EyeNet Magazine
  February 2004  
  Feature Story  
  Ocular Allergies: Fight the Mite  
  Clinical Insights  
  Genetic Tests: High Hopes vs. Reality  
  Journal Highlights  
  Detecting the Ocular Ischemic Syndrome  
  Laser Spot Size: Is Smaller Better?  
  Managing Ocular Toxoplasmosis  
  Morning Rounds  
  What's your diagnosis?  
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  On Procrastination  
     


 
Ocular Allergies:
Fight the Mite

By Laura J. Rongé
 
 

The miseries of allergy affect as many as 50 million Americans. For some, an ounce of prevention goes a long way. For others, a pound of cure is appropriate. Several allergy experts share their approaches to treating the ocular effects of this troublesome malady.

When a susceptible person encounters an allergen, his immune system makes large amounts of immunoglobin E antibody specifically designed to react to that particular allergen. These IgE molecules bind to mast cells and basophils. When the allergen next encounters its specific IgE on a cell, it attaches to the antibody and signals the cell to release inflammatory agents such as histamine, cytokines and leukotrienes.

The most effective way to limit this uncomfortable chain of events is to break the cycle by reducing exposure to the offending allergen. Thus, the first step is for the patient to know what he is allergic to, said Mitchell H. Friedlaender, MD. “If it is not [immediately] apparent, skin testing by the allergist can help.”

An Ounce of Prevention
Some patients will appear in an ophthalmologist’s office just during the peak pollen season; others suffer all year long. In either case, prevention can help relieve their misery. Here are the chief allergen suspects—and strategies for minimizing exposure to them—to discuss with your patients.

Opponent
Dust mites.
The dust in buildings contains a mixture of potential allergens, including fabric fibers, cotton lint, feathers, animal and human dander, bacteria, particles of food, plants and insects, and microscopic dust mites (Dermatophagoides species), the National Institute of Allergy and Infectious Diseases (NIAID) points out. In
a warm, humid house, dust mites can thrive all year round in bedding, upholstered furniture, carpets and the like. Their protein waste products provoke the allergic reaction.

To reduce the dust load, patients can try the following:

Minimize clutter. Keep dust and mold collectors such as books, knickknacks, stuffed animals and other clutter to a minimum, especially in the bedroom. Limit the amount of pillows, bedding, draperies and other linens. For example, avoid using dust ruffles, canopies and layers of curtains, and reduce the amount of unused clothing in closets.

Minimize carpeting. If possible, get rid of wall-to-wall carpeting and area rugs. “It is not possible to clean a rug or vacuum it adequately to get rid of dust mites. Hardwood floors, tile or linoleum are better than any kind of rug. Only rugs that you can wash in hot water would work to deter the mites,” Michael B. Raizman, MD, explained.

Store Data Digitally. At home and at the office, store data digitally, rather than in paper and cardboard files. Reduce the number of stored items and use plastic bins instead of cardboard containers for storage.

Clean Regularly. Clean the house thoroughly and frequently. Use a vacuum cleaner with a HEPA (high-energy particulate air) filter designed to trap allergens rather than blow them back into the air. Wash linens and other washable items often, using water hotter then 130 degrees Fahrenheit. Only hot (not warm or cold) water will kill the mites, Dr. Raizman explained.

Use Barriers and Filters. Cover mattresses, box springs and pillows with impermeable covers designed to limit allergen exposure. Change furnace and dryer filters regularly and install filters on individual air vents throughout the house.

Opponent
Pollen.
One of the most common allergy culprits, and also one of the most difficult to avoid, is pollen. During the spring and fall pollen seasons, certain trees, grasses and weeds release an enormous amount of pollen that is carried over long distances by the wind. A single ragweed plant can generate a million grains of pollen a day, and this pollen has been collected 400 miles out to sea and two miles high, according to the NIAID.

During pollen seasons, avoidance is best, the experts suggest. “Keep the windows rolled up and use air conditioning in the car, at home and at work, if possible. Putting an air conditioner in the bedroom window is better than keeping the windows open if it is too warm, and changing the filters on the air conditioning regularly is important,” said Dr. Raizman.

Another strategy for minimizing exposure is to have the patient wash his hands and brush his hair more frequently and, at home, to change clothes when he comes in from outdoors. “There is pollen everywhere and it sticks on your clothes. Some people take a shower and wash their hair when they get home in pollen season, so they don’t get pollen all over the bed and pillow,” Dr. Raizman said.

Opponent
Mold.
Mold often flourishes in damp basements and closets, bathrooms (especially shower stalls), around fresh food, refrigerator drip trays, house plants, air conditioners, humidifiers, garbage pails, mattresses, upholstered furniture and old foam rubber pillows, according to NIAID.

To reduce exposure to mold spores in the home and office, patients should eliminate water leaks and standing water in washrooms and bathrooms and around pipes, heaters and windows, and avoid areas where molds grow.

