Allergen dose response and late symptoms in a human model of ocular allergy

Allergen Testing: A Review of the Indications, Procedures, and Limitations in Ocular Allergy

Allergen-based diagnostics are essential in the management algorithm of allergic diseases. Unlike systemic allergy, where the indications and interpretation of these diagnostic modalities are well established, their utility in ocular allergy is not well-defined. With the rising prevalence of ocular allergies and the need for personalized treatment strategies, there is a growing demand for precision allergen diagnostics. This review describes the commonly used tests with their indications, procedures, and limitations. A review of the literature was carried out on articles on allergen diagnostics in ocular allergy, and after excluding articles that were not relevant, 82 papers were included in the current review. IgE-mediated pathways contribute significantly to seasonal and perennial ocular allergy and partly to vernal keratoconjunctivitis. Most diagnostic techniques aim to detect IgE sensitization. In vivo tests include skin prick (SPT), intradermal, and patch tests. SPT is considered the gold standard and directly evaluates the presence of allergen-specific IgE in the skin. In vitro tests measure total and specific IgE from either tears or sera. Tear IgE measurement is relatively specific for allergic conjunctivitis and can provide insight into the potential allergens responsible for local sensitization. The conjunctival provocation test can help establish true allergy, especially in patients with polysensitization. This review also provides an overview of evidence in literature segregated based on the test employed. This includes 17 studies on only SPT; 42 studies on IgE measured in serum, tears, or both; and 20 studies which have evaluated both SPT and IgE. The pattern of allergen sensitization can guide recommendations for avoidance measures and immunotherapy. Thus, this could create a corticosteroid-sparing therapy avenue in these patients, reducing disease severity and resulting visual morbidity.

Interorgan rhythmicity as a feature of healthful metabolism

The finding that animals with circadian gene mutations exhibit diet-induced obesity and metabolic syndrome with hypoinsulinemia revealed a distinct role for the clock in the brain and peripheral tissues. Obesogenic diets disrupt rhythmic sleep/wake patterns, feeding behavior, and transcriptional networks, showing that metabolic signals reciprocally control the clock. Providing access to high-fat diet only during the sleep phase (light period) in mice accelerates weight gain, whereas isocaloric time-restricted feeding during the active period enhances energy expenditure due to circadian induction of adipose thermogenesis. This perspective focuses on advances and unanswered questions in understanding the interorgan circadian control of healthful metabolism.

Potential Biomarkers for Allergic Conjunctival Diseases

Allergic conjunctival diseases (ACDs) are a group of ocular allergies that include allergic conjunctivitis, atopic keratoconjunctivitis, vernal keratoconjunctivitis, and giant papillary conjunctivitis. Although a large body of information exists on the pathophysiology of ACDs, this has not yet lead to the development of clear recommendations and guidelines for the diagnosis of ACDs or development of conclusive and objective diagnostic tools. Identification of objectively measurable biomarkers that represent the molecular and cellular mechanisms associated with ACDs will be an important step toward achieving these aims. This is a comprehensive review of biological markers that have the potential to become "biomarker(s)" for ACDs and aid in the classification, diagnosis, and development of new therapeutic strategies for these group of allergic conditions.

Tear and Serum Eosinophil Cationic Protein Levels in Seasonal Allergic Conjunctivitis

PURPOSE

Eosinophil cationic protein (ECP) levels in tear fluid and sera of patients with seasonal allergic conjunctivitis (SAC) were measured to assess local and systemic eosinophilic activity in SAC. The correlation between ECP levels and disease activity was evaluated.

METHODS

Tears and sera were collected from 21 patients with SAC and 13 healthy control subjects. ECP levels in tears and sera were measured before and 4 weeks after treatment with 0.1% lodoxamide eyedrops. Clinical signs and symptoms of SAC were scored and the correlation of ECP levels with the clinical scores was evaluated.

RESULTS

Tear and serum levels of ECP were significantly increased (p = 0.01, p = 0.02, respectively) in patients with SAC compared with the control subjects, but ECP levels were not correlated with the severity of the disease. Following treatment with topical 0.1% lodoxamide eyedrops, the mean level of ECP in tears decreased significantly (p = 0.02), whereas no significant change was observed in serum ECP levels. Furthermore, a significant decrease in clinical signs and symptoms scores was found after treatment (both p < 0.0001).

CONCLUSIONS

Increased serum and tear ECP levels in patients with SAC confirms that both local and systemic eosinophil activation occurs in SAC. However, clinical signs and symptoms of SAC were not found to be correlated with the degree of eosinophilic activity. Thus ECP does not seem to have an important role in clinical manifestations of SAC.

Diagnostic tools in ocular allergy

Ocular allergy (OA) includes a group of common and less frequent hypersensitivity disorders frequently misdiagnosed and not properly managed. The diagnosis of OA is usually based on clinical history and signs and symptoms, with the support of in vivo and in vitro tests when identification of the specific allergen is required. To date, no specific test is available for the diagnosis of the whole spectrum of the different forms of OA. The lack of recommendations on diagnosis of OA is considered a medical need not only for allergists but also for ophthalmologists. This position paper aims to provide a comprehensive overview of the currently available tools for diagnosing OA to promote a common nomenclature and procedures to be used by different specialists. Questionnaires, sign and symptom grading scales, tests, and potential biomarkers for OA are reviewed. We also identified several unmet needs in the diagnostic tools to generate interest, increase understanding, and inspire further investigations. Tools, recommendations, and algorithms for the diagnosis of OA are proposed for use by both allergists and ophthalmologists. Several unmet needs in the diagnostic tools should be further improved by specific clinical research in OA.

