary management. By the time the patient arrives at your office, histamine has been released from degranulated mast cells. The patient won't get relief from mast-cell stabilizers until the histamine is gone and the conjunctival mast cells have been "stabilized," even after the frequent administration some manufacturers recommend.
Recent research on the mechanism of action suggests that the relief patients receive from mast-cell stabilizers may result more from their anti-inflammatory effect than from a true conjunctival mast cell stabilizing effect. Drugs in this class include cromolyn (Crolom), lodoxamide (Alomide), nedocromil (Alocril) and pemirolast (Alamast).
Olopatadine (Patanol) is an antihistamine-mast cell stabilizer. Because olo-patadine delivers these effects in one molecule, it provides the immediate relief of antihistamines and the long-term control of mast-cell stabilizers. There is a long duration of action, and it has a high therapeutic index, making adverse effects such as increased hyperemia or other signs of toxicity rare.
Another option in this area is ketotifen, mentioned earlier. In addition to its 8-to-12 hour duration, it combines mast cell stabilization, inhibition of the recruitment and activation of eosino-phils, and antihistamine activity.

Your next challenge in managing these patients is to use today's various treatments for the right situations. Here are some insights I'd like to share.

• For SAC and PAC:
I prefer to prescribe olopatadine for SAC and PAC. It's safe, even for small children when preservative-free tears haven't been effective. Olopatadine is administered twice daily -- usually when the patient awakens and at 4 PM. Once symptoms are controlled, the dosage is reduced to once a day. Ketotifen is also likely to get consideration in this area.
• For VKC and AKC:
It's more difficult to treat VKC and AKC. Drugs with once- or twice-a-day dosing may be needed every 8 hours in severe cases, and supplementation with topical steroids may be required in some refractory cases.
Patients with corneal epithelial defects should be treated with a nontoxic, nonsensitizing, broad-spectrum topical antibiotic. I usually use topical cipro-floxacin (Ciloxan) four times daily. Other clinicians may prefer ofloxacin (Ocuflox). Patients with eczematous changes of the lid skin may benefit from Eucerin applied to the skin, or Neutrogena eye cream in milder cases.
• For IC:
It's best to treat IC with preservative-free tears. If patients have an allergic component to their IC, they may benefit from treatment with olopatadine once or twice daily.
• For GPC:
Remove the offending contact lens or prosthesis; usually, pa-tients will then improve without treatment. Patients with corneal changes should be treated with a broad-spectrum, nontoxic, nonsensitizing topical antibiotic. Preservative-free artificial tears may relieve irritation and discomfort.
Patients who experience allergy symptoms after removing their contact lenses or prosthesis -- and who are using preservative-free tears -- may benefit from a treatment such as olopatadine. However, don't prescribe a mast-cell stabilizer with the intention of letting your patient continue using the offending contact lens or prosthesis.
The patient shouldn't use contact lenses until the GPC and its associated pannus are inactive, which may take weeks, or months in severe cases. Soft lens wearers with GPC should be refit with rigid gas-permeable (RGP) contact lenses, if the patient can manage them.
Children with GPC resulting from abuse of soft contact lenses shouldn't be refit, even with RGP lenses, until they show that they will wear glasses anywhere they would wear contacts. Their parents must certify that the child can be trusted to care for his lenses reliably, without parental supervision.

Patients using topical or systemic medications present their own set of challenges. Consider these factors:

• Ocular decongestants:
To "get the red out," many patients use an OTC ocular decongestant such as tetrahydrozoline (Visine) for an extended time. Such treatment can cause significant rebound hyperemia that may last weeks.
Although decongestant-antihistamine combinations such as naphazoline-antazoline (Vasocon A) and naphazoline-pheniramine (Naphcon-A) may be beneficial for limited use for a known isolated exposure to an antigen, the decongestant component of these drugs can cause tachyphylaxis and rebound.
Decongestants don't address the cause of the allergic response or modify the response in a clinically beneficial way. In patients with redness and irritation resulting from overuse of topical decongestants, it's best to immediately stop the decongestants and switch to preservative-free artificial tears for a few days. Many cases improve from this intervention alone. Even if you don't see improvement, the true clinical signs and symptoms of ocular allergy will surface, allowing you to more effectively diagnose and treat the condition.
• Concomitant treatment of other allergic conditions:
Patients with allergic rhinitis may have ocular symptoms, despite treatment with a nasal steroid or nasal cromolyn. A careful history will help you in these cases.
Patients with true allergic rhinitis usually have prominent nasal congestion, nasal discharge, sneezing and tearing. However, a patient may have ocular itching as his primary complaint, and may exhibit associated symptoms of tearing and runny nose. This probably isn't true allergic rhinitis; the nasal symptoms are caused by the ocular symptoms.
If you treat the ocular symptoms with an antihistamine-mast cell stabilizer, these patients may improve sufficiently to permit reduction or discontinuation of the nasal medication.
• Systemic allergy medications:
It's well established that ocular conditions usually respond best to topical, not systemic, medications. However, some primary care physicians are more comfortable with systemic agents, so patients with primarily ocular symptoms may be taking loratadine (Claritin), fexofenadine (Allegra) or cetirizine HCl (Zyrtec).
Because these patients are in your office, it's clear that the ocular symptoms haven't disappeared or have worsened. In fact, oral antihistamines may be drying, and the reduction in basal tear secretion associated with systemic antihistamines may worsen the symptoms.
If your patient primarily has ocular irritation and has had no other systemic signs of allergy before taking oral antihistamines, treat him with preservative-free tears and discontinue the oral antihistamine. If ocular allergic symptoms re-emerge, I prescribe olopatadine.
Oral antihistamines should be continued only if necessary to control significant non-ocular allergic symptoms.

Finally, have patients with environmental allergies review items that may be causing symptoms. Your patient may need skin testing and a consultation with an allergist. When an allergen can't be eliminated, immunotherapy is an option to consider.

If we take the time to talk to our patients, make an accurate diagnosis and provide interventions most likely to be safe and effective, we'll stand a much better chance of helping patients when problems first appear. This will mean prompt relief, fewer return visits, and happier, more satisfied patients.

In your fast-paced routine, you may find it difficult to devote adequate attention to the history of a patient's current illness. But, at a minimum, you should get answers to the following questions from allergy patients:

• Is this the first episode? How long has it lasted?
• Has the patient been exposed to a particular antigen? For example, if the patient is a child, did he roll around in the grass at Grandma's house?
• Does the patient have other systemic signs of allergy, such as rhinitis, asthma, dermatitis or sinusitis?
• Did the patient self-medicate with over-the-counter (OTC) medications? Topical or
  systemic? Which ones?
• Is the patient taking oral or topical medications prescribed by his or her primary care physician for the same episode or condition?
• Does the patient wear contact lenses? Soft or rigid gas permeable (RGP)? How old are the lenses? What is the patient's prescribed lens care regimen? What is the patient's actual lens care regimen? Does the patient know the name of his contact lens provider? If he doesn't, his contact lens wear probably hasn't been closely supervised.
• Has the patient consulted other providers for the same case of conjunctivitis?

Robert D. Gross, M.D., F.A.A.P. is associate professor of ophthalmology at the University of Texas Southwestern Medical Center at Dallas, and Chief of Surgery at Cook Children's Medical Center in Fort Worth. He practices pediatric ophthalmology in Arlington, Texas.