Efficacy of lodoxamide eye drops on mast cells and eosinophils after allergen challenge in allergic conjunctivitis

Sustained Delivery of Olopatadine from Vitamin-E Loaded Contact Lenses

Purpose: Topical antihistamines, such as olopatadine hydrochloride, an H1 receptor antagonist, are commonly prescribed for treating allergic conjunctivitis. Drug delivery via eye drops has many deficiencies including a short residence time due to tear drainage via the nasolacrimal duct, which results in a low bioavailability and potential for side effects. These deficiencies could be mitigated by a drug-eluting contact lens such as the recently approved ACUVUE® THERAVISION™ WITH KETOTIFEN which is a daily disposable etafilcon, a drug-eluting contact lens with ketotifen (19 μg per lens). Here, we investigate the feasibility of designing a drug-eluting lens with sustained release of olopatadine for treating allergies using an extended wear lens. Methods: Nanobarrier depots composed of vitamin-E (VE) are formed through direct entrapment by ethanol-driven swelling. The drug-loaded lenses are characterized for transparency and water content. In vitro release is measured under sink conditions and fitted to a diffusion control release model to determine diffusivity and partition coefficient. Results: In vitro studies indicate that ACUVUE OASYS® and ACUVUE TruEye™ lenses loaded with ∼0.3 g of VE/g of hydrogel effectively prolong olopatadine dynamics by 7-fold and 375-fold, respectively. Incorporation of VE into the lenses retains visible light transmission and other properties. Conclusion: The VE incorporation in commercial lenses significantly increases the release duration offering the possibility of antiallergy extended wear lenses.

Management of vernal keratoconjunctivitis: Navigating a changing treatment landscape

Vernal keratoconjunctivitis (VKC) is a chronic, progressive, and potentially sight-threatening form of ocular inflammatory disease that primarily affects children and young adults. Prevalence varies by region, ranging from <2 per 10,000 in the United States to as high as 1,100 per 10,000 in parts of Africa. The rarity of VKC in developed countries can make differential diagnosis challenging, and treatment is often delayed until the disease is advanced, and symptoms are significantly impacting patients' quality of life. Although once viewed primarily as an immunoglobulin E-mediated condition, approximately 50% of patients with VKC do not exhibit allergic sensitization. It is now recognized that the immunopathology of VKC involves multiple inflammatory pathways that lead to the signs, symptoms, and conjunctival eosinophilic and fibroproliferative lesions that are a hallmark of the disease. We examine the evolution of our understanding of the immunopathology of VKC, the expanding VKC treatment armamentarium, the clinical implications of emerging treatment approaches, and future directions for VKC research and practice.

Tryptase and Exogenous Trypsin: Mechanisms and Ophthalmic Applications

Ocular injuries caused by inflammation, surgery or accidents are subject to a physiological healing process that ultimately restores the structure and function of the damaged tissue. Tryptase and trypsin are essential component of this process and they play a role in promoting and reducing the inflammatory response of tissues, respectively. Following injury, tryptase is endogenously produced by mast cells and can exacerbate the inflammatory response both by stimulating neutrophil secretion, and through its agonist action on proteinase-activated receptor 2 (PAR2). In contrast, exogenously introduced trypsin promotes wound healing by attenuating inflammatory responses, reducing oedema and protecting against infection. Thus, trypsin may help resolve ocular inflammatory symptoms and promote faster recovery from acute tissue injury associated with ophthalmic diseases. This article describes the roles of tryptase and exogenous trypsin in affected tissues after onset of ocular injury, and the clinical applications of trypsin injection.