Conjunctival allergen provocation test : guidelines for daily practice

Conjunctival allergen provocation test (CAPT) reproduces the events occurring by instilling an allergen on the ocular surface. This paper is the compilation of a task force focussed on practical aspects of this technique based on the analysis of 131 papers. Main mechanisms involved are reviewed. Indications are diagnosing the allergen(s)-triggering symptoms in IgE-mediated ocular allergy in seasonal, acute or perennial forms of allergic conjunctivitis, especially when the relevance of the allergen is not obvious or in polysensitized patients. Contraindications are limited to ongoing systemic severe pathology, asthma and eye diseases. CAPT should be delayed if receiving systemic steroids or antihistamines. Local treatment should be interrupted according to the half-life of each drug. Prerequisites are as follows: obtaining informed consent; evidencing of an allergen by skin prick tests and/or serum-specific IgE dosages; being able to deal with an unlikely event such as acute asthma exacerbation, urticaria or anaphylaxis, or an exacerbation of allergic conjunctivitis. Allergen extracts should be diluted locally prior to administration. Positive criteria are based on itching or quoted according to a composite score. An alternative scoring is based on itching. CAPT remains underused in daily practice, although it is a safe and simple procedure which can provide valuable clinical information.

In vivo diagnosis of allergic diseases--allergen provocation tests

The allergen challenge test has been the mainstay of diagnosis of allergic diseases for a long time since it offers a direct proof of the clinical relevance of a particular allergen for the allergic disease symptoms and severity. Standardisation and availability for daily practice (including safety issues) are still to be refined but most of the challenge tests have safely crossed the border from research tools to diagnostic tests available for daily practice for a well trained clinical staff.

Prevalence of ocular symptoms in patients with allergic rhinitis: Korean multicenter study

BACKGROUND

Allergic rhinitis (AR) is often accompanied by multiple ocular symptoms. This study aimed to evaluate the prevalence of ocular symptoms and the impact of ocular symptoms on the quality of life in patients with AR.

METHODS

One thousand one hundred seventy-four patients with AR were enrolled from 24 centers in Korea. They were classified into four groups according to the Allergic Rhinitis and Its Impact on Asthma (ARIA) guideline and also classified into perennial AR (PAR) and seasonal AR groups. All patients were asked to complete the questionnaire regarding the presence of ocular symptoms, such as eye itching, watery eyes, and red eyes. The correlation between ocular symptoms and the rest of the quality-of-life areas in the Mini-Rhinoconjunctivitis Quality of Life Questionnaire (Mini-RQLQ) was also asked.

RESULTS

Seven hundred nineteen (61.2%) of 1174 patients had ocular symptoms. In detail, the numbers of patients with eye itching, watery eyes, red eyes, and other ocular symptoms were 605 (51.5%), 313 (26.7%), 207 (17.6%), and 66 (5.6%), respectively. Female patients (72.5%) complained of ocular symptoms more commonly than male patients (55.1%). The patients with moderate-severe persistent AR showed the highest prevalence of ocular symptoms. The correlation coefficients between ocular symptoms and the rest of the quality-of-life areas in the Mini-RQLQ were statistically significant (p < 0.05).

CONCLUSION

Sixty-one percent of Korean AR patients experienced ocular symptoms. The patients who were women and had PAR and more severe AR showed higher prevalence of ocular symptoms. The ocular symptoms might have a significant impact on the quality of life in patients with AR.

Cellular changes in tears associated with keratoconjunctival responses induced by nasal allergy

BACKGROUND

Allergic keratoconjunctivitis occurs in a primary form, caused by an allergic reaction localized in the conjunctiva, and in a secondary form, induced by an allergic reaction originating in the nasal mucosa. Various hypersensitivity mechanisms involved in the keratoconjunctivitis forms result in different keratoconjunctival response types.

PURPOSE

To investigate the cytologic changes in tears during the secondary immediate (SIKCR), late (SLKCR), and delayed (SDYKCR) keratoconjunctival responses.

METHODS

In 61 patients, comprising 20 SIKCRs, 23 SLKCRs, and 18 SDYKCRs, nasal provocation tests (NPTs) with allergens and 61 phosphate-buffered control challenges were repeated and supplemented with cell counting in the tears.

RESULTS

The SIKCR (P<0.01), appearing 10-120 min after the NPT, was associated with increased eosinophil and mast cell counts in tears. The SLKCR (P<0.01), appearing 5-12 h after the NPT, was accompanied by increased counts of eosinophils, neutrophils, basophils, and conjunctival epithelial and goblet cells. The SDYKCR (P<0.05), appearing 24-48 h after NPT, was associated with increased counts of lymphocytes, neutrophils, monocytes, basophils, conjunctival epithelial, corneal epithelial and goblet cells.

