Author(s): Snigdha Sen1 , Himanshu Kumar Yadav2 , Prerana Singh3
BACKGROUND Allergic conjunctivitis is one of the commonly found clinical conditions in ophthalmology practice. Diagnostic features consist of itching, redness and swelling of conjunctiva. Cornea is rarely involved. The physiologic basis of allergy is mast cell degranulation releasing histamine and other pro-inflammatory mediators. Mast cells release histamine which is responsible for early acute phase of allergies and pro-inflammatory mediators like prostaglandins, leukotrienes etc. which are responsible for the late phase. Activation of H1 receptors on conjunctival neurons causes itching while that of H1 and H2 receptors on vascular endothelium is responsible for vasodilation (appearing as redness) and endothelial swelling. Itching and inflammation are caused by response of H4 receptors on immune and inflammatory cells. Olopatadine is an H1 receptor antagonist and mast cell mediator release inhibitor. It is available as 0.1 % formulation used twice daily, and 0.2 % and 0.7 % formulations, both used once daily. Alcaftadine has high affinity and specificity for H1 and H2 receptors, and moderate affinity for the H4 receptors. It is an inverse agonist of H1, H2 and H4 receptors and also acts as mast cell stabiliser. Thus, antihistaminic effect relieves the early phase and mast cell stabilisation relieves the late phase of ocular allergic response. Both have become the most important therapy for allergic conjunctivitis. METHODS This was a prospective, observer-masked, single centre clinical trial conducted at outpatient department of ophthalmology, S.N. Medical College, Agra, from February 2018 to July 2019. Subjects with allergic conjunctivitis (n = 136) were registered for a prospective study and followed up for two weeks. Subjects were randomised using computer generated random number tables into one of the two treatment groups: alcaftadine 0.25 % eye drop and olopatadine 0.2 % eye drop. In this study, efficacy of the drug was taken as mean reduction in severity score of the subjects evaluated at one week and two weeks follow up. RESULTS Patients treated with alcaftadine 0.25 % eye drop showed comparatively early alleviation of signs and symptoms in comparison to patients treated with olopatadine 0.2 % eye drop. Alcaftadine 0.25 % treated subjects experienced significantly higher mean reduction in severity score than olopatadine 0.2 % treated subjects at every follow up visit; after 1 week (p = 0.0205) and after 2 weeks (p = 0.0475). No adverse effects were reported with either drug. CONCLUSIONS Once daily alcaftadine 0.25 % eye drop showed higher efficacy than once daily olopatadine 0.2 % eye drop in relieving signs and symptoms of allergic conjunctivitis at both one week and two weeks follow up. Both treatment arms were found to be safe and effective.