Understanding Vernal Keratoconjunctivitis: Beyond Allergic Mechanisms

Vernal keratoconjunctivitis (VKC) is a chronic, recurrent, inflammatory disease of the cornea and conjunctiva mostly affecting boys in prepubertal age. VKC recurrence is characterized by intense symptoms of itching, redness, and photophobia associated with corneal damage, impairment of visual function, and quality of life. The pathogenesis of VKC has not yet been completely understood, and it is still controversial. In fact, VKC is considered an ocular allergic disease due to the involvement of immunoglobulin E, eosinophils, and mast cells, and of a lymphocyte T-helper type 2 reaction. However, approximately half of VKC patients have negative allergological history and testing, suggesting that other pathogenic mechanisms participate in VKC development and severity. Specifically, evidence suggests that genetic, endocrine, neuronal factors and an imbalance of innate immunity are involved in the pathogenesis of VKC. The purpose of this review is to summarize evidence on the pathogenic role of innate immunity, neuroimmune reaction, and hormonal changes in VKC. Increasing understanding of the pathogenic mechanisms behind VKC may lead to the identification of novel biomarkers for diagnosis and/or potential therapeutic targets in order to improve the management of this challenging condition.

Potential clinical drugs as covalent inhibitors of the priming proteases of the spike protein of SARS-CoV-2

In less than eight months, the COVID-19 (coronavirus disease 2019) caused by the SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) virus has resulted in over 20,000,000 confirmed cases and over 700,000 deaths around the world. With the increasing worldwide spreading of this disease, the lack of effective drugs against SARS-CoV-2 infection makes the situation even more dangerous and unpredictable. Although many forces are speeding up to develop prevention and treatment therapeutics, it is unlikely that any de novo drugs will be available in months. Drug repurposing holds the promise to significantly save the time for drug development, since it could use existing clinic drugs to treat new diseases. Based on the “steric-clashes alleviating receptor (SCAR)” strategy developed in our lab recently, we screened the library of clinic and investigational drugs, and identified nine drugs that might be repurposed as covalent inhibitors of the priming proteases (cathepsin B, cathepsin L, and TMPRSS2) of the spike protein of SARS-CoV-2. Among these hits, five are known covalent inhibitors, and one is an anti-virus drug. Therefore, we hope our work would provide rational and timely help for developing anti-SARS-CoV-2 drugs.

Neurotrophic factors and nerve growth factor in ocular allergy

PURPOSE OF REVIEW

During allergic reaction, nervous and immune systems mutually interact through release of mediators, including neurotrophic factors and nerve growth factor (NGF). These mediators modulate allergic reaction through binding their receptors expressed by immune and structural cells and by stimulating neuropeptide release by nerves. The role of neuropeptides and NGF has been demonstrated in allergic asthma and rhinitis, and, to a lesser extent, in allergic conjunctivitis. The aim of this review are to elucidate the evidence of the role of NGF and neuropeptides in the pathogenesis of allergic conjunctivitis.

RECENT FINDINGS

NGF modulates allergic reaction by stimulating release of cytokines, inflammatory mediators and neuropeptides by immune and structural cells and nerve endings at the site of inflammation. Evidence showed that local and systemic NGF levels increase in patients with allergic conjunctivitis, including allergic rhinoconjuncivitis, vernal keratoconjunctivitis and atopic keratoconjunctivitis. We recently described an increase of conjunctival p75NTR expression in patients with allergic rhinoconjuncivitis, and an increase of tear levels of NGF after conjunctival provocation test with allergen.

SUMMARY

NGF modulates ocular allergic reaction. Increasing understanding of the role of neuropeptides in allergic conjunctivitis may pave the way to the development of novel therapeutic approaches and improvement of patients' management.

Omalizumab in three children with severe vernal keratoconjunctivitis

Background

Vernal keratoconjunctivitis (VKC) is a rare, recurrent form of ocular allergy that can be refractory to topical and systemic treatment. It typically presents as acute and chronic keratoconjunctival inflammation that may lead to visual impairment due to corneal ulcers and scaring. Patients often suffer from atopic IgE-driven comorbidities, especially atopic eczema. Children are frequently affected and often do not tolerate topical treatment well, especially if photophobia and pain impair therapy adherence. We present three children with severe VKC who were not controlled by first- and second-line topical and systemic therapy and finally responded to treatment with the monoclonal anti-IgE antibody omalizumab as third-line treatment.