CONCLUSIONS

The SIKCR, SLKCR, and SDYKCR, induced by nasal allergy, were associated with different cellular profiles in the tears. The cells, except mast, epithelial and goblet cells, displaying no intracellular changes, migrated probably from the conjunctival capillaries, in response to the factors released during the primary allergic reaction in the nasal mucosa and subsequently penetrating into the conjunctiva. These results demonstrate a causal role of nasal allergy and diagnostic value of NPT combined with recording of ocular features and cellular profiles in tears in some keratoconjunctivitis patients.

Conjunctival provocation with airborne allergen in patients with atopic keratoconjunctivitis

BACKGROUND

Atopic keratoconjunctivitis (AKC) is a chronic eye disease with periods of exacerbations. Many patients experience no obvious seasonal variation, although a majority of patients are allergic to common airborne allergens.

OBJECTIVE

To investigate the allergic reaction, to conjunctival provocation with airborne allergens, in patients with AKC.

METHODS

Eleven patients with AKC and birch and/or grass pollen allergy participated in the study, which was performed outside the pollen season. Five patients with seasonal allergic conjunctivitis (SAC) and five healthy subjects were included for validation purposes. The challenge was performed in one eye with the allergen, to which the patient was reactive, and with dilution buffer in the other eye. Signs and symptoms from both eyes were graded at baseline and at 10 min, 8 and 48 h after provocation. Tear fluid was collected from both eyes for cytokine analyses at baseline and at 8 and 48 h.

RESULTS

A significant change in clinical symptoms and signs, (redness and chemosis) was evident 10 min after provocation compared with baseline (P = 0.005) and compared with the unprovoked eye (P = 0.005) in AKC subjects. These parameters were normalized after 8 and 48 h. A significant increase for IFN-γ (P = 0.021) and IL-6 (P = 0.015), and a near significant increase for IL-10 (P = 0.066) were seen in the tear fluid of the challenged eye at 48 h after provocation vs. baseline and vs. the control eye for IFN-γ (P = 0.005), IL-6 (P = 0.028) and IL-10 (P = 0.008) in AKC subjects.

CONCLUSION AND CLINICAL RELEVANCE

In this single dose allergen provocation study, AKC patients responded with a typical IgE-mediated allergic reaction. An increase in cytokines at 48 h after the challenge was demonstrated and might, with further studies, give us a better understanding of the nature of inflammation in AKC.

Mometasone furoate nasal spray reduces the ocular symptoms of seasonal allergic rhinitis

BACKGROUND

Mometasone furoate nasal spray (MFNS), a potent intranasal corticosteroid with proved efficacy in relieving nasal allergic rhinitis symptoms, has demonstrated effectiveness in improving ocular symptoms associated with seasonal allergic rhinitis (SAR) in retrospective analyses.

OBJECTIVE

We sought to evaluate prospectively the efficacy of MFNS in reducing total ocular symptom scores (TOSSs) and individual ocular symptoms in subjects with SAR.

METHODS

Subjects 12 years or older (n = 429) with moderate-to-severe baseline symptoms were randomized to MFNS, 200 microg once daily, or placebo in this 15-day, double-blind, parallel-group study. Subjects evaluated morning instantaneous TOSSs and daily reflective TOSSs, total nasal symptom scores (TNSSs; both instantaneous TNSSs and reflective TNSSs, respectively), and individual ocular and nasal symptoms. Mean changes from baseline averaged over days 2 to 15 (instantaneous) and days 1 to 15 (reflective) were calculated. Quality of life was assessed by using the Rhinoconjunctivitis Quality of Life Questionnaire.

RESULTS

MFNS treatment yielded significant reductions from baseline versus placebo in instantaneous TOSSs (-0.34, P = .026, coprimary end point), instantaneous TNSSs (-0.88, P < .001, coprimary end point), reflective TOSSs (-0.44, P = .005), and reflective TNSSs (-1.06, P < .001). Significant decreases in all individual reflective ocular symptoms and instantaneous eye itching/burning and eye watering/tearing were observed for MFNS versus placebo (P < .05). Numeric improvements in instantaneous eye redness were seen but did not reach statistical significance. Improvements in Rhinoconjunctivitis Quality of Life Questionnaire total scores and individual symptom domains were achieved with MFNS treatment versus placebo (P < .001). MFNS was well tolerated.

CONCLUSION

This prospective study demonstrates that MFNS significantly reduces ocular symptoms in subjects with SAR.

Late-phase reaction in ocular allergy

PURPOSE OF REVIEW

To determine if the late-phase reaction, which commonly occurs in allergic rhinitis and asthma, is also found in ocular allergy.

RECENT FINDINGS

Using PubMed, 542 articles were found; 18 articles in the allergy and ophthalmology literature were specifically related to late-phase reaction. Ocular late-phase reaction is clinically seen in 50-100% of allergic rhinoconjunctivitis patients, is associated with progression to systemic atopic disorders that is allergic rhinoconjunctivitis and occurs in several forms including biphasic, multiphasic and a prolonged response.