Opponent
Pets.
From cats and dogs to gerbils and birds, pets can cause allergic reactions. The major animal allergens are proteins secreted by oil glands in the animals’ skin and shed in dander; proteins in the saliva, which sticks to the fur when the animal cleans itself; and protein in the urine. When dry, these proteins can float into the air, according to NIAID.

Thus, it is important to avoid places where animals have been, not just direct contact with them, suggested Elisabeth J. Cohen, MD. “Some cat-sensitive people can walk into a house and tell if there is a cat in the house,” noted Dr. Friedlaender. Ironically, many people with cat allergy have cats as pets.

If getting rid of the animal is not an option, patients can minimize exposure by not touching their eyes when they are in the house with animals and washing hands frequently. “Keep the animals out of the bedroom, certainly off the bed. A lot of exposure comes when your head is on the pillow for hours through the night,” Dr. Raizman said.

Opponent
Chemicals.
The list of nonallergenic ocular irritants is long and includes chemical fumes (from paints, carpeting, plastics and perfumes), aerosolized sprays (from cleaning products, hair care products and perfumes) and smoke (from candles, fireplaces, cigarettes and factories). Other irritants include smog, high ozone levels and other pollution; dust (even without allergy); chlorine in swimming pools; ocean salt water; construction debris; and even perspiration, the experts noted.

Although some of the symptoms may resemble those of allergies, sensitivity to these irritants does not represent a true allergic reaction involving IgE and the release of histamine or other chemicals. These nonallergenic irritants can, however, add to the effect of pollens or other allergens, exacerbating the condition, Dr. Raizman noted.

“It is pretty easy to differentiate irritant conjunctivitis from allergic conjunctivitis,” Dr. Friedlaender said, noting that allergic conjunctivitis causes itching, redness and swelling during the allergy season, and nasal symptoms usually are present as well. In contrast, irritant conjunctivitis is not seasonal, lacks itching, has little swelling and does not respond to antihistamines, he said.

The key to avoiding irritant conjunctivitis is to identify the irritant and stay away from it or protect against it with goggles, Dr. Friedlaender said. But this may be easier said than done. “Nonspecific irritants may be hard to pinpoint unless the patients notice that certain environments do precipitate eye irritation,” Dr. Raizman said. Dr. Cohen suggested, “Ask patients to consider the time of day and activities when they notice maximum irritation—and to avoid the environment where they are exposed to the irritant.”

A Pound of Cure
If patients would take preventive measures, dependency on allergy drugs would be greatly reduced, Dr. Raizman pointed out. However, allergen avoidance is not always easy or possible.

Treatment for both allergic and nonallergenic irritants starts with cold compresses, ice packs and reservative-free artificial tears kept in the refrigerator, the experts agreed.

A long list of pharmaceutical agents is also available for ocular allergy, when more potent measures are needed (see “When Treatment Is Needed”).

“The latest drugs for allergy are Alocril [nedocromil], Zaditor [ketotifen], Optivar [azelastine] and Alamast [pemirolast]. They all have antihistaminic, mast cell–stabilizing and anti-inflammatory properties,” Dr. Friedlaender reported. He finds a variety of allergy drugs useful. “Which one we use depends on what works for the individual and for the symptoms. If itching is the main symptom, an antihistamine works well. If symptoms persist throughout the allergy season, it makes sense to use a mast cell stabilizer on a regular basis. If redness is the big issue, the over-the-counter antihistamine-vasoconstrictor combinations work well,” he said.

“I like Zaditor and Patanol [olopatadine], the most effective antihistamines,” Dr. Raizman said. “For more chronic allergy, lasting a few months or longer, I generally use a mast cell stabilizer like Alamast or Alocril. I think they work better than the older mast cell stabilizers. Sometimes I have the patient use a mast cell stabilizer every day, adding an antihistamine drop on occasion as needed for the worst symptoms.”

Dr. Cohen prefers to have patients use a mast cell stabilizer plus an antihistamine twice a day. She suggests that patients try different ones and pick what works best for them. “I consider Restasis in severe cases of atopic disease, but this drug is not approved for this indication.”

Restasis (cyclosporine), recently approved by the FDA for moderate to severe dry eye, works well, Dr. Raizman concurred. “I usually reserve it for more severe chronic allergy that is not responding well to standard therapy, especially in patients who require steroids,” he said. “Restasis is certainly much safer, but not always as effective, as steroids. If a patient has to be on steroids chronically, I will certainly try Restasis and see how it works.”

If symptoms are very severe, a corticosteroid eyedrop may be necessary. “Topical steroids can be associated with glaucoma, cataracts and infection. So allergy patients on steroids need to be monitored closely. We try to use these sparingly,” Dr. Friedlaender said.

With the exception of corticosteroids, all of the drops approved for allergy appear to be safe, even with long-term use, Dr. Raizman pointed out. “If safe, older drops are working, I don’t change them. If a patient tells me that he likes cromolyn [Crolom, Opticrom] or emadastine [Emadine], for example, I have him continue it. This is more cost-effective for patients if the medication is working.”

Dr. Cohen prefers to avoid ketorolac (Acular) because of a concern about the potential side effect of corneal melting, she noted. “I think the OTC antihistamines and decongestants work as well or better than the designer ones,” she added.