Methods and results

We retrospectively analyzed three patients with VKC having failed response to first- and second-line treatment. All three boys had very early allergic rhinoconjunctivitis from age 1–3 with polysensitization: birch, grass pollen, house dust mite, and/or pets. All received subcutaneous or sublingual immunotherapy (SCIT/SLIT) for birch and/or grass pollen without major success. Two patients had comorbidities: allergic asthma and severe atopic dermatitis (AD). For at least 6 months after the first administration, monoclonal anti-IgE antibody omalizumab (150 or 300 mg) was administered subcutaneously every 2–6 weeks in all patients achieving improvement of the clinical grading scale from VKC grade 3–4 to grade 1–2. One patient had a relapse mainly of his AD and achieved complete control of AD and VKC by introduction of dupilumab.

Conclusion

Although the clinical benefit of omalizumab in asthma and chronic spontaneous urticaria (CSU) has been established in several clinical trials, there are very little data about its effect on severe VKC. In addition to few previously reported cases we can report the rapid effectiveness of omalizumab in VKC clinically and in terms of quality of life. Randomized trials are needed to include omalizumab in third-line treatment of VKC for prevention of visual impairment and further sequelae such as corneal damage.

Management of vernal keratoconjunctivitis in children in Saudi Arabia

Vernal keratoconjunctivitis is a chronic inflammatory disease of the ocular surface and one of the worst types of allergic conjunctival diseases. Because of its chronic nature, it can damage the cornea, resulting in sight-threatening complications if left untreated. The disease affects mainly young children starting around the age of 7 years. We used keywords to search for published English articles in PUBMED, Google Scholar, EMBASE, and Cochrane Database of Systematic Reviews. Most of the published literature is focusing on general management of the disease and few publications focusing on treatment in the pediatric age group. We highlight the importance of how is the topical management differs between age groups. We focused on the importance of doing cycloplegic refraction for each child as the risk of keratoconus and oblique astigmatism is high in these cases. Furthermore, we highlight the importance of using eye lubricants as a therapeutic and preventive tool for the attacks of the disease. We highlight that most of the recent effective medications (especially the off-label ones) are not available in Saudi Arabia, such as tacrolimus, and some are only available to be prepared in tertiary center pharmacies as Cyclosporine A with higher concentrations.

Comparison of Topical 0.05% Levocabastine and 0.1% Lodoxamide in Patients with Allergic Conjunctivitis

Purpose

The aim of the study was to assess the efficacy and safety of 0.05% levocabastine eyedrops (H1 receptor blocker given BID + vehicle BID) compared with 0.1% lodoxamide ophthalmic solution (mast-cell stabilizer instilled QID) in reducing ocular signs and symptoms of allergic conjunctivitis.

Methods

A randomized, double-masked, parallel-group study was conducted in seven centres in France, in which 93 patients suffering from seasonal or perennial allergic conjunctivitis were randomly allocated to either 0.05% levocabastine (n = 47) or 0.1% lodoxamide (n = 46) in both eyes for a 14-day period. Efficacy was evaluated by subjective (prickling, burning, photophobia, itching) and objective (redness, chemosis, eyelid edema, tearing) sign scores at visits on days 7 and 14, and from data noted daily by the patient in a self-evaluation form. Safety was assessed as tolerance upon instillation and adverse event reports.

Results

The ocular allergy symptom and sign scores were comparable in the two treatment groups at baseline. With time, statistically and clinically significant reductions (p < 0.001) from baseline were observed for the subjective and objective scores, with no difference between the treatment groups. After the first instillation, signs were alleviated more rapidly in levocabastine-treated patients than in the lodoxamide group (p < 0.001). Overall assessments by the patient and investigator were similar in both groups. No serious adverse events were reported.