SUMMARY

The existing literature demonstrates that an ocular late-phase reaction also exists and has implications in the development severity of disease, change of reactivity and progression of the atopic disease state from a localized target organ, such as the nose or eye, to a more systemic atopic disorder. The existence of the clinically relevant allergic late-phase response is not only limited to the nose, skin and lungs but also includes the eyes. The appreciation that the late-phase response may be clinically very important as there is a continuum of ocular mast-cell activation during the waking hours of the day, a better understanding of its clinical impact may be a more appropriate focus in the development of future treatments.

Vernal conjunctivitis

Vernal conjunctivitis is a bilateral, seasonal, external ocular inflammatory disease of unknown cause. Afflicted patients experience intense itching, tearing, photophobia, and mucous discharge, and usually demonstrate large cobblestone papillae on their superior tarsal conjunctiva and limbal conjunctiva. It primarily affects children, may be related to atopy, and has environmental and racial predilections. Although usually self-limited, vernal conjunctivitis can result in potentially blinding corneal complications. Treatment of chronic forms of ocular allergies may necessitate collaborative efforts between the ophthalmologist and the allergist or immunologist.

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.

Evolving paradigm in the management of allergic rhinitis-associated ocular symptoms: role of intranasal corticosteroids

BACKGROUND

Along with nasal symptoms, ocular symptoms such as itching, tearing, and redness are common, bothersome components of the allergic rhinitis (AR) profile. Treatment of the patient with ocular allergy symptoms should take into account a variety of factors, including severity of symptoms, convenience/compliance issues, and patient preferences.

OBJECTIVES

To review from the primary care perspective the epidemiology, pathophysiology, and management of ocular symptoms associated with AR, and to evaluate the emerging role of intranasal corticosteroids (INSs).

FINDINGS

A search of the PubMed database identified clinical trials that assessed efficacy of agents in reducing ocular allergy symptoms. Internet searches identified further information including data on over-the-counter agents for treatment of ocular symptoms. Searches were conducted using search terms such as pathophysiology, epidemiology, ocular allergy, quality of life, drug class, and drug names. Primary care physicians are often the first point of contact for patients with seasonal AR (SAR) or perennial AR (PAR) symptoms. Ocular allergy associated with SAR and PAR (seasonal and perennial allergic conjunctivitis, respectively) is characterized by both early- and late-phase reactions, with symptoms often persisting long after allergen exposure. Non-pharmacologic measures such as allergen avoidance, use of artificial tears, and cool compresses are pertinent for all ocular allergy sufferers, but may not afford adequate symptom control. Pharmacotherapy options have traditionally included topical ophthalmic products for cases of isolated ocular symptoms, and oral antihistamines for patients with both nasal and ocular symptoms. However, this paradigm is changing with new evidence regarding the efficacy of INSs in reducing ocular symptoms. A number of meta-analyses and individual studies, most of which studied ocular symptoms as secondary variables, have demonstrated the ocular effects of INSs versus topical and oral antihistamines. Additional prospective studies on this topic are encouraged to provide further evidence for these findings.

CONCLUSIONS

In light of their well-established efficacy in reducing nasal allergy symptoms, INSs offer a comprehensive treatment option in patients with nasal and ocular symptoms. Oral antihistamines and/or topical eye drops may also be necessary depending on symptom control.

Intranasal corticosteroids reduce ocular symptoms associated with allergic rhinitis

OBJECTIVE: Clinical data and recent guidelines support the positive effects of intranasal corticosteroids on allergic rhinitis-associated ocular symptoms. This article reviews the epidemiology and pathophysiology of ocular allergy symptoms and efficacy, tolerability, and potenti mechanisms of action of intranasal corticosteroids in the treatment of this condition.

DATA SOURCES: MEDLINE database.

REVIEW METHODS: A search of pertinent literature identified in vitro, preclinical, and clinical data that involve intranasal corticosteroids in ocular-related studies. Searches that used epidemiology, pathophysiology, drug class and specific agents, and other appropriate search terms were conducted.

RESULTS: Ocular symptoms, common in patients with allergic rhinitis, are associated with reduced quality of life and substantial economic costs. In the conjunctival epithelium, an early, type-1 hypersensitivity reaction occurs after direct allergen exposure. Progression to late-phase response, with recurrence of symptoms and infiltration of inflammatory cells, may occur 4 to 8 hours later and appears to be dose-related. Alteration of nasal ocular reflex pathways may also contribute to ocular symptoms in allergic rhinitis. Clinical data indicate that intranasal corticosteroids significantly reduce total and individual ocular symptoms in subjects with allergic rhinitis. Meta-analyses have found that oral/topical antihistamines are not superior to intranasal corticosteroids in reducing ocular allergy symptoms. Ocular adverse events from intranasal corticosteroids are rare.

CONCLUSION: Intranasal corticosteroids are effective and well-tolerated in the treatment of ocular symptoms associated with allergic rhinitis. Additional studies are needed to better understand the mechanisms underlying the effects of intranasal corticosteroids on ocular symptoms.

Do skin prick and conjunctival provocation tests predict symptom severity in seasonal allergic rhinoconjunctivitis?

