Classification of ocular allergy

Drug Delivery for Ocular Allergy: Current Formulation Design Strategies and Future Perspectives

The incidences of ocular allergy have been growing with the increase in pollution. Because of challenges in new drug development, there have been efforts to maximize the efficacy of existing drugs through drug delivery approaches. The effectiveness of drugs in ophthalmic conditions is primarily determined by permeability across the barrier, corneal retention, and sustained release. Thus, there have been widespread efforts to optimize these parameters to enhance efficacy through novel formulations. This review aims to analyze the approaches to drug delivery systems to encourage further research to optimize effectiveness. With this objective, research on drug delivery aspects of anti-allergy therapeutics was included and analyzed based on formulation/drug delivery technique, Food and Drug Administration approval limits, residence time, compatibility, pre-clinical efficacy, and potential for translational application. Conventional eye drops have concerns such as poor residence time and ocular bioavailability. The novel formulations have the potential to improve residence and bioavailability. However, the use of preservatives and the lack of regulatory approval for polymers limit the translational application. The review may assist readers in identifying novel drug delivery strategies and their limitations for the development of effective ophthalmic formulations for the treatment of ocular allergy.

Allergic eye disease

Ocular allergy is one of the most common conditions encountered by pediatricians and ophthalmologists and is characterized by bilateral injection with itching as the predominant symptom. Risk factors include history of atopy (asthma, eczema, seasonal allergies). Basic and clinical research have provided insight into the immunologic mechanisms, clinical presentation, differential diagnosis, and pharmacologicmanagement of this condition. New pharmacologic agents have improved the efficacy and safety of ocularallergy treatment. This article discusses the classification of ocular allergy diagnosis and management, and addresses clinical symptoms and signs that indicate more severe allergic disease or alternative diagnosis that should prompt expeditious referral to an ophthalmologist.

The ocular surface epithelial barrier and other mechanisms of mucosal protection: from allergy to infectious diseases

PURPOSE OF REVIEW

Studies completed in the last decade provide new insights into the role of the epithelial glycocalyx in maintaining ocular surface barrier function. This review summarizes these findings, their relevance to allergic and infectious disease, and highlights the potential benefits of exploiting the modulation of barrier integrity for therapeutic gain.

RECENT FINDINGS

The molecular components sealing the space between adjacent ocular surface epithelial cells, such as tight junctions, have been extensively characterized, and their contribution to the paracellular barrier established. A second layer of protection - the transcellular barrier - is provided by transmembrane mucins and their O-glycans on the glycocalyx. Cell surface glycans bind carbohydrate-binding proteins to promote formation of complexes that are no longer thought to be a static structure, but, instead, a dynamic system that responds to extrinsic signals and modulates pathogenic responses. Although functioning as a protective mechanism to maintain homeostasis, the glycocalyx also restricts drug targeting of epithelial cells.

SUMMARY

The traditional model of intercellular junctions protecting the ocular surface epithelia has recently been expanded to include an additional glycan shield that lines apical membranes on the ocular surface. A better understanding of this apical barrier may lead to better management of ocular surface disease.

Vernal keratoconjunctivitis in school children in Rwanda and its association with socio-economic status: a population-based survey

Vernal keratoconjunctivitis (VKC) is an allergic eye disease and an important cause of hospital referral among children in Africa and Asia. Hospital-based studies have suggested a role for parasites in its pathogenesis. To determine the prevalence and risk factors for VKC in Central Africa, we conducted a nested population-based case control study in Rwanda, involving randomly selected primary schools from different environments (rural/urban) and climate. A prevalence of VKC of 4.0% (95% confidence interval 3.3-4.7%) was found among 3,041 children studied (participation rate 94.7%). The intestinal parasitic burden was not related to VKC. Besides hot dry climate (odds ratio [OR] = 1.5, P = 0.05) and male gender (OR = 1.7, P = 0.005), multivariate analysis identified higher economic status as a risk for VKC (OR = 1.4, P = 0.005). The effect on VKC of higher economic status appears not to act through differences in parasitic intestinal load.

A review of non-pharmacological and pharmacological management of seasonal and perennial allergic conjunctivitis

Allergic eye disease encompasses a group of hypersensitivity disorders which primarily affect the conjunctiva and its prevalence is increasing. It is estimated to affect 8% of patients attending optometric practice but is poorly managed and rarely involves ophthalmic assessment. Seasonal allergic conjunctivitis (SAC) is the most common form of allergic eye disease (90%), followed by perennial allergic conjunctivitis (PAC; 5%). Both are type 1 IgE mediated hypersensitivity reactions where mast cells play an important role in pathophysiology. The signs and symptoms are similar but SAC occurs periodically whereas PAC occurs year round. Despite being a relatively mild condition, the effects on the quality of life can be profound and therefore they demand attention. Primary management of SAC and PAC involves avoidance strategies depending on the responsible allergen(s) to prevent the hypersensitivity reaction. Cooled tear supplements and cold compresses may help bring relief. Pharmacological agents may become necessary as it is not possible to completely avoid the allergen(s). There are a wide range of anti-allergic medications available, such as mast cell stabilisers, antihistamines and dual-action agents. Severe cases refractory to conventional treatment require anti-inflammatories, immunomodulators or immunotherapy. Additional qualifications are required to gain access to these medications, but entry-level optometrists must offer advice and supportive therapy. Based on current evidence, the efficacy of anti-allergic medications appears equivocal so prescribing should relate to patient preference, dosing and cost. More studies with standardised methodologies are necessary elicit the most effective anti-allergic medications but those with dual-actions are likely to be first line agents.