Conclusions

Levocabastine ophthalmic suspension 0.05% (BID) appears to be as effective and safe as lodoxamide 0.1% (QID) in the management of allergic conjunctivitis.

Efficacy and safety of 0.1% lodoxamide for the long-term treatment of superior limbic keratoconjunctivitis

PURPOSE

To report the therapeutic efficacy and safety of topical 0.1% lodoxamide in the long-term treatment of superior limbic keratoconjunctivitis.

METHODS

Sixty-seven eyes of 34 patients with active SLK were studied. Therapeutic response was analyzed according to modified-Ohashi parameters. All eyes were treated with 0.1% lodoxamide twice daily, and those with moderate or severe inflammation received a short course (7-14 days) of 0.1% fluorometholone acetate at presentation and during a relapse. Patients were evaluated at regular intervals and followed up for ≥3 months on continuous therapy. Primary endpoints included inflammatory response; rates of inflammatory control and remission; relapses while on therapy or on remission; and therapeutic failure rate.

RESULTS

The mean follow-up time on lodoxamide therapy was 15.3 months. The majority of eyes (82.0%) achieved control of inflammation in a mean time of 2.2 months. Of these, 42 (76.3%) eyes remained under control while on therapy for 13.8 months. There was a significant improvement of SLK-related signs by the third month on therapy (p < 0.05). A total of 24 (35.8%) eyes achieved remission. Relapses presented in 12 (18.0%) treated eyes and in 4 (16.6%) eyes on remission. Only 5 (7.4%) eyes failed to respond to therapy. In the majority of cases (95.3%), lodoxamide 0.1% was well tolerated and minor adverse effects not requiring stopping the medication were reported in only 4.7% of patients.

CONCLUSIONS

Lodoxamide 0.1% is an efficacious therapeutic alternative for the treatment of active and chronic SLK. This medication has proved to be safe and well tolerated.

Vernal keratoconjunctivitis: a severe allergic eye disease with remodeling changes

Vernal keratoconjunctivitis (VKC) is an unusually severe sight-threatening allergic eye disease, occurring mainly in children. Conventional therapy for allergic conjunctivitis is generally not adequate for VKC. Pediatricians and allergists are often not familiar with the severe clinical symptoms and signs of VKC. As untreated VKC can lead to permanent visual loss, pediatric allergists should be aware of the management and therapeutic options for this disease to allow patients to enter clinical remission with the least side effects and sequelae. Children with VKC present with severe ocular symptoms, that is, severe eye itching and irritation, constant tearing, red eye, eye discharge, and photophobia. On examination, giant papillae are frequently observed on the upper tarsal conjunctiva (cobblestoning appearance), with some developing gelatinous infiltrations around the limbus surrounding the cornea (Horner-Trantas dot). Conjunctival injections are mostly severe with thick mucus ropy discharge. Eosinophils are the predominant cells found in the tears and eye discharge. Common therapies include topical antihistamines and dual-acting agents, such as lodoxamide and olopatadine. These are infrequently sufficient and topical corticosteroids are often required for the treatment of flare ups. Ocular surface remodeling leads to severe suffering and complications, such as corneal ulcers/scars. Other complications include side effects from chronic topical steroids use, such as increased intraocular pressure, glaucoma, cataract and infections. Alternative therapies for VKC include immunomodulators, such as cyclosporine A and tacrolimus. Surgery is reserved for those with complications and should be handled by ophthalmologists with special expertise. Newer research on the pathogenesis of VKC is reviewed in this article. Vernal keratoconjunctivitis is a very important allergic eye disease in children. Complications and remodeling changes are unique and can lead to blindness. Understanding of pathogenesis of VKC may lead to better therapy for these unfortunate patients.