BACKGROUND

In the investigation of seasonal allergic rhinoconjunctivitis (SAR), quantitative skin and conjunctival allergen challenge tests are used to measure individual allergen sensitivity. These tests are reproducible and relate well to prevalence but their relationship to symptom severity is less well established.

OBJECTIVE

We wished to determine if quantitative skin prick tests (QSPT) and conjunctival provocation tests (CPTs) using a single grass pollen allergen extract are reproducible and predict symptom severity in SAR.

METHODS

We retrospectively analysed data from 91 participants in a previously published randomized placebo controlled study of low dosage allergen immunotherapy who were randomized to receive placebo treatment. We examined the relationship between pre-seasonal QSPT, CPT and SAR symptoms.

RESULTS

We found a high level of reproducibility when repeated measures were compared for both the QSPT (P < 0.001) and the CPT (P < 0.001) and moderate correlation (0.49) between the standard skin prick test (SPT) and the QSPT (P < 0.001). We found weak negative correlation (-0.27) between the QSPT and the CPT (P < 0.001). We found no correlation between seasonal symptom, use of rescue medication or quality of life (QOL) scores and pre-seasonal QSPT or CPT. Conclusion In the assessment of seasonal rhinoconjunctivitis, quantitative skin and conjunctival allergen challenge tests are strongly reproducible, although there is no correlation between these tests and seasonal symptom, use of rescue medication or QOL scores.

Nonspecific provocation of target organs in allergic diseases: EAACI-GA(2)LEN consensus report

It is widely accepted that nonspecific tissue reactivity is a distinct pathophysiological hallmark of allergic diseases, influenced by genetic and environmental factors different from those involved in causing sensitization and allergen response of target organs. This consensus document aims at reviewing procedures currently used for nonspecific provocation of the bronchi, nose and eye and for measuring their responsiveness to nonspecific stimuli.

Les tests de provocation conjonctivaux

The conjunctival provocation test (CPT) is a human model of ocular allergy that has been used to study the ocular response to allergenic stimuli and to evaluate antiallergic therapy. Considerable useful information has been gained on the ocular allergic response and drug efficacy using the conjunctival provocation test and naturally occurring seasonal allergic conjunctivitis. The safety and the efficacy of these CPTs has resulted in many authors using this tool in the etiologic diagnosis of allergic conjunctivitis. This article summarizes the possibilities of these CPTs as a tool for the study, evaluation, diagnosis, and therapeutic follow-up of allergic conjunctivitis.

Efficacy of levocabastine hydrochloride ophthalmic suspension in the conjunctival allergen challenge test in Japanese subjects with seasonal allergic conjunctivitis

BACKGROUND

This study was conducted to investigate the efficacy and safety of 0.025% levocabastine hydrochloride in Japanese subjects with seasonal allergic conjunctivitis and its duration of action using the conjunctival allergen challenge (CAC) test.

METHODS

Twenty-four asymptomatic subjects were randomized to instill 0.025% levocabastine ophthalmic suspension in one eye and vehicle in the other eye 10 minutes before the CAC test. Signs and symptoms of allergic conjunctivitis were scored 10, 15, and 25 minutes after the CAC test. The duration of drug effects was also evaluated by allergen rechallenge 4 hours after levocabastine administration. The itching score for each eye as the primary efficacy endpoint was assessed 15 minutes after the CAC test using a 5-point scale.

RESULTS

The mean itching score in the levocabastine-treated group was 0.08 +/- 0.06, which was significantly lower than the mean score of 1.98 +/- 0.16 in the vehicle group (P < 0.0001). The redness and chemosis of the conjunctiva were also improved significantly compared with the vehicle group. Levocabastine showed prolonged efficacy in inhibiting itching (0.42 +/- 0.12 vs 0.94 +/- 0.17, P < 0.0002) and redness (1.04 +/- 0.18 vs 1.42 +/- 0.22, P < 0.01) of the conjunctiva upon the rechallenge test. No significant topical or systemic adverse safety findings were observed in the levocabastine group.

CONCLUSIONS

The results indicate that 0.025% levocabastine ophthalmic suspension is effective and safe in the treatment of allergic conjunctivitis with a duration of action of at least 4 h.

Emerging drugs for ocular allergy

Ocular allergy is a common condition that usually affects the conjunctiva of the eye and is, therefore, often referred to as allergic conjunctivitis. The severity of the disease can range from mild itching and redness, as seen in seasonal allergic conjunctivitis, to the more severe, sight-threatening forms such as vernal and atopic keratoconjunctivitis. The central mechanism in the pathogenesis of these diseases is IgE-mediated mast cell degranulation and activation of T lymphocytes, eosinophils and conjunctival structural cells. The pharmacotherapy of allergic conjunctivitis consists of several classes of drugs: antihistamines, mast cell stabilisers, dual-acting agents and corticosteroids. None of the available drugs completely abolishes the development of ocular allergy. For this reason, new topical antiallergic/anti-inflammatory agents are currently and continually under clinical trials. This review provides a background to ocular allergic diseases, the medical need for therapy and current and potential new treatments.