Oral antihistamines can aggravate dry eyes, she said, but one can compensate for this with frequent use of preservative-free artificial tears. “Dryness does occur with oral antihistamines,” Dr. Friedlaender agreed, “but I have not found it to be a problem with the eyedrops.”

_____________________________
When Treatment Is Needed

H1-receptor antagonists + mast cell stabilizer
Alavert (loratadine)

Allegra (fexofenadine hydrochloride)3

Claritin (loratadine)3

Zyrtec (cetirizine hydrochloride)3
CategoryOptionsComments
OTC antihistamine/
vasoconstrictors
Naphcon-A (naphazoline hydrochloride +
pheniramine maleate eye drops)

OcuHist (naphazoline hydrochloride +
pheniramine maleate eye drops)

Opcon-A (naphazoline hydrochloride +
pheniramine maleate eye drops)

Vasocon-A (naphazoline hydrochloride +
antazoline phosphate eye drops)
Pheniramine is less effective against itch than newer high-tech antihistamines, but is a low-cost alternative for acute symptomatic relief of mild allergic conjunctivitis. The vasoconstrictor naphazoline does remove redness temporarily but can cause chronic rebound redness with long-term use.
Mast cell
stabilizers
Alomide (lodoxamide tromethamine 0.1%)

Crolom (cromolyn sodium 4%)

Opticrom (cromolyn sodium 4%)
Mast cell stabilizers are especially useful for chronic allergy, as opposed to symptomatic relief of acute episodes. The drugs in this group are effective but require more frequent (four to six times daily) dosing than newer combination drugs. Cromolyn sodium can cause burning and stinging on application.
Topical NSAID1Acular (ketorolac tromethamine 0.5%)
Ketorolac inhibits prostaglandins in the aqueous humor. Though fairly effective against itching, it stings and burns when applied, and it can be toxic to the corneal epithelium with prolonged use.
H1-receptor
antagonists
Emadine (emedastine difumarate 0.05%)

Livostin (levocabastine hydrochloride
  0.05%)
These were the first pure H1-specific antihistamines. They remain good choices when an antihistamine alone is needed. When newer combination drugs don’t work, these can be used with pure mast cell stabilizers to create an alternative combination.
Patanol (olopatadine hydrochloride
  0.1%)
Patanol is widely prescribed because of its twice-a-day dosing and its effectiveness against the itching and redness of allergic conjunctivitis.2
H1-receptor antagonists + mast cell stabilizer + NSAID

Alamast (pemirolast potassium 0.1%)

Alocril (nedocromil sodium 2%)

Optivar (azelastine hydrochloride eye
  drops)

Zaditor (ketotifen fumarate 0.025%)

This class of triple-action drugs is the first group shown to have NSAID properties. All have twice-a-day dosing and are effective against itch and, to a lesser extent, redness.
Corticosteroids

Alrex (loteprednol etabonate 0.2%)

FML (fluorometholone 0.1%)

HMS (medrysone 1%)

Lotemax (loteprednol etabonate 0.5%)

Vexol (rimexolone 1%)
These and other steroids can be useful in serious cases. Patients should be selected carefully and warned about risks associated with prolonged use: IOP rise, secondary glaucoma, cataract formation and secondary ocular infections related to reduced host response.
Oral antihistaminesWhen ocular allergy symptoms accompany other allergy symptoms, like rhinitis, oral systemic antihistamines can be helpful for symptomatic relief. All can cause dryness of the eye, so supplement with artificial tears and/or topical antihistamines. Some of these medications are now available over the counter.
1 While other topical NSAIDs are on the market, they are not used for ocular allergy.
2 A once-daily formulation is expected on the market soon.
3 The extended-release formulations Allegra-D, Claritin-D and Zyrtec-D are available; all contain pseudoephedrine.

Note: FDA approval was withdrawn for Hismanal (astemizole); do not prescribe.



______________________________
For More Information

www.niaid.nih.gov. The Web site of the National Institute of Allergy and Infectious Diseases.
www.weather.com. For pollen counts, ozone reports and other related information in your area.

______________________________
Meet the Experts

Michael B. Raizman, MD
Associate professor of ophthalmology at Tufts University, director of the cornea service at New England Eye Center and with Ophthalmic Consultants of Boston. Financial interests: Has done clinical trials and research for Alcon, Allergan, Bausch & Lomb, Novartis and Santen.

Mitchell H. Friedlaender, MD Head of ophthalmology at the Scripps Clinic, director of the Scripps Clinic Laser Vision Center and adjunct professor of ophthalmology at the Scripps Research Institute, La Jolla, Calif. Financial interests: Has done contract work for all of the ophthalmic pharmaceutical companies, but does not have an employment or ownership relationship with any of them.

Elisabeth J. Cohen, MD Professor of ophthalmology at Jefferson Medical College and director of the cornea service at Wills Eye Hospital, Philadelphia. Financial interests: Participated in the clinical trials of Restasis.

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