Management of vernal keratoconjunctivitis

Vernal keratoconjunctivitis (VKC) is a relatively rare, chronic form of ocular allergy that can potentially cause severe visual complications. Affecting mainly children and young adults, it is an IgE- and T cell-mediated disease, leading to a chronic inflammation in which eosinophil, lymphocyte and structural cell activation are involved. Treatment of VKC requires a multiple approach that includes conservative measures and pharmacologic treatment. Patients and parents should be made aware of the long duration of disease, its chronic evolution and possible complications. Treatment should be based on the duration and frequency of symptoms and the severity of corneal involvement. Mast cell stabilizers and antihistamines have been proven to be effective for the treatment of mild to moderate forms of VKC. In the most severe cases, topical steroids can be used as rescue medication to reduce conjunctival and corneal inflammation. Immunomodulators that have been investigated for VKC treatment include topical ocular preparations of cyclosporine A and tacrolimus. Topical cyclosporine A has been proven to be effective in the long-term treatment of VKC, significantly improving signs and symptoms without significant side effects.

Prospective, multicenter demographic and epidemiological study on vernal keratoconjunctivitis: a glimpse of ocular surface in Italian population

PURPOSE

To evaluate the frequency and epidemiological features of vernal keratoconjunctivitis (VKC) in Italy.

METHODS

a specific electronic clinical chart for vernal keratoconjunctivitis was created to standardize: 1) medical history; 2) diagnostic criteria; 3) signs and symptoms; and 4) treatments. This study involved 6 Italian referral centers for ocular surface diseases: between March 2005 and March 2006, all referred patients were included, clinical data collected and statistically examined.

RESULTS

The mean age of the vernal keratoconjunctivitis population (n = 156) was 13.8 +/- 8.8 with 64.1% of subjects under 14 years of age and a male/female ratio of 3.5:1. Among VKC patients, 48.7% showed associated systemic allergic diseases. Only 32.1% of patients were positive for RAST and/or prick test. The limbal form (53.8%) was the most frequent subtype of vernal keratoconjunctivitis. Approximately 9% of patients showed a severe form of vernal keratoconjunctivitis. At the first visit patients were treated with: multiple action or mast cell stabilizer eye drops (58.1% and 41.3% of cases, respectively), topical corticosteroids alone (0.6%) or in association (26.8% of cases). All patients used topical steroids at least once in the studied year. Systemic antihistamine therapy was used by 25.6% of patients. In this cohort, 32.7% of patients required two or more examinations per year for exacerbations of their symptoms.

CONCLUSION

Vernal keratoconjunctivitis is a severe ocular condition that mainly affects young males. Vernal keratoconjunctivitis is characterized by different clinical features and therapeutic responses, suggesting the need for a standardized therapeutic approach on the basis of a grading of disease severity.

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.

Topical 2% cyclosporine A in preservative-free artificial tears for the treatment of vernal keratoconjunctivitis

BACKGROUND

A double-masked, placebo-controlled trial to evaluate the short-term efficacy and safety of topical 2% cyclosporine A in preservative-free artificial tears for patients with vernal keratoconjunctivitis.

METHODS

Twenty patients with severe vernal keratoconjunctivitis were included in the study. All were treated with topical 2% cyclosporine A eye drops. One eye of each patient was administered 2% cyclosporine A in preservative-free artificial tears; the fellow eye received the placebo (vehicle) for the first 2 weeks, in a double-masked, placebo-controlled trial. Thereafter, the placebo eye received cyclosporine A (open trial). Symptoms and signs were scored on the day of enrollment and at the end of week 2, 4, and 14.

RESULTS

At the end of week 2, no statistically significant decrease was noted from baseline in mean scores of either signs (p = 0.18) or symptoms (p = 0.50) in the eyes that received placebo. On the other hand, a statistically significant decrease was observed in both sign and symptom scores (p < 0.001, for both) of eyes that received cyclosporine A. Significant differences were also noted at 2 weeks in mean scores of both signs and symptoms (p < 0.001, for both) between the eyes that received cyclosporine A and those that received placebo. At week 4 and 14, statistically significant decreases in both sign scores and symptom scores were noted compared with baseline in the eyes that received cyclosporine A and in the eyes that had initially received placebo (p < 0.001, for all).

