Ocular allergy.

PURPOSE OF REVIEW: Ocular allergy is often encountered by allergists, ophthalmologists, pediatricians, and primary care physicians. An understanding of the immunologic mechanisms, the differential diagnosis, the clinical features, and the treatment of ocular allergy will be useful to all physicians who encounter these patients. RECENT FINDINGS: Basic and clinical research has provided a better understanding of the cells, mediators, and immunologic events which occur in ocular allergy. New pharmacological agents, including more potent mast cell stabilizers, and low-dose corticosteroids, have improved the efficacy and safety of ocular allergy treatment. SUMMARY: Physicians who currently treat ocular allergy have a greater familiarity with the signs and symptoms of allergic disease, a better understanding of the mechanisms and clinical features of allergic conjunctivitis, and improved therapeutic tools to deliver satisfactory outcomes in the management of ocular allergy.

Allergic conjunctivitis.

Allergic conjunctivitis is common, especially during the allergy season. Consultation with the allergist to perform skin tests or in vitro tests may be useful and confirmatory in the diagnosis of ocular allergy. If treatment is necessary, antihistamines, mast cell stabilizers, and nonsteroidal anti-inflammatory drugs are safe and reasonably effective. Corticosteroids are an order of magnitude more potent than noncorticosteroids; however, they have attendant side effects that are best monitored by the ophthalmologist. The development of "modified" corticosteroids has been a boon to the treatment of ocular allergy because these drugs may reduce potential side effects without sacrificing potency.

Clinical development of 1% azithromycin in DuraSite, a topical azalide anti-infective for ocular surface therapy.

Conjunctivitis, or inflammation of the conjunctiva, refers to a diverse group of ocular surface diseases of viral or bacterial origin that primarily affect the conjunctiva. In developed countries, the most common causative bacterial pathogens are Staphylococcus aureus, Haemophilus influenzae, and Streptococcus pneumoniae. Most varieties of conjunctivitis are self-limiting; however, some cases can be extremely contagious or cause serious complications if left unchecked. New ocular antibiotics are needed to keep pace with the increasing incidence of bacterial resistance and provide options that decrease the overall treatment burden and encourage patient compliance. Azithromycin is a well known systemic anti-infective with broad spectrum activity against gram positive-, gram negative-, and atypical bacteria species. Ocular use has been limited because its solubility and stability profiles in aqueous media were not favorable for delivery to the eye. An eyedrop of 1% azithromycin in DuraSite((R)) (AzaSite, InSite Vision, Alameda, CA, USA), a bioadhesive ocular drug delivery system, was recently developed and evaluated in clinical trials. This formulation is well tolerated, delivers a high concentration of azithromycin to the conjunctiva, has a broader eradication profile than aqueous azithromycin, and can be effectively dosed with 7 drops, a 65% reduction in the amount of drops required by the most popular antibiotics currently used for conjunctivitis.

The dilution of benzalkonium chloride (BAK) in the tear film.

The claim that benzalkonium chloride (BAK) synergistically enhances the antibiotic efficacy of gatifloxacin ophthalmic solution 0.3% (preserved with 0.005% BAK [50 microg/mL), Zymar; Allergan Inc., Irvine, Calif, USA) has been the subject of several studies. The purpose of this prospective clinical study was to test the hypothesis that BAK would be significantly diluted shortly after topical ocular administration and would thereafter have little or no effect on the enhancement of the antibiotic efficacy of commercial gatifloxacin on the ocular surface. This hypothesis was tested by investigators who measured the concentration of tear film BAK at successive time points after topical administration of commercial gatifloxacin. After subjects (N=10) received 5 separate instillations of a single 35-microL drop of gatifloxacin 0.3% ophthalmic solution in each eye, tear samples were collected at 30 sec, 1 min, 3 min, 5 min, and 20 min, with the use of graduated 5-microL glass microcapillaries. A validated high-performance liquid chromatography method was used to measure the concentration of BAK in each tear sample. The results showed rapid BAK dilution to 6.4 microg/mL, 3.2 microg/mL, 1.4 microg/mL, below the detection limit, and below the detection limit at 30 sec, 1 min, 3 min, 5 min, and 20 min after instillation of a single 35-microL drop of gatifloxacin. Because such rapid dilution reduces the concentration of BAK to near zero in minutes and does not allow the time (1 h) required for effective bacterial kill power, BAK is not expected to have a clinically significant effect on enhancement of the antimicrobial efficacy of gatifloxacin on the human ocular surface.

Objective measurement of allergic reactions in the eye.

PURPOSE OF REVIEW: Conjunctival allergen challenge has become a useful model of human ocular allergy and an accepted method for studying the effects of topical antiinflammatory medications. Conjunctival allergen challenge reactions are typically evaluated in a subjective fashion. Erythema and edema are graded by observation, using a 0 to 4 scale. Itching is graded on a 0 to 4 scale by questioning the subject. We have reviewed the recent literature on conjunctival allergen challenge, including recently developed methods aimed at objective assessment of ocular allergic reactions, such as the erythema, edema, sensation, or EES, method. RECENT FINDINGS: Conjunctival erythema can be measured objectively using a spectroradiometer, or colorimeter, a device which measures the chromaticity of reflected light, and provides the x, or u', and y, or v', coordinates of any color. Edema of the eyelids and conjunctiva can be measured using a fractional millimeter reticule in the eyepiece of a slit lamp microscope. Ocular surface sensation can be evaluated using the aesthesiometer of Cochet and Bonnet, or by using a 'sensation index', a measurement that takes into account the intensity and duration of itching. SUMMARY: CAC reactions can be measured objectively using the erythema, edema, sensation method, as well as subjectively by observation and questioning.

Conjunctival provocation testing: overview of recent clinical trials in ocular allergy.

PURPOSE OF REVIEW: The conjunctival provocation test is a human model of ocular allergy that has been used to study the ocular response to allergenic stimuli and to evaluate antiallergic therapy. The review will discuss recent studies using the conjunctival provocation test and other models of ocular allergy, and evaluate the relative merits of different models. RECENT FINDINGS: The conjunctival provocation test has allowed investigators to recruit large numbers of allergic individuals who, although asymptomatic, can be challenged with the conjunctival administration of allergen. Observations of the eye can be made before and after challenge, and cells and mediators may be sampled from the ocular surface. In addition, the effectiveness of antiallergic therapy can be evaluated, usually by pretreating the two eyes with different forms or doses of drug. SUMMARY: Considerable useful information has been gained about the ocular allergic response and drug efficacy using the conjunctival provocation test and naturally occurring seasonal allergic conjunctivitis.