Synergistic induction of eotaxin and VCAM-1 expression in human corneal fibroblasts by staphylococcal peptidoglycan and either IL-4 or IL-13

BACKGROUND

Common features of allergic or atopic ocular and skin diseases are the participation of Th2 lymphocytes and eosinophils and colonization by Staphylococcus aureus. To examine the role of interaction between Th2 cells and bacterial infection in tissue eosinophilia, we determined the effects of Th2 cytokines and peptidoglycan derived from the cell wall of S. aureus on corneal fibroblasts.

METHODS

Chemokine concentrations and the cell surface expression of adhesion molecules were determined by ELISAs, and chemokine and adhesion molecule mRNAs were quantitated by real-time PCR analysis. Signaling by the transcription factor NF-κB was evaluated by immunoblot and immunofluorescence analyses as well as by assay of DNA binding activity.

RESULTS

Among Th2 cytokines tested, only interleukin (IL)-4 and IL-13 induced a low level of eotaxin release by corneal fibroblasts, as did peptidoglycan. However, the combination of peptidoglycan and either IL-4 or IL-13 induced a marked synergistic increase both in eotaxin release (without affecting that of IL-8) and in the abundance of eotaxin mRNA. The combination of peptidoglycan and IL-4 or IL-13 also synergistically increased the surface expression of VCAM-1, but not that of ICAM-1. Peptidoglycan activated NF-κB in corneal fibroblasts, and inhibitors of NF-κB attenuated eotaxin release induced by peptidoglycan alone or in combination with IL-4 or IL-13.

CONCLUSIONS

Interaction of innate and adaptive immunity, as manifested by synergistic stimulation of eotaxin and VCAM-1 expression in corneal fibroblasts by peptidoglycan and Th2 cytokines, may play an important role in tissue eosinophilia associated with ocular allergy.

Causes and management of red eye in pediatric ophthalmology

Red eye is the most common ocular sign encountered in emergency and outpatient settings. Recognition of vision-threatening causes and those requiring referral to an ophthalmologist is of utmost importance. This article reviews causes and management of red eye in children with an emphasis on allergic etiology, pathophysiology, and recent advances in therapy.

Clinical trials in allergic conjunctivits: a systematic review

BACKGROUND

Ocular allergy represents one of the most common conditions encountered by allergists and ophthalmologists. However, there is wide variability of study designs in clinical trials of allergic conjunctivitis, which results in conflicting evidence on their optimal management. We conducted a systematic review of clinical trials to critically evaluate their quality and to highlight biases to be avoided in future clinical research in ocular allergy.

METHODS

Clinical trials in allergic conjunctivitis performed since 1965 were retrieved, and data on patients, interventions, comparison of interventions, and outcomes were extracted. Four authors independently assessed articles for inclusion in the systematic review and assessed trials' quality using the Jadad scale.

RESULTS

Three hundred and sixty-two trials were included in the study. Only a minority of trials fulfilled all the criteria of proper clinical trial design. In most of the studies, there was a very limited use of objective (quantifiable) parameters for both patients' selection and evaluation of drug efficacy and safety. Several outcomes of primary importance, such as disease relapses and recurrence rate, were omitted in clinical trials of allergic conjunctivitis.

CONCLUSIONS

Evidence coming out of clinical trials in ocular allergy is limited, and this affects the strength of recommendations to health care providers and policy makers for optimal management. Standardized diagnostic criteria for patient selection and quantifiable primary outcomes are recommended to improve the design of future clinical trials in allergic conjunctivitis.

Vernal keratoconjunctivitis--a rare but serious comorbidity of allergic rhinitis and eustachian tube dysfunction

OBJECTIVE

To determine the prevalence of symptoms and signs of allergic rhinitis (AR) in children with vernal keratoconjunctivitis (VKC) and evaluate eustachian tube (ET) function using tympanometry.

METHODS

The patients underwent an otolaryngological examination and symptoms of rhinorrhoea, nasal obstruction, nasal itching and sneezing were evaluated for the diagnosis of AR. Tympanometry was performed by a middle ear analyzer (Impedance audiometer AZ 26, Interacoustics A/S, Assens, Denmark). Blood samples were collected for determination of peripheral blood eosinophil count (PBEC) and serum total immunoglobulin E (IgE). Allergen sensitivity was also determined by skin prick test.

RESULTS

The study included 26 males (96.3%) and 1 female (3.7%) with a mean age of 12.1+/-4.4 years. Eight out of 27 subjects (29.6%) had blood eosinophilia and 11 out of 27 subjects had elevated serum IgE (40.7%). A positive skin prick test was identified for at least one allergen in 40% of patients (10/25 subjects). Symptoms and signs of AR were found in 10 subjects (37%). Median serum IgE level in subjects with AR (262.5 kU/L) was higher than without AR (40.2 kU/L) (p=0.08), whereas there were no differences in PBEC or eosinophilia percentage (p>0.05). Mean middle ear pressures in the right and left ears were -66.4 daPa (range between -268 and 4 daPa) and -57.3 daPa (range between -308 and 0daPa), respectively. The tympanometry results were abnormal in 5 subjects (18.5%) (3 type C and 2 type B tympanogram). Three out of 10 VKC patients with AR (30%) and 2 out of 17 VKC patients without AR (11.8%) had abnormal tympanograms (p=0.33).

CONCLUSION

AR is commonly associated with VKC and subjects with AR are almost three times more likely to have ET dysfunction than those without. Therefore, opthalmologists should refer VKC patients to otolaryngologists to delineate associated AR and ET dysfunction. Conversely, patients with OME and/or AR who have persistent allergic eye symptoms may well benefit from opthalmologic evaluation for seasonal allergic conjunctivitis and VKC.