INTERPRETATION

Topical 2% cyclosporine A in preservative-free artificial tears is effective in alleviating signs and symptoms of patients with severe vernal keratoconjunctivitis and had no observed side effects over the course of the study.

Effect of 0.03% tacrolimus ointment on conjunctival cytology in patients with severe atopic blepharoconjunctivitis: a retrospective study

PURPOSE

To evaluate the efficacy and effect of tacrolimus ointment on conjunctival cytology in patients with atopic blepharoconjunctivitis or keratoconjunctivitis.

METHODS

Ten patients with severe atopic blepharoconjunctivitis treated with 0.03% tacrolimus ointment once daily as an intermittent treatment were analysed retrospectively. The main outcome measures were clinical response to topical tacrolimus, adverse events and changes in the inflammatory cells obtained from conjunctival brush samples.

RESULTS

Marked clinical responses in blepharitis and conjunctivitis symptoms were seen after a mean follow-up time of 6 weeks. Clinical scores decreased by 67% in blepharitis and 74% in conjunctivitis symptoms. No severe adverse events or signs of immunosuppression such as herpes simplex infections occurred. No significant changes occurred in visual acuity, refraction, anterior chamber, retina or intraocular pressure. Median decreases were 85% (p =0.01) in conjunctival eosinophils, 50% (p = 0.01) in neutrophils and 58% (p = 0.02) in lymphocytes.

CONCLUSIONS

Tacrolimus ointment is potentially a safe and effective treatment for atopic blepharoconjunctivitis. Regular treatment of the eyelids once daily may also lead to clinical and cytological improvement of the conjunctivitis.

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.

Effects of ketotifen 0.025% and lodoxamide 0.1% on eosinophil infiltration into the guinea pig conjunctiva in a model of allergic conjunctivitis

The effects of ketotifen and lodoxamide on eosinophil infiltration were assessed in a guinea pig model of allergic conjunctivitis. The two active treatments were coded in this masked study in which 30 male guinea pigs, sensitized to chicken egg albumin (ovalbumin), were randomly assigned to one of three groups: Group 1, instillation of 0.9% NaCl into the conjunctival sac of both eyes; Group 2, instillation of 0.025% ketotifen into the left eye and 0.9% NaCl into the right eye; Group 3, instillation of 0.1% lodoxamide into the left eye and 0.9% NaCl into the right eye. Ovalbumin was administered topically to each eye, except in Group 1 where it was only applied to the left eye. (111)In-oxine labeled eosinophils were injected into the jugular vein of each guinea pig; the animals were sacrificed 17 hours after ovalbumin had been applied. The level of radioactivity in the ketotifen- and lodoxamide-treated eyes was approximately 60% of that in the saline-treated eyes. Moreover, the mean level of radioactivity in the ketotifen- and lodoxamide-treated eyes was comparable with the mean level of radioactivity in the saline-treated eye of Group 1, which had not been exposed to allergen. These results indicate that the therapeutic effects of ketotifen and lodoxamide in allergic conjunctivitis may be partly mediated by an inhibitory effect on eosinophils.

Topical immunopharmacology of ocular allergies

PURPOSE OF REVIEW

To review the histamine-1 receptor antagonists, mast cell blockers and natural agents with such actions that can be used for the topical treatment of ocular allergies.

RECENT FINDINGS

Increasing evidence indicates that some histamine-1 receptor antagonists have additional actions to inhibit secretion of inflammatory mediators, especially cytokines, from ocular mast cells and other cell types. Emerging information suggests that such actions may be through regulation of intracellular calcium ion levels of NF-kappaB activation.

