Approach to Red Eye for Primary Care Practitioners

Therapeutic efficacy of topical blockade of substance P in experimental allergic red eye

PURPOSE

Allergic conjunctivitis is the most common cause leading to ocular redness (OR). Herein, using an animal model of allergic OR, we evaluated the therapeutic efficacy of topical blockade of substance P (SP) in treating red eye.

METHODS

Allergic OR was induced in guinea pigs with topical histamine. Ocular SP was blocked using a specific SP receptor (neurokinin-1 receptor, NK1R) antagonist, L-703,606, via topical application 10 min before or 10 min after histamine instillation. Animal eyes were examined and a series of images were taken for up to 60 min post-OR induction. The severity of redness was analyzed using the quantitative ocular redness index (ORI). At the end of clinical examination, conjunctival tissues were collected for histological examination of conjunctival blood vessels and infiltrating eosinophils and neutrophils. In addition, SP concentration was quantified in the tear fluid and expression levels of inflammatory cytokines were assessed in the conjunctival tissues.

RESULTS

Topical histamine application successfully induced red eye, evidenced by the significantly increased ORI during the observation period, with peak values at 10 min, along with significantly increased levels of SP in the tears. Topical treatment with L-703,606, either before histamine application or at the time of peak ORI, effectively reduced ORI and suppressed conjunctival blood vessel dilation, along with decreased eosinophil and neutrophil infiltration, and inflammatory cytokine expression in the conjunctiva, as well as reduced SP levels in the tears.

CONCLUSIONS

Topical blockade of SP effectively prevents and treats allergy-related ocular redness by suppressing blood vessel dilation and allergic inflammation.

Brimonidine tartrate ophthalmic solution 0.025% for redness relief: an overview of safety and efficacy

INTRODUCTION

Ocular redness, or conjunctival hyperemia, is a common ophthalmic sign associated with reduced quality of life. For redness without apparent underlying pathology, topical ophthalmic decongestants have been widely used.

AREAS COVERED

Brimonidine tartrate was approved in 2017 as a topical vasoconstrictor at a 0.025% concentration for relief of ocular redness. Since then, investigators have reported on efficacy and safety findings from studies evaluating low-dose brimonidine for reducing ocular redness.

EXPERT OPINION

Brimonidine is highly selective for α₂-adrenergic receptors. Clinical trials have so far shown that the drug in low doses significantly reduces ocular redness in comparison to vehicle for up to 8 hours. Brimonidine-treated eyes did not present side effects of other vasoconstrictors, such as hypotension, cardiac arrhythmia or drowsiness. Ocular adverse events such as allergic reactions and redness rebound were also minimal. In this review, we examine in detail published literature on the mechanism of brimonidine tartrate and its efficacy and safety in relieving conjunctival hyperemia.

Ocular redness - I: Etiology, pathogenesis, and assessment of conjunctival hyperemia

The translucent appearance of the conjunctiva allows for immediate visualization of changes in the circulation of the conjunctival microvasculature consisting of extensive branching of superficial and deep arterial systems and corresponding drainage pathways, and the translucent appearance of the conjunctiva allows for immediate visualization of changes in the circulation. Conjunctival hyperemia is caused by a pathological vasodilatory response of the microvasculature in response to inflammation due to a myriad of infectious and non-infectious etiologies. It is one of the most common contributors of ocular complaints that prompts visits to medical centers. Our understanding of these neurogenic and immune-mediated pathways has progressed over time and has played a critical role in developing targeted novel therapies. Due to a multitude of underlying etiologies, patients must be accurately diagnosed for efficacious management of conjunctival hyperemia. The diagnostic techniques used for the grading of conjunctival hyperemia have also evolved from descriptive and subjective grading scales to more reliable computer-based objective grading scales.

Ocular redness - II: Progress in development of therapeutics for the management of conjunctival hyperemia

Conjunctival hyperemia is one of the most common causes for visits to primary care physicians, optometrists, ophthalmologists, and emergency rooms. Despite its high incidence, the treatment options for patients with conjunctival hyperemia are restricted to over-the-counter drugs that provide symptomatic relief due to short duration of action, tachyphylaxis and rebound redness. As our understanding of the immunopathological pathways causing conjunctival hyperemia expands, newer therapeutic targets are being discovered. These insights have also contributed to the development of animal models for mimicking the pathogenic changes in microvasculature causing hyperemia. Furthermore, this progress has catalyzed the development of novel therapeutics that provide efficacious, long-term relief from conjunctival hyperemia with minimal adverse effects.

Inpatient Ophthalmology Consultations

Comprehensive patient care requires an integrated approach that often includes different specialties. Of these specialties, Ophthalmology stands out with its variable pathologic conditions, unique tools, and special examination techniques, which are not part of the standard training of internal medicine or other specialties. The authors review prior studies focused on inpatient ophthalmology consultations, common reasons for inpatient ophthalmology consultation, and the recommended approach to the most common ocular complaints that could present to the inpatient provider. They also shed light on the basic ocular history and eye examination that should be obtained before requesting an ophthalmic evaluation.