A review of the use of olopatadine in allergic conjunctivitis

Ocular allergies are very common and range in intensity from mild, self-resolving, acute conditions to serious, chronic disease that can severely affect vision. The vast majority of sufferers experience relatively mild symptoms, which are often seasonal in nature. Treatments should be simple, comfortable and very safe. They should be able to respond to an ongoing attack but also provide long-term relief from symptoms. Mast cell degranulation is central to all forms of ocular allergic disease and so treatment has concentrated on preventing this process or antagonizing the effects of the primary mediator, histamine. Olopatadine is a relatively new selective H1 antagonist that has mast cell stabilizing properties and has been shown to affect release of TNFalpha and various cytokines from conjunctival epithelial cells. This paper reviews the local ocular use of olopatadine and discusses the place of the drug in the treatment of allergic eye disease.

Provocation testing with recombinant allergens

In the past few decades, DNA technology has enabled the production of defined recombinant allergen molecules for diagnostic and therapeutic purposes. Recombinant allergens containing most of the relevant IgE epitopes present in natural allergen sources are now available and allergen proteins can be produced that are identical, without biological or batch-to-batch variation. A great advantage of recombinant allergens is that they can be used for component-resolved diagnostics, which makes it possible to establish the patient's individual IgE reactivity profile before therapy is selected. However, before recombinant allergens can be applied in clinical practice their biological activity has to be carefully investigated in vivo. We here describe the most commonly used provocation methods (skin tests (prick and intradermal), nasal, bronchial, and conjunctival provocations) and how they can be performed. We also discuss the results so far obtained with in vivo testing using recombinant allergens and envisage their future use for immunotherapy.

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.

Vernal keratoconjunctivitis

Vernal keratoconjunctivitis (VKC) is an allergic eye disease that especially affects young boys. The most common symptoms are itching, photophobia, burning, and tearing. The most common signs are giant papillae, superficial keratitis, and conjunctival hyperaemia. Patients with VKC frequently have a family or medical history of atopic diseases, such as asthma, rhinitis, and eczema. However, VKC is not associated with a positive skin test or RAST in 42-47% of patients, confirming that it is not solely an IgE-mediated disease. On the basis of challenge studies as well as immunohistochemical and mediator studies, a Th2-driven mechanism with the involvement of mast cells, eosinophils, and lymphocytes has been suggested. Th2 lymphocytes are responsible for both hyperproduction of IgE (interleukin 4, IL-4) and for differentiation and activation of mast cells (IL-3) and eosinophils (IL-5). Other studies have demonstrated the involvement of neural factors such as substance P and NGF in the pathogenesis of VKC, and the overexpression of oestrogen and progesterone receptors in the conjunctiva of VKC patients has introduced the possible involvement of sex hormones. Thus, the pathogenesis of VKC is probably multifactorial, with the interaction of the immune, nervous, and endocrine systems. The clinical management of VKC requires a swift diagnosis, correct therapy, and evaluation of the prognosis. The diagnosis is generally based on the signs and symptoms of the disease, but in difficult cases can be aided by conjunctival scraping, demonstrating the presence of infiltrating eosinophils. Therapeutic options are many, in most cases topical, and should be chosen on the basis of the severity of the disease. The most effective drugs, steroids, should however be carefully administered, and only for brief periods, to avoid secondary development of glaucoma.A 2% solution of cyclosporine in olive oil or in castor oil should be considered as an alternative. The long-term prognosis of patients is generally good; however 6% of patients develop corneal damage, cataract, or glaucoma.

Atopic keratoconjunctivitis

Atopic keratoconjunctivitis (AKC) represents a disease usually classified under the term of allergic conjunctivitis together with seasonal allergic conjunctivitis (SAC), perennial allergic conjunctivitis (PAC) and vernal keratoconjunctivitis (VKC). However, AKC and VKC have clinical and pathophysiological features quite different from SAC and PAC, in spite of some common markers of allergy. This article aims to review personal studies suggesting that allergic conjunctivitis (similarly to asthma, rhinitis and atopic dermatitis) is a heterogeneous disease entity with different preferential pathogenetic mechanisms and a spectrum of clinical expression which varies according to individual cases. AKC and VKC may thus represent a model of atopy quite distinct from the classical type-1 hypersensitivity mechanism.

Allergic chronic inflammation of the ocular surface in vernal keratoconjunctivitis

PURPOSE OF REVIEW

The purpose of this review is to describe the new immunopathologic features of vernal keratoconjunctivitis: the involvement of cytokines, growth factors, cells, mediators and neurotransmitters, as well as the mechanism leading to tissue remodelling.

RECENT FINDINGS

Vernal keratoconjunctivitis is an allergic eye disease affecting young boys living in a warm climate. It is characterized by conjunctival giant papillae, hyperemia and frequent involvement of the cornea. Approximately 50% of the patients with vernal keratoconjunctivitis do not have a family or medical history of atopic diseases, and do not show IgE sensitization, suggesting that this disease is not solely IgE mediated. Vernal keratoconjunctivitis is a Th2 lymphocyte driven disease with a Th2 cytokine derived pattern, increased levels of mRNA for IL-3, IL-4, IL-5 and IL-13. Th2 lymphocytes induce IgE hyperproduction, activation of mast cells, eosinophils, neutrophils and their toxic products. An overexpression of adhesion molecules, RANTES, eotaxin and metalloproteinases contribute to chronic inflammation. A role for substance P and nerve growth factor has been postulated, as well as for other growth factors (epidermal growth factor, fibroblast growth factor and transforming growth factor beta 1) that induce fibroblast growth and new collagen production. Recent studies have also pointed out the role of resident conjunctival cells, such as epithelial cells and fibroblasts, in the inflammatory and remodelling process of vernal keratoconjunctivitis. The pathogenesis of the condition is probably multifactorial, with the interaction of the immune, nervous and endocrine systems.