SUMMARY

A number of available drugs and natural non-prescription agents may have anti-histaminic and anti-inflammatory actions.

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.

Ocular allergy guidelines: a practical treatment algorithm

The treatment of ocular allergy requires a better understanding of the spectrum of clinical disorders involving various components of the immune system, and of interactions at the conjunctival surface. The immune response focuses primarily on the different levels of activity of Th2 lymphocytes and various other immune cells associated with allergic disorders, including mast cells, eosinophils, fibroblasts, and epithelial and endothelial cells. Ocular allergic disorders include seasonal allergic conjunctivitis (SAC), perennial allergic conjunctivitis (PAC), vernal keratoconjunctivitis (VKC), giant papillary conjunctivitis (GPC) and atopic keratoconjunctivitis (AKC), which, through immunopathological and molecular immunological techniques, can all be better appreciated as being part of a larger spectrum of an atopic disease state. In SAC, pathological changes, such as increased mast-cell activation, the presence of migratory inflammatory cells, and early signs of cellular activation at the molecular level, are minimal. In PAC, these changes are more pronounced in line with the increased duration of allergenic stimulation. In more chronic forms of allergic conjunctivitis, such as VKC in children and AKC in adults, the following changes are evident: a persistent state of mast cell, eosinophil and lymphocyte activation; noted switching from connective-tissue to mucosal-type mast cells; increased involvement of corneal pathology; and follicular development and fibrosis. The treatment of acute and more chronic forms of allergic conjunctivitis has focused in the past on symptomatic relief of symptoms, but with a better understanding of the mechanisms involved we can now provide interventional therapeutic strategies and symptomatic relief. Our advances in the basic understanding of these conditions are providing the foundation for guidelines that improve the ocular health of patients with ocular allergies.

Update on ocular allergy treatment

Allergy affects > 15% of the world population with a higher prevalence of 30% in westernised industrialised countries, such as the US. Allergy commonly affects various target organs including the eyes, nose, sinuses, ears, lungs and skin. However, the ocular component may be the most common and initially the most prominent disabling feature. Some patients are affected for only a few weeks to months while others have symptoms that last throughout the year. The associated healthcare costs related to allergic conjunctivitis has been commonly nestled with allergic rhinitis and has been reported to be as high as US$5.9 billion in the US, with 25% (US$1.5 billion) of it related to medication use. The expenditures related to ocular prescription medication has only recently risen in the past decade from US$6 million in early 1990s to > US$200 million in the new millennium with a projected continuous expansion of 25% per year. This appears to be due to improved prescription medications and their clear benefit over the less efficacious over-the-counter products. The actual cost of the medications and their relative price increases over the past year have ranged from 0 - 49% with an average cost of < US$ day. The newer topical medications (multiple acting agents) are focusing on multiple actions that include an antihistaminic effect to provide an immediate relief and additional delayed effects to act on the mediators of the late phase reaction without steroid side effects (glaucoma, cataracts). The paradigm for the treatment of ocular allergy ranges from primary measures (avoidance measures, cold compresses and lubrication), to secondary measures (various combination of topical agents) and tertiary measures that would include topical steroids and immunotherapy. The increased interest in advancing ocular treatment will lead to the development of additional therapies, novel pharmacokinetic delivery systems and, thus, improved healthcare outcomes for patients with allergic conjunctivitis.

Overview of ocular allergy treatment

A plethora of drugs is available for the treatment of ocular allergy. Traditional treatment includes antihistamine and antihistamine/vasoconstrictor combination eyedrops. These drugs are useful, safe, and readily available. Mast cell stabilizers are safe, effective, and an important component of antiallergic therapy. Nonsteroidal anti-inflammatory drugs also have antiallergic effects. In recent years, drugs with multiple mechanisms of action have proven to be effective antiallergics. These drugs often have mast cell stabilizing, antihistaminic, and anti-inflammatory properties. Corticosteroids are considered to be more potent than other antiallergic drugs, and modifications in their molecular structures have made certain corticosteroids suitable for the treatment of ocular allergy.