Over-the-Counter Ocular Decongestants in the United States - Mechanisms of Action and Clinical Utility for Management of Ocular Redness

To manage ocular redness effectively, health-care practitioners require an understanding of the pathophysiology, clinical features and differential diagnosis of ocular redness, as well as comprehensive knowledge of medical therapies available and their pharmacologic properties. This review aims to provide a clinically relevant summary of the current literature on the mechanism of action, efficacy, and safety of current over-the-counter (OTC) decongestants available for reduction of ocular redness due to minor irritations. Currently marketed OTC products indicated for such use in the United States include topical solutions of tetrahydrozoline 0.05%, naphazoline 0.012% to 0.03%, and brimonidine 0.025%. All 3 agents are adrenergic receptor agonists but vary in their receptor-binding profiles: tetrahydrozoline is a selective α1 receptor agonist; naphazoline is a mixed α1/α2 receptor agonist; and brimonidine is a selective α2 receptor agonist. These OTC decongestants produce vasoconstriction of conjunctival blood vessels, which results in a rapid reduction in ocular redness. In general, ocular adverse events reported in published studies of these OTC decongestants were minimal, mild, and transient, with no significant adverse systemic effects. However, ocular decongestants with α1-adrenergic receptor agonist activity can be associated with loss of effectiveness with continued use (ie, tachyphylaxis) and rebound redness upon treatment discontinuation. In clinical trials of the selective α2-adrenergic receptor agonist brimonidine 0.025%, tachyphylaxis was not observed, and rebound redness was rarely reported.

Low-dose brimonidine for relief of ocular redness: integrated analysis of four clinical trials

BACKGROUND

The aim of this study was to provide an integrated analysis of safety and efficacy data for brimonidine tartrate ophthalmic solution 0.025 per cent (low-dose; Bausch & Lomb Incorporated), a topical vasoconstrictor for relief of ocular redness.

METHODS

Integrated efficacy data from two randomised, double-masked, vehicle-controlled studies in subjects with ocular redness as well as safety data from the two efficacy studies, a vehicle-controlled safety study, and a pharmacokinetic study were analysed. Efficacy outcomes analysed included investigator-assessed ocular redness (scale, 0-4) before treatment instillation and at five to 240 minutes post-instillation on Day 1, at five minutes post-instillation on Days 15 and 29, and one week after treatment discontinuation (Day 36), and redness self-assessed by subjects recorded daily in diaries. Safety assessments included adverse events, ophthalmic examinations, and rebound redness upon treatment discontinuation. Drop comfort (scale, 0-10) was a tolerability measure.

RESULTS

The efficacy population included 117 subjects (brimonidine, n = 78; vehicle, n = 39). The safety population included 635 subjects (brimonidine, n = 426; vehicle, n = 209). Investigator-assessed ocular redness was significantly lower with brimonidine versus vehicle at all post-instillation time points on Day 1 (mean change from pre-instillation of -1.4 units for brimonidine and -0.2 units for vehicle; p < 0.0001). Subject-assessed ocular redness was also significantly lower with brimonidine versus vehicle (mean treatment difference in average daily ratings of -0.9; p < 0.0001). There was no evidence of tachyphylaxis through Day 29 and rebound redness was rare. Incidence of ocular adverse events was low, the most common being reduced visual acuity (brimonidine, 4.0 per cent; vehicle, 4.3 per cent) and conjunctival hyperaemia (2.6 and 2.9 per cent, respectively). Both brimonidine and vehicle were rated as very comfortable (mean post-instillation scores, 0.4-0.5).

CONCLUSION

In this integrated analysis, low-dose brimonidine significantly reduced ocular redness with no tachyphylaxis, and minimal rebound redness, and was generally safe and well tolerated.

Clinical implications of mast cell involvement in allergic conjunctivitis

The conjunctiva is a common site for the allergic inflammatory response due to it being highly vascularized, having constant exposure to environmental pollutants and allergenic pollens and having a unique conjunctival associated lymphoid tissue. The primary morbidity of anterior surface conjunctival disorders that include allergic conjunctivitis and tear film disorders is associated with its high frequency of involvement rather than its severity, although the more chronic forms can involve the cornea and lead to sight-threatening conditions. Ocular allergy is associated with IgE-mediated mast cell activation in conjunctival tissue leading to the release of preformed mediators including histamine and proteases and subsequent de novo formation of lipid-derived mediators and cytokines that trigger a cascade of cellular and molecular events leading to extensive migration and infiltration of inflammatory cells to the ocular surface. The trafficking of neutrophils, eosinophils, and lymphocytes to the ocular surface is due to establishing various chemokine gradients (mainly CCL11, CCL24, CCL5, MCP-3, and MCP-4), cell surface expression of adhesion molecules (such as VCAM-1 the ligand for VLA-4), and leukocyte adhesion to vascular endothelium. The release of preformed mediators underlies the acute ocular surface response while the secondary influx of inflammatory cells leading to the recruitment and activation of eosinophils and the subsequent activation of Th2 and Th1 lymphocytes at the level of the conjunctiva reflects the late-phase reaction.

Differentiating Urgent and Emergent Causes of Acute Red Eye for the Emergency Physician

Patients commonly present with an acute red eye to the emergency department (ED). It is important to distinguish between benign and sight-threatening diagnoses. Here we provide a comprehensive overview on the acute red eye in the ED.