SUMMARY

Vernal keratoconjunctivitis is a chronic inflammatory and potentially blinding disease. Understanding of the complex interactions and cross talk between cells, cytokines and other mediators is relevant for new therapeutic approaches.

Animal models of ocular allergy and their clinical correlations

Ocular allergic diseases represent a wide spectrum of disorders, from the acute self-limited, mild form of seasonal allergic conjunctivitis to the chronic, severe, sight-threatening atopic keratoconjunctivitis. The least problematic forms are the most prevalent, and several animal models have contributed to elucidate their etiopathogenetic mechanisms and have served to test numerous anti-allergic compounds. The most severe and chronic, although less prevalent, ocular allergic problems have not benefited from a similar advance, with the subsequent lack of full understanding and a limited therapeutic armamentarium. Research in this field is currently concentrating efforts in developing more protracted models of ocular allergic inflammation involving the cornea and mimicking more closely the human disease caused by chronic ocular allergy. Most recent experimental models are demonstrating that inhibiting Th2 cells and their secreted cytokines might be one important therapeutic target for inhibiting chronic allergic inflammation in the ocular surface.

Modulation of IL-8 and RANTES release in human conjunctival epithelial cells: primary cells and cell line compared and contrasted

PURPOSE

Recent research indicates that epithelial cells of the ocular surface can contribute to the allergic reaction by the release of inflammatory and/or chemotactic mediators. In this study, the role of two inflammatory mediators, previously identified in the tear film of ocular allergy subjects, TNF-alpha and IFN-gamma, were evaluated for their effect on the release of two chemotactic mediators, IL-8 and RANTES, from cultured human conjunctival epithelial cells.

METHODS

Human conjunctival epithelial cells (primary cells or HC0597 cell line) were grown to confluence and stimulated with various concentrations of TNF-alpha, IFN-gamma, or a combination of both. Supernatants were collected at 6, 24, and 48 hours and stored frozen for subsequent ELISA analyses of RANTES and IL-8.

RESULTS

RANTES and IL-8 release from HC0597 cells was stimulated in a dose- and time-dependent manner following treatment with TNF-alpha. However, only RANTES release was modulated by IFN-gamma treatment. Treatment of HC0597 cells with both TNF-alpha and IFN-gamma resulted in a synergistic increase in the release of RANTES. This synergistic effect was confirmed using primary cultures of human conjunctival epithelial cells.

CONCLUSIONS

Stimulation of conjunctival epithelium with proinflammatory mediators, TNF-alpha and/or IFN-gamma, generated the release of the chemotactic factors IL-8 and RANTES, which could act to prolong inflammation. These two chemokines may prolong inflammation by recruiting eosinophils to the ocular surface. This is the first study to compare chemokine release in a cell line and primary cells; similar chemokine release after mediator stimulation was demonstrated, indicating that the two cell types are phenotypically similar.

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.

Efficacy and safety of desonide phosphate for the treatment of allergic conjunctivitis

PURPOSE

To study the safety and efficacy of the topical corticosteroid, desonide 0.25% ophthalmic solution, for inhibition of the clinical allergic reaction induced by conjunctival provocation (CPT) and for the treatment of seasonal allergic conjunctivitis (SAC).

METHODS

For the CPT study, 12 allergic but inactive patients were exposed in both eyes to increasing doses of a specific allergen until a positive bilateral, symmetrical early- and late-phase reaction was obtained. After 2 weeks the last positive dose was readministrated and their positive response confirmed. After an additional 2 weeks, CPT was performed 30 minutes after topical administration of desonide in one eye and placebo in the contralateral eye (Group A) or after topical desonide or placebo four times a day for 2 days (Group B). Clinical signs and symptoms were recorded after 15, 30, and 60 minutes, and after 6 hours. Regarding the seasonal study, 96 patients with active SAC were treated bilaterally with either desonide or fluorometholone for 3 weeks, and allergic signs and symptoms evaluated at regular intervals. The safety of the drugs was assessed by identification of any side effects or adverse events of any kind.

RESULTS

For the CPT study: individual itching and redness, and the sum score for signs and symptoms were all statistically (p < 0.05) and clinically (greater than 1 change between treated eyes) significantly lower in desonide versus placebo eyes. Both early- and late-phase reactions were reduced by desonide pretreatment. Seasonal study: desonide and fluorometholone were both highly effective in reducing itching, tearing, and conjunctival hyperemia over time (p < 0.0001). Both drugs appeared safe, with no statistically significant changes in IOP observed with either treatment.