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.

Inhibition of nitric oxide synthesis augments pulmonary oedema in isolated perfused rabbit lung

The role of nitric oxide (NO) in precipitating pulmonary oedema in acute lung injury remains unclear. We have investigated the mechanism of involvement of NO in the maintenance of liquid balance in the isolated rabbit lung. Thirty pairs of lungs were perfused with colloid for up to 6 h, during which pulmonary vascular resistance (PVR) and capillary pressure (PCP) were measured frequently, and time to gain 5 g in weight (t5) was recorded. Four protocols with different perfusate additives were studied: (i) none (control, n = 11); (ii) 10 mmol NG-nitro-L-arginine methyl ester (L-NAME) (n = 6); (iii) 10 mmol L-NAME with 100 mumol lodoxamide, an inhibitor of mast cell degranulation (n = 7); (iv) 10 mmol L-NAME with 10 mumol 8-bromo-3',5'-cyclic guanosine monophosphate (8Br-cGMP), an analogue of cGMP that may reduce vascular permeability by relaxing contractile elements in endothelial cells (n = 6). Neither PVR nor PCP differed between protocols. L-NAME markedly reduced t5 from 248 (27) min (mean (SEM)) in protocol (i) to 144 (5) min in protocol (ii) (P < 0.05). Both lodoxamide (t5 = 178 (7) min) and 8Br-cGMP (t5 = 204 (10) min) substantially corrected the effect of L-NAME (P < 0.005). Results suggest that maintenance of a low permeability by NO may involve mast cell stabilization and endothelial cell relaxation.

Ocular allergy: causes and therapeutic options

Ocular allergic eye conditions are among the most common anterior eye problems encountered in optometric practice. There are six common forms of ocular allergy: seasonal allergic conjunctivitis, perennial allergic conjunctivitis, vernal keratoconjunctivitis, atopic keratoconjunctivitis, contact lens associated papillary conjunctivitis and contact ocular allergy. Here, we review the current understanding of the pathophysiology underlying ocular allergic conditions and describe the different causes and forms of allergic eye disease and different treatment options.

The role of mast cells in ischaemia-reperfusion injury in murine skeletal muscle

To determine the role of mast cells in ischaemia-reperfusion (IR) injury to skeletal muscle, W(f)/W(f) mast cell-deficient and their corresponding wild-type mice were subjected to 70 min tourniquet ischaemia and 24 h reperfusion. As measured by nitroblue tetrazolium (NBT) staining, muscle viability was 9% in wild-type and 94% in mast cell-deficient animals (p<0.001). Assay of residual lactate dehydrogenase activity within the injured muscle (p<0.05) and histological examination confirmed the greater muscle necrosis in treated wild-type than in treated mast cell-deficient mice. There was no significant difference in the degree of neutrophil infiltration, tissue myeloperoxidase content or water content of IR-injured muscle in the two mouse phenotypes. To determine further the role of mast cells in IR injury, wild-type mice were treated 30 min prior to reperfusion with an intraperitoneal dose of either saline or the mast cell-stabilizing agent lodoxamide trometamol (2.5, 7.5, 25 or 75 mg/kg). Twenty-four hours after removal of the tourniquet, saline-treated gastrocnemius muscle had a mean viability of 14% compared with 28% (p<0.05) and 48% (p<0.01) after 25 mg/kg and 75 mg/kg of lodoxamide treatment, respectively. The ability of lodoxamide to stabilize mast cells was confirmed by histological examination. Ischaemic muscle reperfused for 1 h showed much less degranulation of mast cells in mice pretreated with lodoxamide (50 mg/kg) than in saline-treated controls. These findings suggest that mast cells are a major source of mediators of necrosis in IR injury to skeletal muscle.