CONCLUSIONS

Desonide has a significant therapeutic effect on both the induced conjunctival early- and late-allergic reaction and in active SAC. It was also safe, with no side effects such as increases in intraocular pressure observed by physician or patient.

Comparison of the clinical efficacy and tolerability of olopatadine hydrochloride 0.1% ophthalmic solution and loteprednol etabonate 0.2% ophthalmic suspension in the conjunctival allergen challenge model

BACKGROUND

Olopatadine hydrochloride 0.1% ophthalmic solution and loteprednol etabonate 0.2% ophthalmic suspension are topical antiallergic agents indicated for treatment of the signs and symptoms of allergic conjunctivitis and seasonal allergic conjunctivitis (SAC), respectively.

OBJECTIVE

The purpose of this study was to compare the efficacy and tolerability of olopatadine, loteprednol, and placebo in inhibiting the early-phase allergic reaction (within 30 minutes) after conjunctival allergen challenge (CAC).

METHODS

This was a single-center, randomized, double-masked, parallel-controlled CAC study. It consisted of 3 visits, with CAC performed at visit 1, confirmation and randomization at visit 2, and evaluation of the treatments at visit 3. Subjects with a history of allergic conjunctivitis were randomized to receive olopatadine, loteprednol, or placebo in a 2:2:1 ratio. Because loteprednol requires a loading period to achieve maximum efficacy, subjects assigned to this treatment received loteprednol QID bilaterally for a 14-day period; the olopatadine and placebo groups received placebo QID bilaterally during this period. At the evaluation visit, subjects received 1 drop of the assigned treatment in each eye. Fifteen minutes later, they were challenged with allergen. Subjects evaluated itching at 3, 5, and 10 minutes after challenge using a standardized 5-point scale; the investigator evaluated redness at 10, 15, and 20 minutes after challenge. Intraocular pressure (IOP) was measured at baseline and after the 14-day loading period. Nonparametric analyses were performed on the change from visit 2 to visit 3 in mean itching and redness scores for each time point, and on the change in mean IOP from visit 1 to visit 3.

RESULTS

Fifty subjects (86% white; 42% male, 58% female; age range, 21-71 years) were enrolled and completed the study (20 olopatadine, 20 loteprednol, 10 placebo). The allergens to which subjects reacted were ragweed pollen (40%), cat hair or dander (30%), grass pollen (24%), and tree pollen (6%). The difference in inhibition of itching and redness was clinically significant (> or =1 unit difference) and statistically significant (P < 0.05) in favor of olopatadine compared with loteprednol at all 3 time points. The loteprednol group had a statistically significant increase in IOP after 2 weeks of treatment (P < 0.001).

CONCLUSION

In the population studied, olopatadine was more efficacious than loteprednol in reducing the acute signs and symptoms of SAC during the early phase of the ocular allergic reaction and appeared to be better tolerated.

Allergic and immunologic disorders of the eye. Part II: ocular allergy

Allergy affects more than 15% of the world population, and some studies have shown that up 30% of the US population has some form of allergy. Most of these patients have various target organs for their allergies, and most have ocular involvement. The ocular component may be the most prominent and sometimes disabling feature of their allergy. Some are affected for only a few weeks to months, whereas others have symptoms that last throughout the year. The seasonal forms may present to clinical allergists, whereas the more chronic forms may present to ophthalmologists. Thus, in the second of this 2-part review series (Part I: Ocular Immunology appeared in the November issue of the Journal), an overview is provided of the spectrum of ocular allergy that ranges from acute seasonal allergic conjunctivitis to chronic variants of atopic keratoconjunctivitis. With a better understanding of the immunologic mechanisms, we now can develop better treatment approaches and design further research in intervention of allergic eye diseases.

Tear and conjunctival changes during the allergen-induced early- and late-phase responses

BACKGROUND

Allergic eye disease is common, but little is known about the underlying disease mechanisms. Conjunctival allergen challenge causes symptoms similar to those of seasonal allergic conjunctivitis and is a useful model to study.

OBJECTIVE

We have used allergen challenge to investigate the course of the ocular response, tear inflammatory mediators, tissue adhesion protein expression, and cellular infiltration.

METHODS

Eighteen atopic patients and 4 nonatopic control subjects were challenged with extracted mixed grass or Dermatophagoides pteronyssinus in one eye and control vehicle in the other. The clinical response was recorded, and tears were collected over a 6-hour period. Conjunctival biopsy specimens were taken from the challenged eye at 6 or 24 hours.

RESULTS

An early-phase response (maximal at 20 minutes) showed a significant increase in tear histamine and tryptase levels, reducing to control levels again by 40 minutes. At 6 hours, a late-phase response occurred with increased symptoms, a second peak of tear histamine and eosinophil cationic protein but not tryptase, upregulation of the adhesion molecules E-selectin and intercellular adhesion molecule, and a cellular infiltrate of mast cells, neutrophils, eosinophils, macrophages, and basophils, with T cells increased only in bulbar biopsy specimens.

CONCLUSIONS

The early peaks of tear histamine plus tryptase indicate that the mast cell is responsible for the early-phase response, but basophils may be involved in the late-phase response. Both tear and biopsy findings underline the significance of the late-phase response as the transition between a type I response and clinical disease.